DSO lucky imaging

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fantalorenzo
Posts: 2
Joined: Thu Jul 22, 2021 9:12 am

DSO lucky imaging

Post by fantalorenzo »

Good morning.
I would like to realize a DSO Lucky Image with the 462C and a newton 10” F/4 and I need
help about the best practice.
I already tried in the past this technique (with a different camera). I used 3” subs (Fits) for a
couple of hours, and then with DSS I calibrated them with darks and flats and stacked. I liked
the result but i was a little bit time and space consuming for the stacking.
Now I wanted to try again, collecting much more hours, but the problem is the huge amount
of space needed for the Fits, not forgetting the time to stack 10.000 or more images.
So I was thinking that would be useful to use LiveStacking in the following way:
using LiveStacking, I would like to stack and save after 5 minutes of exposure, a single Fits
made of 3” subs (300 secs / 3” = 100 images). So at the end of the session, I would have N
fits, and every fits is the result of the LiveStacking of 100 subs each (i.e., 120 minutes of
exposure, I would get 24 Fits, from 2400 images of 3” subs).
Then I would stack those 24 Fits in DSS to get the final calibrated image (much better for
time and space saving to stack in DSS ‘N’ images than 100x times more, especially when
numbers are higher).
I tried, but yesterday immediately a problem to solve, for which I call for your help.
LiveStacking can’t save raw frames with the Pre-Processing applied (Dark Subtraction and
Flat correction). It means I was saving the stacking of uncalibrated images (with hot pixels,
amp glow, vignetting adding problems). So the final result it’s impossible to calibrate,
because i.e. the hot pixels become already huge walking noise in a 5 minutes stack made of
3” subs; not more hot pixel in a single point but all around. I also tried the stacking with
Sigma Clipping but it was not helping. So I was useless / impossible to calibrate later this
kind of stacking.
Probably I can Pre-Process and save the images like ‘exacly as Seen’ but in a PNG lossy
quality, which is not what I need.
My question is if I am doing something wrong; or if there is a different Best Pratice to stack
tons of 3” stacking.
Or is it possible in the future to allow Sharpcap to stack and save Pre-Calibrated (dark and
flats) 16 bit Fits thru Live Stacking? By what I can see, Sharpcap is very quick to
Pre-Calibrate images.
Thanks for your help and support in advance.
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admin
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Re: DSO lucky imaging

Post by admin »

Hi,

normally if you want re-do the stacking from a live stacking session you have two options

1) Use the RAW files that are saved and stack them completely (including dark/flat processing) in another application such as DSS

2) Capture multiple live stack images, each stacked for a short time like 240s, then stack those in another application like DSS. In this case you must let SharpCap handle dark/flat correction and not try to apply them in DSS.

There aren't any other ways to do it at the moment that make sense in terms of the processing flow.

One thing you could try is to capture RAW frames during live stacking and then later run them through SharpCap's virtual folder monitor camera - this would let you apply SharpCap's dark/flat correction and then re-save the output with corrections applied.

Something to note is that PNG is not lossy - it is a lossless format (JPG is lossy). SharpCap supports reading and writing 16 bit bit depth PNG files, but some other software will silently reduce the bit depth to 8 bit when loading, so watch out if you use PNG.

thanks,

Robin
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turfpit
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Re: DSO lucky imaging

Post by turfpit »

would like to realize a DSO Lucky Image with the 462C and a newton 10” F/4
You might find this useful/interesting https://www.cloudynights.com/topic/5338 ... second-16/ . See post #20. Poster MvZ is Emil Kraaikamp, author of Autostakkert. He uses a 16" Dob and captures 2000 x 1s SER files which he then stacks using Autostakkert. This is an example result https://www.astrokraai.nl/viewimages.php?id=266&cd=7. I would be happy with that.

Dave
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