What's going wrong?

[Ben Benson]

Hi, 
Last night I spent just over an hour imaging Sadr, in Cygnus. I managed to get about 50 minutes of total exposure time, taking 10 darks and 220x 15 sec exposures. It was nearly a full moon, which probably didn't help, but all I managed to get was this:

Having spent a while out in the cold making sure everything was tracking and imaging correctly, I'm a little (very) disappointed. I've been doing astrophotography since November, using a 100mm lens and I now have a Skywatcher 50ED 250mm APO Refractor, which I would have thought should give me some nice wide field images? The camera I'm using is the Raspberry Pi HQ Camera. I know it's far off being a perfect astrophotography camera, but I've got some decent images, with the horsehead and flame nebula being the best to date, which I only spend 40 minutes or so on (see attached). 
My main question is, what do I need to get some decent results?
I'm imagining that the camera is the main downfall, but I've spent most of my budget, and I definitely cannot buy a new DSLR or camera - an old second hand one could be justified however. Or am I just not spending enough time on targets - is 50 minutes under a full moon, with 15 second exposures ever going to yield good results?
I did also image the flame nebula with a focal reducer, I have not been using that recently, will this change much, other than the view?

Thanks

[Planitair]

I think the Camera is the problem,  what capture software  are you using,

the images have lots of noise & other issues which could be the camera plus it doesnt help under a big Moon, maybe a LP filter could help.

I know its an expensive hobby & most of us have thrown good cash at equipment not really up to the job when we first started out.

50 mins is borderline  for a decent image in the conditions you were imaging in, 2hr at 15 sec gives decent results.subs at 15 secs is fine to avoid star trails if not guiding.

The new CMOS cameras are popular I know you cant afford one but a second hand one will be better in the long term for you than a DSLR.

Are you imaging in alt az or eq, Sharpcap is good software and for the pro version only £10 pa  where you can do easy Polar Alignment and have good histograms to play around with, having said all this I go back to the issue of the Camera you are using, maybe someone on here knows a bit more about that make.

Good Luck

Eric

[Clarkey]

I think 50 minutes under a full moon with the camera you have is always going to be difficult. Using 'proper' astro gear I rarely image anything under 4 hours unless it is very bright just to keep the SNR higher. Extending the imaging time will really help. The is a recent post about integration time which would give you an idea.

Testing increasing integration times (OSC, Bortle 8) - Getting Started With Imaging - Stargazers Lounge

 

If you could give a little more detail regarding your rig it would help. Are you using a EQ or AZ mount for example? Do you dither at all? What is your processing? Looking at the image I suspect you have had to really stretch the data to get anything which is why the noise is so bad.

A second had modified DSLR can be picked up relatively cheaply and this really would improve your results. A second hand Canon 600D or similar can be picked up for around £200 or less.

[ollypenrice]

The colour in the Horse and Flame is perfectly convincing so the debayering and stacking process was being done more or less correctly in that one.

In the Sadr image the red channel is overwhelming and there is clear evidence of black clipping. The sky is flat jet black and the clipping is confirmed using Photoshop's Levels. As you can see, the histogram peak is jammed up against the left hand side. The left hand half of the peak has been discarded, meaning we don't know what it contained.

This test was performed on a JPEG screen grab but I have found by experiment that it is, none the less, reliable. In order to analyse an image properly we need to see it in its linear, unprocessed form, straight from the stacking software. There is always a temptation to remove light pollution (including that from the Moon) by black clipping, ie moving the black point slider to the right. Resist this temptation because it simply discards a large part of your image.

The stretched image should have a histogram with a fully formed peak away from the left hand side and at least a small strip of flat line to its left.

It also looks as if you have an issue with alignment since there is a 'frame within a frame.' Before trying to analyse or process an image it is vital to crop away any such edge artifacts so you are working only on an image to which all the sub exposures have contributed.

Olly