OSC camera single captures

Discussion of using SharpCap for Deep Sky Imaging
Post Reply
umasscrew39
Posts: 316
Joined: Fri Apr 28, 2017 1:28 pm
Location: Central Florida
Contact:

OSC camera single captures

Post by umasscrew39 » Sun Jan 26, 2020 1:24 pm

I usually save live stacks of stacks as 32 bit fits from my OSC camera and then use star alignment and image integration in PixInsight to align and stack all of them and post-process. It works extremely well. If I want to capture individual subexposures (like 180s) to stack them later but still view each live view, what is the best way to do that? Do I simply click save from each subexposure then clear the screen to do the next one and so on? Or can I setup individual capture frames as fits files and just observe what is on the viewing screen? If I do the latter, will not the fits image be black and white?

Bruce

User avatar
turfpit
Posts: 1215
Joined: Mon Feb 13, 2017 8:13 pm
Location: UK
Contact:

Re: OSC camera single captures

Post by turfpit » Sun Jan 26, 2020 3:04 pm

Bruce

Checking the box Save Individual frames described here https://docs.sharpcap.co.uk/3.2/#The%20 ... 0Interface results in the individual frames ending up in a folder rawframes. These files are 'straight off the sensor' - no dark/flat applied and no debayering.

rawframes-folder.JPG
rawframes-folder.JPG (30.46 KiB) Viewed 837 times


Opened in FITS Liberator, note we only get Image 1, Plane 1 (no debayering applied)

raw-frame.JPG
raw-frame.JPG (89.92 KiB) Viewed 837 times


Open a saved stack in FITS Liberator, note we get Image 1, Plane 1 & Plane 2 & Plane 3 (debayered during SharpCap's Live Stack process).

saved-stack.JPG
saved-stack.JPG (68.82 KiB) Viewed 837 times


To use the contents of the rawframes folder, will require the imager to provide their own calibration frames.

Saving the individual frames and the stacks will give you the best (or worst) of both worlds. I think that is what you asked ...


Dave

umasscrew39
Posts: 316
Joined: Fri Apr 28, 2017 1:28 pm
Location: Central Florida
Contact:

Re: OSC camera single captures

Post by umasscrew39 » Sun Jan 26, 2020 3:38 pm

Thanks, Dave. That answers my question on what you get collecting individual frames. Not sure I benefit from collecting individual raw data. I guess someone with a lot of experience would say that is the best way to do things. Sounds like I'll stick to either doing what I have been doing (stacking stacks and save them from the live views- frankly, the results have been very good after using PI to post-process) or just save each individual sub-exposure from the live view and stack them in PI.

Thx again,
Bruce

User avatar
turfpit
Posts: 1215
Joined: Mon Feb 13, 2017 8:13 pm
Location: UK
Contact:

Re: OSC camera single captures

Post by turfpit » Sun Jan 26, 2020 4:01 pm

Bruce

Both ways have their pros and cons. Live Stack is a good tool; especially beneficial in outreach type work - where a near immediate result is desirable. This image https://www.astrobin.com/330099/?nc=user (cheers Minos) built with a combination of multiple Live Stacks and some conventional processing is, in my opinion, one of the best examples of what can be achieved (mainly) in SharpCap.

Collecting the raw data is no additional effort and some conventional processing would give you something to do on those rare cloudy nights :lol: .

As you know, I use SharpCap but capture data for processing in the more traditional way (lights, darks, flats, biases). For me, that has led to a better understanding of the imaging process. I appreciate not everyone wants/needs that level of detail.

Both routes can lead to decent end results but many people underestimate the stamina and determination needed to get there.

Dave

umasscrew39
Posts: 316
Joined: Fri Apr 28, 2017 1:28 pm
Location: Central Florida
Contact:

Re: OSC camera single captures

Post by umasscrew39 » Sun Jan 26, 2020 5:03 pm

Well, I never get cloudy nights in Florida :roll: .

I'll probably give it a go as I am really getting a handle on PI and can do everything in it once I use SC to collect my darks, lights, and flats. Not sure I'll like it as I prefer to see a nice image stacking while sitting up in my observatory which is why I like the stacking stacks approach and then do post-processing. I have that approach down pat now and SC is perfect for doing it. I saw Minos' image - very nice. Its sort of in-between doing just live stacking for outreach and traditional AP. In fact, most traditional AP folks don't even realize it until you tell them how you did it. Also going to try some Ha/LGRB with my ASI1600MM.

