View Full Version here: : Rho Ophiuchi from dark skies
20-06-2012, 11:21 PM
My latest take on the Rho Ophiuchi cloud complex from the relatively dark clear skies of backyard Griffith NSW.
Guided 19 x 8min calibrated subs @ ISO800, using a modded 400D with a newly acquired Nikkor 135mm f3.5 AI prime wide open at f3.5. Ambient temps of around 0.5 C. Processed in PixInsight.
high res version here (http://astrobin.com/13250/)
I also collected 38 x 4min subs earlier that evening, on the other side of the meridian so the framing is not quite the same (close but not exact). Any tips on how i could combine the two image sets in Pixinsight welcomed.
20-06-2012, 11:25 PM
Deep Sky Stacker would handle it very well. :)
21-06-2012, 09:24 AM
a different processing attempt of the above 8min set. which do you prefer?
high res version (http://astrobin.com/13250/B/)
21-06-2012, 09:25 AM
New version much better!
Amazing difference. What did you do differently?
Mate, the repro is much much better! Well done.
I will be trying the trial version of PI soon, so like Mike, I would also be interested in what you did differently.
21-06-2012, 11:12 PM
thanks guys - good to get a bit of feedback so i know whether or not i'm on the right track.
There were several changes with the second repro.
1. less aggressive with the dynamic background extraction
2. stretched much more this time with the histogram transformation
3. more layers with the HDR wavelets
4. second stretch, using a luminance mask so as not to unduly blow out the bright stars
5. beefed up the saturation with curves
Here's another look at the Rho Ophiuchi region from a few weeks back using a 50mm Nikkor prime, given a similar pixinsight treatment to that outlined above. (26 x 4min calibrated & guided subs @ ISO800)
22-06-2012, 06:45 AM
A very nice Rho shot.
The magenta in the bright stars is from chromatic aberration in the lens.
In Photoshop you correct this using selective colour tool and set to magenta and adjust the sliders until it goes away which it will.
In PixInsight I am not sure how that is done but it must have a similar tool.
22-06-2012, 07:40 AM
Great colors and processing. :thumbsup:
22-06-2012, 07:51 AM
I much prefer the second version Richard.
Not sure why you're having trouble merging data from either side of the meridian. I simply calibrate the files and then do a Star Alignment to register all the files (pick your best sub to use as the Master). PI will usually rotate the images 180degrees as required. Then integrate all of the registered images.
There will obviously be areas were things don't overlap properly - just crop these out.
22-06-2012, 10:43 AM
David - it's not the alignment per se that's the problem, it's that they're at different exposure times.
During image acquisition, i initially dialled up a series of 4min subs to finish about 11pm as i was expecting cloud from about midnight onwards. however with no sign of clouds i thought I would set up another set of subs, this time at 8mins. So, i have a ~3hr set of lights/darks at 4mins, and a ~3hr set of lights/darks at 8mins (plus flat and bias masters).
I've still got my Pixinsight trainer wheels on, but what im looking for is the best way in Pixinsight to combine those two sets of subs.
Anyway, thanks for all the tips guys - i'm learning heaps :)
22-06-2012, 11:10 AM
The normalization/weighting process should take care of that. Just do a normal integration and it should turn out fine.
22-06-2012, 12:34 PM
well that makes it easy! cheers for that :cheers:
22-06-2012, 12:38 PM
Sorry - I didn't realise you mean different times.
You could process them as two separate groups and then do a HDR combine - have a look at Rogelio's website for a tutorial.
22-06-2012, 01:19 PM
Very nice view Richard. All the best.
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