Thanks, I have added one FITS and one CR2 light frame to the same folder.

I'm somewhat surprised by your comment about my flats. It was my understanding that it was best to let the camera choose the exposure when pointing at the flat panel (light source). When I do that, my camera selects 1/4000sec. I then selected that in Ekos.
The next higher exposure setting seems to be 1/100 (0.001sec). When I use that the flats are over exposed. When I open the CR2 flat it looks good to me (if a bit blue-ish), but I'm by no means an expert...
Is my flat panel too bright? It's an old LED TV with the display removed and only the backlight left, which I made remote controllable. It is mounted on the wall in front of the telescope when it's parked.

Your pixel size X,Y are wrong - surely they should be 22.2 and 14.8 ??????????

ah, is that supposed to be the sensor size in mm? "Pixel Size" is a bit confusing then...

Does that mean it is also wrong for my QHY5?


Here I don't seem to have a way of changing it.

Just your FITS produces this in DSS 64 BIT Windows

maybe it accepts both in X & Y - naughty should state unit of measurement as per Pixel Size. I use MM and mine works - maybe a fluke LOL

Plus doesn't Indi get most properties from the drivers except for DSLR as it uses a re-engineered piece of software GPHOTO - might be wrong - await an expert !

Your light frames are absolutely fine, except they are just underexposed.

Re-read devices - DSLR appear to be in micron's in the D600 example shown - so I am confused to what they should be and why mine work !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Anyway your FITS file is OK as Radek say's and my test shows DSS works with your Lights.

OK, so it's just me then. I didn't actually stack them.
What do you get when you just load the light frame in DSS (add to list) and then click on it to see the preview? Does that show data for you? This is where I see it completely black, including the flat.

Yes, they are only 30sec frames. I will ramp up exposure time once I get guiding working.

Thanks for testing this for me, guys!

I would say it's typical pitfall Exposed frames always look totally black before you shift histogram to right. No matter before or after stacking.
I remember my disappointment when I finished my very first session with a camera many years ago. I was so excited and stayed long during night and the first thing I did in the morning was checking the results... But there was nothing there on the pictures, just a few stars and totally black background
Your light frames are taken with unmodified DSLR and each capture is 30 sec @ ISO 800 and 250/1200 newtonian (f/4., which is too low for M51. Just for comparison when imaging this object I was taking 300 sec exposures with dedicated CCD camera and f/4 newtonian, which is 20% "brighter".
All the best and lots of clear sky!

Radek , do you know why the Indi system,dealing with DSLR's, has Pixel size in UM but allows the X & Y in both MM and UM - which is correct? it seems both !!!!

Yes, I know.
I've been imaging for a few years already, just on Windows, had a 4 year break (other priorities) and I'm now starting again with the whole observatory control moved to Astroberry / KStars.
I've never used FITS files before though, only CR2.

I know that light frames are usually very dark. But not completely black.
When I load a CR2 file with the same exposure and everything else the same into DSS, I see the image. It is very dark indeed, but I do see stars and a hint of the galaxy / nebula. When I load the FITS it is completely black. No stars. Not even hot pixels.
The same for flats. When I load a CR2 flat in DSS, I see a rather light image with the gradient. When I load a FITS flat, I get a completely black image.

But since you guys have shown that there is actual data in these FITS, I'll just put it down to a difference in how DSS displays CR2 and FITS in the preview. Or something like that.
And I'll probably stick with CR2 for now.

Thanks for all your help. I've definitely learned something here.