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INDI Library v2.0.6 is Released (02 Feb 2024)

Bi-monthly release with minor bug fixes and improvements

Brand new ASI120MC works on Windows 7 but not Ubuntu 16.04

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Thank you, nmac. Shortly after I posted I realized that perhaps Jasem meant to say "flash" not "flush"!

I am attaching an image that I made last evening of the Moon and Mercury at 8:09:52pm EDT, 41.3 deg North latitude. The location is a cemetery built on the side of a mountain near where I live. (I was surrounded by a mausoleum to the left and right with the howls of coyotes in the distance!) Here is the metadata provided by SharpCap:
[ZWO ASI120MC]
Pan=0
Tilt=0
Output Format=AVI files (*.avi)
Binning=1
Capture Area=1280x960
Colour Space=RGB24
Temperature=6.5
Discard Split Frames=Off
High Speed Mode=On
Turbo USB=56(Auto)
Flip=None
Frame Rate Limit=Maximum
Gain=50
Exposure=0.2
Timestamp Frames=Off
White Bal (B)=95
White Bal (R)=52
Brightness=0
Gamma=50
Auto Exp Max Gain=50
Auto Exp Max Exp=30
Auto Exp Max Brightness=100
Mono Bin=Off
Subtract Dark=None
Display Brightness=1
Display Contrast=1
Display Gamma=1
I had the camera on a fixed tripod, no guiding. The video clip is 100 frames in length. At 200ms exposure per frame, the clip spans 20 seconds. I used RegiStax to stack all the frames, then cropped the image with Microsoft Paint and erased a few hot pixels. There was quite a lot of wind so the trees are blurred somewhat.

RegiStax did a great job canceling out the noise but there is an anomaly in the image that I cannot see in the video. Do you see it? Vertically, from the horizon to the tree tops, there are bands of light/dark/light/dark. Normally, I would say that this is the direct effect of quantization given the mere 8-bits of red, green, and blue. But I would have expected to see steps from lightest-to-light-to-dark-to-darkest, and not the bands that I see. The best explanation I have is that conditions were changing rapidly during that 20 seconds of video, and you get that effect after stacking those 100 frames. That, or I am using RegiStax improperly!
6 years 11 months ago #15850
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Here is an interesting discovery that I made last evening while imaging the Moon and Mercury with a 12mm lens attached to my ASI120MC:

Yes, the atmosphere was turbulent; even Mercury was twinkling. I could see that with my naked eye. But when I switched my attention to the computer screen I saw something else in addition to the twinkling: a secular change of color from white to blue to red and back to white again.

I am trying to rationalize what I saw. I don't think it was chromatic aberration. I have a refractor and I know what it looks like. For now I will rule that out. What I think was happening is this:

The camera was on a fixed tripod -- no guiding. Mercury steadily moved across the pixel matrix. Since the sensor has a color mask there are adjacent pixels that are red, green or blue. The center of the diffraction disk, where the light intensity is greatest, moves across the matrix from one color-filtered pixel to the next.

What I failed to understand a couple weeks ago when I did the math was that the diffraction disk is not of uniform intensity. My calculations told me that for a 3.5-inch aperture at prime focus that the diffraction disk would cover a 2x2 pixel matrix for this particular sensor. I (incorrectly) surmised that a red star would be seen as red by the sensor since the light touched all pixels in the 2x2 matrix. That would be true if only the light from the diffraction disk were uniformly distributed. Now I see my error.

So having said that, now I completely understand that "serious" astronomers only use monochrome cameras with a filter wheel.
6 years 11 months ago #15851

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6 years 11 months ago #15853

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