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Early Crescent Moon with SV50 and QHY5III-178C

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#1 james7ca

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Posted 18 October 2020 - 01:43 AM

Taken on October 17, 2020 at 6:33pm PDT when the thin crescent moon was just over seven degrees above my horizon. I tweaked the colors to produce a more neutral tone, since the moon and sky was still  a red/orange from the sunset which occurred just 20 minutes earlier. I may try to produce a more sky-color accurate version to complement this initial attempt.

 

Taken at the prime focus of a Stellarvue SV50 (50mm aperture, f.l. 330mm, f/6.6 ED doublet) using an QHY5III-178C camera and all carried on a Celestron AVX mount.

 

Captured with SharpCap, processed with AutoStakkert!, PixInsight, and Photoshop CC2019. Best 300 of 512 frames using an exposure time of 100mm at gain zero. I was hoping to capture some of the earthshine but the moon was so low in the bright and somewhat hazy sky that I'm not sure there was enough contrast to record that feature (but I have more sequences to try).

Attached Thumbnails

  • Early Crescent Moon Oct 17 2020 Labeled (small).jpg

Edited by james7ca, 18 October 2020 - 01:46 AM.

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#2 Tom Glenn

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Posted 18 October 2020 - 01:48 AM

Nice crescent, James.  I wonder about your zero gain setting.  With my cameras, I've found that moderate gain usually produces a better result than low (or zero) gain, despite theoretical dynamic range issues, when capturing images of the Moon.  I initially thought the lowest possible gain would be ideal for Earthshine images as well, but this has not proven to be true, at least for stacked images that are then stretched.



#3 james7ca

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Posted 18 October 2020 - 01:52 AM

Nice crescent, James.  I wonder about your zero gain setting.  With my cameras, I've found that moderate gain usually produces a better result than low (or zero) gain, despite theoretical dynamic range issues, when capturing images of the Moon.  I initially thought the lowest possible gain would be ideal for Earthshine images as well, but this has not proven to be true, at least for stacked images that are then stretched.

Thanks for the comments. But, gain is one thing that I varied and I still have several other sequences to process. Also, I wasn't sure how many frames I was going to be able to capture since I was running out of both disk space and time (before moonset). So, I wanted to make certain that I got at least one sequence that wouldn't be too "noisy."



#4 Tom Glenn

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Posted 18 October 2020 - 01:55 AM

The interesting thing that I've noticed when stretching "normal" stacks of the Moon (exposed for the sunlit side) to detect Earthshine, is that the lowest gain settings always produced banding in the Earthshine region, whereas the higher gain captures did not.  Will be interesting to see your results.  



#5 james7ca

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Posted 18 October 2020 - 02:14 AM

A greater stretch on this particular sequence showed some dust and sensor blocking artifacts but nothing in terms of earthshine. Plus, the glint on Mare Smythii caused overexposure in the red channel and in fact the entire image was bright red before I neutralized the color balance (so, this initial version is NOT color accurate). Plus, there were some high clouds at the horizon which I'm sure affected both the color and contrast.



#6 james7ca

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Posted 18 October 2020 - 07:22 AM

Here is something that is probably truer to the actual color and the brightness of the sky (actually, still somewhat darker than the actual scene, trying to hide the noise and some sensor artifacts and dust on the camera sensor window). However, the image stack wasn't of very good quality (too few subs) and the JPEG compression introduced some contouring in the upload so the final result isn't very satisfying. I don't know whether anyone will be able to see the earthshine, it's there but very faint (it shows up on my uncompressed 16-bit version, but...). There is also a large dust donut right on the edge of the dark limb of the moon (flats would help, or even a synthetic flat, but I don't think the image is good enough to warrant that extra effort).

 

This was taken nine minutes later than the first image with the moon just over five degrees above the horizon. It's a stack of 512 subs using an exposure of 30ms and a gain of 20 on the QHY5III-178C.

Attached Thumbnails

  • Early Crescent Moon with Earthshine Oct 17 2020 (small).jpg

Edited by james7ca, 18 October 2020 - 08:41 AM.

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#7 aeroman4907

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Posted 18 October 2020 - 07:24 AM

Nice work James on catching such an early crescent.  In the second image I can detect the Earthshine, but just barely on my well calibrated monitor.




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