#1  
Old 12-05-2009, 11:38 AM
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dugnsuz (Doug)
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H alpha Newbie Questions

Hi all...
Last night saw first light with the Astronomik 12nm Ha EOS Clip filter on board - imaging under a 95% moon!
Dodgy focusing and variable cloud cover play played havoc with the session, but overall quite happy and keen to proceed with HaRGB imaging.

7x10 min subs, 280mm f5.6 iso1600 - pic is the red channel only.
http://s327.photobucket.com/albums/k...Go-Low-Res.jpg

Wasn't too sure what to do when I saw all these dark red images on screen - guessed that all the relevant Ha data is in the red channel only!?

Question - how do others deal with Ha filtered images from a DSLR?
Channel split the RGB image and use the red channel or something else??

Happy to see no reflective light cone on image like that obtained with the Hutech LPS2 filter - that was my major concern.

Focusing and framing was a pain - could focus easily on bright stars via LiveView, but framing Eta was impossible with filter in place. Had to remove filter...frame Eta...replace filter...shoot.
This obviously lost the focus so had to take multiple test shots to find best focus - pic shows I wasn't 100% successful!!!

Eta's core is very burned out - wonder if I'll have to try shorter exps and a layer mask method. That surprised me as the FSQ Ha shot I obtained from GRAS 012 was rich in detail around the core. Also noticed that the Green and Blue channels were the ones that had detail on the Keyhole nebula (but they were discarded!!).

Noise looks likely to be an issue too!

Any ideas comments, advice, gratefully accepted.
Cheers
Doug
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  #2  
Old 12-05-2009, 01:06 PM
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multiweb (Marc)
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Cool pic Doug Yeah I just keep the red channel for Ha. The core burns out pretty quick. At f/5 on the ED80 , 10min subs is pushing it. I guess you can do masks with different exp time in PS like M42 just for the keyhole area.
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Old 12-05-2009, 01:21 PM
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Cool pic Doug Yeah I just keep the red channel for Ha. The core burns out pretty quick. At f/5 on the ED80 , 10min subs is pushing it. I guess you can do masks with different exp time in PS like M42 just for the keyhole area.
Cheers Mark - so you get core burn out too! I think that GRAS FSQ 106 + SBIG CCD Ha shot spoiled me a bit in terms of my expectations!!
I will persevere (...my old school motto!)
Doug
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Old 12-05-2009, 03:47 PM
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Go Duggie, new toy, atta boy.
Just focus on a bright star closeby, and then re-frame.
Even when I had a OSC camera I split the image into R,G, and B, so do this again with yours, and biff the G and B. Convert to mono with the software you are using and process that.
Ask yourself though, could have gotten an image like that with the moon as close prior to this filter, LOL.
Gary
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Old 12-05-2009, 04:18 PM
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Go Duggie, new toy, atta boy.
Just focus on a bright star closeby, and then re-frame.
Even when I had a OSC camera I split the image into R,G, and B, so do this again with yours, and biff the G and B. Convert to mono with the software you are using and process that.
Ask yourself though, could have gotten an image like that with the moon as close prior to this filter, LOL.
Gary
Cheers Gary!

Another Qu. - Is it best to extract the red channel on each individual sub and then stack or stack the RGB subs then extract the stacked red channel?? Or, does it matter!!??

Agreed re moonlight imaging - S'wonderful!!!!
Doug
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Old 12-05-2009, 05:23 PM
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Doug,
not sure, and I suspect it will depend on the processing software. Foe example, CCDStack de-bayers all the subs into Red, then later you do them into green, and later still blue, if you get my drift. So I just do them into red, and don't bother with the rest.
What software?
Am doing the moonlight thing myself, new camera, and a break in the abysmal wild weather we have had, and are continuing to have, a short hiatus so to speak.
Gary
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Old 12-05-2009, 05:31 PM
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What software?

Gary
ImagesPlus (mainly) or Nebulosity for stacking/aligning/combining and PS CS4 for processing.

Doug
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Old 12-05-2009, 05:45 PM
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For the 1st time in a long time, I took a pic of a star cluster with my 40D a couple of days ago with the same Ha clip filter installed. Counterintuatively, there was significant data in the green and blue channels (no idea why). I tried a whole lot of combinations with DP pro, CCD stack and PS, (red only, RGB into PS and CCD stack, converting to mono in CCD stack/DP/PS in each before the next step etc) and Im hard pressed to tell the difference bettween them. Mind you, I only had stars in the image.

One odd thing was, converting to tiff in DP, processing in CCD stack and saving as fits and then opening in PS via fits liberator showed a res of 72 pix/in. Clicking "open in PS" in DP then showed 360 pix/in (same image size) in PS, havent worked that one out yet (I also captured in sRAW by mistake BTW).

I would say now, use all the data you have (RGB) and convert to mono in DP or PS, cant see an advantage in chucking data out. And its probably easier, rather than seperating out just the red channel.
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Old 12-05-2009, 06:23 PM
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I would say now, use all the data you have (RGB) and convert to mono in DP or PS, cant see an advantage in chucking data out. And its probably easier, rather than seperating out just the red channel.
Interesting Fred - would certainly save a lot of faffing about!!

When you say 'mono' do you mean convert to greyscale in PS?

Doug
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Old 12-05-2009, 06:24 PM
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Bassnut (Fred)
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yes

And...... yes framing is a pain , focus was soooo easy though, live view is so cool, beats cooled CCD focus hands down (on stars anyway). BTW, automated rigs go to the trouble of slewing to a specific mag star (via a catalog) to focus and then slew back to the target and plate solve again etc, such a convoluted excersice.
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Old 12-05-2009, 06:41 PM
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yes

And...... yes framing is a pain , focus was soooo easy though, live view is so cool, beats cooled CCD focus hands down (on stars anyway). BTW, automated rigs go to the trouble of slewing to a specific mag star (via a catalog) to focus and then slew back to the target and plate solve again etc, such a convoluted excersice.
Just tried converting a sub to grayscale - awful!!!
All the contrast/detail in the red channel became washed out and bland looking.
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Old 12-05-2009, 07:26 PM
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oh, OK, ill have another look at it then...........mmmm
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Old 12-05-2009, 07:46 PM
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oh, OK, ill have another look at it then...........mmmm
No dramas Fred - I'll just stick with the RGB split method...seems to yield the best results for me.
Thanks for the help.
Clouds rolling in down here in SA stuffing up my plans for a nights experimentation!!
Doug
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