StuartT

thanks. But just to be clear, you are suggesting I will need to stack for an image like that? How would I make several light frames given that this is a 16m exposure (so the stars would be in very different positions for each one)? Or do you mean just take a bunch of darks and stack them with this one light?

thanks. Actually, they are barely there on the JPG version I attached here, for some reason. They are really prominent on the RAW file.

Last night I took this image (16min, ISO 100, f/11) with a 17mm lens on a Canon EOS750D. Can anyone tell me what the red dots are? They are clearly not stars.

YES!! That was it! I installed the Dawson driver and it now works 😃 Thank you!

Ok, so I installed ASCOM platform 6.5 SP1 and the Meade Autostar driver (#494, #495, #497) and have set up my scope in Stellarium using the correct COM port for my USB. Stellarium is telling me the scope is connected (see screenshots), but it won't slew anywhere. Any suggestions?

I was using JPG images, so I re-shot some RAW images last night and it worked a lot better Maybe JPGs are too noisy?

Ok thanks everyone. I seem to have it working ok now. I got an aligned image at least 😊 This is Regulus I think my biggest problem is that my tracking won't allow me exposures longer than 10 sec, so I am prob not catching enough photons

ok, so I have the threshold for star detection set too low. Thanks. I didn't read the user guide 😬 but I shall now! So I tried again with a higher detection threshold (in case it was just finding hot pixels). But still it can't seem to align them.

When you say 'stretched' do you mean using the levels control in Photoshop to move the midtones point? If so, here's how one of them looks

Results tab : Standard and Alignment tab : automatic Thanks. I'll check out your tutorial 🙂

I am dipping my toe into the water of image stacking. Last night I took a relatively small number of images (20) of a star field with a bright star in the centre. I have not taken any flats or whatever, I just wanted to try DSS in a very basic way to see if I could align the images and stack them. The 20 images were shot at the prime focus of an SCT with a Canon EOS750D (10sec exposure at ISO800). An example is the first image below. The tracking is slightly off, so the stars drift slowly in position through the set. But I am assuming the registration process takes care of that. Problem is, the first go at stacking makes them into trails (so doesn't seem to be registering them properly (second pic below). I set the threshold quite low and it was detecting plenty of stars (about 300) Can anyone help me with the basic settings I should be using? I was basically following this article by way of a tutorial.

this sounds like exactly what he was saying. Thanks!

I don't think he did. He was explaining that you have to balance ISO and noise. Dynamic range decreases with ISO, but noise increases. So you want the sweet spot between the two. He pointed to a rather nice site called photons to photos which allows you to see this noise vs ISO profile for any camera. Here is mine (screenshot)

I was watching a nice youtube video about imaging M31 and stacking with a DSLR. The guy said something which surprised me. He said that noise decreases with increasing ISO. This is the opposite to what I always understood - that the higher the ISO, the more grainy your image. Can anyone explain this for me?

Smashing. Thanks. I still need to figure out the right exposure I reckon. But focusing is def still my biggest issue.

apologies. I thought you were joking. yes indeed I had solar film on the front of the scope. I'd be surprised if you could get any kind of image without it (it would completely destroy the sensor)

Ooh! thank you! What did you do?

Only problem is I have a 750D and it can't be connected wirelessly to a laptop with EOS Utility for some reason. And I really don't want to have to buy the world's longest USB cable! (If you know a solution, please shout!). Also, I don't have an electric focuser on the scope, so I don't think I could do that. That image was 1/60s at ISO 200

aha! I think I got it!

yes, it's really hard to focus. I am using an EOS 750D. I magnified the live view mode to try and get the edge as sharp as I could, but it still looks off to me

I can't seem to see any of the sunspots supposed to be there at the moment. 😕 These were taken at prime focus of my 20cm SCT with a Baader white light filter on the front and a Baader continuum filter at the back. Why are they so featureless?

Thanks for this explanation vlaiv! I really appreciate it. So far I have been mostly taking images of the moon (where obviously this is not a problem). But I decided I'd see what happened if I pointed the scope at some stars instead. I am considering buying an EQ mount so I can then consider guiding (if I am clever enough to figure out how to do it!)

This evening I took a couple of star field exposures at the prime focus of my 20cm SCT. It's only on an alt-az mount with tracking, but I was surprised I was seeing trails at fairly short exposures (30s and 60s). Does this mean my tracking is rubbish?

and tonight

slightly happier with this one. I used my 20cm SCT at prime focus (100 ISO, 1/50 sec)