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Another Horsehead and Flame

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#1 SergeC

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Posted 17 December 2013 - 10:51 PM

Well, this can't compare with Wem's outstanding shot, but it's my best effort. Blend of H-alpha and RGB (as OSC), 9.8hr total integration over 3 nights, 6.75hr of that as Ha. Gear, location, etc. are the Usual Suspects (click the thumbnail for full tech details).

Thanks for looking, comments and critiques are always welcomed and appreciated. CS!

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#2 orlyandico

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Posted 18 December 2013 - 03:41 AM

Serge, this must be with the AT8IN. Is this at native focal length? or with a reducer?

#3 SergeC

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Posted 18 December 2013 - 09:49 AM

Yep, this is with the AT8IN and the Baader MPCC MkIII. Baader claims there's no change in focal length or FOV, so I'll take their word for it and assume it's still at f4. With the QHY8 I get a FOV of ~101X67 arcmin with a 2 arcsec/pixel resolution.

#4 terry59

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Posted 18 December 2013 - 10:11 AM

You have some nice definition going. The flame a bit red though?

#5 SergeC

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Posted 18 December 2013 - 10:52 AM

Thanks Terry. I agree, but I think: a) I don't have enough color data; B) Alnitak overwhelms the chip's sensitivity in that area; c)the Ha is so strong there it swamps the other channels; d) my processing attempts to reduce the halo around Alnitak also reduces color in the Flame, contributing to ©; e) a combination of all of the above.

I may re-process this after collecting some more OSC once the moon wanes, but there are some other targets I'd like to try first.

#6 mpgxsvcd

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Posted 18 December 2013 - 11:46 AM

What spacing are you using from the coma corrector? Also what are you using to collimate with?

I have the Astro Tech coma corrector and I never can get collimation spot on across the whole frame. Yours looks great.

#7 rflinn68

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Posted 18 December 2013 - 12:48 PM

Serge, I'm not familiar at all with HaRGB processing but I did stay at a Holiday Inn Express last night, uh, I mean I did own an h-alpha filter for a whole week once. :p It looks to me like you never converted the H-alpha data to greyscale. Looks very red over the entire image. I'm sure with almost 10 hrs of integration that you have some great data there. Can you post just the h-alpha data converted to greyscale?

Travis, I also have the Baader Mark III MPCC with my AT8IN and it works tons better than the original Baader MPCC I had. Spacing should be 55mm with it. I'm not sure about the AT version but if your spacing is correct you could be getting flexure in the tube at the focuser. They are very thin tubes and are known for this. If I keep my AT8IN I will be looking into either beefing up the tube around the focuser or buying a carbon fiber tube. Other than this problem I absolutely love the scopes after I replaced the focuser with a Moonlite. The Moonlite focuser helped a ton using my DSLR but I am worried I'll have problems once I add a CCD and filter wheel. I highly recommend the Baader Mark III MPCC for these scopes though.

#8 SergeC

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Posted 18 December 2013 - 01:15 PM

Thanks Travis. I use a pair of spacers totaling 35mm for OSC and 33mm for Ha on my QHY8 on the MPCC MkIII. The MPCC Mk III is designed for a nominal flange-to-sensor distance of 55mm, which is the standard for most DSLRs. My QHY has a flange-to-sensor distance of 21mm, so I'm actually at 56mm for OSC, but it seems to work fine.

I use a slightly shorter distance with my Orion Ha filter in place because I found I couldn't get rid of some edge distortion on the stars with that filter no matter how carefully I collimated. I wound up taking 2 identical shots of a target with and without the Ha filter, plate solved the images, and found the Ha filter resulting in a slight narrowing of FOV. Experimenting with various rings I found that shorter distance optimal for my Ha filter.

I use an Orion laser collimator held in place with their precision centering adapter. I'm very particular about collimating before every session, and spend a bit of time trying to get t exactly right.

Richard, since I'm shooting Ha through an OSC, my stack is RGB. The first thing I do after generating the stack is to separate the channels and throw away G and B. Everything else I do from then on is only with the red channel.

This is that red channel Ha data I used for the final image, above, after I ran it through StarTools for some initial post-processing (Development, sharpening, HDR and wavelet noise reduction). Before I blend it with the OSC red channel I run a sequence of Dust&Scratches filter on it in PS to remove the stars so the color info for the stars comes only from the OSC data.

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#9 rflinn68

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Posted 18 December 2013 - 01:33 PM

Very nice Serge. I've always admired the fov you get with that scope/camera combo. I wish they made a mono version of that sensor. IMO, $1299 for the QHY8L is a bargain. I get a 95 X 63 arcsec fov with that scope and my Canon T3.

#10 shawnhar

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Posted 18 December 2013 - 01:53 PM

Yea really nice!
Bit vibrant on the red though, I took the liberty of messin with your image.
Using your HA data as a luminance layer in PS yields a pretty good result, but I see what you are saying about Alnitak....I hate that star!

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#11 SergeC

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Posted 18 December 2013 - 03:03 PM

OK Shawn, you have to tell me how you can add a luminance layer in PS without getting that ridiculous pink color! It's fine on a salmon, but not on an emission nebula...

#12 shawnhar

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Posted 18 December 2013 - 03:38 PM

All I did was take your color image and pasted the HA as a new layer, changed the layer mode to luminosity and dropped the opacity to 82%, merged the layers and save, then open again and paste the HA data as a new layer, changed mode to luminosity and left the opacity at 100%.
Are you saying my version was Salmon?
Once you have the color and luminosity layers you can select the color layer and go to Image/Adjustments/Selective Color and change the tone from salmon to purple, green or fire engine red if you want.

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#13 SergeC

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Posted 18 December 2013 - 03:46 PM

Any better? I applied the Ha as Lum as did Shawn, then applied selective color enhancements via layer masking.

Edit - Shawn, I was posting at the same time you were. Thanks for that!

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#14 shawnhar

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Posted 18 December 2013 - 03:49 PM

Very Nice!

#15 rflinn68

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Posted 18 December 2013 - 03:52 PM

That looks a lot better to me Serge. I can even see more of the detail around and behind the Horsehead.

I have a question. I noticed you used both bias and dark flats. Why is this? I thought you were supposed to use one or the other. Is there an advantage to using both? :shrug:

#16 Madratter

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Posted 18 December 2013 - 04:14 PM

I like this version much better.

#17 SergeC

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Posted 18 December 2013 - 04:33 PM

Thanks again, Shawn, and to you Richard.

As to your question, in Nebulosity I apply dark flats to light flats, but bias are not applied to flats in that case since bias is built into the dark flats. Bias are applied to lights during dark subtraction. So yes I use bias on my light frames, but not for calibrating my flats.

#18 SergeC

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Posted 18 December 2013 - 04:34 PM

Thanks MR, me too.

#19 TimN

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Posted 18 December 2013 - 04:39 PM

I also really like the last version. Well done!

#20 terry59

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Posted 18 December 2013 - 06:16 PM

I like this version much better.


:ubetcha:

#21 CounterWeight

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Posted 19 December 2013 - 10:33 AM

Wow, what a great difference! Very nice work, way to keep at it :).

#22 SergeC

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Posted 19 December 2013 - 02:13 PM

Thank you, Tim, Terry and Jim.

#23 Wembley2000

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Posted 19 December 2013 - 09:40 PM

Second version is very nice.

Wem

#24 SergeC

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Posted 20 December 2013 - 12:22 PM

Thanks, Wem!






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