Deep Sky Stacker help processing m51 image *newbie*

[nitram100]

Hi guys,

I'm quite new to imaging and tried to take an image of M51 last night.

I took 20 x 60 sec light frames, I chose RGB in sharp cap.

I am trying to stack them in DSS but just get a single gray image. It doesn't even let me save the image for processing as it says no picture detected.

I've changed it to RGGB in settings as that is the bayer pattern of my 183c Altair cam.

I always seem to have issues with this software, is there a more straight forward alternative?

Thanks for any help.

[Astronomist]

1 hour ago, nitram100 said:

is there a more straight forward alternative?

Lots of people use siril for stacking, but it isn't really more straight forward than DSS, just different. You might want to give it a try and see if you get on better with it, it has (IMHO) a more streamlined UI than DSS.

[Elp]

I started with DSS, still use it for a quick check on a stack but Siril is better as it also has post process operations (background extraction being one vital one).

A screenshot of your software setup in DSS may help. The stack will generally look black unless if you change the levels sliders at the top right of the screen (it's a preview adjustment, doesn't change the image in any way).

[nitram100]

Thanks for all the info guys, I was being stupid. I was registering pictures then getting the grey screen and not clicking stack checked pics. Sorry!!

I was wondering though, the final image was pretty awful with star trails and quite useless. I took 1 min subs and on the screen they looked good but each individual FIT file shows m51 moving slightly, should M51 be centered 100% of the time in all images to avoid star trails? Maybe my polar alignment was off.  I thought deep sky stacker was able to align stars even if they were slightly off.

 

I've attached a pic of my m51 with 4 frames of 1 min subs where I could see the stars moved around slightly. Is there a way to fix this? Or do I have to get all the images again with perfect polar alignment. The night was windy, so that may have caused it too.

 

Thanks for any help, Mart

Edited June 23 by nitram100

[Elp]

I think the images aren't good, you can tell as the star patterns repeat around each star to suggest wobbling whilst taking the images. If this is the case I'm surprised registration worked. Also any slight elongation of stars and this will also cause registration to fail.

If the target was moving sub to sub it's likely your tracking wasn't fast enough (or the right setting, it should be on sidereal when doing DSO), bad PA can also do this, as well as an unbalanced payload, or a too heavy payload for the mount.

A good mount, well balanced will keep the target fairly central with minimal movement, but you also want to dither (move the optics in a random direction a few pixels every 5-10 minutes) otherwise your stack will likely contain walking noise (looks like a dark rain pattern across your whole image once stacked). When autoguiding you can set dither to be done automatically via the computer controller, without this you have to do it manually.

Edited June 23 by Elp

[alacant]

23 hours ago, nitram100 said:

the stars moved around slightly.

Hi

That's normal, although the amount of movement is perhaps a touch large.

That's the sort of result you get when the stars haven't been aligned/registered before stacking.

I don't use windows, so not sure if there's a setting you may have missed...

HTH

Edited Monday at 10:07 by alacant

[900SL]

20 hours ago, nitram100 said:

Thanks for all the info guys, I was being stupid. I was registering pictures then getting the grey screen and not clicking stack checked pics. Sorry!!

I was wondering though, the final image was pretty awful with star trails and quite useless. I took 1 min subs and on the screen they looked good but each individual FIT file shows m51 moving slightly, should M51 be centered 100% of the time in all images to avoid star trails? Maybe my polar alignment was off.  I thought deep sky stacker was able to align stars even if they were slightly off.

 

I've attached a pic of my m51 with 4 frames of 1 min subs where I could see the stars moved around slightly. Is there a way to fix this? Or do I have to get all the images again with perfect polar alignment. The night was windy, so that may have caused it too.

 

Thanks for any help, Mart

That looks like wind.

Movement during a sub usually results in trails, or dumbbell shapes.

Significant PA error causes trails. Mechanical glitches usually causes double stars or dumbbell shapes, as does wind or a knock

Frame to frame drift is addressed during frame registration

 

EDIT Is that a single sub or a stack of four? 

If a single sub it's likely wind or periodic error. If its a stack there's something wrong with registration

Edited Monday at 07:15 by 900SL

[nitram100]

3 hours ago, 900SL said:

That looks like wind.

Movement during a sub usually results in trails, or dumbbell shapes.

Significant PA error causes trails. Mechanical glitches usually causes double stars or dumbbell shapes, as does wind or a knock

Frame to frame drift is addressed during frame registration

 

EDIT Is that a single sub or a stack of four? 

If a single sub it's likely wind or periodic error. If its a stack there's something wrong with registration

Thanks for all the info guys.

This is a stack of 4 x 1 min subs.

None of the single frames have star trails, a couple of the single frames have a slightly comet shaped star but other than that each single frame looks good. It seems like although the pictures aren't great, DSS should be registering it better than this.

I'm quite to new to AP and with the UK weather I haven't had too much time to practise!

 

 

I've uploaded my FITS to google drive if anyone is bored today and wants a bash at them! haha, its about 2gb.

https://drive.google.com/drive/folders/1T38Z9KO8CbSrVtcg47R2jexdGt00dmXD?usp=drive_link

Edited Monday at 10:33 by nitram100

[nitram100]

Just an update, not sure why DSS is being such a pain in the butt.

I just googled other software and tried ASTAP. Loaded the lights and a few darks and it aligned straight away. I'll stick to ASTAP from now on, thanks for the help guys.

 

This is the image it popped out with default settings, not sure what the smudge marks are but I'm happy enough that everything seems aligned at least!

[Elp]

With DSS I've found it generally registers better if you keep your star detection threshold relatively low (detected stars in their low hundreds).

[nitram100]

2 minutes ago, Elp said:

With DSS I've found it generally registers better if you keep your star detection threshold relatively low (detected stars in their low hundreds).

thanks mate, i did mess with the detection and tried stacking with 8 stars, 100 stars, 400 stars but nothing changed, it always gave me a mis aligned image. I'll stick with ASTAP from now on as it just gets the job done for me! Just need better images to work with haha

[WolfieGlos]

49 minutes ago, nitram100 said:

not sure what the smudge marks are but I'm happy enough that everything seems aligned at least!

The smudge marks are dust motes on either the scope or the sensor of the camera. It looks like you didn't take any calibration frames.

The dust can be fixed (and the corner vignetting) by taking a series of flat frames along with bias or dark-flats. These will be picked up by the stacking software and used to calibrate each of your frames before stacking the final image.

[TiffsAndAstro]

2 hours ago, nitram100 said:

Just an update, not sure why DSS is being such a pain in the butt.

I just googled other software and tried ASTAP. Loaded the lights and a few darks and it aligned straight away. I'll stick to ASTAP from now on, thanks for the help guys.

 

This is the image it popped out with default settings, not sure what the smudge marks are but I'm happy enough that everything seems aligned at least!

I would be very happy with this. Stars maybe a bit out of focus? Really nice image though

[nitram100]

On 24/06/2024 at 13:16, WolfieGlos said:

The smudge marks are dust motes on either the scope or the sensor of the camera. It looks like you didn't take any calibration frames.

The dust can be fixed (and the corner vignetting) by taking a series of flat frames along with bias or dark-flats. These will be picked up by the stacking software and used to calibrate each of your frames before stacking the final image.

Thanks mate, I only took about 4 darks  but I will try with bias and dark flats tonight as I am going to have another crack at it.