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Saturday, October 06, 2012


My Images of the Jupiter-Moon Graze, October 6, 2012

Jupiter and Moon at 5:37 am ACST, October 6. A brief thinning of clouds allows Jupiter to be seen.6:30 am, first usable shots through the telescope with the Canon IXUS (400 ASA automatic exposure length) using 20 mm Plossl lens. Jupiter is the pale blob near the top (remember the telescope inverts the image from what you see with the unaided eye, which is why Jupiter is on a different side to the camera image on the left)
6:34 am6:44 am, Jupiter is clearly moving closer to the Moon.
6:51 am, Switch to 12 mm Plossl Lens. Black dots and such are rubbish on the CCD chip.6:58 am, despite a big gap in the clouds, seeing is degenerating rapidly.
7:07 am, gaps in cloud fewer and further between7:17 am, thin cloud making things difficult.
7:20 am, almost at graze, very poor seeing7:26 am, last "usable" shot before clouds move in completely. Barely visible Jupiter is just touching the Moon.
I love occultations, but I like grazes better, where the planet just skims over (or is only partly hidden by) the Moon better, as these are more dramatic.

Today's graze broke a long drought in bright planet occultations for me. Okay, it was during daylight, which is not so good for observation or photography as both the Moon and Jupiter are very washed out, but seeing a planet move behind the Moon in daylight is pretty cool too.

Of course it was cloudy (see my semi-live blog here), but I set up just in case there were holes in the cloud coming through. And I was rewarded with sufficient gaps to take some half-way (but only half-way) decent shots.

I used my little 4" scope, as I could rapidly move it out of the way if the cloud turned to rain (unlike the 8", which is a pain to move and have to be partly disassembled). I also used the through lens camera adapter and my Canon IXUS digital camera rather than the webcam and laptop combination for the same reason (and the laptop screen is difficult to read in daylight). 

This reduced the image quality I could get a bit  (especially as the IXUS CCD chip has started accumulating rubbish on it) but gave me better flexibility. I started off shooting through a 20 mm Plosssl lens, then swapped to a higher magnification 12 mm Lens when Jupiter got close. Give the poor seeing from atmospheric turbulence and  the persistent cloud, this was probably a mistake. Although the images were bigger, the planet and lunar brightness was better in the 20 mm.

I did a telephone interview with Ashley Walsh on 891 ABC radio, sadly the clouds were fully over at that time so I couldn't describe the telescope view for the listeners, but hopefully it inspired a few people to look. I was going to mention the scientific benefits of occulations, but got a bit carried away descibing what I hoped people would see and emphasising safety for daylight telescope use,

I did also check the view with binoculars, while I couldn't see Jupiter with the unaided eye (probably too much cloud), it was very clear near the Moon  with binoculars.

Sadly, just as the most interesting part of the occutlation turned up, the actual graze itself, thick clouds with absolutely no breaks in them came over and lurked heavily. I packed up then.

Nonetheless, despite the cloud hi-jinks and relatively poor seeing, it was a pretty fascinating and beautiful even, well worth getting up for and persisting with.

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