Centaurus A

[aarong]

Hi all,

I finally got fed up with the fork mount my Meade lx90 was in due to it's unreliability. I never really knew if I was going to be able to image or not, when first setting up for the night. So I bit the bullet and went to Bintel and got a Losmandy G11. The guys at Bintel sorted me out and even de-forked the scope for me!

While testing the mount and then after, I collected some data on Centaurus A. I have been trying to image this galaxy for the past few years, with no luck. But now that has change! The new mount is awesome (it wanta be ;))!

I'm hoping time and the weather will let me collect more data, but in the mean time I need to practice my processing skills. I also couldn't resist and share where I'm up to :P

Image details:
HaLRGB
21:33:15:15:16 all @ 10 min subs
Total: 16.7 hours

Ha and lum bin 1x1
RGB bin 2x2
All subs at -20 C
QSI683
Meade lx90 8"

Processed in PixInsight and minor edits in Lightroom and PS

High res on Astrobin (http://www.astrobin.com/191459/).

Always after pointers in ways I can improve.

Cheers,
Aaron

[peter_4059]

Great result - nicely processed

[Robert9]

Lovely result Aaron. Well done. Makes the expense well worth while. ;)
I've been chasing this target for a while too, but Melbourne weather is hopeless.
Robert

[doppler]

Not sure how you can improve on that.... it's better than good. Lots of detail and colour, love it :thumbsup:. Definitely too good for the beginers section.

[BruceG]

What are you doing in this beginners area. That 5128 is superb in every respect! Well done and congrats on your new acquisition.
Bruce.

[raymo]

Now now, you're just looking for gratuitous praise for your image from
the beginners. :lol::lol::lol:. It should be in the main forum. Lovely.
raymo

[rmuhlack]

That's pretty good Aaron! :thumbsup:

In terms of some feedback, looking at the large version on Astrobin it seems focus is perhaps a little soft. Might be worth checking your subs using the SubframeSelector Batch processing script and checking the FWHM of each frame, perhaps discarding any which are obvious outliers. Looks like you've hit the noise reduction pretty hard too, it has a kind of mottled look in the dimmer parts - MultiscaleMedianTransform by any chance...? I'd be tempted to dial the settings on that back a little.

[aarong]

Thanks all.

Thanks for the feedback too. I agree. I have been trying to improve focus, but haven't got much further with it. I will keep trying. I will also back off on the noise reduction too.

I was hoping there would be more detail to be found, but not sure where I'm losing it yet. Focus, collimation and processing are all things to work on now I have a mount that works!

Aaron

[carlstronomy]

Aaron,

That's a sweet image, pops really nice where it needs too, the center has some very good detail. Certainly a good use of 16 hours!

:thumbsup::thumbsup:

Carl

[andyc]

16 hours and a good result! Definitely worthy of the main forum. Though that's a phrase often used out of politeness, when you're imaging at your high standard and technical challenge (10-min subs, HaLRGB etc), you want to get some feedback from the top-class astroimagers there.

From my limited experience, I would add a couple of thoughts. First, as already said, the processing is a little heavy, giving the mottled look in the dimmer parts. It might be best to leave a little of the noise rather than going too hard on the noise reduction?

Second things is the quite soft and irregularly-spiky stars. I'm not sure this is a focus issue, and it looks like something I'm dealing with (though on a Newt, not a Cass) - could it possibly be collimation? If anyone else knows what produces these kinds of spikes/flares on brighter stars, I'd love to know too! I'd guess that an ideally set-up SCT wouldn't normally have stars looking so spiky, but apologies if I'm wrong!

But forgive me, it's a minor criticism (as you asked :D) of a very fine and deep image indeed, and a lot of time and effort you've put into it! :thumbsup:

[aarong]

Thanks Carl

Thanks Andy. All good things to point out and work on. I suspect my focus is not there yet. I can't lock my mirror down with the lx90 so there is some mirror flop going on. I'm still fine tuning my collimation. Going to try and get it better with Metaguide when I next get the chance.

Also there may be some field curvature going on around the edges. I think my spacing distance is slightly different than what it should be, due to the focuser. The focal reducer is f/6.2, but plate solving on astrometry.net says it around f/7. All these things may be contributing to some funny star shapes, particularly as you move to the edges of the frame. There could be the odd frame the was accidentally included that had some bad tracking too.

I use Sequence Generator Pro (SGP) as my image acquisition program. It's great! I'm trying to work on an automatic focus routine to re-focus, say every hour, are try and help with mirror flop and temperature changes. I'm getting closer to trusting it some more, but it's a bit tricky with a DC electronic focuser (Meade zero-shift focuser).

I want to run some tests with ccd inspector (trial vs) or MaxPilote to check for collimation and curvature. Still working all that out.

In the mean time I'm collecting more data and will be more careful with my processing. I'll also give the sub-frame inspector script in PixInsight a go. See here (http://trappedphotons.com/blog/?p=693)for some useful info that script.

Cheers,
Aaron

[codemonkey]

That's a cracker, Aaron. Awesome work.

[5ash]

Really lovely image , I don't think I could ever manage 16 hrs of exposure , I'm lucky to manage 2hrs weather permitting .
Regards philip

[aarong]

Hi all,

I managed to get some more data on this interesting galaxy. Details are:

Ha 18x10 min -20C bin 1x1
Lum: 50x10 min -20C bin 1x1
RGB 61x10 min -20C bin 2x2

Integration: 21.5 hours

Meade lx90 8"
QSI 683WGS
Optec Lepus 0.62x Reducer

More details and high(er) res on astrobin (http://astrob.in/195884/0/).

I took all your advice on board and processed a little differently to the first one. I backed off on the noise reductions, particularly for the lum channel. I also ran the subframe inspector script and weighted the images using a similar approach to here (http://trappedphotons.com/blog/?p=693). Lastly I applied a little deconvolution. Other then that, my work flow was pretty similar to the first image.

This image has come out sharper and better than the first. I was happy to get some of the jet filament! It's still a little soft, but not sure if I can improve on that yet. My setup has some serious field curvature going on, as measured by ccd inspector.

Always after pointers in ways I can improve.

Cheers,
Aaron

[raymo]

Regardless of your imaging abilities, what is this doing in the
beginners' section?
raymo

[rcheshire]

+1 Lovely work Aaron. Extremely well done. Post it in the deep sky section.

[aarong]

Thanks guys. I though I'd post here to show how I delt with the great advice I got from this thread. Am I allowed to repost this pic in a different section now?

[rcheshire]

I think you can make request to have it moved.

[MGTechDVP]

I agree that this is definitely not a "beginners" image.... absolutely fantastic image.