Ritchey–Chrétien enjoyers thread

[harsh matrix]

blue

so yes, not just narrowband

[runic violet]

There was a CN thread between optics nerds arguing about where the rings in amateur images come from and last I heard they were mumbling about microlensing

I should check on that maybe they got to the bottom of this

[harsh matrix]

that doesnt make sense imo

the microlensing on my camera doesnt look like this

[runic violet]

No

The idea is that the sensor forms a sort of etalon that results in an interference pattern

Not to do with any other microlensing effect

[harsh matrix]

[runic violet]

Image scale?

[harsh matrix]

0.72"/px

for both

and no blurx here

on all

[runic violet]

If you seriously think that's from your scopes airy diffraction you realize it would mean that you're severely aberrated

Which I do not think

[harsh matrix]

it sounds like you dont even really know what it is

and the narrowband only argument is out the window now

[runic violet]

You can know what it is not

The spacing is several arcseconds

[harsh matrix]

correct

and i understand that normally severe oversampling is the only way to pull out the airy disk

[runic violet]

Because the airy disk spacing is going to be just about subarcsecond

It also diminishes very quickly

[harsh matrix]

that wouldnt be surprising considering the "mirror flop" and astigmatism which is introduced

so is this some artifact of the microlenses?

something else?

the part which doesnt make sense to me is that this DOES happen to show up most often when my seeing is 2 to 2.5"

if it's much higher, it's invisible

I have noticed a correlation with seeing

in my observations

[runic violet]

They can happen because the star is being tossed around so any diffraction effect of any kind goes out

Since the star is moving on the sensor

[harsh matrix]

RBG, on a night of much worse seeing, it's less pronounced in red and not even visible in the other 2

it varies with wavelength

[runic violet]

As it should?

It would be very weird if it didn't

[harsh matrix]

the microlense explanation could make sense in this case due to the interaction of the wavelength with the lenses

[harsh matrix]

well yeah

[runic violet]

Ok someone modeled it

I'm pretty convinced it's CO modulation

It should be around 3x the period of the airy disk

You can go measure it

[harsh matrix]

central obstruction is the reason?

[runic violet]

Yes

[harsh matrix]

that's what I suspected from the very beginning

[harsh matrix]

how would I go about that?

[runic violet]

Figure out the spacing

[harsh matrix]

hang on

spacing of what?

[runic violet]

The rings

Use Ha

It's less annoying

[harsh matrix]

alright

[runic violet]

The rings should show up even without great seeing though moderately diminished

[harsh matrix]

okay do you wn the spacing in arc seconds or pixels?

ill do my best to measure peak to peak

[runic violet]

Arcsec

It's just a conversion anyways

[harsh matrix]

it's 4" peak to peak

using the caph example

i tried other Ha data but the rings were either super faint, invisible, or too faint to measure accurately

id say it's closer to 3"

[runic violet]

6"?

[harsh matrix]

yeah let's call it 3"

peak to peak

[runic violet]

6" rc I mean

[harsh matrix]

yes

counting pixels peak to peak * my image scale of 0.72"/px yields 3.6"

[runic violet]

Focal ratio?

[harsh matrix]

f/6

[runic violet]

I calculate it should be around 5.2 pixels

[harsh matrix]

that's what im counting

that correlates

[runic violet]

0.656 microns * f ratio of 6 * modulation factor of 5 for 47% CO = 19.7 microns

[harsh matrix]

yeah that looks right

so it is CO modulation...

that does mean that it's due to diffraction of light around the secondary mirror, right?

I am not crazy?

At least in some part

maybe not the entire cause

[runic violet]

For OIII you should get 4 pixels

[runic violet]

It's due to the obstructed aperture

Put a sticker on a refractor and you'll get it

The funny thing is someone tried to prove it's not CO modulation by showing the rings on an unguided trailed exposure

So this effect is pretty resistant to disturbances

[harsh matrix]

yes that's also correct

[harsh matrix]

that's why it's showing up despite astigmatism due to primary mirror movement

ive observed it remaining despite the mirror shifting position

it even molds to the shape of the rest of the PSF

[harsh matrix]

and doesnt that only prove that it is CO modulation?

what a bad way to try to discredit the argument

[runic violet]

No the idea is that it would smear the rings

If it's actually an effect of starlight on the scope and not on the camera

But the explanation is that the rings are too fat and contrasty that you need to have smear it hard to lose them

[harsh matrix]

yes

[harsh matrix]

that's what im thinking

i just dont see how or why they would smear out due to trailing

i havent observed that happening in practice either

[harsh matrix]

like normal sub trailing, your stars slightly grew in size

etc.

[runic violet]

For comparison the actual "airy disk" first order diffraction has 1 pixel spacing on your setup

[harsh matrix]

your FWHM is a pixel or 2 larger whatever

[runic violet]

So that should remain completely invisible

[runic violet]

Trail harder

[harsh matrix]

which it does so far

i will refute your argument if i ever catch it not doing that

but i do not expect to have to

[runic violet]

Refute what argument

[harsh matrix]

not shooting reduced

[harsh matrix]

the airy disk being one pixel in size lmao

[runic violet]

That's a fact of physics

You can't refute that one

[harsh matrix]

if i somehow resolved a 1 pixel star in another galaxy and saw the disk id poop myself for instance

[harsh matrix]

oh no i understand that

the point im making is i think you are 100% right in that i should never see it

but i will point it out if i ever did, i just think it's utterly absurd that i would ever see it in reality

without doing a 5x barlow on Rigel or something lmao

[runic violet]

also when i was saying its a narrowband thing: that's because it should smear normally due to being well broadband

it does smear in low CO setups

but they're too big in high CO setups

656nm to 500nm only reduces it from 5 to 4 pixels

so you still have ringing

https://www.cloudynights.com/topic/731780-obstructed-optics-and-rings-around-stars/

fairly good summary

[harsh matrix]

yeah ill read it

the diffraction rings have been baffling me for a while

although idk what to call it

CO modulation now?