User avatar
turfpit
Posts: 1215
Joined: Mon Feb 13, 2017 8:13 pm
Location: UK
Contact:

Re: OSC camera single captures

Post by turfpit » Sun Jan 26, 2020 5:33 pm

going to try some Ha/LGRB with my ASI1600MM
Welcome to the world of traditional Astro-imaging then - a whole new level of pain. If its not too late for you, think about getting the ZWO LRGB filter set which is balanced for the ASI1600. That way you can capture equal numbers of RGB frames and still have colour balance. I have to deal with ratios to get mine balanced otherwise hard sessions in pixel mangling software destroys the data. In time, you might come to appreciate this effort viewtopic.php?f=16&t=2072

Going the hard route, I have learned how to set black_level/brightness/offset correctly for a given gain and deal with flats. None of it wasted.

mAnKiNd
Posts: 303
Joined: Sun Jun 11, 2017 4:55 pm
Location: Long Island, NY
Contact:

Re: OSC camera single captures

Post by mAnKiNd » Mon Jan 27, 2020 2:24 pm

Thanks for the shoutout Dave.

Stacking of live stacks was a fun experiment that worked out better than I expected. One of the reasons I believe that was the case, is that each individual live stack, already has a very good statistical representation of signal intensities in each pixel, having averaged multiple sub frames and subsequently clipped outliers outside the normal distribution. Therefore, when stacking live stacks, you're working with clean, high SNR "frames".

I would add though, that I would I believe it would work even better to stack even more live stacks, say 20. This would enable even better/tighter sampling of the signal intensity in each pixel from each live stack, creating an even tighter guassian distribution for even more accurate clipping of outliers - higher SNR.

Having said that, I haven't revisited this approach in a while, mainly because of inconsistent weather - I moved from clear, dark skies in Cyprus, to light polluted random weather skies in Long Island, New York... Now I use live stack to enjoy the target whilst acquiring and save individual frames for more meticulus and laborious post processing purposes in Pixinsight and Photoshop.

Here's a recent example with my OSC camera:
https://www.astrobin.com/72lpuk/?nc=user

Cheers
Minos

umasscrew39
Posts: 316
Joined: Fri Apr 28, 2017 1:28 pm
Location: Central Florida
Contact:

Re: OSC camera single captures

Post by umasscrew39 » Mon Jan 27, 2020 3:03 pm

Minos

Nice work and I agree. Actually, I have used this approach up to 7 hrs integration with great success.

Here is my version of the Crab at 1 hr:
https://www.astrobin.com/blmvjv/?nc=collection&nce=1255

Here is the Cocoon at 4 hrs:
https://www.astrobin.com/dhj7sm/?nc=collection&nce=1255

Here is the tough Little Dumbbell at 7 hrs:
https://www.astrobin.com/8yrw4v/?nc=collection&nce=1255

With a little effort doing some post-processing in Pixinsight, these newer OSC cameras keep narrowing the gap between mono LRGB and OSC for image quality. Of course, lost of this is personal preference and one's comfort zone on effort, time available, sky conditions, etc, etc.

All the best,
Bruce
https://www.astrobin.com/users/umasscrew39/collections/

mAnKiNd
Posts: 303
Joined: Sun Jun 11, 2017 4:55 pm
Location: Long Island, NY
Contact:

Re: OSC camera single captures

Post by mAnKiNd » Mon Jan 27, 2020 4:58 pm

Good stuff Bruce.

I agree, with so little clear skies and so much light pollution around here, I cant be bothered to keep switching through filters all night and build an image that way. I tried this approach and its not for me and my current situation. Right now, if I get a small window to play, I just throw on my OSC with some LP filter of choice and shoot away, no downtime switching filters through the night and less processing. Do I see a worse quality color imagewith the OSC vs monoLRGB; not from where I'm shooting..

Since I do have the same camera in mono, I have decided to use it for shooting either narrowband or a luminance layer for the OSC stack.

Cheers, all the best and clear skies.
Minos

Timothy S
Posts: 2
Joined: Sat Feb 29, 2020 4:41 am

Re: OSC camera single captures

Post by Timothy S » Sat Feb 29, 2020 5:12 am

I have been successful shooting 20 sec unguided exposures with a C 9.25 at 2350mm focal length and saving every 10 minutes with LiveStack. Save as "fits" then process the 10 min subs (30 x 20 sec) in Pixinsight. Calibration with flats and darks in Sharpcap. Using a ZWO 294 MC Pro. The ZWO Dual Band filter works wonders on Planetary and Emission Nebula or just a UV/IR cut filter for visible light. For long captures collecting hours of data this cuts down on the pre-processing in Pixinsight.

Post Reply