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Free live-stacking with SharpCap

Posted: Sun Nov 19, 2017 10:51 am
by rwilkinson
Last night I tried out the new Live Stacking function in the SharpCap software (version 3.0).
This takes a sequence of long-exposure images from the camera and aligns and stacks them on the fly - just as the Atik Infinity does.

For this test I used my old Atik 16IC one-shot colour camera (although the program will work with even a humble LX-webcam). I fitted my Pentax 135mm telephoto lens (and an LPR filter) and set it up on a Celestron LCM alt-az mount, clamped to an upstairs windowsill (looking through a double-glazed window).
I aimed it at a couple of galaxies in Ursa Major and once I'd set up its Star Detection parameters, the software automatically aligned each new 30-sec image and added it to the stack displayed on the screen. This was the result after half an hour:
The displayed stack of 59x 30-sec exposures of the M81 & M82 galaxies, taken from indoors.
Stack_59frames.png (291.98 KiB) Viewed 2783 times
The frame-rotation over this half-hour imaging run is clearly visible, and the green artefact near the centre is due to a single hot-pixel, scattered by the tracking errors of my alt-az mount.
The"Pro" version of the program (registration fee £10 per year) does include the facility for dark-frame and flat-field compensation.

There will be a more detailed write-up in the January edition of The Bolton Astronomer.

Re: Free live-stacking with SharpCap

Posted: Sun Nov 19, 2017 11:05 am
by bbones
Nice one Ross, have not had time to check it out yet but on my list of things to do

Re: Free live-stacking with SharpCap

Posted: Sun Nov 19, 2017 1:31 pm
by rwilkinson
I'd saved the individual raw image-files from last night's run, so we can see what the stack would have looked like without SharpCap's alignment processsing:
What the stack of 62 raw images would look like without the benefit of Live Stacking!
simplestack.png (437.53 KiB) Viewed 2775 times
The alt-az mount's tracking program did a fair job of keeping it pointed at the right part of the sky, but these star-trails clearly show the field-rotation and periodic errors (as well as any vibration from me moving around the room!).
The static green, blue and red dots are individual hot-pixels (which could be removed by a dark-frame subtraction).