Crescent Nebula NHO

[DaveS]

A first iteration, just 2 hours each of HII and [NII] plus 80 mins [OIII] I was aiming for more [OIII] but got clouded out.

Stacked in AstroArt Sigma Add, Darks and Bias but no Flats as they were making things worse, something to investigate. Each stack aligned then given DDP while keeping a close look at the Histo before Trichomy. Finally a bit of Histo Stretch.

The green clouds in the background are expected as they're almost pure HII. Perhaps taking a set of [SII] and mixing them into the red channel might help, but they will come later.

I need a new set of HII, as the stars look bloated in this, I suspect slightly off focusing. plus a lot more [OIII]. There are also coloured speckles that look like hot pixels, but the removal tool in AA won't touch them.

Any other suggestions (Yeah I know. Dump it and start again) welcome.

[DaveS]

Oh, NOO...

While waiting for darkness, and still debating whether to get more [OIII] or a new set of HII I did a bi colour version, using N, O, O rather than the more usual HOO, given the rubbish HII.

Got some alignment errors which I couldn't be bothered to crop off. After alignment, DDP on each while looking at their histograms (Both open), followed by Trichomy and a bit of gentle linear histogram stretching.

Just a bit of fun really.

Edited July 3, 2019 by DaveS

[AbsolutelyN]

This second version looks much better, lots of blown out details in the original which are far better controlled here. What's it taken with?  

[DaveS]

Thanks, yes I think the bloated HII may be giving me problems.

TS Photoline 130 f/7, TS 2.5" flattener, Astrodon 3nm filters, SX Trius 694 mounted on an ASA DDM60 Pro, encoder guided. Capture with Maxim DL6

[Tom OD]

2nd version looks  much better. very nice detail.

Tom.

[DaveS]

Thanks Tom

Going to get a new set of HII data, 2 hours of 10min subs.

 

Edit: that's if the IT allows me to. Getting so many errors it's doing my head in. Could well be USB related, possibly in the camera.

Edited July 3, 2019 by DaveS

[Dark Horizon]

That second image is much better. This target is a really nice in Bicolour as the Sii doesn't really come through in a Tricolour.

Well done, very nice!

 

[DaveS]

Thanks, yes it's much better.

Knowing that this object is relatively weak in [SII], I took 2 hours worth of [NII] instead, since Wolf-Rayet objects are often rich in nitrogen emissions.

May try to get a bit more [OIII], but I think the time's come to send the camera off to SX for servicing and move on to another target.

[DaveS]

Last night I took a new set of HII subs, paying more attention to focus, plus four more [OIII] to bring the total to 6 hours. Unfortunately the camera had rotated so I've had to do some pretty severe cropping

Nitrogen, 12 x 600 sec mapped to Red

Hydrogen, 12 x 600 Sec mapped to Green

Oxygen, 12 x 600 sec mapped to Blue

ie, as the HST but with [NII] replacing [SII]

After alignment and Trichomy, DDP then a gentle Histogram Stretch, slight boost to green to try and clear the magenta tint in some of the BG. Slight reduction in saturation from 50 to 40 on the AA slider as I thought the original was a bit gaudy.

The green clouds are due to HII. The slight yellow tint may be due to overlap between HII and [NII]

There are red speckles in the background which hot Pixel removal won't touch, I think they are due to cooling problems when taking the [NII] data causing the camera to warm up and become noisy.

[Gina]

That's different - like it.

[DaveS]

Thanks Gina

I think I'll park this for the time being, as I've become a bit dubious about the data. My stacks are only showing 12 bit instead of 16, and in fact the Sigma Average of 1 hour HII only showed 8 bit .

I've sent an email to SX so hopefully at some point it will be going back for servicing.

Disappointingly the [NII] hasn't brought as much as I'd hoped. There's a slight orange > yellow gradient implying a variation in abundance, but it's subtle and needs a gaudy saturation boost to see it.