Advice please - NGC6888

[steviemac500]

Thisis my first attempt at any other nebula other than the popular ones (Ring, Dumbbell etc). Not a huge amount of data, 10L @ 360s each, RGB 5 each @ 250s, binned 2x2. No flats as my current method isnt working and 25 bias each. I'm reasonably happy as a first go but there are lots of things wrong that I need some help with please. I know there is an aeroplane streak and I can sort that with Kappa stacking and more data and the hot pixels are not bothering me either, but the colours always seem off. My histogram is aligned and level on each side but the star field just doesnt look right. Can anyone offer suggestions please? I have watched Doug's tutorials and I try to follow particular work flow too. Thanks in advance.

 

[ollypenrice]

I'm not sure that binning the colour is a good idea. Your pixel scale with the ED80 and 414 is getting pretty course in Bin 2 and it won't help your starfield.

This target responds brilliantly both in Ha and in OIII, the OIII adding a wonderful external shell scarcely visible in other filters. I would add the Ha to red and the OIII to green and blue using Photoshop's Blend Mode Lighten.

The image probably has more colour to give. There are two low-noise ways to boost it.

1) Be sure to save an original then create two copy layers. Set the top one to blend mode Soft Light and flatten onto the mid layer. Set that layer to blend mode Colour and flatten. Repeat if you wish.

2) Make a copy and change the Image Mode to Lab colour. In channels select the 'a' channel and increase tohe contrast in Brightness and Contrast by 35. Do the same to the 'b' channel. COnvert back to RGB and paste it over the original in blend mode Colour.

Anything with an Ha component (even if it was just taken via a red filter) can be enhanced in Selective Colour by moving tthe top slider in reds to the left to lower the cyans in red. This is often spectacularly effective.

AstroArt 5 (or it may now be 6) has a stunning 'remove line' facility and its hot pixel filtration is also excellent.

Olly

[steviemac500]

Thanks Olly, I'll give it a try later. I think the stars are looking blocky which is down to the binning.

[steviemac500]

Tried the first method you suggested and it's definitely brought out more colour. Could you explain about adding the OIII to the green and Blue please?

[nightster]

Great improvement in the second image. Did you check your focus between filter changes?  

[steviemac500]

Hi, no i didn't. I didnt think focus was off in this though? I should add, i had another go last night and didn't bin the RGB and it made a big difference to te star field. Can someone recommend a decent HA filter to start off with. I was looking at the BAADER from FLO? The 35mm one/

https://www.firstlightoptics.com/narrowband/baader-narrowband-ccd-emission-line-h-alpha-filters-125.html