M13 RGB

[RikM]

M13 certainly is a photogenic wee thing

I have been practising 'Stars' and have convinced myself of two things:

1. RGB stars work better than LRGB, if you can match the star sizes.

2. From my location, 'seeing' has at least as big an influence as focus on getting things matched up.

This is an hour per colour in 10min subs. I combined it according to the G2V weightings I had measured for my kit, but it initially came out very strange. Red sky and blue stars, so I had to tweak it using the white balance tool in Maxim. This seemed to work better than playing with the levels in Photoshop (for this image at least).

I hope I got it right?

[Black Knight]

That's a terrific image Rik

Sent from my RM-821_eu_euro1_342 using Board Express

[Qualia]

That's just gorgeous. Thank you.

[JamesF]

Lovely image, Rik.

James

[Sam]

There some awesome colour in that image, often images of M13 lack colour and can look a little flat. Your image is fantastic and it give real depth to the cluster, nicely composed too.

[Gina]

Very nice

[peter shah]

A beautiful shot there Rik, superb star colour...top job....although you might have measured your G2v exposure weights so you would expect your colour to work perfectly when processing, however variable sky condition will cause issues to your colour weights. I also understand where you are coming from when you say RGB gives better colour results, but as I understand it getting good colour from RGB is only better as its a simpler process than LRGB. The difficulty with LRGB is getting your colour signal to match your Luminance. Its very easy to push the luminance to where is looks great in mono but when you process the RGB frames to match the noise starts to show before you get anywhere close. The result is a weak RGB layer making the image look washed out when the Luminance is added. LRGB will give a much cleaner result and can still be very rich in colour providing the processing in RGB and Luminance matches.

[AndyUK]

Very nice indeed Rik - I love the star colours and the detail... Whenever I've taken globular cluster images I've always found it tricky to get the outer parts without blowing the core - Is this a single process, or a composite? Whichever, you've done a really good job!

Peter - Would you advocate taking luminance for ALL DSO's? I too have found (with my very limited experience!) what Rik's noted [RGB stars work better than LRGB, if you can match the star sizes] for open / globular cluster images, but that may just be down to my lack of skills / knowledge of using luminance effectively...

[RikM]

Thanks

This was a single image rather than a composite (6x 10min each colour) but I did the processing in masked layers.

I did a basic DDP stretch in Maxim, as that does a good a job of heavy lifting once you get the background and mid-level values right. Then transfered to Photoshop as a 16bit TIFF. I duplicated the layer, pinned the background and the core, then added a control point for the halo and gave it a gentle stretch. Then applied a hide-all layer mask and painted over the outer parts of the glob with a large soft round brush to let the stretched stars show through. This lifts the faint stuff, without increasing background noise or blowing the bright stuff. Flatten and repeat...I think I did about three iterations using this method.

I also used a neat trick for low-noise saturation increase. Make three duplicate layers. Set the top one to luminosity and the middle one to softlight then merge the three new layers into one, ontop of your background and adjust the opacity to suit. Ridiculously easy but very effective

[michael.h.f.wilkinson]

Very good image!

[AndyUK]

Thanks Rik - Some very useful tips there...

[Martin-Devon]

Yep, agree on all of the above - great image and really helpful processing tips as well - thanks for sharing.

Martin

[peter shah]

hi andy

I bin all my data at 1x1, so im able to increase signal to my image by adding the rgb to the Luminance. I dont always take Luminance frames but i do make a Luminance layer even when only imaging rgb only, by combining all my frames i am able to put my rgb data through a much more agressive noise reduction without spoiling the resolution. There are many ways to process but this is the way i tend to stick to.

[AndyUK]

Thanks Peter - That's very helpful... and logical - Even I can understand it!

[robbie c]

That's a lovely image Rik so much detail and colour

[Spikey]

I like that very much Rik, beautifully resolved and coloured.

[andyo]

Great image I think the colour balance is very good and superb detail