M83 - sorry - first time for me!

JohnH · #1 10-05-2011, 10:34 AM

A clear night!

Here is M83 LRGB with 40mins L and about 30 or RG and B with the latter binned 2x2. 127mm triplet and Opticstar 145m. Not a classic I relaise but I am quite pleased - this is only the second time I have attempted LRGB imaging (Sydney light pollution!) and I am far from good at the processing required plus I had many faults (flats need to be re-done, which is why the image shows clipping (avoid visible dust bunnies), gradients are present and I lost most of my L data by leaving binning at 2x2 and overexposing as a result!)....still as it is only my second galaxy image so I am quite happy...

renormalised (Carl) · #2 10-05-2011, 10:59 AM

It's a good start and that's the main thing

Keep shooting!!!

CoolhandJo (Paul) · #3 10-05-2011, 11:26 AM

Nice one. Thre is actually quite a bit of detail in there! Stretch it out a bit maybe? Keep it up! Great start to LRGB!

multiweb (Marc) · #4 10-05-2011, 11:39 AM

Excellent shot. Just gotta tweak the color balance and you've got a corker. Natural!

bmitchell82 (Brendan) · #5 10-05-2011, 11:39 AM

Nice crack of the whip John. Like Jo said, there is a lot of detail within the image but light pollution is your enemy! As for dust bunnies, if you are using Photoshop i think CS4 and better the heal tool with local adaption will all but rid you of them.

Keep up the work, youll be well versed so that future trips into pristine skies will yield good data!

Brendan

Hagar (Doug) · #6 10-05-2011, 12:10 PM

Nice image John. This one requires a lot of exposure to pull up the colours and show all the Ha areas etc.
Nice start on a pretty galaxy.

JohnH · #7 10-05-2011, 12:39 PM

Thanks all for the feedback - I will have another go and try for better lights and calibration data and do a better job of processing too...M83 is one of those classic targets so I want to do justice to it before I move on so if the skies permit I may be back here shortly!

gregbradley · #8 11-05-2011, 07:15 AM

For a 2nd attempt at LRGB imaging it is very good. You did a lot of things right so you should be pleased about that.

Flats can be done after the fact quite easily. I have actually been doing flats lately in the morning in my observatory with the roof closed and a white t-shirt over the end of the scope. Works really well.

So if you can put your camera and scope in a room that is a bit dark but a bit of light and make sure you point it at an evenly illuminated part of the room you may be able to take some flats now. As long as you haven't moved the camera or if you have move it back to the same position and put the scope at the same focus you should be fine.

Also as a processing tip avoid doing sharpening to the whole image. It damages the stars. Ideally you want your stars to have softish edges and not harsh sharp edges.

Louie has posted some free tutorials on how to use masks to selectively adjust parts of an image and you have to learn how to use these as it is really the bread and butter of your image processing. What one part of an image may need is not the same as another. For example dimmer areas need noise control (usually a form of smoothing) whereas brighter areas don't and in fact need sharpening.

Greg.

Ross G · #9 11-05-2011, 06:18 PM

A nice Galaxy photo John.

I like the detail.

Ross.

JohnH · #10 11-05-2011, 06:45 PM

Greg,

Thanks for the tip - I have been meaning to get into layer marks and selective application of sharp/blurr/noise reduction etc Attached is my attempt at this styple of prcessing - I think the result is better but I have so much to learn with this technique - there are just so many variables it is hard to know what to do for a best result.

BTW I am still having a few issues with my flats - even after re-doing them some of the darkest bunnies are not removed by calibration. I used the T-shirt technique early this am - I folded 4 layrs to avoid having to use very short exposures - so the flats were at 0.2s.

Attached is a new M83 and a sample flat, is this typical or am I in trouble with this much gunk on my sensor?

JohnH · #11 15-05-2011, 04:50 PM

Re-processed and added another 16 mins each or RG and B, moon is too bright now for the L so this is it for me for now on m83 -promise...

renormalised (Carl) · #12 15-05-2011, 05:22 PM

Quote:

Originally Posted by JohnH

Attached is a new M83 and a sample flat, is this typical or am I in trouble with this much gunk on my sensor?

Ick!!!...that sensor needs cleaning. You need to get a can of air or a hurricane blower to clear off the dust. Plus, some lint free buds that won't leave any junk behind when you wipe off the more stubborn dust bunnies. Make sure you have your sensor pointing downwards when you blow the dust off.