M42 with layer mask

[imakebeer]

I posted an image of M42 early last December, one of my first pics with my 150PDS, and very pleased with the result at the time.

But in an effort to keep upping my skills I went back and had another go at processing it in GIMP, this time using layer masks to try and bring out more nebulosity yet preserve the bright core.

The original stack was only 60 x 15s @ ISO 400 + 10 darks, so not ideal. The difference in the processed results is quite subtle but it's definitely there and I'm encouraged to keep trying with this technique (plus when the opportunity arises I plan to re-image M42 capture way more data, like 120 x 60s!)

Original Image

Re-Processed Image with Layer Mask

[ollypenrice]

Clearly much better. I've always imaged M42 using radically different exposure times, with 10 seconds for the Trapezium itself. I then place the short exposures on top of the long, copy the long onto a layer mask, blur the mask, increase its contrast and then blend the layers.

Olly

[imakebeer]

Thanks @ollypenrice , and thanks also for the suggestion👍 In addition to layer masks I think I'd also heard about your technique of different exposure times for areas of different brightness.

I suppose the big investment is the longer exposure part to get the faint areas (say, 120 x 60s), but from there it's less investment to do an additional, say, 120 x 10s.

My only uncertainty here is you'd end up with 2 different stacks - isn't there a possibility they'd be slightly out of alignment with each other, and so how do you ensure your layers are perfectly aligned? (I'm certain it can be done, I just haven't learned how yet!)

I suppose it's no different to challenges you might face if you're collecting data on multiple nights, and possibly even related to the challenge of how to merge together different areas of a mosaic 🤔

[ollypenrice]

41 minutes ago, imakebeer said:

Thanks @ollypenrice , and thanks also for the suggestion👍 In addition to layer masks I think I'd also heard about your technique of different exposure times for areas of different brightness.

I suppose the big investment is the longer exposure part to get the faint areas (say, 120 x 60s), but from there it's less investment to do an additional, say, 120 x 10s.

My only uncertainty here is you'd end up with 2 different stacks - isn't there a possibility they'd be slightly out of alignment with each other, and so how do you ensure your layers are perfectly aligned? (I'm certain it can be done, I just haven't learned how yet!)

I suppose it's no different to challenges you might face if you're collecting data on multiple nights, and possibly even related to the challenge of how to merge together different areas of a mosaic 🤔

You're right. I use a program called Registar to align images because it does other things as well and is devastatingly accurate.

However, you can align Layers in Photoshop. Paste one on top of the other, make them both active, and then go to Edit - Auto Align Layers - and choose to stack them. Your layers will now be aligned and you can proceed as explained above.

I think you can auto-blend layers in a high dynamic range mode as well but I don't do that, I use the method explained earlier because there are things like colour saturation which can be manually adjusted as you go along. (Bright parts often need a colour stauration boost.)

Olly

Edited January 30, 2023 by ollypenrice
Clarification

[Elp]

And here's me manually aligning them...

[wesdon1]

7 hours ago, imakebeer said:

I posted an image of M42 early last December, one of my first pics with my 150PDS, and very pleased with the result at the time.

But in an effort to keep upping my skills I went back and had another go at processing it in GIMP, this time using layer masks to try and bring out more nebulosity yet preserve the bright core.

The original stack was only 60 x 15s @ ISO 400 + 10 darks, so not ideal. The difference in the processed results is quite subtle but it's definitely there and I'm encouraged to keep trying with this technique (plus when the opportunity arises I plan to re-image M42 capture way more data, like 120 x 60s!)

Original Image

Re-Processed Image with Layer Mask

Hi @imakebeer. My friend, It appears that the layering technique has done wonders for the core! As a side note, I would suggest maybe adjust/lower the Blue channel in post, to give it a more balanced colour profile? Mate you're progressing so fast with this game! I am still struggling with various aspects of the hobby, most notably, polar alignment, and post processing. I'm still loving it all though mate!