This is another one of my bucket list shots. I’ve attempted it once in a with a wide field image but it lacked detail and I had a tilted image plane which sapped it of a bit more niceness.
I captured 12 hours of data from a Bortle 6 backyard in the burbs of Melbourne but for this version I culled all subs over 1.8” so this stack is 146x120s all below 1.8”.
I’ve used a small amount of deconvolution to try to sharpen up the dust lanes in the galaxy but I’ve never been happy with the way deconvolution appears on OSC data, even with a bayer drizzle which is supposed to remove the issues from interpolation.
In the future I’d like to see if I can run more of the 12 hours while still keeping a sharp image but I’m not sure how much more of the 1.8-2” or 2”+ frames I can add before the SNR increase from more data vs SNR from lower FWHM makes it worse overall.
This particular stack is at 1.71” in the centre of the frame so it’s come up pretty sharp so far.
That's excellent Colin. Your one shot colour must be very sensitive as its come out way better than I would expect for "only" 4.9 hours.
A little bit of residual noise and part of that is because the background is too black (perhaps black clipped in the histogram). That would also accentuate the noise.
Great detail and you picked up the faint jet a bit.
Thanks Lee! The fine details aren’t quite as fine as in your last rendition but I’m pretty happy with the results from a OSC.
Quote:
Originally Posted by RobC
You nailed it Col. As Lee said "Nice and Sharp"
Cheers
RobC
Thanks Rob!
Quote:
Originally Posted by gregbradley
That's excellent Colin. Your one shot colour must be very sensitive as its come out way better than I would expect for "only" 4.9 hours.
A little bit of residual noise and part of that is because the background is too black (perhaps black clipped in the histogram). That would also accentuate the noise.
Great detail and you picked up the faint jet a bit.
Greg.
Shooting with a OSC under light pollution isn’t great on any kind of fainter area. The brightness of the galaxy overpowers it all but once moving past the halo it’s all just noise, shooting from my Bortle 2-3 dark site would have had that jet pop but alas, the backyard is all I could do at the time.
I haven’t entirely black clipped but I’ve certainly cut a lot more than I “should”
Inspired by your work, Trish and I must experiment with some very short exposures, for the very brightest parts, and longer exposures to get the fainter parts.
You've already got quite a bit of relativistic jet showing.
What percentage of subs actually taken met the 1.8 sec arc threshold and went into the image?
Looks like you got the pickles and relish in that one. A very fine hamburger indeed.
I've still used yours as a bit of a benchmark, not quite there yet. I'd be interested to see how much the AO helps or whether it's the SNR on my end that's really limiting things. The ASI094 has a fairly sensitive and clean output but it has smallish pixels (4.8 microns) on a slow F/10 telescope with a bayer matrix throw in there as well.
Quote:
Originally Posted by DavidU
Wow Col, excellent image !!
Thanks Dave
Quote:
Originally Posted by Placidus
Unbelievably sharp.
Inspired by your work, Trish and I must experiment with some very short exposures, for the very brightest parts, and longer exposures to get the fainter parts.
You've already got quite a bit of relativistic jet showing.
What percentage of subs actually taken met the 1.8 sec arc threshold and went into the image?
Thanks Mike & Trish! You two are a part of the reason I wanted to get into longer focal length imaging, along with others like Peter, Mike, Lee and others obviously with their endless galaxy images
I managed 360x120 exposures over two nights and shot down as low as 45º as an end target. I had some 22 below 1.6; 6.1%. 146 below 1.8; 40.5% and for what I considered acceptable I've had 324 (90%).
Using all 324 with the weighting I've used for stacking (use both FWHM and star count) I end up with 1.71" around Cent A so I'm finding this afternoon that limiting it to the 146 best isn't really improving as much as I'd have thought. Doing a direct comparison between the two shows that the bottom of the stars is larger in the larger stack due to having some exposures in there reaching around 2.5" but they're not adding much due to the weighting being used.
Quote:
Originally Posted by graham.hobart
that is wonderful!! so sharp. Did you have any collimation issues with the mewlon?
Thanks Graham. When I was installing the corrector I had to remove the mirror, unscrew the original baffle tube and install the new one. I put the mirror back in and used a Tak Collimation Scope, spent a few minutes moving the secondary around a fair bit learning what moves what in what direction (so large movements). Spent maybe 15 minutes tweaking it on the kitchen table and haven't touched it since. That was nearly 12 months ago, several trips out to dark sites, in and out of the house and never felt the need to touch it.
Thanks Lee! The fine details aren’t quite as fine as in your last rendition but I’m pretty happy with the results from a OSC.
Hmm, I reckon your data is just as sharp as mine. I selectively applied Topaz AI sharpening to mine in addition to deconvolution and I think that accounts for the apparent difference.
Quote:
Originally Posted by Andy01
It's a very good picture of a very unattractive subject Col - well done!
This is another one of my bucket list shots. I’ve attempted it once in a with a wide field image but it lacked detail and I had a tilted image plane which sapped it of a bit more niceness.
I captured 12 hours of data from a Bortle 6 backyard in the burbs of Melbourne but for this version I culled all subs over 1.8” so this stack is 146x120s all below 1.8”.
I’ve used a small amount of deconvolution to try to sharpen up the dust lanes in the galaxy but I’ve never been happy with the way deconvolution appears on OSC data, even with a bayer drizzle which is supposed to remove the issues from interpolation.
In the future I’d like to see if I can run more of the 12 hours while still keeping a sharp image but I’m not sure how much more of the 1.8-2” or 2”+ frames I can add before the SNR increase from more data vs SNR from lower FWHM makes it worse overall.
This particular stack is at 1.71” in the centre of the frame so it’s come up pretty sharp so far.
Hi Colin,
That is a lovely sharp image of Centaurus A, and taken from Bortle 6 skies, it doesn't get much better than that.
