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Old 11-02-2019, 03:51 PM
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ChrisV (Chris)
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Thor's Helmet

Thor's Helmet taken with an ASI071 OSC using my new toy an STC-duo filter. So fake HOO? Using an 8"F5 GSO newt on CGEM mount. 40x 6min subs over 2 nights. Processed in PI as an OSC image.

I probably should have taken longer subs as I wasn't swamping read noise. But was nervous enough about 6min subs - I've never had to go this long before on my OSC camera before.

Comments please, thanks for looking.
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Old 11-02-2019, 05:08 PM
glend (Glen)
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Looks great Chris. Certainly looks like narrowband, and sub lengths are right. Your still going to be Moon affected though, if it is allowing Oiii through. At least it stops sky glow pretty well. I am curious as to how you process to allow Orange stars to show up, which should be blocked, did you colour rebalance?
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Old 11-02-2019, 07:27 PM
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Thanks Glenn. I was blown away by the low background level and even more so - the lower noise associated with it.

I didn't do any color balancing. The filter lets through HO and the O hits G+B on the Bayer matrix, so looks like enough to maintain star colors. But I have to check what colors the stars in this image are actually supposed to be.

I'm doing tarantula and ngc3324 tonight to see what something with more Halpha looks like.
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Old 11-02-2019, 11:06 PM
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Lovely image. Just did some reading about the filter. Sounds intriguing.
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Old 12-02-2019, 08:58 AM
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Stunning image, by far my favourite DSO.
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Old 12-02-2019, 09:55 PM
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Nice one Chris, the duo filter certainly making it look like a HOO image.
I'd be tempted to bring out the red a bit more, but that's personal preference.
A good image.
Bo
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Old 12-02-2019, 10:00 PM
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multiweb (Marc)
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Looks great! Very sharp and deep. Beautiful.
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Old 15-02-2019, 12:14 PM
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Looks good Chris. Nice wide field but still keeps a good size for the helmet.
Maybe needs a bit more of the Ha to show through.
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Old 15-02-2019, 05:36 PM
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Thanks Graeme, Jacob, Bo Marc & Geoff.

No, the image doesn't have much H-alpha. I tried to push the H-alpha but it didn't improve it. Maybe I'll try and separate the colour channels and redo it - I'll have to read that bit of the pixinsight book as I have onyl done OSC processing before. I've tried other regions with more intense H-alpha (NGC3324, NGC2070) and they have much stronger reds. Or maybe I just need more/longer subs.
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Old 17-02-2019, 12:25 PM
Stevec35 (Steve)
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That's a nice sharp wide field image Chris. As others have said maybe there should be a bit more red but I would still be pretty happy with it.

Cheers

Steve
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Old 06-03-2019, 05:54 PM
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Looks great. Very sharp
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Old 07-03-2019, 05:18 PM
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Thanks Nev. Now updated to 8 hours of 6min subs. Got some red in it now.
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Old 07-03-2019, 05:49 PM
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Quote:
Originally Posted by ChrisV View Post
Thanks Nev. Now updated to 8 hours of 6min subs. Got some red in it now.
That's a great image Chris

In as much as needing more red, I'd have to agree. Based on the fact that you're using the STC filter and a OSC camera, you could (should?) consider doubling the red intensity/saturation in processing, since the OIII band is represented by 3 times as many pixels as the Ha band (Bayer Matrix: 1Red, 2 Green, 1 Blue), albeit at slightly lower camera relative sensitivity around the OIII band (approx 55%) versus approx. 80% for the Ha band.

Given that it's bicolour image, that works out that the red channel should be pumped up 2.06 times its existing value to represent "reality" and correct for the differences in number of representing pixels ([Ha] RED vs [OIII] BLUE +GREEN) as well as the differences in the camera's sensitivity in the OIII area of around 500nm and Ha area around 650nm as can be seen in the Relative Sensitivity Curve for the ASI071 below.

It would be interesting to see the change to the image. The only penalty may be that it might bring out some background noise, but given the exposure time you might be OK with that.

Best
JA
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Last edited by JA; 08-03-2019 at 11:50 AM. Reason: corrected sensitivity to 55% (was 65%)
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Old 08-03-2019, 09:31 AM
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Atmos (Colin)
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I've been curious to see how this filter performs and it looks to do quite a good job. A few months ago I received an ASI094 that I'd be interested in being able to use in Melbourne and this does appear to be a possible way of fighting the light pollution with an OSC.

The colour balance may not yet be perfect but it's certainly nothing to scoff at considering what you can now do from light polluted suburbs.
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Old 08-03-2019, 12:13 PM
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ChrisV (Chris)
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Its worth a go. I'm 15km from Sydney CBD, so there's a reasonable amount of light pollution.
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