Something more familiar: NGC 253 in colour

[Placidus]

From this weekend. Just looked at the same beast from Star Shadows Remote Observatory in New Mexico where they report 0.5 sec arc seeing, and wept. Ours is much less sharp, but feature by feature it seems to be the same galaxy. (In our favour though, all our scope control electronics, firmware, and software, and all our image processing software is written in house so ours is more home baked. :) )

A 1:1 version (1.8MB) is here. (http://www.mikeberthonjones.smugmug.com/Category/Astrophotography-at-Placidus/i-XCVtWG5/0/O/0073%20NCG%20253%20L%207hrs%20RGB%2 01hr%20each.jpg)

Of interest is the way the highly detailed, colourful, dusty, clumpy spiral arms are embedded in a relatively featureless grey halo which is surprisingly wide.

Luminance 7x1hr unbinned subs, RGB 1 hr each, 2x2 binned. Aspen 16M on 20" PlaneWave CDK on MI-750 fork.

Best,
Mike n Trish

[NOMH]

Great image, Mike. New Mexico is about an 8 hour drive for me and I swear I will make it there some day to image. Whether I rent a place in the mountains for a week or drive out and camp. It really is a beautiful mountainous area with some of the darkest skies in the US. Sure beats my Bortle 6 home or my Bortle 4 "dark site".

JB

[RickS]

Hi Mike & Trish,

At 1:1 it looks a bit "wormy" like a decon went wrong? Even with ordinary seeing I would have expected more detail. Perhaps a reprocess would produce a much better result...

Cheers,
Rick.

[Placidus]

Guilty as charged. Too much wavelet sharpening.

[RickS]

I have been guilty of far worse :lol:

[strongmanmike]

As usual Mike, plenty to love about viewing this image mate, grand and with beautiful colours :thumbsup: Heck you are loving these 1hr subs too huh?.. very cool... buuut I do agree with Rick, actually I have noticed the same effect in some of your other recent work but it wasn't quite as noticable and so I didn't pass comment. Wavelets and decon can kill an image I recon creating what I call psuedo-detail that looks kinda like turning all the detail shapes into point sources and it is often very noticable. If you get rid of this effect this NGC 253 should be an incredible image and I hope you do as I would love to see it :)

Mike

[gregbradley]

Nice image Mike but tend to agree I would have expected more detail. Perhaps the seeing was not too good as well.

I use a CDK17 and its quite susceptible to seeing. On poor seeing its not really worth it. Sometimes the long focal length/aperture works against you but on some nights its unsurpassed.

Are you using an AO unit? It could be a great benefit.

Greg.

[Placidus]

Guys I think you are right. Thanks for the frank and helpful insight!

I am also a bit disappointed with the sharpness that I'm achieving. The FWHM on a 10 second focus shot on a good night near the zenith is typically about 2.2 sec arc. I think collimation is ok. We like living where we live, and it's a good dark site. Can't have everything. So as you quite rightly point out, I've been trying to over-compensate by decon and wavelet sharpening. Doesn't work.

Here is a reprocess of the monochrome stack only (http://www.mikeberthonjones.smugmug.com/Category/Astrophotography-at-Placidus/i-95g4sKT/0/O/NGC%20253%20L%205hrs.jpg)


The stacked FWHM was 4.7 pixels, or 2.6 sec arc. So guiding, tracking, and stacking can only have added 0.5 sec arc and aren't really the main culprits. After gentle decon, the FWHM was 3.5 pixels, or 1.9 sec arc. The non-linear stretch brought it back up to an apparent 3.8 pixels or 2.1 sec arc. Trying to stand back a bit, I think these numbers aren't shameful. Moving forward, I think I can try to pick the best nights, and go easy on the sharpening.

Accepting the limits of the seeing, short of selling the farm and moving, I think the strength of our set-up is the ability to do pretty long runs on very faint objects in narrowband, but I hope you will put up with us posting the occasional galaxy even if it isn't our forte. It's fun.

Best,
Mike

[marc4darkskies]

Nice going Mike, the monochrome version looks very good! :thumbsup: Now bung the colour on and you're cooking with gas! :)

Your decon is actually quite heavy though IMO. By way of comparison my "gentle" decon is about half what you do. Also surprising that I appear to be getting better seeing than you here on the outskirts of Sydney!! For my 253 the stacked FWHM was just under 2.1" before decon (best sub was 1.79"). I don't get that seeing very often though. :sadeyes:

Cheers, Marcus

[RickS]

That's looking much better.

[Placidus]

Thanks, Rick, Marcus,

that's been very helpful.

Very best,
Mike

[strongmanmike]

Nice improvement Mike, looks less waveletted :)

Mike

[gregbradley]

Yes I think the same, that is a nice improvement.

Greg.

[Placidus]

Thanks Mike, Greg,

All is a little clearer now. No more over-processing.

Best,
Mike

[Ross G]

Hi Mike,

A great looking galaxy photo.

Nice composition and I really like the colours.

Ross.