Flats problem solved.

[ollypenrice]

I've posted a couple of times with regard to the fact that Yves' SXVH36 running on a Mac in Nebulosity in my observatory has almost always had a big problem with flats. They over correct, causing inverse vignetting and inverse bunnies. Harry Page, ever the star, pushed the idea that it was inadequate flushing between subs which lay behind the problem. I do know that you have to subtract a dark from flats, and I know that a master bias is all you need by way of a dark for short exposures. I run several other rigs using Artemis Capture and a PC and Atik cameras and flats are not a problem.

Finally I tried running the problem rig in AstroArt on a PC for flats capture. I did try SGP but it refused to find the camera and filterwheel, but AstroArt did find them. And, glory be, the flats it took worked perfectly.

I had a guest last week who found that his flats always over corrected, so the problem is not unknown.

Well, there you go. You know, I do like Artemis Capture. Wonder programmes abound but I'm a simple soul and if something works I tend to love it.

Thanks to all who have advised on this flats palaver in the past.

Olly

[steppenwolf]

Good news, Olly but I am a little confused (or more likely being thick):-

Quote

Finally I tried running the problem rig in AstroArt on a PC for flats capture.......................................... And, glory be, the flats it took worked perfectly.

Quote

Well, there you go. You know, I do like Artemis Capture. Wonder programmes abound but I'm a simple soul and if something works I tend to love it.

Which resolved the problem, AstroArt or Artemis Capture?

[ollypenrice]

15 minutes ago, steppenwolf said:

Good news, Olly but I am a little confused (or more likely being thick):-

Which resolved the problem, AstroArt or Artemis Capture?

Sorry Steve, it was Astro Art. You are not being thick, I am being garbled! I can't run the SX camera in Artemis, of course. What I meant was just that I can buy an Atik camera, run it in Artemis and do everything that I want to do, including flats.  In earlier posts Harry mentioned that he had asked the AstroArt developers to include multiple flushes and this may be the reason why my flats now work. They certainly don't work in Nebulosity. 

I wonder why SGP can't see the SXVH36? It's on the same PC as AstroArt which can see it. In the next life I'm going to come back as an IT guru.

Olly

[steppenwolf]

No problem, Olly - I wasn't being pedantic, just wanted to understand the solution as we had some discussions about this issue and my solution to the problem, albeit with a totally different sensor/manufacturer, was very different! The clue, of course, was that Artemis designed for ATIK cameras NOT SX cameras - Doh!

That is strange that SGP can't see the SXVH36 - I assume that you are using an ASCOM driver for SGP? I suspect that SX supply a specific driver for AA just as they do for MaxIm.

[harry page]

Hi Olly

Glad to see you have it all working well , I am not saying this was everybodys problem but it was mine

As for SGP I presume all Ascom drivers have been installed , see here for a SGP prep vid http://www.harrysastroshed.com/SGP%20main/sgpvideo.html ==cant beat a good video

I nearly like SGP as much as Pixinsight

Regards

Harry

[swag72]

Glad that you've finally got to the bottom of this annoying problem Olly. What is it with software?

I found the answer to my flats issue..... Don't calibrate in pixinsight and calibrate in maxim instead.... Perfect! Flats issue resolved for me too

What an utterly crazy situation to find yourself in.

[ollypenrice]

Cheers, all. I'll look into the ASCOM situation on the relevant PC but SGP runs a guest's QSI happily enough on that machine.

As long as it works I call myself happy. Oh boy, working with bad flats or no flats is a horror if you're after the faint stuff, and I nearly always am. Thanks for the moral support!

Olly

[Pompey Monkey]

Glad to hear you got it sorted out, Olly  

I had a similar problem (among others) with over correcting flats last week - I was creating them using PI and it turned out that I was combining them additively  when I should have been combining them multiplicatively . I re-integrated using the correct method and it all worked fine.  I don't use Astro art or Artemis, so can't comment on either piece of software.

Thanks to Kayron for his excellent tutorials for that one, which, incidentally, is independent of the camera used to capture the flats. http://www.lightvortexastronomy.com/tutorial-pre-processing-calibrating-and-stacking-images-in-pixinsight.html

[opticalpath]

Great news, Olly.  From 'flat broke' to 'luxury flat'.   Finally got that stone out of your shoe.

Adrian