Society for Popular Astronomy

RGB experiments with Jupiter
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Author:  smerral [ Wed Jan 29, 2014 2:57 pm ]
Post subject:  RGB experiments with Jupiter

Well I've just about exhausted the data I grabbed on the 25th, on a night, it must be added, when the seeing, as per usual, was not particularly great. It's been great fun playing around with the data and I've learnt a lot and discovered some interesting things. Winjupos is an exceptional piece of software once you get used to it and I find it useful not only for the de-rotation of RGB images, but also - as I have an alt-az mount - for aligning images displaced by field rotation.

The first thing I found was quite fortuitous. I had been using the Astronomik proplanet 742 IR pass filter in order to counter the poor seeing. It works well but it does cut out a lot of light. When moving to the red filter I forgot to replace the IR cut filter. Now I need this with my cheapo baader filter set as the filters are not automatically IR blocking. I then realised that the baader filter is ALSO an IR pass filter, but with a broader bandpass into the red and therefore giving a far brighter image - the results are virtually identical. :))

During processing I experimented, compiling images from standard RGB, then using RB only and synthesising the green image from red and blue (all of which Winjupos will do for you); using LRGB (with and without synthesised green) i.e I used the red for luminance detail and the colours simply as colour values. Here are the results (synthetic green in brackets). Each capture was with the 1.5x barlow on the C8 using the ZWO ASI120MM. I put each image through wavelets etc. before combining ;)









And finally here is a prime focus enlarged 150% using LR(G)B.


Author:  Brian [ Thu Jan 30, 2014 7:43 pm ]
Post subject:  Re: RGB experiments with Jupiter

Hi Brian.

Coming along nicely 8)

It's interesting to follow the improvement in the image through that sequence. The LR(G)B image certainly looks best to me. BTW on your image, just S of the GRS is clearly seen the group of white spots that Chris GO refers to as "Mickey Mouse ears". It's like Mickey just peering over a wall, but upside down and in negative. A bit like the wartime cartoons "Wot no......?" :)

I use the Baader IRpass filter , 685nm pass but it also passes a little in the long red so visually you can see something to help visual centring.

I've now got the 120MC camera (arrived in about 2 days). Camera works with AMCap software but not with my old version of K3CCDTools that I use with the Toucams. Spent last evening installing .NET Framework so that Sharpcap will download onto my XP laptop. Took 3 hours to download and install nearly 20 updates with it!

Just off to install Sharpcap2 now :D


Author:  smerral [ Thu Jan 30, 2014 10:23 pm ]
Post subject:  Re: RGB experiments with Jupiter

Hi Brian,

I use Firecapture. It has lots of useful features. :)

Yes the LR(G)B - or more accurately IR- R(G)B - is definitely the best. Having read a few articles on this it appears that RGB is generally reckoned to be the best IF the seeing is excellent; but in our climate that is a VERY big IF - how often do we get near perfect seeing?

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