I am Cr#p at Galaxies

[dcalleja]

Hi
I've been having big fun with the new SBIG and decided to have a go at a galaxy shot (M83 of course). I went for broke and the with the auto guiding gods smiling on me (it all worked for once inc goto's), I bagged 70 mins of M83 (7x10mins at -29c). This is the first time I got more than an hour of anything so naturally I thought it would be great.

I had of course forgotten that I am cr#p at processing galaxies.

Its a bigger image (cropped) so I've left it at www.dancalleja.com. Very unhappy. I've also left the uncropped version

It has a cast that I cant get rid of but more irritating is a background of 'sand' that I can't seem to process out. I've seen this before in my galaxy imaging and cant seem to overcome it. My workflow is:

CCSDtack
Convert to colour; register and normalise; remove hot pixels; combine median; convert to tiff; process in CS3.

CS3
Three curve stretches; colour range and background gaussian blur; some noise removal; some saturation tweaking.

I'd appreciate any tips from the galaxy imaging gods!

[peter_4059 (Peter)]

Dan,


I'm not claiming to be a galaxy guru but it looks like you are suffering from light polution judging by the gradient. I'm not familiar with the 8300C - what arc second/pixel do you get with this camera/scope combination?

Peter

[supernova1965 (Warren)]

Originally Posted by dcalleja

Hi
I've been having big fun with the new SBIG and decided to have a go at a galaxy shot (M83 of course). I went for broke and the with the auto guiding gods smiling on me (it all worked for once inc goto's), I bagged 70 mins of M83 (7x10mins at -29c). This is the first time I got more than an hour of anything so naturally I thought it would be great.

I had of course forgotten that I am cr#p at processing galaxies.

Its a bigger image (cropped) so I've left it at www.dancalleja.com. Very unhappy. I've also left the uncropped version

It has a cast that I cant get rid of but more irritating is a background of 'sand' that I can't seem to process out. I've seen this before in my galaxy imaging and cant seem to overcome it. My workflow is:

CCSDtack
Convert to colour; register and normalise; remove hot pixels; combine median; convert to tiff; process in CS3.

CS3
Three curve stretches; colour range and background gaussian blur; some noise removal; some saturation tweaking.

I'd appreciate any tips from the galaxy imaging gods!

Hey don't beat up on yourself so much everyone has to start somewhere every one you do will be better and you have to have something to look back at and say look how far I have come

[dcalleja]

Peter
I agree - I do have a street light to contend with so I use a CLS filter to try to combat it.

The combo gives about 1.48 arc secs according to the SBIG site. Thats 600mm FL with pixel size of 5.4 microns (Unbinned - its OSC anyway)

I did also have the wrong versions up on the site so I've now fixed that.

[leon]

Hey mate, trust me, my first attempt a astro stuff was horrific.

I all comes to those that wait, and it took me 40 years plus to go from film to digital.

Hang in there.

leon

[gregbradley]

A couple of points.

Firstly, 80mm is not a lot of aperture for galaxies. So it will need to work hard to build up a signal.

You will also need pretty dark skies to get a decent M83 or any galaxy for that matter.

The "sand" you refer to is colour noise. It reduces quite well with Noise Ninja so it is less intrusive. Your workflow seems fine although you did not mention you did dark subtraction and flats. Flats may not be vital but your darks are with the noise you are battling.

Bottom line- 5 hours exposure time, camera as cold as it'll go, none of this 80% of power supply stuff, as long exposures as you can do - perhaps 15 minutes or 20 or even 30 suits a one shot colour camera better due to drop in QE from the Bayer matrix. You have to get the signal (the image) above the noise of the camera - read noise and dark current. Dark current is reduced by heavy cooling. My STL11 used to start to shine at about -30 to -35C. With the cold weather you should be able to get to -35C?

So colder, longer and darker skies is your formula. Your autoguiding is quite good so take a win on that eh? That can be quite a battle in itself.

Greg.

[TrevorW]

Agree with Greg on this I've seen a lot of people lately trying for galaxies with ED80's and wondering why they don't get the results.

I've even done it and learned fast that the LGP nor FOV is just not there on dim objects where you need to go 10 minute or longer with your subs.

I know with my RC that objects below 40 arc minutes fit nicely in the FOV and provide plenty of detail.

The ED80 is now reserved for those bigger brighter objects such as Eta and Andromeda (M31) which at 190 arc minutes and Vb 3.4, would suit it to a tee if I ever get to image it from a dark site

Nor are you crap with galaxies if the data is there a lot can be extracted via processing just takes time

[dcalleja]

Thanks for the tips guys

Greg\Trevor - I had not thought of the effect a small aperature and FL would have. I'll have to try this out on the LX200 - also had not considered the QE effects in a OSC cam.

And it sounds like its onto 20 min subs and 5 hours as the next adventure.