Veil Nebula- processing issues

Questions and answers about processing in StarTools and how to accomplish certain tasks.
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el_hop87
Posts: 11
Joined: Wed Mar 24, 2021 8:23 am

Veil Nebula- processing issues

Post by el_hop87 »

Hello

I am trying to process an image of the veil nebula but it is not working out very well at all. I am not sure whether its the images themselves or an issue with the way I am process it...

This is the file, would be extremely grateful if anyone had any guidance on this please:

https://www.dropbox.com/s/oknlpjw92uv35 ... e.fts?dl=0

Thank you! Elly
decay
Posts: 406
Joined: Sat Apr 10, 2021 12:28 pm
Location: Germany, NRW

Re: Veil Nebula- processing issues

Post by decay »

Hi Elly,

I'm sorry, but I'm afraid there are some severe issues regarding your dataset / image acquisition, that can't be addressed / healed by processing in ST :cry:

First of all I think the focus position was not met. There are these typical doughnut shaped stars with a darker centre:
2023-11-25 13_53_45-Window.jpg
2023-11-25 13_53_45-Window.jpg (8.04 KiB) Viewed 32475 times
Depending on your equipment and seeing conditions setting the right focus position can be tricky. I failed a couple of times, too. If you would like to tell us about your equipment and procedure, people here may be able to give some advice.

The stars are a bit elongated/ egg shaped due to problems with tracking and/or guiding. As above, if you like, give us some details ...

There are some dust specks and vignetting visible:
2023-11-25 14_14_01-Window.jpg
2023-11-25 14_14_01-Window.jpg (639.61 KiB) Viewed 32475 times
Probably not the main problem here, but taking flat frames would help to get rid of both problems. I know, that's a whole bunch of things at once, but setting up correct calibration will make processing much easier and would be a great benefit for image quality. Taking flats is quite easy, once you have figured out, how it works. So again, if you like, I guess people here could help ... :)

I hope this helps. Let us know, how you get on!

I will try to process your image and get back with a second post later.

Best regards, Dietmar.
decay
Posts: 406
Joined: Sat Apr 10, 2021 12:28 pm
Location: Germany, NRW

Re: Veil Nebula- processing issues

Post by decay »

Sorry Elly, that's all I've managed to get out :( Maybe others here have more success ...
2023-11-25 15_05_39-Window.jpg
2023-11-25 15_05_39-Window.jpg (123.17 KiB) Viewed 32475 times
el_hop87
Posts: 11
Joined: Wed Mar 24, 2021 8:23 am

Re: Veil Nebula- processing issues

Post by el_hop87 »

Thank you so much for looking into this and for your advice - very grateful!

I think you are right- my current set up is Nikon D800, Skywatcher AZ GTI tracker, Skywatcher Evostar 72ED.... I think the problem was that the AZ GTI Synscan inbuilt wifi dropped whilst shooting. I thought I had noticed it in time, but probably not, hence the tracking issues!

Thanks so much for having a go at processing the image, much better than my attempt!

Elly
dx_ron
Posts: 227
Joined: Fri Apr 16, 2021 3:55 pm

Re: Veil Nebula- processing issues

Post by dx_ron »

There's still a bit more information that would allow people to offer more useful advice.

How do you focus? Using the display on the back of the camera? If so, make sure you zoom in on a bright enough star. A bahtinov mask would be better, you can probably find a 3d-printed one that will fit your scope.

How long are your exposures? It doesn't sound like you are guiding, so the intrinsic tracking error of your mount will limit the exposure length you can use and still get round stars, even if your wifi remains connected.

How are you controlling the exposures? With an intervalometer, or are you running a computer program session manager like NINA, Sharpcap, APT, etc?

Is your camera modified for astrophotography? If not, it is filtering out nearly all of the deep red color from ionized hydrogen (which is what gives the Veil Nebula its red colors), so you will greatly decrease the signal you can get. With an unmodified dslr you might want to work on galaxies and reflection nebulae (M31, M33, M45, for example).
decay
Posts: 406
Joined: Sat Apr 10, 2021 12:28 pm
Location: Germany, NRW

Re: Veil Nebula- processing issues

Post by decay »

el_hop87 wrote: Sat Nov 25, 2023 3:52 pm I think the problem was that the AZ GTI Synscan inbuilt wifi dropped whilst shooting. I thought I had noticed it in time, but probably not, hence the tracking issues!
OK, I understand - just bad luck. But I think the main problem here is the focus position. As far as I can judge it's way off. No way to fix it :( I know, it's always very annoying to throw away a whole session. Trying to process such stacks is usually just waste of time.

Do you often have problems adjusting the focus position? Or was it just bad luck in this case, too? What's your approach to setting the focus position?

Dietmar.
decay
Posts: 406
Joined: Sat Apr 10, 2021 12:28 pm
Location: Germany, NRW

Re: Veil Nebula- processing issues

Post by decay »

@dx_ron Ron, Elly, I just saw, that our posts crossed. But I think, they both go in the same direction. :)
Mike in Rancho
Posts: 1120
Joined: Sun Jun 20, 2021 10:05 pm
Location: Alta Loma, CA

Re: Veil Nebula- processing issues

Post by Mike in Rancho »

Hi Elly,

I'll join the crowd to say that some more info might help us to help you, and maybe start breaking things down step by step. :)

Seems to be acquisition here, and perhaps then calibration and stacking. Just unload all the details.

I see from a search that you've been using this setup for a while, though with a different DSLR before.

I started out myself with a Nikon and an Evostar 100, albeit on an HEQ5 Pro, but also using SynScan wifi. If you have the capability, perhaps change wifi modes. I changed mine right away so SynScan is just another "end user" of my home wifi router, rather than being its own router. Likely much better range and stability that way.

Are you using uncompressed 14-bit RAW NEF mode for your D800? Then also, you'll want to take flats and set up full calibration properly, at minimum with bias.

Using that alt-az mount, you may be limited to quite short exposures. You'd have to test to see when you start trailing. And of course cull any subs that are too "eggy" from inclusion in the stack.

Finally, I first used my D5300 live view for focus. The trick there is to use a bright star, but, you really know you are close to critical when the little surrounding faint stars suddenly pop into view. I always tried to include them when using the display zoom. Eventually though I made a B-mask that fit the the ED100, which is a big help.
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