16 Dobson

[icy pewter]

I've got a 16" F4.5 Meade Lightbridge for free. The Rockerbox is Destroyed but this is easy( hope so) to repair.

I am now asking if you guys have any tipps ore things i need to know about such big telescopes.

[willow fable]

you can wrap a shroud or some black cloth around the truss if you don't want too much stray light to enter.

[icy pewter]

I am currently trying to use a black bedsheet the want like 250€ for such things

[willow fable]

ok, just make sure it wraps around tightly.

[thin kiln]

if you want to be thrifty you can use black trashbags as a light shroud

also, that's an awesome telescope, you should be able to see the most amazing things, and you can also rig it up for lucky imaging

[icy pewter]

Nice, the only problem is, that the quality of the Mirrors Reflective Surface is in a bad shape, but when i have the money i am gone send them to a company to recote them

Wouldn't a Motorised Dob mount or even a eq mount be required for good lucky imaging?

[thin kiln]

No, for lucky imaging you don't need a motorized mount because you literally take exposures of less than a second length

I mean, it would be nice for AIMING the telescope, but with time you'll be able to star hop properly and it won't be that big of a deal

[icy pewter]

Ok I already did untracked with my 6" Newton, but i think this is gone need time, because getting a good astro Camera is very expensive (i am a student so not the biggest budget)

[thin kiln]

yeah, fair enough

[icy pewter]

But I am very exited to do Planetary with it first

[thin kiln]

fwiw there's EQ platforms, some people are good at DIY and build those themselves

planetary should be really nice as you can achieve insane resolution with that aperture

btw, if you attempt to clean the mirror be super careful and read up on it beforehand, it's easy to scratch them accidentally and ruin them

[icy pewter]

I am currently attending a mechanical engineering school and when i am finished, and with help Form some very some people i know have good electronic skills a diy Eq mount could be possible

[icy pewter]

I was very careful at cleaning and scratches aren't the problem

[thin kiln]

good! yeah if it is patchy translucent it will need a recoat. you might want to ask people in #🔨-do-it-yourself about cleaning options, this looks like it can take more cleaning

I think for recoating you need highly specialized equipment like an aluminizer—if you don't have that lying around let the professionals do it

[icy pewter]

I think i just spend the 300-350€ It needs to do that

[thin kiln]

tbqh those mirrors don't look that bad, they might just need more some more thorough cleaning. they often still work very well even when they look very bad

[icy pewter]

When i would build a one Eq mount, it would only need to be exact enough so that the target stays in the frame, because I would do exposures that (at the best condition) like 0,1-0,5 Second long

[icy pewter]

I did a little bit more cleaning and did (i know it is stupid to risk that) use some limescale cleaner on the Secondary, and Id did help a lot.

And i think/hope objects like the moon the planets ore Iss are so bright that the loss of light isn't that noticeable

Especially at f 4.5

[thin kiln]

for planetary you want something like f/12 to f/20

they're really bright

so get yourself a 4x barlow

some people like even more, like f/15 to f/22

[icy pewter]

I don't have the best Planetary Cam (small sensor) I first try it with no and a 2x or 3x Barlow, i don't know how hard tracking with a Dobson is.

[thin kiln]

tracking only depends on balanced and smooth your rocker is

if it's nice it's not hard to do

[icy pewter]

But with my 6" Newton at f15 i could use the lowest gain setting at jupiter and only like 6ms while jupiter was still a long way away from opposition

[icy pewter]

I and my Dad gone build the rockerbox in the next time, I hope it's gone be as God/ better then the original

*good

[prisma wigeon]

Where are you located, I would be happy to pay you for your telescope

[icy pewter]

I want to keep It 😅 And i don't think you live in Austria 🇦🇹

[high estuary]

If you are repairing the rocker box I would advise you to use PTFE pads to support the trunnions like I did with my 14 inch Dobsonian. The trunnion bearing surfaces are well polished which gives a very smooth action when moving the telescope. Needless to say, lonitudinal balancing of the tube is important. Also, I have materials for making a Poncet platform which will give the mount a few hours of motor driven RA motion.

[icy pewter]

👌

[icy pewter]

Thanks for the good advice, but there is the Needle bearing from the Old Rockerbox left, should i use it?

[high estuary]

If those needle bearings are free running and don't feel 'gritty' when you rotate them then that should be fine. It may be necessary to take the bearings out and clean them in a solvent bath if they are not free running and then re-grease and re-mount them. If you find them running to freely then adding a clutch of some form to provide a little 'stiction' may be needed. I have never owned a Lightbridge myself but after many years building telescopes I have found the old principles hold true, despite the many different materials and methods used for telescope mount construction these days.

[high estuary]

Additional with reference to planetary photography. Besides using a Barlow lens, it is possible to use a positive eyepiece, say a 20mm fl Erfle or some similar focal length, and project the image onto the camera sensor, whereby, the camera sensor is about 100mm away from the eye lens of the eyepiece. This method is called positive eyepiece projection and it was a method I use frequently during the 1970's with my 12 inch Newtonian and SLR camera body which used photographic film. So working at an effective focal ratio of about f/50, Jupiter would be a measurable disk on the film of about 0.125mm diameter or more. If you increase the separation between the eyepiece and the camera then the planetary disk increases and so does the effective focal ratio. I have used f/90 in the past and I attach a few photos of the 12 inch with separate camera bracket for you to see.

[icy pewter]

Ok thx, I guess a Adapter for Eyepiece and cam i could just 3d print

[thin kiln]

Wow this is fascinating! Love hearing about the pioneering days in amateur astrophotography. We have it so easy these days in many ways.

[high estuary]

Thank you. I moved onto the 14 inch project plus Observatory after building the 12 inch done during 1977 to 1982.

[icy pewter]

Wow that's nice is this still in use?