[runic violet]

CO modulation of the airy pattern

[harsh matrix]

so is what is going on here basically the CO amplifying the effects of the airy disk to a degree which is detectible?

[runic violet]

no, its modulating the airy disk

its introducing new maxima

[harsh matrix]

oh fuq

[runic violet]

that are unrelated to the normal first order effect

[harsh matrix]

i didnt learn about this in my physics class

[harsh matrix]

okay that's what i needed to know

[runic violet]

https://www.telescope-optics.net/obstruction.htm

[harsh matrix]

now im having an existential crisis

[runic violet]

well they're "related" as in they're both features of the PSF but the two should not be confused

[harsh matrix]

One does not cause the other

right.

There is not a causation correlation

[runic violet]

well they're both effects not causes

[harsh matrix]

ofc

[runic violet]

in essence this is why CO has less contrast, light is being scattered away from the central peak

this is where its going

[harsh matrix]

yes but the fact that theyre not related in that sense makes them effects

[vapid patio]

https://tenor.com/view/asuka-bark-yap-gif-1854879270727789514

[harsh matrix]

in my mind the nature of the airy disk has been the cause of the modulation

like the CO amplifying it but that's not at all what's happening here

[runic violet]

think of it like this

[harsh matrix]

it was a futile hope to simplify something which i do not understand yet

[runic violet]

if you take the FT of a donut instead of a full circle

[harsh matrix]

alright that makes much more sense now

[runic violet]

you get this stupid thing happening

[harsh matrix]

that makes the importance of the CO much larger to me

[harsh matrix]

alright

gotcha

[harsh matrix]

[runic violet]

so circling back

this effect disappearing often just means you get really atrocious seeing

to smear 5 pixel rings

[harsh matrix]

yes that's what ive gathered now

well im glad i finally learned something about this

holy fuq

[runic violet]

imma be real with you idk how the heck you thought this was diffraction limited

cotton candy elongated stars over here

[harsh matrix]

this has been such an anomoly to me and i didnt know who to believe

[harsh matrix]

it's collimation error there lmao

my primary slipped about halfway through that project

[runic violet]

if you have collimation error you can't be diff limited lol

your collimation limited

[harsh matrix]

that is what I thought yes lmao

but when you have 20 demons chirping in your ear that are saying it's something it is not

you start feeling like you are the crazy one

im going to read about the Hubble PSF too while im at it

that will be fun

[runic violet]

One thing I've learned in this hobby is a lot of people with less than ideal understanding of physics will defend to the death whatever theory they concoct

[harsh matrix]

Yes

and we saw that last night

I happened to take a physics course which went over optics and behaviour of light rigorously very recently

that tied in almost everything i learned about optics through starting this hobby and gave me a deeper understanding than i otherwise would hav had

[runic violet]

btw the guy testing this had a phd in optical physics

so even people who do understand

[harsh matrix]

i would not have passed the class truth be told, had i not started this hobby

[harsh matrix]

so this is reliable and rigorous testing

[runic violet]

no

the guy saying smearing proved it wasn't CO modulation

[harsh matrix]

wait wtf

im too naive lmfao

i really hated the fact that i picked physics of all things to get full science credit for in college but after that physics 2 class, im pretty glad i did

it helped me understand what exactly astronomers are doing, and deepend my understanding of optics

but even with what I learned, it did not prepare me for what an obstruction does to a system lmaoooo

or at least not a large one

[runic violet]

https://www.cloudynights.com/topic/769710-another-i-hope-final-explanation-for-annular-rings-on-stars/page-9#entry11251276

[harsh matrix]

we discussed diffraction, and diffraction gratings in depth

[runic violet]

kind of a funny thread

oh lol the hubble zone thing comes up

[harsh matrix]

it probably comes up a lot

I thought the same reason Hubble got these rings was the same reason I did

CO

i do wonder how much of an impact those zones make over the central obstruction on Hubble, though

[runic violet]

hubble doesn't have a really big central obstruction

since its a large scope

it also is very undersampled, which is why they invented drizzling for it

[harsh matrix]

yup

[harsh matrix]

hm really?

I dont know how big the CO is on it

never knew

why did airy use inches in his formula

😭

[runic violet]

i think its around 13%

[runic violet]

CO size diminishes as RCs get larger

[harsh matrix]

this must be the Rayleigh criterion mb

[harsh matrix]

oh snap

[harsh matrix]

yeah so ive heard

doesnt it have 6 micron pixels?

the WFC3

[runic violet]

uvis is 15 micron

sampling at the dawes limit

[harsh matrix]

i calculated the angular resolution of my RC8 to be about 0.81" in the H-alpha wavelength

that appears to be correct or pretty darn close

i did not take CO into account

[harsh matrix]

wait really?

i thought it was 6 rip

i need to start on my economics homework or else ill never finish it

this was a can of worms i was not ready to jump down today

[vapid patio]

Nerd

[harsh matrix]

Obviously

[vapid patio]

I helped a kind man in ask a nerd yipeee

I have done the same thing as him so many times 😭

[vapid patio]

What even is it?

[harsh matrix]

I am seeing CO modulation with my lum filter atm

Never seen this before

[harsh matrix]

What is what?

[vapid patio]

that uh chat thing

chart

[harsh matrix]

It's quite strong on lum too

[harsh matrix]

It's a break down of the correlation of telescope size to angular resolution

[vapid patio]

nerd

but cool

[harsh matrix]

im going to attempt to split the blobs in M87's black hole jet

seeing is fantastic

i think this is my chance

collimation is also perfect

[vapid patio]

what

oh the blue jet thing?

@harsh matrix show me

[harsh matrix]

this

[vapid patio]

oh yes yes that

the blue jet thing

[harsh matrix]

can see a little bit of the jet here

[vapid patio]

how long

exp

[harsh matrix]

donut is really bad tonight

because of the moon

[harsh matrix]

90 seconds

[vapid patio]

short?

[harsh matrix]

i forgot to cool the camera so that's uncooled as well

[vapid patio]

how????

