Short exposures + LP = NOISE!

[bobharmony]

Larry, I'm not sure there is anything wrong. Have you tried loading the output from DSS into another program, like StarTools, and seeing what is there. The histogram DSS is showing indicates that the three colors have been aligned in the stacking process (possible RGB calibration is on), but it looks pretty normal for data that is ready to be stretched.

If you want to use DSS for post-processing, Henk's advice is the best. I have seen him do some pretty amazing things using DSS over the years.

Don't panic, and don't assume something is wrong. A different approach is to think there is a lot to learn about post-processing astro data, and you are at the beginning of the process. It's too early to draw conclusion about the quality of your data!

Bob

[Larry 1969]

Thanks Bob but I'm pretty sure I screwed something up.
I did load the stacked image of NGC 7331 into StarTools and I couldn't pull anything from it. Even AutoDev didn't bring anything out.
I've stacked some images with DSS and I have it set to save as a .fits file on my desktop as soon as it's finished stacking.
I only stretch it a bit in DSS to see what I have. With the CLS-CCD filter my images were very dark and required a little stretch in order to see anything at all.
I would then open the unaltered image that was saved on my desktop into StarTools and work from there.

As it sits right now, I can't even re-stack my original data.

I'm going to try to work on it tonight.
Of course, I'll post if I find the solution.

Larry

[Larry 1969]

I tried reinstalling DSS to no avail.
I really don't understand what's going on here...…
I re-processed the same raw images of NGC 7331 and keep getting a terrible, unrecognizable result....

Here is a link to my DSS settings file.
https://www.dropbox.com/s/jd6wvrms9flwb ... tings?dl=0

This is a link to my new stacked image.
https://www.dropbox.com/s/regnefdenxqzm ... e.fts?dl=0

I'm perplexed...……

Larry

[Larry 1969]

OK. I totally forgot that someone, either here or the other site sent me their DSS settings.
I loaded them and stacked some images and it worked!
I have data from 2 nights on NGC 7331. Two different exposure times and two different ISO settings.
I put all the data from the first night into the first tab along with a master dark and master bias.
I did the same for the second night in the second tab.
It's stacking 250 images...... We'll see......

I'd still like to know what was wrong with my settings if someone can take a look.

Thanks!

Larry

[ram]

First of all, I think these are pretty encouraging results for the type of set up you have. I have an 18" Obsession which I rarely use since I've gotten into the AP thing a lot but it's decent and highly encouraging you're able to do this that I want to stick a camera on it and do this short exposure stacking thing.

I use Sharpcap which I don't think can work with a DSLR but if you can find a way to get things to stack live as you're taking these short exposures (TheSkyX now has a live stacking algorithm too) that would make things a bit more efficient. Your one hour of total exposure should be enough to get at a lot of targets and produce a decent image with your setup.

If you can go after M31, I recommend trying that: these M31 images are a result of me stacking 600 x 15 seconds exposures with an OSC (so similar to your DSLR): https://www.astrobin.com/413890/

--Ram

[Larry 1969]

Thanks ram!

DSS has a "Live Stacking" feature but I've never used it. I usually start my imaging plan in APT and walk away for a bit.

M31 is a bit of a challenge for me because of my 1,200 mm focal length. Very nice image BTW!

How did you go about stacking 600 images? Diod you load all of them int DSS at once or did you batch stack?

Larry

[ram]

Sorry, I didn't think about the FL - that makes sense but then you could think of a mosaic. It's just that M31 is unusually bright so given your short exposure requirement it would seem to be that you could perhaps even find one frame per panel and put it together with ICE or other tools.

I use PixInsight but yeah, it is kind of like a batch process but the final integration does combine the data from all the individual frames that are calibrated, debayered, and registered.

--Ram

[Larry 1969]

OK so I think I found my problem with DSS.
If I uncheck the "reduce noise by applying a median filter" box the result is a completely unusable stack like I was experiencing before.
I'm re-stacking an image right now with this box checked just to test. With the box unchecked it stacked 115 of 304 and the result was unusable.

Larry

[Larry 1969]

All this DSS stuff is taking this thread down a rabbit hole..... My fault. Sorry. I have many more questions and I'll start a different thread.

Larry

[ram]

How many darks are you using to create a master dark? I would start with only the master dark frame for calibration (ignore the bias frames unless you're sure you're doing it correctly). You're doing the dark subtraction live as you capture the frames or do you capture your light frames and then do the calibration later? In other words, do you have your raw light frames without any calibration (darks or bias or flats) saved somewhere?

Then I believe in DSS you an rank each calibrated and debayered frame by multiple criteria like the FHWM, eccentricity, SNR, # of stars, etc. This can be used to determine what are the best frames. Then you register them and then you integrate them - this is what I do but it can be done with any piece of software including Photoshop.

Looking at your comprehensive setup, I really want you to succeed and I'll again reiterate that your initial images are promising except for M45 but someone else reprocessed it for you as you saw so that's a good start too. When I bought my UC18, I wanted to do what you are trying to do. I never have gotten around to it (yet) since there's so much else to do in terms of WF imaging but I think it's a worthwhile route to take esp. in your case since you have a modified DSLR.

--Ram

[Larry 1969]

Thanks again ram!

My routine goes something like this:
I will shoot all my light frames (100 - 200) then I shoot 50 darks (same ISO and exposure time) then 50 bias (same ISO 1/4000 sec exposure time).
All of my RAW lights go into a folder by themselves. Same with darks and biases.
I then go through all light frames manually to get rid of obviously poor frames.
Then I "Load picture files" into DSS. This is where I enter all of my light frames.
Then I load my darks, then biases.
I "check all" then "register checked files".
I try to pick a star detection threshold that shows around 100 stars.
Then it's off to the races. I only enter a master dark or bias if I'm reusing one or re-stacking an image since I don't have a master until after stacking.

I'm not giving up. I'm just getting started!

Larry