Southern Pinwheel Galaxy - M83

[starfinder (Russ)]

Hi all. An image I'd like to share with you all. Taken under dark skies through my Takahashi FS128 into a self-guided SBIG STL11000M camera. Two hours total exposure in 20min subs (LRGB 60:20:20:20); image is approx 25% of original frame. Processed in CCDStack and finished in Photoshop CS4. Comments always welcome. Russ

[Hagar (Doug)]

Very nice image Russ but I would like to see a bit more colour saturation on this pretty galaxy.

[dpastern (Dave Pastern)]

Nice shot Russ - plenty of detail there.

Dave

[Ric]

Lovely capture Russ, very nicely detailed and a couple of little bonus galaxies at the bottom by the looks of it.

Cheers

[Jen]

Beautiful pic Russ

[starfinder (Russ)]

Many thanks for your comments.

Picking up on Doug's suggestion - I've tried increasing saturation in Photoshop (+25-+35 in Master or Red) without significant increase in colour, just brought out red noise. BTW this is the first galaxy I've imaged using the LRGB method and I've only been doing this type of imaging/processing since the beginning of the year. Sooooooo much to learn, soooooo little time! Any advice from the Forum about how to improve saturation would be greatly appreciated.
Thanks in advance for your help. Russ

[spacezebra (Petra)]

Hi Russ

This is a beautiful galaxy. You have captured so much detail.

Cheers Petra d.

[gregbradley]

Basically a nice shot Russ. A few possible improvements would be to get more colour into the galaxy which has a bluish hue with some red Ha patches and a yellowish core, some colour into the stars and to repair the star elongation from the tracking errors.

Star repair:
1. make a duplicate layer
2. set it to darken mode
3. lasso the galaxy and select invert so everything except the lassoed galaxy is selected.
4. filter/other/offset
5 adjust horizontal and vertical numbers until you get more round stars.
6. You can enter then edit/fade to reduce the effect for fine tuning as the offset filter only takes whole numbers.

Now select the stars and increase the colour saturation. Use the colour range tool to select out the stars only.

Then use colour balance tool to bring up the overall colours of the galaxy or if that is affecting the stars too much then use the sponge tool, set to saturate 5% and rub it on the galaxy only.

A bit of smart sharpening on the galaxy only (lasso it first and feather 25 pixels) - not too much should polish it off.

Cheers,

Greg.

[rat156]

Hi Russ,

Your stars are elongated. I don't know if this is tracking or misregistration. If it's tracking you may need to take shorter exposures. Misregistration can be fixed in CCDStack by better selection of the reistration stars, DON'T use saturated stars, smaller ones are usually best as the centroid is better defined. Starsnap in CCDstack works best with roughly aligned images, for subs you can turn off the scale function and just use the rotate and shift functions. Sometimes the different colours require a little scaling though, particularly if there's a focus shift.

Cheers
Stuart

[starfinder (Russ)]

Thanks guys for your extremely helpful advice. Exposures were 20mins and were taken before I'd done PEC on the mount. You're right- exposures were too long under the prevailing sub-optimal conditions, but it's good to push the boundaries to see how far we can go. I'm intrigued about elongated star repair. I will give it a try, but nothing beats good data! Thanks again and clear skies. Russ