[harsh matrix]

yeah i just needed to test if id blow out the galaxy or not

[vapid patio]

sad

[vapid patio]

ah ok thought so

[harsh matrix]

it was super bright in my redcat subs

[vapid patio]

and uv/ir?

[harsh matrix]

yeah

[vapid patio]

yeah

[harsh matrix]

well the lum filter that came with my LRGB set

[vapid patio]

ahhh

ok sick

[harsh matrix]

guys

i think it's been done

[tight lodge]

M-87?

[vapid patio]

@harsh matrix you are in cat right?

[vapid patio]

mr picklesss

[tight lodge]

Yes?

[vapid patio]

idk

but yes m87

[tight lodge]

[vapid patio]

what bands do you like?

seem like the kinda guy to have good taste

[tight lodge]

Musical bands? My favorites are definitely Behemoth, IA, Cannibal Grandpa, God Seed and Gorgoroth. But I like stuff outside of metal as well. If it's good and I vibe to it, I listen to it

[vapid patio]

sick! the only one i recognize is gorgoroth. but yeah if it is a vibe i will listen to it

[tight lodge]

Well, some bands names are definitely not allowed here

[harsh matrix]

yes

[harsh matrix]

no

[tight lodge]

I want to try to image it... but nebula season begins . Galaxies can wait

[harsh matrix]

i have a galaxy killer

galaxies can never wait

this is why I need a 585 tho

i have another system that i can run alongside the galaxy killer but i cant run it without a camera which is worth my time to use

[tight lodge]

I can tell😂

[tight lodge]

For me they can. I shot my galaxy for this season. I don't need another one

[harsh matrix]

I split it alright lol

with blurx and noisex

[tight lodge]

I want ti image something similar. The bubble nebula near Tulip Nebula

[tight lodge]

Wait... aren't those circular fringes created by the secondary mirror?

[tight lodge]

Question. My telescope has a resolution of 0.92 arcsec/px. And the diffraction limit is 0.38 arcseconds. So theoretically speaking I'm far from being limited by the telescope. The question is, my guiding RMS should be lower than 0.92 arcsec/px in order to get the sharpest image. (Atleast that's my theory)

So if my intuition is right, with an OAG you can't get a guide RMS lower than the diffraction limit. In my case 0.38 arcsec

But then... my main cam and guide cam have same pixel size... What the??!!! Something ain't right

[vapid patio]

mine is 0.533

[vapid patio]

yes but no. i had thought that yes your guiding should be lower than that but aslong as you have dot stars your good, i can never get under 0.5 guiding

i really need a new guide camera haha

[tight lodge]

I have between 0.4 and 0.6... stars are pinpoints. But then the math ain't mathin. How it's possible to guide at a lower resolution when both the main camera and guide camera use the same OTA and have identical pixelscale

I'm missing something

[vapid patio]

wait what? your asking why is your guiding is better than your pixelscale?

[tight lodge]

Yes

[vapid patio]

dude haha with my redcat pixel scale around 3 i think, i would guide at 0.23ish

maybe im dumb but that doesnt really make sense

[runic violet]

You mean you have an image scale of 0.92 arcsec/px

Idk how you're calculating the diffraction limit, there's no one figure for that

[tight lodge]

In my case I calculate it for the Hα line

[runic violet]

Youre probably calculating the Rayleigh limit

[tight lodge]

It's just a reference, I don't trust that number

[runic violet]

That's not the same thing

[tight lodge]

DL=1.22*λ/d

[runic violet]

Thats the Rayleigh limit

[tight lodge]

Aaah.

[runic violet]

And no, if you're imaging at 0.92"/px, guiding rms doesn't need to be below that

It needs to be well below that

Like 2-3x lower

[tight lodge]

My RMS is between 0.4 and 0.6 so in the ok zone

[runic violet]

Depends on what you're guiding with

[tight lodge]

OAG

[runic violet]

Ok

[tight lodge]

I know I can probably get better guiding, but idk what other settings to mess with😅

[frosty shard]

yeaboiiiiiiiiiiiiiiii

Now if only that big light polluting rock wasn't in the way

[harsh matrix]

@runic violet I split the blobs in M87's black hole jet

[harsh matrix]

my flats must not have been good

M87 looked rough

this is even more rough

i tried to fix the focuser tube thing by adding an internal lip which would act as a light stopper and a baffle, it either didnt work, or it did but also amplified my issue

another problem may be that my sky flats were ruined for some reason

[vapid patio]

just your luck

oh vel

[harsh matrix]

it really is

it did go through a tree and that made it significantly worse, i forgot to purge the bad subs

didnt fix the problem entirely

[vapid patio]

im ready to finally summit my ask to join CAT. i havent put many many hours into a single target yet but i feel like i get good data

[vapid patio]

mann

[harsh matrix]

the extra light from the moon just exaggerated an already bad problem

[vapid patio]

yeah im shooting narrow band now

your in cat right? i swear i asked this and i forgor

[harsh matrix]

same for me from now on until the moon goes away

[vapid patio]

ahem @harsh matrix

[harsh matrix]

im not

[vapid patio]

ahh ok

[harsh matrix]

you did ask and i think i responded no

[vapid patio]

then who is? i forgot there name

[vapid patio]

well im a tomato

[harsh matrix]

[vapid patio]

haha

@harsh matrix i cooked

[harsh matrix]

yeah the CO modulation is possible with the 8

quite easily too

no blurx

possibly the best looking hour glass ive seen

[runic violet]

How it look with blurx

[harsh matrix]

idk, idk how high to run it yet

[runic violet]

Ditto

[harsh matrix]

or low

[runic violet]

Do 0.4

It runs fast on previews

But the preview needs stars lol

[harsh matrix]

https://tenor.com/view/chris-pratt-andy-shocked-parks-and-rec-クリプラ-gif-5045050

0.4 non stellar sharpening and 0.25 stellar

it might be able to handle higher tbh

slightly lmao

yo imma have to make a post or a story on my IG for this

this is way too cool

[runic violet]

Yeah this isn't as high as I pushed mine

[harsh matrix]

im trying to avoid the fringing i got last year

[runic violet]

I meant .4 nonstellar btw

[harsh matrix]

both on this thing and eagle

[runic violet]

Stellar doesn't matter

[runic violet]

Wdym

[harsh matrix]

it does to me to an extent because i dont like my stars being too small

theyre already super tiny

[runic violet]

No for analysis

[harsh matrix]

ah fair

[harsh matrix]

🧑‍🍳

oh god that looks a bit worse than i thought it did

[runic violet]

I don't know what you mean

[harsh matrix]

yoiu see the stuff like this?

