Author Topic: NGC6995 (Eastern Veil Nebula - part of)  (Read 38 times)

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NoelC

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NGC6995 (Eastern Veil Nebula - part of)
« on: Sep 12, 2019, 23:17:47 »
Taken last night in an unexpected clear night, after finally getting plate solving to work in APT (yipee).

Taken at f8, bin 2x2 (1.2"/pixel) H.O.S pallet, stacked in AA5.
May have a go at the rest of it later.  Is the colour too bright? - I don't think so, but it's unusual for me to get any colour in my images.
Synta mount, a bunch of telescopes and a shed (on wheels).

Carole

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Re: NGC6995 (Eastern Veil Nebula - part of)
« Reply #1 on: Sep 12, 2019, 23:50:09 »
Making progress Noel.

Two comments, I think you have clipped the data in the red channel, this will result in loss of nebulosity.
I'd go back to the stacked image and start again.

I would also have a fiddle with the colours and try to get the Oiii blue rather than green.

Otherwise a good effort.

Carole

Apophis

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Re: NGC6995 (Eastern Veil Nebula - part of)
« Reply #2 on: Sep 13, 2019, 07:30:30 »
Nicely framed with the best part of it,colours aren't a problem but Oiii does come out Blue usually ,like me its getting the most of the fine detail out of the data , i still struggle. Try in astroart TRICHROMY using Ha for red and Oiii for BLUE and GREEN OR Ha for RED with BLUE and Green.

then you can load into PS and do a simple stretch and fine tune.If you need any help PM me.

HTH
Roger

NoelC

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Re: NGC6995 (Eastern Veil Nebula - part of)
« Reply #3 on: Sep 13, 2019, 09:23:14 »
Thanks Carole and Roger
Roger - used Trichrometry to assemble it as you suggested, but had used OIII as green and SII as blue.
Carole - will take another look at it; I stacked it half a dozen times because nothing was coming out when using a bias frame.  Suspect there is a problem with my darks (may have used a bias frame on them), but did do flats and flat darks for once!  There are some guiding artifacts, the guiding was good (0.5')when it was near the zenith (for once), but degraded in RA as it moved west (balance?).
Will have another look at it.

Noel
Synta mount, a bunch of telescopes and a shed (on wheels).

Carole

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Re: NGC6995 (Eastern Veil Nebula - part of)
« Reply #4 on: Sep 13, 2019, 10:36:18 »
Regarding your question in your E mail which i forgot to Answer.

There are no real rules with narrowband how to assemble the channels, but there are some traditional methods.

HOO (but you have also used Sii so HOS is not unreasonable).
SHO but the hydrogen does have a tenancy to be brown/muddy tones (once you have tamed the Green).

I think in this instance you have used the right palette, SHO in this target looks pretty revolting.
Carole

Apophis

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Re: NGC6995 (Eastern Veil Nebula - part of)
« Reply #5 on: Sep 13, 2019, 12:12:29 »
Apparently BIAS frames are problematic and muck things up , i haven't used them for years. Try HOO in astroart see what comes out and then save and stretch in PS , then split the channels in PS and paste the SII to the blue channel and choose the best blend mode merge channels back and play with hue/saturation.
Roger

Carole

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Re: NGC6995 (Eastern Veil Nebula - part of)
« Reply #6 on: Sep 13, 2019, 13:10:38 »
I must confess I have had problems with Bias frames over the years too.  But not all the time.  My images come out a right mess when I do have a problem, I then re-stack without the Bias and the image is fine.

Don't understand it or why it only happens sometimes.  So much of the time I don't bother to use them.
I keep meaning to post up an example (with and without) for the more techy people to comment on, but keep forgetting.

Carole