help with star colour

[rustigsmed (Russell)]

Originally Posted by vlazg

This is an image taken with a saxon ed 120 using the same camera, the stars are now much better.
Could the problem with the WO FLT 110 be a collimation issue somewhere in the image train, either the lenses or the focuser or both? If so is there somewhere to send it, i don't have the confidence or the knowhow to do it myself.
George

hi George I think you need to take a few shots of objects higher in the sky away from the horizon to rule out atmospheric chromatic aberration with your scope. I've got a feeling that was what your problem was I think you mentioned it was quite low.

Russ

[vlazg (George)]

Thanks Russ,
The new image is of the Butterfly Cluster, and it was of a similar altitude to the olde one.
I recently posted an image of the Triffid taken with the WO and up close he stars are showing the same aberration

[rustigsmed (Russell)]

Originally Posted by vlazg

Thanks Russ,
The new image is of the Butterfly Cluster, and it was of a similar altitude to the olde one.
I recently posted an image of the Triffid taken with the WO and up close he stars are showing the same aberration

ok sorry George its past my level of knowledge now - I don't use refractors - but sounds like it could be the scope, good luck I hope you get to the bottom of it soon

[vlazg (George)]

Originally Posted by rustigsmed

ok sorry George its past my level of knowledge now - I don't use refractors - but sounds like it could be the scope, good luck I hope you get to the bottom of it soon

thanks mate, you've been really helpful

[willik (Willik)]

Looks like your are out of focus and there was dew on your mirror halos
around the stars
Willik

[vlazg (George)]

Originally Posted by willik

Looks like your are out of focus and there was dew on your mirror halos
around the stars
Willik

I am using a refractor, no mirror, no dew that night.
I also used a Bhatinov mask, with the Bhatinov grabber in sharp cap, and focusing was as good as i could do

[willik (Willik)]

Don't rely on the mask do fine focus the lowest numbers count and it could be condensation on your camera chip.
Willik

[cometcatcher (Kevin)]

Post #22 looks like CA to me.

[vlazg (George)]

Originally Posted by cometcatcher

Post #22 looks like CA to me.

Thanks Kevin, with my limited experience i think the same, is this what an apo triplet should do? i have seen other pics taken with an flt 110 and this does not seem to be the case, is this correctible?
George

[cometcatcher (Kevin)]

Originally Posted by vlazg

Thanks Kevin, with my limited experience i think the same, is this what an apo triplet should do? i have seen other pics taken with an flt 110 and this does not seem to be the case, is this correctible?
George

Hi George, I don't have any direct experience with that scope so I'm not familiar with it. If they are blue stars it may not be CA at all?

I have two ED refractors, a fast Kson ED80 at F5.5 and the Skywatcher ED100 at F9. The ED80 has noticeable CA, the ED100 has to be pushed hard for it to show. I have a bunch of achro refractors at various F ratios which of course all have CA.

A Baader Semi-Apo filter will probably help a little. I've found it to be beneficial on the ED80.