[runic violet]

You clipped the highlights but that's not something Blurx typically does

[harsh matrix]

where the edges look a little bloated?

[harsh matrix]

yeah that's whatever, no BX fault

some of the edges look and feel bloated in my image

from last year

[runic violet]

Yeah... cause seeing

I don't really see Blurx artifacts

[harsh matrix]

or aperture?

[runic violet]

I just see clipped highlights and blurriness

[harsh matrix]

this was with a 4" achromat

[runic violet]

Oh

Not seeing

Shit scope

[harsh matrix]

i sold that for an RC6

and didnt regret it

that scope also had egg shaped stars without a reducer

so idk if the optics were any good to begin with

i didnt know what i know now back when i had it so i couldnt tell you at this point

it could handle 0.5

i think much more will be too much, i really like this

[runic violet]

Looks like you're still seeing limited

You can confirm with fwhm

[harsh matrix]

4.5 pixels on the dot

[runic violet]

Arcseconds

[harsh matrix]

which i was

2.77"

conisdering how low this thing is on the horizon for me, i will take that

that's quite good for 31 degrees max altitude lol

im glad we figured this out

[tight lodge]

Actually it's blurry be a of NoiseX . I heard that so many times that I just can't take it seriously anymore 😂

[harsh matrix]

it was heavily denoised with NoiseX AI2

which did mull out and flatten details

in my experience that is

but in this case, there were more problems than denoise lol

there was aperture as the main limitation

[tight lodge]

So far, right now NoiseX does a really good job a keeping details. Especially hand in hand wit BXT

[harsh matrix]

it does extremely well now

that is very much true

today's image wasnt denoised at all

generally i dont see much of a reason to denoise my H-alpha images atm

theyve come out so flat and clean from the get-go

id even argue there's not much of a point to shoot beyond an hour on Lagoon if i didnt know any better

there's still details left to resolve though, and that's why i will get more than an hour or 2

[tight lodge]

Hα just has an SNR that just goes trough the roof. I usually denoise just the OIII and SII depending on how much signal is present

[harsh matrix]

i wont have to denoise it much if any once i go hard on these targets

[tight lodge]

True,

[harsh matrix]

im hoping for like 10 hours of ha, and 20 of Sii and Oiii at least

i want to dump a collective 100 hours into Lagoon and Eagle this season if i can, in just narrowband

i will probably revisit them in broadband and NIR since there arent too many images like that at my focal length

[tight lodge]

Ooo NIR as luminance for SHO

Ok... list for things to buy next week.
2" IR pass filter,
VNA
Food (Optional)
Gas

[harsh matrix]

i dont think that would work too well

[tight lodge]

Doesn't hurt to test one.

[tight lodge]

And if you don't want to try it, send me the data, I will sacrifice myself into committing this blasphemy

I could just plop the SetiAstro PPP (Perfect Palette Picker) and get an idea how they look like

[harsh matrix]

Guys I reached out to HPS about the donut of death on my RC6 and my findings regarding the baffle tube length.

To my surprise, they did some extensive, rigorous testing.

In house, unrelated to my outreach.

They've found this is a consistent anomaly, they tested it with a full frame camera and an oversized baffle tube to test if this was really related to off axis light.

It turns out it's not.

They don't know what's causing it

My guess is that maybe it's something to do with the way the mirrors are figured, who knows.

This was some of the most insightful information I've ever found.

Cudo's to the guys over at HPS

I did a gross summary of the information, it's much deeper than that, but I don't want to copy and paste it here. I'd like to see if they're okay with that first.

BTW they included a flat with both the mega baffle and the stock baffle and the donut structure was still present in both.

That way i know they aren't spoofing.

[vapid patio]

Well, that’s pretty weird

It even shows up in mine

Mine came out over 20 years ago

[harsh matrix]

They tested an old RC6, one which came out long before the carbonstar series and found the same anomaly.

So honestly, that's to be expected.

We actually have a much bigger mystery on our hands

Good news is, it seems to be entirely restricted to the RC6's.

Bad news is, it degrades their usability.

They said that the stock baffle length isn't actually too bad, and isn't nearly as influential on stray light protection as is otherwise stated online.

It's not a bad idea to upgrade, but there will still be an illumination anamoly.

They told me that you should take sky flats though

Sky flats seem to remedy it more than traditional flats.

[vapid patio]

I take sky flats hehe

Well thats gay

[harsh matrix]

What does a normal flat look like for you, then?

[vapid patio]

Let me send one

@harsh matrix how do i send a flat? in pix they are super green

[harsh matrix]

Just do an unlinked stretch

And send a screenshot

[vapid patio]

green still

lol i know how to do that

[harsh matrix]

You can do background neutralization

[vapid patio]

ok

ah i had to do color cal

[harsh matrix]

Dafuq

That actually looks really good

I dislike you

[ripe crystal]

stars are too smoll

[harsh matrix]

[vapid patio]

aw man

[harsh matrix]

I can't make them bigger lol...

My 8 has really tight stars

[vapid patio]

i think its my camera, i am only in the center center

[harsh matrix]

No its not

You will get a clear broad ring from the anomaly

I think sky flats do fix it mostly or entirely just by looking at that.

[vapid patio]

hm maybe

[harsh matrix]

What's important to note which i forgot to add is that HPS's testing was done with a reducer

Idk which reducer, I'll have to ask them later.

