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Old 27-12-2012, 08:27 AM
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Shiraz (Ray)
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Shiraz is offline
Join Date: Apr 2010
Location: ardrossan south australia
Posts: 4,820
hi Dave

main trick is to ensure that the AVIs are short enough that the target does not blur too much due to target planet rotation. You can easily work out the maximum exposure times for your system from the planet rotation rates (eg Jupiter features move at about .25 arc sec/minute on the meridian) - with typical systems, a good starting point would be to use a Jupiter limit of about 60 seconds per colour and Saturn about 120 seconds. I use RGB (60Hz all) on Jupiter and LRGB (60,30,30,15Hz) on Saturn, with L taken at higher frame rate to beat seeing. Set your exposure time/gain to get about 75-80% histograms - leave a bit of headroom to ensure that the final result does not end up with any saturation, particularly on Saturn.

Often you will throw away most of the frames in an AVI, using AS!2 to stack say 25% (or less) of them unless the seeing is very good, so signal to noise can suffer with such short imaging times. If the seeing is very stable, consider reducing the framerate to reduce read noise. You can improve SNR by taking multiple short R, G, B AVIs and then combining the stacked results in WINJUPOS, which derotates the stacked images by cylindrical projection before RGB combining. WINJUPOS also allows you to take longer AVIs and derotate each frame before you stack in AS!2 or Registax - this removes rotation blurring from quite long sequences. Haven't had much success with that yet, probably because seeing has not been good enough.

I usually take multiple RGB (or LRGB) sequences with no delay between them and then it is possible to choose an RGB, GBR or BRG sequence that has the best combination of seeing in the channels. Its also possible to compile RGBs from non-sequential R G and B images, provided they are not separated by more than about 10+ minutes, by combining them using frame derotation in WINJUPOS. You really do need to battle your way through WINJUPOS - nothing about it is particularly intuitive, but it works exceptionally well in getting the best from your RGB data.

regards Ray

Last edited by Shiraz; 27-12-2012 at 09:50 AM.
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