What to do on a braw bricht moonlicht nicht?

Blog the previous nights viewing. Link to images on the gallery or simply describe what you observed the night before. Leave the technical and howto in another forum.
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What to do on a braw bricht moonlicht nicht?

Post by rwilkinson » Tue Oct 15, 2013 11:09 am

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:
Uranus 14_10_2013.jpg
Stack of 100 (best of 300) 1.1-sec images from my LX webcam, processed in IRIS
Uranus 14_10_2013.jpg (3.25 KiB) Viewed 3006 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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