[vapid patio]

true

and mine has no flattner

[harsh matrix]

Yeah you have no other optics in the system minus the 2 mirrors in the tube itself right?

I found with my RC8 that I had no calibration related issues without a reducer too

Adding the reducer introduced artifacts.

[vapid patio]

i have my uv/ir as my clear filtet but thats it

[harsh matrix]

It could of course be down to the reduced back focus but I'm not sure yet.

[harsh matrix]

Yeah interesting

I'm going to ask them if they did any testing without a reducer.

[vapid patio]

wait i have some heavy moon data on koi galaxy let me show you

[harsh matrix]

They tried 3 different configurations, one with the stock baffle tube, one with the 11mm one that was recommended online, and an over engineered MEGA baffle.

[vapid patio]

i dont think its all a baffle problem from what ive researched

[harsh matrix]

Don't think what is?

[vapid patio]

like a light leak from the baffle being too short

people say your reducer can be a problem with it

[harsh matrix]

Yes 100%

Thats what the primary concensus was.

It's looking like HPS has evidence to support it being something else entirely.

I thought you were talking about something in your Koi galaxy data.

[vapid patio]

The large secondary mirror can also contribute to contrast drop or odd brightness distribution if the optical alignment is off or if the collimation isn’t perfect.

[harsh matrix]

Also jfc this CO modulation lmfao

[vapid patio]

stop flexing

[harsh matrix]

Thats not flexing actually

Turns out this isn't the airy disk

[vapid patio]

what???

[harsh matrix]

It's light scattering caused by the massive secondary lmao

You're seeing what actually causes the loss of contrast.

[harsh matrix]

Yeah everyone who told me it was the airy disk completely misunderstands what the airy disk is.

[vapid patio]

Bright Star Saturation right?

[harsh matrix]

So i was wrong about it being diffraction limited.

[vapid patio]

ohhhh

[harsh matrix]

This is probably not the cause of this bright circle of illumination.

[vapid patio]

your right i feel like it would be reverse

[harsh matrix]

Should be if it was the case imo

[vapid patio]

noww thats light leak right?

[harsh matrix]

Mostly

It's like 95% a light leak

But if you were to remove the light leak as I did, there would still be an illuminated donut.

[vapid patio]

Let me see your imaging train

[harsh matrix]

I'll send uncorrected examples and flats once I get off work

[vapid patio]

Ok

[harsh matrix]

The scope, focuser, reducer, OAG, AFW, camera in that order.

[vapid patio]

I might know

Its a weird one

[harsh matrix]

The reducer is the bit between the OAG and the set screw on the focuser.

[vapid patio]

Whats the name of your filter wheel?

[harsh matrix]

Touptek 7x2 AFW

This one doesn't have the IR led inside to track the position though.

If it was, this would have been solved months ago.

Doesn't make sense why my narrowband images have flawless calibration.

[vapid patio]

Wait

I have seen instances where these caused a light leak

[vapid patio]

Oh really? Narrow band is fine?

[harsh matrix]

Yes

[harsh matrix]

And I've taped off the holes that are on the outside.

[vapid patio]

Wow so weird

[vapid patio]

Do you have a uv filter?

[harsh matrix]

I don't think I taped over the holes on the inside? I'm pretty sure my filters are fat enough that they cover them up.

[harsh matrix]

No

[vapid patio]

I thought so, maybe if you had just a filter for some reason

[vapid patio]

Hmm

Well that narrows it down

well this came out fine other than miss circle

[harsh matrix]

Yeah looks great

[vapid patio]

hmmmmmmmmm

i say try sky flats

and see if that somehow fixes them

dont you own a micro 3/4 sensor?

[harsh matrix]

Another thing they said people typically blame is light pollution but they stressed that this issue is replicable in flats so it can't be.

[harsh matrix]

I have a 533 and a Canon 600D

Nothing else.

[vapid patio]

perfect

take off your reducer and throw on 533

stars will still be fine

and it reduces a possible fault

just strip things until it fixes its self

if not then well we got a bigger problem

[harsh matrix]

these are my lights from the last major project i did with the RC6

i think 5 hours per filter

these are the flats

this is the broad circular illumination structure ive been talking about

it's in HPS's test flats too

this was their mega baffle

this was their flat frame with the mega baffle and full frame camera

you can see a bright illuminated ring, just to a lesser extent due to the mega baffle

it's still in their full frame, stock baffle image here too

although it appears to be buried under stray light, somewhat.

a quick gradient extraction on the stock baffle flat reveals it clearly

looks an awful lot like what i have

this was their mega baffle test flat and it's still there as proof

gradient removal only makes it easier to see

unfortunately typical gradient removal techniques cannot get rid of it, no matter how hard you try

that's why i can ADBE these and it stays

[vapid patio]

@harsh matrix Man that sucks

And super weird

And high point didn’t know either

Hmmmmm

[harsh matrix]

tell me about it

[analog portal]

reminds me of newton's rings

[harsh matrix]

omfl i forgot about those

[oblique sun]

ouch

maybe i might hold off on buying an rc

[vapid patio]

Well mines fine

Thats the weird part

Came out in 2009

[oblique sun]

I ain't rich so i am not risking anything

If mine doesn't turn out good then im stuck with it

[harsh matrix]

It seems like its only a problem if you shoot reduced...

That's incredibly frustrating...

[oblique sun]

Which i will be doing bc my seeing sucks

and i don't have time to wait a million hours for f/9

or whatever f ratio it is i forgot atp

[harsh matrix]

I just took some test flats on my RC6 with my DSLR

the field illumination is surprisingly good

VERY good

there wasnt any light drop off until the very corners of each image

i did these without the reducer since that is on my RC8 rn

this was a test flat with my 533, lum filter on the RC8 without the reducer

after ADBE

this is a flat on the RC6 and my DSLR

something weird going on...

after ADBE

the bright ring here isnt occuring until well after it is beyond the center of the frame...

