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 Post subject: What to do on a braw bricht moonlicht nicht?
PostPosted: Tue Oct 15, 2013 11:09 am 
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Joined: Mon Oct 12, 2009 6:47 pm
Posts: 1267
Location: Bolton
When it's clear(-ish) but the sky's too bright for deep-sky imaging, I sometimes try for a planetary image. But as none of "the usual suspects" (Venus, Mars, Jupiter or Saturn) were visible last night, I decided to give Uranus a try.
I'd made one attempt at this planet some years back, but with it being so much fainter than the others, I couldn't get a bright enough image onto my webcam's sensor. However now that I've modified the camera for long exposures, I could have another go.

The main difficulty in imaging planets at high magnification is the seeing - the turbulence in our atmosphere. And with Uranus being relatively low in the sky (only 27 degrees above the horizon at 9pm), I'd be looking through quite a thick column of air. The usual technique is to take very short exposures (less than 1/30-sec) to try to "freeze" the brief moments of good seeing, but with exposures of >1-sec I couldn't do this. Nonetheless, I captured a few sequences of 300 images (as .AVI files) over 1.5 hours - the results got steadily better as the air in my telescope tube settled and the planet got higher in the sky - but then it started to cloud over. :(
All I'd managed to capture was a fuzzy blue disk, so I decided to try the planetary registration functions in IRIS for a change (rather than RegiStax). It was soon apparent that the Blue channel was suffering more dispersion than the red or Green, so this was all I managed to salvage:
File comment: Stack of 100 (best of 300) 1.1-sec images from my LX webcam, processed in IRIS
Uranus 14_10_2013.jpg
Uranus 14_10_2013.jpg [ 3.25 KiB | Viewed 2703 times ]

Well, it's clearly showing a disc, and some colour - and it's my first image of this planet. 8-)

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