C8-xlt, f6.3 reducer, dew heater ring, dew shield, Optolong L-Pro, imx533 cooled camera, iguider. Testing with 15s exposures. Focus is good. What things could it be that I can check?
#What causes my stars to do this?
timid crystal
timid crystal
Could it be non-perfect backpacking?
full tide
Pinched optics? All over the frame?
vernal sundial
C8-xlt, f6.3 reducer, dew heater ring, dew shield, Optolong L-Pro, imx533 cooled...
That spike is likely a hair, fingerprint smudge, or something similar creating diffraction spikes, i had it from a fingerprint, on the reducer. It can also be a crack in the corrector plate or maybe the mirrors (However unlikely unless you have dropped your SCT at any time)
timid crystal
That spike is likely a hair, fingerprint smudge, or something similar creating d...
So I looked a bit closer and I did find a fingerprint+smudge on the focal reducer and fixed that. Next clear night I'll give it another test to see if that fixes the diffraction spikes and report back.
Also, as FYI, I laid out my image train with measurements. It does add up to 105mm exactly.
timid crystal
Looks like it was the dew shield. It's not a tight fit so it slightly angled relative to the scope. Not sure how to fix that... glue some felt or something to the end to make it fit tighter? it's the Celestron 8" metal one.
Those big stars is where it was very noticible, now it's gone after removing the dew shield (it still existed after fixing the fingerprint & smudge on the reducer).
closer up
timid crystal
Thought I fixed it with some cardboard, duct tape, and masking tape... fits way tighter now, but they came back. Not sure what to do...
Okay to use with the dew heater ring and without the dew shield? What can I look for with the shield to see why it's happening? Marine layer just came in so I can't test anymore. Super thick fog-like clouds now 😦
vernal sundial
Thought I fixed it with some cardboard, duct tape, and masking tape... fits way ...
Got a hair on your corrector plate? possibly on the reducer? maybe collimation?
timid crystal
Got a hair on your corrector plate? possibly on the reducer? maybe collimation?
It's definitely the dew shield. With it off, it's fine, with it on, the diffraction spikes on brighter stars.
vernal sundial
It's definitely the dew shield. With it off, it's fine, with it on, the diffract...
Id assume then its some sort of reflection on the dew shield causing it, besides that (if the dew heater is enough) you can just use the dew heater
But usually diffraction spikes are caused by some form of obstruction, like a hair, fingerprint or anything in the way of the mirrors
timid crystal
Id assume then its some sort of reflection on the dew shield causing it, besides...
This image is slightly exaggerated to make the point clear, but could a slightly angled dew shield cause it like below?
vernal sundial
This image is slightly exaggerated to make the point clear, but could a slightly...
That would likely cause Elongated stars which i cant see in your example images
timid crystal
That would likely cause Elongated stars which i cant see in your example images
When I look through the shield, I don't see anything sticking out. What should I look for?
vernal sundial
When I look through the shield, I don't see anything sticking out. What should I...
Id be looking for things sticking up in the dew shield, like some thread from the flocking material hanging, and stuff like that. But to verify that its not the elongation of the dew shield, see how a star looks when perfectly in collimation (without the dewshield on) if it isnt elongated on a bright focused star without the dew shield, then put the dew shield on and see if its elongated or not
timid crystal
Id be looking for things sticking up in the dew shield, like some thread from th...
It's not. I do my focusing without dew shield. I found some felt and put it around where the clips are which makes it a tight fit. I'll try that in a couple hours to see if it helps.
timid crystal
Still waiting for some clear skies to test