[frosty shard]

How the chungus do you fix this

[harsh matrix]

btw mine is the AFW-L

this is what it looks like

changing the position of the focuser made a difference

the right image is with the focuser about where it would achieve focus

left is all the way in

both have been ADBE'd

[vapid patio]

Ah ha!

Looks a good bit better

[vapid patio]

Ahhhh

[vapid patio]

[frosty shard]

Like that's my gripe with the Touptek filter wheel

There's a lot of holes to patch

[vapid patio]

I don’t know what purpose they serve anyways

Cutting weight lol

A whole .5 gram

[frosty shard]

Well the ones on the outside are for attaching a Touptek OAG, but I have an Askar one. So there's the six holes I have to patch with electrical tape

[vapid patio]

I get the ones on the outside what’s the point of the ones on the actual filter disc?

[frosty shard]

They could have just provided extra screws or a ring to cover those holes

[frosty shard]

Those are for attaching 36mm unmounted filters directly to the disc

But the screws that came with them don't fit when there's a 1.25" filter screwed in

[vapid patio]

The 3 tiny circles

[analog portal]

the screws that hold the gasket over the filter fills them in

[vapid patio]

Gasket?

[frosty shard]

Did your filter wheel come with gaskets? Mine didn't

The screws have heads that are too wide to fit with 1.25" filters installed

[analog portal]

yeah, i have a player one 7x36mm wheel and it came with like 3 extra gaskets and about 12 extra screws

[vapid patio]

GASKETS???

[analog portal]

yeah

[vapid patio]

huh

[analog portal]

small little gaskets that hold the unmounted filter in place

[frosty shard]

Mine did come with 24 screws

[vapid patio]

Oh the metal circles

With four screws

[analog portal]

sorry, "filter mask" lol

[frosty shard]

My filter wheel has only three screw holes per filter slot

[vapid patio]

Yeah yeah

[vapid patio]

I miscounted

What do they do?

I use them as OAG spacers haha

[analog portal]

lol

[frosty shard]

Filter gaskets? or a different part

[vapid patio]

These

[analog portal]

hopefully he's talking about the 1mm spacers and not those lmao

[vapid patio]

Super lost “1:29am”

[analog portal]

https://tenor.com/view/we-lost-lost-super-lost-fucking-lost-war-gif-13104370

this is what i hope you're using for your oag spacers

[vapid patio]

Yes

I think

Uhh

Let’s let’s look

Ah ha i am useing those

I still got it

[analog portal]

https://tenor.com/view/walter-huston-dancing-gif-dancing-a-jig-jig-dance-a-jig-gif-24983101

one of my friends is a compulsive notification checker. he's out drinking, and quite drunk right now. so i keep sending him different videos on Telegram with the same audio spliced into each one (an embarrassing one) and he opens it and plays it every time, followed by a message telling me not to message him because he's drunk.

and this is how i dance each time i get that msg from him.

[harsh matrix]

I'm doing some rigorous testing with the RC8 now

[analog portal]

https://tenor.com/view/trembling-beavis-mike-judge-mike-judges-beavis-and-butt-head-s2-e12-gif-17864910306251402733

currently 40 outside, high of 80 tomorrow. it became clear after midnight, but i cba to set anything up with this moon for such a short time.

[harsh matrix]

Turns out the light leak blocker tube for the focuser, and the "improved" version I made isn't the cause of the bright ring in my frames

It definitely caused more reflections and light scattering, which probably hindered calibration, but was not the root cause of the ring.

And without the reducer and without that tube, my flats look flawless

Something tells me it's the reducer...

[harsh matrix]

i went ahead and tested with and without the reducer, and without the reducer but the camera in the same place it would be in focus if i used a reducer

the ring of illumination is completely absent without the reducer

meaning back focus, and the baffle, are not at fault

at least on the RC8

this is a flat without the reducer in the position where the camera will achieve focus without it

this is one with the reducer, where the point of focus is.

and this is without the reducer in the same spot where the camera will reach focus with the reducer

now i might sound crazy here, but does this not look like the reducer is the problem?

this is all of those in that order from left to right

what's interesting is ring is still there, but the flat with the reducer amplifies it a couple of times over...

i could be mistaken about the first image being at point of focus for no reducer, i think this one is it

it's completely flat except those corners

that means back focus probably is the problem...

or a part of it

[tight lodge]

I like that instead of saying... let the facts fix the image, you are like imma take the whole thing apart and find what's wrong with it

Fixing the issue and not finding a way around it. Good thinking

[harsh matrix]

if some "unfixable" issue has bothered me for as long as this particular problem, i will tear down all of the walls to get rid of the issue

I am highly suspicious of the reducer.

[tight lodge]

To be honest I do the same. I took my telescope apart more often than I imaged with it

[harsh matrix]

i cant stand it anymore

[tight lodge]

I mean one night I got this result. Everyone was saying... oooh borked flats

[harsh matrix]

nah that's a light leak

[tight lodge]

Yes and internal reflection at the same time

[harsh matrix]

yup

i had the exact same issue with my RC6 at the start

[tight lodge]

This is how I figured out the leak

[harsh matrix]

that's how this happened

[harsh matrix]

howd you find out it was a shadow from the primary?

or do you mean secondary?

doesnt make sense that the primary would cast a shadow

[tight lodge]

Primary

[tight lodge]

It can cast a shadow on the secondary

[harsh matrix]

OMFL

[tight lodge]

My light leak was around the primary mirror. So I had my PC monitor behind the primary mirror. Took a dark and found the leak. Then I covered the rear of the telescope with something g and it went away

[harsh matrix]

if it's leaking through the mirror itself or from behind it...

yeah that's classic newtonian beezwax

[tight lodge]

Ez fix

Altho, imma 3D print a rear cover eventually. Trashbags look so redneck🤣

[harsh matrix]

i left the rear primary mirror cover off my quattro one night and about shat myself when i walked out to pull the rig back in to see i had left it off

i tried to call it by the nickname Cuiv gives it but the server wasnt too happy about that

[harsh matrix]

luckily that data was mostly usable

it's not good

but i could make something out of it

[tight lodge]

Also what do you think was the cause of the doughnuts?

