M83

[codemonkey]

Had another crack at M83 this year. I spent a bit over 10hrs gross on this, and netted about 6hrs of data. I was shooting mere 35s exposures at high gain (250) for all LRGB filters to try and optimize resolution. The problem with that is with SGP and my imaging computer, the overhead between downloading frames, settling and filter changes it about 17-18s, so I lost a *heap* of imaging time doing it that way.

On the bright side, I got some of the sharpest broadband subs I've gotten, with some G frames down to 1.6" The resulting super luminance had a median FWHM of 2.17" in the central 1000px of the frame (flattener spacing isn't *quite* perfect, so I tend to focus on the middle :p)

Not sure about the processing on this one. Optimised for the stars and thus compromised some other aspects of the image. May re-do it yet...

Bigger, higher quality version on Astrobin here (http://www.astrobin.com/297002/).

Edit: Replaced image with re-processed version.

[Atmos]

Exceptional job for a sub 5" scope Lee! The resolution is fantastic!
Out of curiosity, how often were you changing filters?

I must say that settling time is the absolute biggest improvement that I get upgrading from the EQ6. The EQ6 would sometimes settle nicely in 5s, sometimes 30s+!
I don't even have one anymore :thumbsup: Due to the theoretical smoothness of your guide graph, your Linear should be significantly better than your EQ6 was in that regard too :)

[atalas]

Very nice result Lee:thumbsup:

[glend]

Great Lee, nice central detail coming through.

[cometcatcher]

Very sharp Lee. 35 sec subs hey..... Well you've just given me all sorts of ideas now with astro cams. :P

[codemonkey]

Thanks Colin :-) In order to try and balance out overhead whilst overcoming FPN, I was running LLLLRGB<dither>. I could have run multiple RGB but that would have come at the cost of less luminance and wouldn't have decreased the overhead that significantly.

Settling isn't *too* bad, usually a couple of seconds between frames. To be honest I only want to settle when dithering, but that's not an option as far as I can discern. Currently I settle at < 1px for 2s which means guaranteed 2s overhead every frame. After dithering it can take a bit longer to settle (I use extreme dithering x2).



Thanks Louie :-)



Thanks Glen :-)



Thanks Kevin :-) Short subs can work well but you need a camera with low read noise. I wouldn't try this with an 8300 for example, but with the new low read noise CMOS chips it becomes an option. Of course you don't really *need* one of those cameras, but it hurts your integration a lot less with them than with traditional higher read noise CCDs.

[cometcatcher]

Thanks Lee. That is a VERY useful piece of information that I was looking for. The ZWO CMOS cams are in my sights. Don't know which one yet exactly but I'll decide when Bill stops sending me letters.

[topheart]

Very very nice...lovely colour!! Sharp!
Cheers,
Tim

[traveller]

Very nicely resolved Lee.
Great job.
Bo

[codemonkey]

No worries Kevin, glad I could help. That Bill's a right ol' prick! It's hard to beat the ASI 1600 in this price range.



Thanks Tim :-)



Thanks Bo :-)

I've uploaded a reprocessed version, which I'm happier with. Stars aren't as nice, but the target is better. Pretty sure I'm going to get a visit from Mike soon though, muttering something about worms... ;-)

[alpal]

Hi Lee,
great work - one of the sharpest M83's ever posted.
That ASI camera is really performing well for you
& enables the shorter frames to be stacked well.
The low read noise of 1.2e @30db gain is making a difference.
You also had superb guiding & a low FWHM.

cheers
Allan

[cometcatcher]

That's even nicer. :thumbsup:

[RickS]

Very nice, Lee! The detail is great. That's definitely an advantage of a low read noise camera and short subs. I would have gone for a less cyan look and fixed the pink stars but not everybody agrees with my sense of colour (especially my wife...)

[codemonkey]

Thanks very much Allan, I'm pretty pleased with the resolution given a 5" scope in Australian skies :-)



Thanks Kevin! :-)



Thanks Rick :-) Funny you should say that, I just had it open in Photoshop and was thinking it looked a little too cyan. I think pink stars is due to some bloating in the blue channel and me being too lazy to reduce the stars to compensate.

I'm thinking I may actually get a bunch more data (skies/weather permitting), perhaps switching back to more traditional exposure lengths, at which point I'll reprocess and probably tweak the colour some.

If I had an infinite amount of spare time I'd like to write some software that minimizes the overhead for this kind of capture, but right now it's pretty nuts to try and go deep whilst throwing away ~40% of your imaging time.

[Slawomir]

I love it! So many little galaxies in the background!

It would be awesome to add more data and thus give a bit more contrast to those tiny smudges and fuzzies. Cannot see anything wrong with flattener spacing either.

Top image Lee :thumbsup:

[Placidus]

Heartfelt congratulations. That is extraordinary. Both beautiful, and amazing technically.

[marc4darkskies]

That really is a very nice result Lee. Nice work! :thumbsup:

If it were mine though I'd tone down the HII regions a little bit.

[strongmanmike]

A really beautiful M83 Lee, I like it just the way it is, a joy to view :thumbsup:

Mike

[Camelopardalis]

That's smashing Lee :thumbsup: and check out the spiral in the bottom right corner :eyepop:

Were you refocusing for blue?

[RobC]

Spot on Lee. Congratulations. I am moving to Woodford this week. My first acquisition after 18 months in the Astro doldrums will be a ZWO camera .

Cheers

Rob

[multiweb]

Superb shot. The highres is very well processed. :thumbsup::thumbsup::thumbsup:

[SimmoW]

Wow, still marveling at this one Lee! Really good demo of the advantages of the cam. Great colours

[LewisM]

You know, wearing fluoro pink hats and My Little Pony shirts is kind of weird Rick. :eyepop:

Lee, nice shot. I am NOT an M83 fan (no offence and NOT your image, just not liking the GX itself much for some reason), but you have captured it very nicely.

[codemonkey]

Thanks very much Suavi! I think I've got about 10% curvature at the edges of the frame, so it's not terrible and I happily use the whole frame when the target warrants it, I just reference the center 1000px when analysing FWHM.

So far I've managed to get no additional data on this and I'm starting to get a mild itch for new targets... we'll see



Thanks very much Mike and/or Trish! :-)



Thanks Marc :-) Fair call, I think I pushed the whole thing pretty hard in terms of saturation to be honest, the HII regions did cop it.



Thanks Dunk! :-) I was not refocusing for blue. I did some tests a while ago and found that LRGB were all well within the critical focus zone of each other. I don't recall the discrepancy in FWHM being so bad between blue and the others though... it's a bit odd, not sure what to make of it at the moment.



Thanks Rob! Welcome to the neighborhood :-) Which ZWO are you going with, and is it for planetary or deep sky?



Thanks Marc! :-)



Thanks Simmo! :-)



haha. All good, I hear you Lewis. To be honest I'm pretty sick of looking at it. It was the first galaxy I photographed, and by far the one I've imaged the most. I was hoping this year to do it well enough that I won't feel compelled to re-do it next year.

[Camelopardalis]

If the blue channel is bloated compared to the others, either the seeing coincidentally deteriorated during the blue frames or it's out of focus. Blue being shorter wavelength than green and red implies that under the same conditions you should get sharper blue than red and green...assuming of course, each channel is perfectly focused.

[Retrograde]

That's just lovely Lee. Personally I like the saturation as it is and the detail you've captured with a scope of relatively modest aperture is quite amazing!