NGC3132 - yet another version

[Shiraz]

Couldn't get near Mike's beaut image, but was still pleased at the result. In particular, efforts to clean the optical system and suppress stray light seem to have paid off.

A lot of processing was required to control the dynamic range - and the stars and noise show the damage. Have also tried to ensure that the masking did not introduce "features" - but there may be some spurious structure and I intend to do a careful reprocess to check/correct. Also have some RGB and will tidy up the stars when the winter sets in and astronomy stops.

Used 6/7nm NB filters, with 6 hours Ha ( mix of 2 and 5 minute subs) and 3 hours of O3 (2m subs). 250/f4 and ASI1600, gain 100. Had more data, but all of the imaging was carried out with the moon up - the stuff I used was the highest-resolution/lowest-sky cull from a larger dataset. Seeing was about average at ~2.2 arcsec or thereabouts.

thanks for looking - advice on colour/processing welcomed. Regards Ray

[Atmos]

It is very nicely resolved Ray! Mike appears to still have a stronger SNR but he also has more exposure :)

[Stevec35]

I think that's still extremely good Ray

Cheers

Steve

[RickS]

Looks good, Ray. I would have said "great" before Mike lifted the bar on this object ;) Look forward to the final version.

Cheers,
Rick.

[strongmanmike]

Well it's pretty bloody close Ray!..an excellent image of this tiny blighter! :thumbsup:



I agree Ray, the processing required on this one was indeed difficult. I also totally agree that it is always important to make sure ones processing doesn't introduce spurious, shall we say, "make believe" detail or features and yes masks and lassoing as well as Decon, wavelettes and selective curves and sharpening etc can easily create bogus features and detail when processing objects like this one...in fact most objects really? However, in science when one reveals potential new and/or faint structures etc, in fact any structures really, in an image, they mean very little until they can be confirmed in separately collected data...so, here is a comparison of my results with another very deep image taken by the CTIO guys using a 16" RC under the excellent skies of Cerro Tololo observatory at 2200m up in the Andes:

CTIO vs Wallaroo
(http://www.pbase.com/strongmanmike2002/image/165174441/original)
Clearly all our structures and faint outer details match essentially perfectly...so they must be real :shrug:...also the OIII extends right into the outer shells and not just inside the central oval.

Again a great result Ray :thumbsup:

Mike

[Shiraz]

Thanks Colin. I should have given it a bit more sky time - particularly dark sky - but I was also working on 3 other projects at the time -no excuse, just a choice and it shows.


thank you Steve - appreciated


thanks Rick. am trying to understand some dynamic range issues with this camera - hopefully can sort it all out and improve the image.


thanks very much Mike. It is a real problem to make sure that new "features" are not introduced. That is one of the reasons I like PI so much - there are almost no mechanisms for fiddling with an image (eg no "lassoo" selection or paint facilities), so any features that creep in have their origins in the data. However, there are still user choices in mask thresholds, degree of stretching, sharpening etc that affect the outcome - so I try to stick with automated methods or mathematically sound processes such as deconvolution that are driven by measured data content rather than a whim. Also, when deciding on what is real, I always find it useful to do an automated stretch of the stacks, before any processing - that shows where the real data extends to and what general structure the dim bits have (attached). And of course, everything to do with colour is up for grabs.

On that basis, it is comforting that there is so much similarity in images of such high dynamic range (or very faint) objects.

Regards Ray

[strongmanmike]

Why'd ya take away the tri-comparison Ray? I thought it was a good illustration and confirmed you had more or less got the same as CTIO and I :shrug: :thumbsup:

Mike

[Shiraz]

because mine is not as good!!:rofl:

ok here is - image sources as in your post.

[strongmanmike]

:lol: bah! it's excellent, until now all images I had seen of this baby were nowhere near as extensive as yours! :thumbsup:

Mike

[Atmos]

Looking at those Ray, I'd say that seeing plays a big part as well. Scale and aperture are much of a muchness but Mike appears to have had better seeing when capturing. Just looking at 7-9 O'Clock

[Shiraz]

FWHM ended up about 1.8arcsec after deconvolution, so it was fairly good. The difference in structure may well be just down to preference - I tried a (very) quick and (very) dirty selective enhancement on the posted jpeg and it extracted the same sort of structure as in the CTIO and Mike's image. Of course it also mashed the stars, but that can be managed - main thing is, the detail in the outer structure probably depends mainly on the aggressiveness of the processing and that is somewhat of a choice - maybe I should have pushed it harder.

[Tandum]

Ray that looks like it's 2000 L/Yrs away.
What scope and FL are you using?

[Atmos]

Maybe a bit more exposure would allow you to push it a bit harder. Being able to decon longer before you dredge up the worms.

[Shiraz]

yep it is a fair way away and about an arcminute across. Am using a Skywatcher 250f4 Newtonian with ASI1600 camera (3.8micron pixels) giving about 0.78 arcsec sampling.


agreed, it could have done with more signal as Mike showed. I used a normal deconvolution, but then went a bit light on wavelet boosting of intermediate spatial frequencies to keep the noise at reasonable levels.

[Atmos]

I'd still be very happy with it Ray :)

[Peter Ward]

There are faint fuzzies and stars in the background field that don't show in Mike's image but are in both your and the CTIO images.

In terms of "bang for buck" the depth of the data is impressive

A very tidy effort. :thumbsup:

[Shiraz]

thanks Colin


thanks Peter. The stars etc in my image are native HaO3, whereas, I assume that Mike's are RGB - that might explain the difference. Don't know re CITO.

[Paul Haese]

Nice work Ray. You clearly had enough imaging speed to get that glow around the outer areas. I could not manage that. I did conduct the 1 hour subs test and yes it did work better, but even at 12 hours the Ha was still not really bright around the outer chevrons.

Well done.

[Shiraz]

thanks Paul. this is certainly a difficult little object and I was pleased to be able to get something in the outer regions.

I guess that 1 hour is about the practical limit for subs - do you have any plans brewing on a next phase for your setup?