m15

[alacant]

Hi everyone

Try as I may, I can't get to see individual stars in the core of the cluster. Maybe this calls for that layering thing; less stretched image on top?

On a non imaging point, I never did understand why globular clusters persist where they are. I would have thought they'd have been sucked in by the milky way ages ago...

Anyway, thanks for looking and clear skies.

canon 700d 90 minutes

[Skyline]

Wonderful image here, one of my objects to image, just asking what equipment was used?

[ollypenrice]

First you need to look at the linear data to see if that is saturated. If it isn't, then careful processing will allow you to retain everything that's in there. Sometimes (but rarely) you actually do need a set of short subs. More often a softer stretch of the core can be layer masked onto a harder stretch. Here's how to do it in PS but I expect any layers-based programme could follow a similar method. http://www.astropix.com/html/j_digit/laymask.html

As for the globulars not falling into the centre of the MW, why would you expect them to behave differently from other matter in stable orbit around the centre?

Olly

PS another useful trick if using LRGB is to use the RGB layer, with colour discarded, as a 'short' set for the core. The RGB has considerably less signal, normally, so it may not be saturated when the L is saturated.

[vlaiv]

Try following approach for color processing:

1. Do color calibration (white balance) on one or few bright stars (just to get coefficients for channel mixer), while this step is not necessary, it might improve overall color cast / tone (white balance) of image.

2. Load your image prior to any stretching and convert it to mono - this will be your luminance layer

3. Take your R, G and B channels and create a small stack of those three images - do max stacking on those to get one image that will contain max(R,G,B) values. Divide each R, G and B channel with this newly created stack - this will produce "normalized" color image (each pixel will be pure color ratio in range 0-1).

4. Take color ratio image and split it into luminance and chrominance (LCH or LAB color space, try each and see what you like better, you might even do both and combine results with layers).

5. Stretch original luminance layer (from step 2) so it is "exposed" properly.

6. Take luminance from step 4 and multiply it with stretched luminance from step 5 to get final luminance channel.

7. Combine final luminance from step 6 with chrominance channels from step 4 and convert back to RGB space.

This should preserve both color, max saturation and avoid any clipping that you've possibly made when stretching luminance in step 5.

[alacant]

35 minutes ago, ollypenrice said:

stable orbit around the centre

Hi. Yeah. I was likening them to artificial Earth satellites which always eventually fall. Too simple an analagy maybe.

 

39 minutes ago, Skyline said:

what equipment

A Canon 700d on a 254mm reflector.

HTH

[Skyline]

thank you