Helix Ha

[Peter Ward]

Typical Sydney weather....Just when you think you are getting up a head of steam, the clouds and rain roll in again.

A smidge of 2022 and more of 2021 Ha data can be seen here (http://www.atscope.com.au/BRO/gallery528.html)

Pleasingly, the faint arc-shaped shock fronts (upper left) are just starting to peep
through, proving for narrowband at least, uber-dark skies don't matter.

As to when I'll finally get a reasonably deep OIII and RGB set to finnish this puppy off....meh...who knows :shrug:

[LKD]

Very impressive start to the project, can't wait to see the next instalment.

[Dave882]

Wonderfully deep and detailed. Nice one!!

[Retrograde]

Looks great so far Peter. Great depth and image scale.

[Bassnut]

Impressively deep Peter, even with the dont-matter urban skies.

[rustigsmed]

Great seeing a combo of deep exposure and excellent resolution on this, looking forward to the final product - great project.

[gregbradley]

Fabulous.

Greg.

[petershah]

Lovely detail ....looking forward to seeing how it progresses :thumbsup:

[Nikolas]

it's great how you got the outer edges of the Helix.

[Peter Ward]

Thanks to one and all for your encouragement. Might get a clear night or two this week to keep hammering away at this one.
As an aside, I'm now using a short backfocus version of the QHY600m to get within a millimetre or so of the AFR's optimum focal plane. But...careful what you wish for.....as the OAG is no longer par focal with this model camera without a 10mm spacer! (defeating the reason for shifting to that model) :doh:

The fix I subsequently came up with was to place a concave lens ahead of the STi autoguider...which thankfully pushed the OAG focal plane back just enough to make it parfocal with the camera.

[AdamJL]

Great start. You hinted at something in your post… the best images of this object require tens or possibly hundreds of hours of total integration time. This is one to build up over multiple seasons I think. You’re there with Ha, now for the others…. OII is quite bright but SII is going to be fun!

[Peter Ward]

Ta. As far as I have able to determine, there is no significant SII emission from the helix.

Time better spent on RGB, more Ha or OIII. ;)

[Startrek]

Peter,
Another superb image
The level and quality of your images are more professional than amateur to be perfectly honest
What makes them even better is they are captured from the edge of the Shire ( National Park, where I’m guessing would be Bortle 6 skies
I’m down in the Basin ( St George area ) and it’s Bortle 7/8 ( SQM 18.5 )
Can’t wait to see your final result

Cheers
Martin

[Peter Ward]

Thanks Martin. With NB, only transparency becomes problematic . Sky glow really does not affect 5nm, and even less so 3nm, pass filters. You could probably shoot from Pitt Street and get similar results. :)

This was taken with a 5nm AstroDon. I do have a 3nm in my SBIG CFW (which are square filters, hence incompatible with the QHY wheel)

However, I'm getting a Frankencam part made by Precise Parts which hopefully will allow the QHY to sit behind SBIG guider/filter combination in a few weeks.

SBIG's Starchaser uses a wide field optic which picks up quite a few more guide stars than the QHY OAG.

All that said, the faint banding noise of these CMOS sensors is proving almost impossible to eradicate within narrow field images that have little to no signal. I remain optimistic however and hopefully can tame their output with refinement of the USB traffic and gain settings.

[markas]

Terrific image, Peter. The depth and detail are spectacular.

I guess a major contributor to this result is the very low camera read noise. After 5 hours Ha on Helix with my 16200 CCD camera, the chevron is still very faint.
Looking forward to the colour image.....



Mark

[Bassnut]

But what is your sub exposure time?. I suspect if you exposed long enough to overcome read noise the diff with CMOS becomes irrelevant and you could go arguably deeper with a CCD.

[Peter Ward]

Ten minutes and despite that, with CMOS, fixed pattern noise eventually dominates over extremely low signal noise (read noise is moot here)

As far as I can tell, there is no fix.

CCD's for very low flux targets would be my tool of choice.

I still have a perfectly good KAF16803 CCD based camera....and suspect for those wanting go uber-deep, these sensors will become very desirable and rare birds for those who want to push the envelope.

I'm hopeful CMOS sensors will have all of their advantages and none of their disadvantages in time.

Just not quite there yet. :shrug: