playing with the moon

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lpammann
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playing with the moon
4 months ago

Last night I took out my 8" EdgeHD to play around using my K3. This scope has a 2000mm focal length at f/10. Its field of view at prime focus is slightly larger than the moon. I wanted to compare how single shots compared to images obtained by stacking frames using the K3's video mode. The first shot was taken at 1/250 sec., ISO 1000. After PP, the image was downsized to a height of 1920 pixels to match the video output and then cropped to match the width of 1080.

The next image was obtained by stacking the best 75 frames out of 150 from a video taken with the K3. Details about stacking are given below.

Not a whole lot of difference and the single shot image before downsizing is 4000x5500 compared to the stacked image size of 1080x1920. However, there was plenty of light for a single shot at f/10.

Then I put my 2x PowerMate on the scope to give 4000mm at f/20. This is where stacking begins to make a difference. First I took an 8 shot additive composite at 1/250, ISO 400. Here is the first shot in that sequence:

and here is the additive composite after cropping to 4000x4000 and downsizing to 1080x1080:

Next is a stacked image using 48 out of 60 frames from a video:

and here is a stacked image showing the northern half of the moon using the best 50 of 100 frames:

Stacking details: I did this on a MacBook Pro. Individual frames were extracted as uncompressed tiff files using MPEG Streamclip (File -> Export to other formats -> Image sequence). Stacking was done using Registax running in a Win8.1 VirtualBox VM. I applied a small amount of wavelet sharpening after stacking.

Since Saturn was nearby, I took a video of it with the K3 even though Saturn was fairly low in the sky and seeing was poor. Here is a stack of the 50 best frames out of 100 from that video shot at 4000mm:

In spite of the poor atmospheric conditions, this image still manages to show Cassini's Division in the rings, cloud belts on Saturn, and Saturn's shadow on the rings

LPA

 lpammann's gear list:lpammann's gear list
Pentax K-5 Pentax K-3 Pentax smc DA* 300mm F4.0 ED (IF) SDM Pentax smc FA 31mm F1.8 AL Limited +1 more
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