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pete_l

Checking out a Point'n'Shoot

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Last week Canon were selling off some refurbished A490s on their eBay site. I was lucky enough to grab one of these for £25 and decided to give it a run, astronomy-wise. I'm pleasantly surprised with the result

orionrawstackthumb.png

Click here for the full sized version

Before I took these, I loaded some modded firmware, CHDK, onto the camera. This gives lots of extra features, some are even useful - such as the ability to shoot RAW mode which I used here.

I limited the length of each exposure to 15 seconds, as longer times produced trailing, which limits the sensitivity of the frame. The CHDK firmware includes some user-written scripts and I used the intervalometer script to automatically take a series of shots. Being RAW images, there was some glow from the CCD inthe top left corner. Usually this is processed out as the camera performs dark image subtraction for long exposures. I suppose I should take some darks too. However, being a 10MPix image, the affected portion was a long way from this cropped part of interest.

The RAWs were imported into DeepSkyStacker (v3.3.2) and the best 35 were selected. A small amount of Photoshop was applied to remove my light pollution gradient and sharpen up the image slightly.

Edited by pete_l

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a nice find for £25........and a nice little aeroplane at the top of the pic :-)

I have a Canon Ixus 70 which I might mod with CHDK if that's possible, I'll check it out on t'internet

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on closer inspection I can see evidence of 3 planes :-)

Yes, living within 50 miles of LHR, we have an additional source of light pollution. That cropped image is about 1600x1600, so it's only around ¼ of the full FoV.

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Looking at the 'plane' at the top I dont think it is a plane. It has 35 distinct dots on the trail meaning it was in every shot. At 15 seconds per shot that is roughly 9 minutes. A plane would cover that section of the frame much much quicker even at a great distance. It must be something else

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Looking at the 'plane' at the top I dont think it is a plane. It has 35 distinct dots on the trail meaning it was in every shot. At 15 seconds per shot that is roughly 9 minutes. A plane would cover that section of the frame much much quicker even at a great distance. It must be something else

that's a good point Philip, I hadn't taken the time it would take to get the 35 exposures into consideration

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on closer inspection I can see evidence of 3 planes :-)

good lord how? I cant see **** all!

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