Hi-res(ish!) Saturn Nebula, NGC 7009 in Aquarius

[Dennis]

Hello,

Here is an updated Saturn Nebula, aka NGC 7009, a Planetary Nebula in Aquarius at magnitude 8.3, size 28" laying some 3200 light years away. The central star has a magnitude of 12.8. My previous best effort is shown here (http://www.iceinspace.com.au/forum/showthread.php?t=47458).

Tak Mewlon 180 F12 with Tak 1.6x extender giving F19.2 (3450mm), taken with an SBIG ST7. Brisbane, Qld, 9th October 2009.

Luminance: 6 x 10 minutes.
R, G, B: 1x10 minute each.
Calibrated, aligned, combined and maximum entropy de-convolution in CCDStack. Finished in CS4.

Overall, I am very pleased with the results; both in terms of how the system performed at this relatively long focal length and the general appearance of the final image.:)

There are some obvious faults; the max ent routine produced some dark haloes and due to frame drifting between exposures, it was difficult to normalize the background. The processing required to flatten the background and “render invisible” the frame overlaps has resulted in some unnatural looking stars and overall, the final result has the appearance of an image assembled from several parts, rather than looking like a smooth, integrated image.:(

However, I’m very pleased with my progress at capturing the data and making inroads into the LRGB process; Rome certainly wasn’t built in a day! Thanks for looking!:)

Cheers

Dennis

[Lester]

Very nice Dennis, look at the internal structure in that.

[[1ponders]]

Well now, branching out 'eh Dennis.? Nice shootin' :thumbsup: Great detail there.

[AlexN]

Fantastic work Dennis.. I dont think I've ever seen an amateur image of the Saturn Nebula that showed internal detail like that...

Absolutely stunning mate..
Well done.

[Dennis]

Thanks Lester, Paul and Alex!

I almost wrote “hi-res” in the title line, but after looking at this image (http://www.astrosurf.com/antilhue/ngc7009.htm)taken with an RCOS14.5” and ST10, I added the suffix ‘ish!

I browsed the web just to check that I was seeing actual structure in the nebula and not just processing artifacts.

Cheers

Dennis

[spearo]

well done!
a real challenge of a target this!
frank

[Dennis]

Thanks Frank!

I imaged NGC7009 when it was just past the meridian, so I had the benefit of a high altitude for the luminance data. Also, a short lived thunderstorm passed through on the previous evening which helped settle some of the dust in the murky skies around SE Qld, leading to much improved transparency. It all adds up!

Cheers

Dennis

[AlexN]

It all added up to a very nice image thats for sure Dennis.. I must say the ST7 did a very good job at F/19. The sensitivity of the ST7 over your 40D would have been a big help! It would be very interesting to see the results from the 40D on a bright nebula... Something like the Tarantula core, or M20. I would think that

[Dennis]

Hi Alex

Ahh, yes, the bliss of cooled, sensitive sensors!:)

I’m still in an auto guiding daze at the moment! Previously I had been struggling with side by side auto guiding at focal lengths of over 1500mm, using the WO 66mm Petzval as the guide scope. Now it seems, I may be able to auto guide at 3450mm for 10 mins although it’s early days yet and I need to consolidate everything to make sure that the systems “new” behaviour hasn’t just been a lucky fluke.:shrug:

Over the months of experimenting and trials, I made the following changes to my side by side set up:

Imaging ‘scope:

Removed brass compression ring in Moonlite focuser as it tended to seat just on the edge of the safety undercuts on my various 2” adapters.
Increased the number of clipping points on the mount and side by side plate to better route all my cables to minimise drag

Guide scope:

Drilled side by side plate to mount the 3 point adjustable guide rings closer to the imaging ‘scope.
Increased separation between guide rings – one close to lens cell, the other almost on the focuser.
Removed all focus tube extenders from guide scope.
Replaced grub screw based adapter with a Baader 1 ¼” rotating clamp adapter.
Fitted a WO 1.25” diagonal to reduce cantilever at focuser.

In addition:

I went through the entire system and checked all nuts, bolts, fasteners, etc and at one stage noticed that my Moonlite focuser had some slight rotational play, having worked loose over the years.
I keep the system slightly heavy against the direction of the RA drive and carefully balance the system before each session.
Adjusted backlash in RA axis.
I also tweaked the parameters in PHD Guiding, reducing guide corrections to 50% to minimise the potential for over correcting.

All in all, it has been quite a herculean endeavour as I somewhat simplistically though that just owning an EM200 conferred upon me the right to obtain round stars, straight out-of-the-box!:rolleyes:

Cheers

Dennis

[AlexN]

Yes, as is usually the case, owning a great mount is the beginning of awesome images, although I think a lot of the time people assume that if you spend big dollars on the mount that you'll get great stars from day one... I have seen the setup and configuration of a Paramount, I can tell you now that quite a bit of work goes into achieving round stars with a paramount, despite their ability to take 10 minute unguided exposures once the configuration has been properly attended too...

Sounds like you've done the hard yards to get to this point, however your efforts have not gone unrewarded! I too have recently gone to great lengths to address all the issues with my setup, and now regularly run 20~30 minute exposures without effort.. My biggest problem was my adjustable guide scope rings... Its of my opinion that adjustable guide rings were designed by satan in an effort to make astro-photographers cry. I now have my guides scope bolted directly to a dovetail by its L bracket, and since doing so I've been able to achieve very good results... All that I have left to address now is focusing... Im just too lazy to stand up and adjust focus, so its time for a motorized option.. :)

[Dennis]

Hi Alex

During the course of my investigations, I did exactly that and hard bolted the guide scope to the side by side plate in favour of the WO guide rings, but that didn’t appear to fix my elongated star issues. So, I went back to the guide rings just for the flexibility of aligning the imaging and guide scope OTA’s optical axes in an attempt to minimize field rotation.

It would have been nice to have a permanent set up, to maintain continuity between trials and help consolidate any successful changes made to the system.:)

Cheers

Dennis