[harsh matrix]

the dark ones are dust for sure

[tight lodge]

Nope. It was those 4 screws around the sensor

[harsh matrix]

omg

your rig was giga fuqed jfc

[tight lodge]

But now it's perfect. I used some electrical tape made of fabric to cover the screws and no more reflections, no more leaks

[harsh matrix]

[tight lodge]

I get better stars than the all praised Carbonstar

[harsh matrix]

the carbonstar seems to have a lot of issues so idk if thats a high bar to reach

unfixable issues that is

related to the optics

[tight lodge]

I can not think of a similar telescope that people say it's the "goat". TS-Photon is an amazing telescope, but you don't really see people using it

[tight lodge]

I forgot my tribathinov mask in the car...

[vapid patio]

Devious

[frosty shard]

Mine snapped

[tight lodge]

How did you do it? 😂

[frosty shard]

I thought I could toss it in my scope cart and it would be fine. It was not, in fact, fine.

[tight lodge]

acrylic?

[frosty shard]

Yup

I really need more cases for things

[tight lodge]

same... i keep my OTA on the back seat when i travel somwhere XD

[analog portal]

i do that with my rc8, my little 80mm frac will fit in the case with the EAF on it, so i do at least use that

[vapid patio]

I see he’s smooth with the ladies

[frosty shard]

Nah, the real chick magnet is the Ritchey–Chrétien

On that note: even the astronomy majors here haven't heard the name Ritchey–Chrétien used before

[tight lodge]

Idk why you let someone touch your RC

[vapid patio]

Never said you were smooth with the ladies, I said “he's” smooth with the ladies

[frosty shard]

Unironically I do encourage people to touch the scope (certainly the focuser at least)

[tight lodge]

That rig is like... 4grand right?

[frosty shard]

It's much more fun than a "no don't touch that!" experience

[frosty shard]

More lol

If I was doing EAA it would be a very different story though

Visual, I'm all for people touching the scope

[frosty shard]

@harsh matrix I also got to use the SV220 for outreach last night

Aside from the fact that it's an effective and fun moon filter (everyone loves the moldy cheese) I also used it to show people the Ring Nebula

Turns out it really helps when the filter is aggressive enough to render it the only visible object in the field

[runic violet]

You shouldn't be surprised

Instrumentation isn't a big focus

[frosty shard]

I'm a little surprised that nobody seems to have even heard the name, but not too surprised overall. Most of the astro grad students I know are doing X-ray, gamma ray, neutrino, or radio astronomy after all

[runic violet]

There's a big exoplanet group at your uni though

[frosty shard]

Also true, I only know a few astronomy grad students. Mostly people working with IceCube or the Cherenkov telescope array

[harsh matrix]

Huh

[harsh matrix]

[harsh matrix]

this stock focuser from my RC8 is awful lmfao

im sitting here goofing with it and the rail keeps slipping

it gets caught up like the friction rod has flat spots on it

[harsh matrix]

That illumination anomaly is gone in NIR

[vapid patio]

I might know whats wrong

and its common for scopes, but not as much in rc scopes

Your scope is maybe having a hard time focusing uv/if light, maybe its focusing it weird causing the circle

[harsh matrix]

no absolutely not

not on an RC

light would not scatter that much over such a large area if it were due to focus issues, and that's ignoring the fact that my filters all cut out UV and IR light except for the NIR filter

doesnt explain why the anomaly shows up in broadband images

[vapid patio]

@harsh matrix Oh, maybe im thinking of someone elses setup, whoops

[runic violet]

Give it back to me

jk

[harsh matrix]

[runic violet]

It's a reflection off the filter?

[harsh matrix]

that's what I thought it could be for a little while

did you see any of what HPS told me?

[runic violet]

No

[harsh matrix]

Oh boy

TLDR; Apertura/HPS knows about this, it's got nothing to due with the baffle tube length, and it seems to be related to using a reducer.

They're calling it an illumination anomaly as they don't know what's causing it.

[runic violet]

On rc8s?

[harsh matrix]

I found through my own testing (on the RC8) that it shows up to an incredibly faint degree at the back focus distance required to reach focus with a reducer.

Once you add the reducer, it becomes multiple times brighter.

[runic violet]

I've never seen it

You saw my flat

[harsh matrix]

They tested the carbonstar RC6 and an old GSO version.

[harsh matrix]

I know and I'm wondering if its something to do with the particular reducer i use.

They didn't tell me which specific reducer they tested with.

Also can you send that flat again?

I want to check something.

[runic violet]

You're going to dbe it aren't you

[harsh matrix]

Why do you ask?

Thats exactly what I intend to do

The illumination anomaly isn't visible if i don't DBE the flat at the back focus distance required to reach focus with a reducer.

[runic violet]

I don't have access to the raw file for a few days that computer is shutoff

[harsh matrix]

If I DBE it, it reveals the structure very faintly.

I'll probably go dig it up then

[runic violet]

I posted a screenshot

Unless you're planning to dbe a screenshot lol

[harsh matrix]

wow the modulation is extra bad tonight

my seeing is 2.33" so it makes some sense

got it on Oiii for the first time on the RC8 too lmfao

[vapid patio]

Ouches

[tight lodge]

What's the angular distance between these 2 stars?

[harsh matrix]

not sure

not very big i know that

[tight lodge]

Saturday I went shooting. The seeing was so bad + the moon, that I couldn't get the guiding to settle below 0.9". The worst it got was 2.4" RMS . I started swearing and packed up

[harsh matrix]

my guiding might be insane tonight we'll see

it was at 0.4 RMS after I did a calibration run

[tight lodge]

That's usually where I sit at. But idk what happened Saturday

Plus I'm guiding in NIR, how bad can the seeing be to affect even IR guiding?

[harsh matrix]

lol...

secondary modulation in broadband too

ngl, i think sky flats are going to work this time

the donut doesnt seem to be as aggressive this time, and im placing my bets on the fact that i fixed the possibility of internal reflections

this is no flats after DBE

[frosty shard]

Bahtinov analyzer, why are you like this?

Here's my RGB gamer scope in all its glory

Featuring a random shoe

[tight lodge]

Looks like the back on an average gamer PC

[tight lodge]

What did you image?

[frosty shard]

Take a guess

[tight lodge]

Uuuhn some dark nebula?😅

[frosty shard]

That's part of it.
It's a tiny section of NGC 7000

It's just a test image so I wanted to pick a good H-alpha target far from the moon

(I have no internet connection on the control PC so I'll have to get home to send any data directly)

[tight lodge]

That was my plan for Saturday. Didn't worked

[tight lodge]

LBN 354?

[harsh matrix]

a few hours in, and still stable

[frosty shard]

@harsh matrix eat my pillars.

[harsh matrix]

holy fuq wtf

[frosty shard]

Ignore my guiding graph

[harsh matrix]

ive had worse

[frosty shard]

I had to collect my jaw off the floor for that one.

[tight lodge]

Should I ignore the HFR graph as well?

When are you gonna do Crescent nebula?

[frosty shard]

Yes, but that's because those are for the test exposures

[brisk swift]

Crazy

[frosty shard]

Good news: my light panel will do IR flats easily!

INCOMING!

[harsh matrix]

@frosty shard eat my crescent.

[tight lodge]

[harsh matrix]

like minds think alike

[tight lodge]

Ain't no way that's Hα

[harsh matrix]

it's a single 5 minute Ha sub yes

[tight lodge]

How fast is your scope?

[harsh matrix]

f/5.36 atm

[tight lodge]

And mine is f5. How is possible that you got so much less Hα in 300s?

[harsh matrix]

how much aperture do you have?

oh wait you said less

[tight lodge]

130mm

[harsh matrix]

what bandpass is your Ha filter?

another

it's also possible that it's still pretty low for me

although i guess it's not?

[tight lodge]

5nm

[harsh matrix]

Nina says 63 degree alt

[harsh matrix]

mine are supposed to be 5nm but are likely in the ballpark of 6 to 6.5nm

that could be part of it

oh wait

are you using a 585?

[tight lodge]

It should technically let mor light trough

[tight lodge]

Yes

[harsh matrix]

oh that's why lmfao

the 585 has like 30% higher QE in H-alpha than my 533

[tight lodge]

Better QE?

[tight lodge]

Aah...

[harsh matrix]

at least mine is stupid sharp

[tight lodge]

Mine is also sharp... when I don't use my phone to photograph a crappy LCD screen

[harsh matrix]

just got an Oiii sub with an HFR of 1.96

2.4" seeing atm

[harsh matrix]

okay fair

[tight lodge]

How do you check that?

[harsh matrix]

multiply the HFR by 2 and then multiply the result by your sampling

[frosty shard]

This is my first ever SHO image. 3 x 3 min subs

[tight lodge]

Here's 15 minutes on it. Foraxx, 1x300s a pop

[harsh matrix]

WR136 btw

[frosty shard]

I love how the rings make it look like the star has made a splash

[harsh matrix]

lol

also i just remembered that the actual reduction from the reducer is much less than what it's supposed to be mathematically

so it might be closer to f/6.5 or something

i might have to play with the back focus some more to dial it in

[tight lodge]

Technically it did. That's why we have the crescent nebula

[frosty shard]

Here's that tiny region of NGC 7000

And that is about where I landed. I didn't attempt to try to get any particular region, I just decided to roll with where my mount slewed lol

Wait I got the rings though

[tight lodge]

Guy proceeds to underestimate the word TINY

[tight lodge]

Why you didn't aim for this?

[frosty shard]

I'm stunned at the quality of data I managed tonight

[frosty shard]

Didn't know about it lol

I really just wanted to see if the rig would even work

I guess it does

[harsh matrix]

one of each?

[frosty shard]

Yup

9 minutes of data total

The H-alpha sub came out so nice that I had to try with all of SHO

[harsh matrix]

ah

[tight lodge]

Totally worth it

[harsh matrix]

my actual f ratio is 6.25 atm

since it seems the backspacing on my reducer isnt quite right

not because of an error i made i dont think

and im not using it with the scope it was made to be used with...

one 300s Ha and one 300s Oiii with no processing

[harsh matrix]

btw that tripod on turf is probably why your guiding is bad

as well as the general lack of weight holding the tripod in place

[tight lodge]

Can you resolve these in your crescent nebula image?

[harsh matrix]

my poor M101 in NIR ruined by idk wtf

no flats for one

idk what's going on with the image circle though, tbh

it's not centered and i dont think it's tilt...

cant be too sure though

[harsh matrix]

now you get to deal with all the people who thing youre diffraction limited too

[frosty shard]

Yeah I should figure out a way to suspend my power supply

[harsh matrix]

btw this is some bonkers resolution on M101, NIR sub

[harsh matrix]

did the tripod not come with some sort of sling to attach to the legs at the bottom?

[tight lodge]

Wait! People believe that those rings form when you're diffraction limited?😂

[harsh matrix]

yes

its a misconception that a lot of people frequently buy into

i got told it so many times that i started to believe it 😭

cause nobody could tell me why it wasnt diffraction limited

beyond them just saying that it wasnt

finally M63 came along and cleared the waters for good

with a really fascinating CN post

this RC8 is killer, it's been a lot of fun to use and test

[frosty shard]

Nope

[harsh matrix]

i really hope that i can figure out this calibration nonsense

[harsh matrix]

that's annoying

[tight lodge]

Even if you tell them those are created by the central obstruction in SCT, RC, Newtons... they still won't believe I guess

[harsh matrix]

correct

it's because they think it's the airy disk

the unfortunate truth is that it is related to the airy disk

but it is not at all the same thing or even generated through the same process

it's just another artifact of diffraction

a really weird one at that

with blurx