m13

[DannyUK]

Thought I`d jump straight in with an image.

The star I have highlighted shows the miss alignment of the colour channels which really bugs me. I understand that If I don`t use my field flattener whilst imaging I get some coma near the edges but I would have thought that the rgb data would still align even with the coma. I have tried freeform manipulation on the separate channels but without success. I used my flt98 with a zs66 piggybacked which, as Im starting to learn with this method of guiding, can intoduce flexure. Could flexure be causing it? I have just started using a TS oag but as of yet not had a chance to capture a Lrgb series of subs.

Thanks for any advice with this issue or anything else regarding this image

Dan

[DaveS]

The 'cluster' itself Danny, is pretty good, with nice granular looking stars.

You don't say what software that you are aligning/stacking your images with, and if you are using 'auto' or 'manual' star alignment?

I have seen this effect myself, when I have captured the RGB subs during different imaging sessions, and its usually caused where the rotational position of the camera has shifted slightly from session to session.

I always align manually on two stars, and try to use the same two stars in each sub.

Theoretically, the alignment algorithm should alway use the centroid of the star, but it doesn't need to be very much adrift to misalign the colour planes.

As I said, I've only ever seen this where rotational alignment has been involved.

Dave

[DannyUK]

Thanks for your input Dave. At the moment I am using deepskystacker for alignment which is set to automatic and all of the data was captured in one session. The options that are available within the stacking paramaters are a little over my head to be honest which is why I take the easy option and click "automatic".

All the best

Danny

[DaveS]

I think that its most likely that the auto star alignment is where the problem lays Danny.

I don't know 'Deep Sky Stacker' so I can't comment on what alignment options it has, but I'm pretty sure that we have some DSS users on the forum, and they will probably be able to help on this one.

Dave

[DannyUK]

Thanks for the advice Dave.

[Dennis]

Try some short, 5s or so, exposures on a bright star field such as found in Orion. There will be no flexure in that time so you can eliminate it. Leaving DSS to one side (where it should be!!) you most likely have chromatic aberration from the scope. Try a single, bright star and re-focus for each of the short exposures. The plain fact is that many scopes that claim apo are not.

As Dave said, manual alignment is the most reliable.

Dennis

[Harry Page]

Hi

As the problem you have seems to be where the field is not flat I also think it may be chromatic aberration problem which is magnified by the curves field

If you can see this problem in a single sub the stacking is not the problem

Regards Harry

[DannyUK]

Thanks for your comments and suggestions. Plenty to go on