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Jupiter, 19th Feb with the ASI120MC

JamesF

By JamesF
in Imaging - Planetary

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JamesF

JamesF

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I'd pretty much decided to call it a day on imaging Jupiter this apparition, but a conversation yesterday spurred me into another effort. These are still with the ASI120MC and 127 Mak, but I've dropped the barlow down to 2x rather than 2.5x as in my previous images, bringing the focal ratio down to about f/23.5. This may still be a shade more than desirable, but it's the closest I can easily get.

I ran five capture sequences. The first used my settings from the previous session with the gain backed off a little because of the change of focal length, but still 20fps. The top left image is from this run. The camera settings for the red and blue as mentioned by Darryl (58 red, 96 blue or something like that, from memory) gives me a very blue-heavy histogram and I had the brainwave of adjusting those numbers until the three colour histograms were about equal. The next four pairs of images (left to right, top to bottom) are from runs at 20fps, 30fps, 40fps and 50fps with the gain adjusted to keep the histogram at about 85% to 90%.

I'm much happier with these images than my previous ones. The colour is much better even without tweaking it and I don't think I've lost anything in resolution over the 2.5x versions. There is a clear ring outside the brighter limb however. I think that might be down to excessive gain because it gets more obvious as the gain goes up though I've not yet ruled out a problem with the barlow or other optical issue. I'm not really sure I can see a huge difference between the 20fps versions and the 50fps ones, but if I had to pick the ones I'm happiest with I'd probably go for the 30fps ones (middle row, left and centre).

All in all a useful evening's work for me. I feel as if I've made a definite step forward here.

montage2.png

James

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JamesF

JamesF

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I was observing Jup at that time and made a sketch at 21.00 and can see that your image reflects my sketch,i noted a small white halo on the NEB but wasnt 100%,but i can see it on your image so i can confirm it.

Excellent :)

James

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budski

budski

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Hi James, I was also doing much the same thing last night with the 120MC and am also getting that faint halo effect around the limb. I don't think it's due to using hi gain because I also did some lunar images and see the same effect there at very low gain settings. I'm out tonight but shall have a good look my other test exposures from the last few nights to see if its there on the original avi files.

Will be in touch soon.

Bud

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JamesF

JamesF

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That's interesting to hear, Bud. I'd assumed the halo was due to high gain causing some sort of "spillover" effect on the pixels around the limb, but if you saw it as well then it definitely warrants further investigation. Win7 won't play the avi files from FireCapture, so I'll transfer them to Linux to view and also have a look at them frame by frame in Registax to see what they look like. I'll post a few frames if I can.

James

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JamesF

JamesF

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Cracking images again James! They look a little washed out on my screen so I've tweaked the contrast hope you don't mind. As you say that limb artifact is a concern.

A bit more contrast really works to bring out more detail, doesn't it? How are you doing that? With the contrast tool in Photoshop?

James

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tich

tich

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Very nice James when I first done some half decent images using the QHY I had a ring appear round the edge although I haven't had it since, not sure why it happened in the first place. :icon_scratch:

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