Eta C

rcheshire (Rowland) · #1 14-07-2010, 08:35 PM

Not sure what to think of this one? 5 x 60 second subs 5 darks @ iso 800 - stacked by hand - contrast, brightness, despeckle and median filter - Ivo's Star Bright. Can't quite get the fudgy background right. No favours with jpeg and light pollution needs sorting out. Comments?

dugnsuz (Doug) · #2 14-07-2010, 10:11 PM

Nice amount of detail Rowland, and your focus and tracking look very good too. The violet halos around the stars are quite obvious though - are you using an achromatic scope to image?
Still, very good image - the detail you've catpured in the Humunculous is great. I'd love to see a higher res and perhaps an individual 60 sec sub??
Doug

Moon (James) · #3 15-07-2010, 03:46 PM

What did you mean by 'darks stacked by hand'? Did you try DeepSkyStacker to stack the images and darks? If not, give it a go.
James

rcheshire (Rowland) · #4 15-07-2010, 06:48 PM

Hi Doug. Here is a jpeg version of one sub. Higher res versionof jpeg

Telescope is apochromatic. I haven't seen fringing quite like that before. 2nd image taken 5 days earlier! Similar arrangement of subs and darks - iso 400 auto wb.

...fringing is evident around the brighter stars.

I changed only 2 parameters on my camera - iso and white balance. Whether this contributed to increased fringing, I don't know.

Thanks James. I corrected the typo. On this occasion I did all the processing by hand - subtracting the darks and stacking the resulting images - no brainer.

rcheshire (Rowland) · #5 16-07-2010, 06:14 AM

I'm not at all happy with the colour fringing and wonder if collimation may be an issue, or possibly focus is not quite right. Could it be the field flattener? I really don't know?

Moon (James) · #6 16-07-2010, 07:19 AM

Rowland
What scope is it? It's unlikely to be collimation - more likely to be focus or the quality of the optics. The focus position you select will determine the halo colour and size.
James

adman (Adam) · #7 16-07-2010, 08:50 AM

On my Skywatcher ED80 I get colour fringing either side of focus - but when focus is spot on, there's none at all

Adam

dugnsuz (Doug) · #8 16-07-2010, 10:24 AM

Quote:

Originally Posted by rcheshire

I'm not at all happy with the colour fringing and wonder if collimation may be an issue, or possibly focus is not quite right. Could it be the field flattener? I really don't know?

Looking at your high res single sub indicates that it's a focus issue.
Thanks for taking the time to post it up.

rcheshire (Rowland) · #9 16-07-2010, 02:48 PM

Thanks Guys. Interestingly, I thought that I had focus nailed with the Bahtinov mask. But evidently not good enough. I'll keep working on it. Thanks for your input.

The scope is an 80mm Explore Scientific triplet apo. Hoya ED glass and all that. I prefer to think that it's a focus problem - if not, I'll be terribly disappointed. Else, it's time for a Fringe Killer - I sincerely hope not.

rcheshire (Rowland) · #10 17-07-2010, 03:21 PM

Just in case anyone is still following this thread.

I've learned a lot processing this image. It's by no means good, but there are a number of issues that I have been able to resolve or improve.

Removed colour fringe, but this bloated the affected stars. Stars are rounder and better defined, except for the seagulls. Background is improved. .jpeg really doesn't carry it off.

Included a clip before colour adjustment, showing better resolution of clusters of stars. So I think the scope is performing OK. Better focus, tracking and processing should produce reasonable images in the future.

Welcome the feedback. Thanks again for your help.