First light (ever)

[Martyn87]

So I've tried stacking again without the darks, and now I'm seeing this weird noise across the image. What would cause this?

 

Edited July 28 by Martyn87

[ONIKKINEN]

31 minutes ago, Martyn87 said:

So I've tried stacking again without the darks, and now I'm seeing this weird noise across the image. What would cause this?

 

Hot pixels being smeared across the screen with drift from polar alignment errors. Dithering will get rid of those too.

Also, the vertical grain pattern of your background noise is walking noise and will get removed with dithering as well.

I think for this image you do want to keep the darks, since the data was not dithered but moving forward you should dither and drop the darks.

[Martyn87]

Thanks @ONIKKINEN, I guess it's time to get a guide camera ordered! 

[ONIKKINEN]

1 minute ago, Martyn87 said:

Thanks @ONIKKINEN, I guess it's time to get a guide camera ordered! 

Actually you can dither even without one, although it takes some work. I did that with a 550D when i first started, and it helped a lot with the noisy sensor.

Basically you just move the scope by a random amount (10+ pixels) to a random direction every now and then. The more often you dither the better it works, but when you have close to or more than a hundred subs you dont need to as often. As a starting point something like once every 5 or 10 minutes will work well. What i did was set the camera to 30s exposure with the batch shooting mode set to 10 exposures. When those were finished i just bumped the scope a little bit, while keeping an eye on the framing of course. Downside is of course that you need to babysit the scope and manually do the movement.

[alacant]

12 hours ago, Martyn87 said:

What would cause this?

Removal of hot pixels after dither works only when stacking with a clip algorithm (CA). Even if you haven't dithered, stack with a CA anyway. Sigma high=low=3 or high=2 low=4 should do it, but experiment with others.
HTH

Edited July 29 by alacant

[WolfieGlos]

On 28/07/2024 at 08:40, Martyn87 said:

How did your image come out? 

Yeah, not so bad as it happens! Here's a quick process in PixInsight, with a somewhat overexposed and saturated core, but a better process when I have more time, and data for the outer shells, will sort that out.

122 x 180s, 585mc with UV/IR filter + Starfield 102 with 0.8 reducer. Approx 2 hours captured during astro-dark, the rest captured in nautical darkness, with a 60% waning Moon.

[Martyn87]

Well guys, I just wanted to say thanks for some of your suggestions, I had another go at the Dumbbell last night and I'm so much happier with the result this time. Dithering has made a huge difference to the image noise and I made a much better job of calibration frames. Flats still seem to be a weakness though! 

This is 30 x 120s at ISO 800. Still far from perfect but it's a step in the right direction! 

[2manytrees]

Very interesting read, this thread, and well done with the pictures. It's interesting that hubby and myself were intending to use a DSLR and a tracker-mount for our "return" to astrophotos.....but we somehow ended up with a HEQ5, a 430mm refractor and two dedicated cams....I think the DSLR has a lot going for it, have seen some beautiful photos on here that I never thought were possible.

[Martyn87]

4 hours ago, 2manytrees said:

Very interesting read, this thread, and well done with the pictures. It's interesting that hubby and myself were intending to use a DSLR and a tracker-mount for our "return" to astrophotos.....but we somehow ended up with a HEQ5, a 430mm refractor and two dedicated cams....I think the DSLR has a lot going for it, have seen some beautiful photos on here that I never thought were possible.

Thanks! I bought a "cheap" C6 and DSLR from ebay, followed by an EQ6R that cost 3 times the rest of the kit. It's funny how this hobby seems to always cost more than you planned 😂

 

[Mr Green]

Great progress, always nice seeing others new to the hobby doing well and benefiting from all the help on offer.

You'll soon learn that you've spent wisely as that mount will keep you going for a while.

I myself started with a DSLR (unmodded) and it's amazing what they can do.

Next you'll be looking at cooled astro cameras. 😉

 

[Martyn87]

Thanks @Mr Green, I've been looking at dedicated cameras for a while but can't justify the outlay at the moment, but I'm planning on modding my DSLR at some point soon to see if I can get rid of the IR filter without killing it...

I've found myself looking through Stellarium for "blue things" just to give myself a bit of a fighting chance! 

[Mr Green]

They're definitely not cheap, that's a dead cert. 

If you're happy with the DSLR, that's all that matters. 

Modding your camera will be a massive upgrade in its self.