M42 image

[Moonshed]

Last Thursday I decided to image M42 for the first time, my first  ever image was a very poor show of The Andromeda Galaxy last month, I made lots of mistakes and learned from them. I took 30 x 90 second subs at 800 asa for M42. I finally stacked them today using DSS and below is the result. I know it's not great, but I love it, we all have to start somewhere. I have Photoshop but have yet to master layers and masks and will study tutorials on YouTube for that. I will improve in time.

 

 

[Owmuchonomy]

Excellent start. You have the imaging bug now. One tip from me would be to advise that you don't black clip your image during processing. The above image looks like the black point is clipped. You might be losing some finer nebulosity.

[Moonshed]

6 hours ago, Owmuchonomy said:

Excellent start. You have the imaging bug now. One tip from me would be to advise that you don't black clip your image during processing. The above image looks like the black point is clipped. You might be losing some finer nebulosity.

Thanks for the advice. Could you please tell me what you mean by "the black point is clipped". I don't have much experience in PS. Thanks. Keith.

[cjdawson]

Black clipping is something that happens when you are playing with the levels.    When you make the levels adjustment, you'll bring the white level to the left - if you do it too far, you'll turn everything white and loose data.    At the same time, you'll most likely be moving the black marker from the left to the right, if you do it too far you'll start to turn everything black.   This is black clipping.

 

For astronomy processing, it's better to do these two actions seperately.  Ideally, don't do any black clipping at all until you are almost done stretching the image, and only do it on the last pass.  This way, you'll not accidentally wipe out the very feint almost blacks which get lost too easily.

[Moonshed]

Thank you for the detailed explanation cjdawson, that will help me a lot I am sure. I have of course kept all the subs and the stacked image so will be able to have another go or two. I am sure there is a lot more detail there as you suggested, and will try and tease it out. Thanks again. Keith.

[ollypenrice]

Not clipped...

Clipped:

In Photoshop you can measure the background sky values using the Eyedropper colour sampler tool. I aim for about 23/23/23 in each colour channel.

When you feel like using short exposures to fill in the Trapeziulm region this is the method I'd recommend:

http://www.astropix.com/HTML/J_DIGIT/LAYMASK.HTM

Olly

[Moonshed]

Thank you  so much Olly, that really is most helpful showing the screen shots, it really makes the point clear, and that site you put in the link to looks a must for me. With some serious head down study time, and practice, I am sure I will soon get the hang of it and produce an image of M42 that will put my first effort to shame. "This time next year we'll all be millionaires!"  (With apologies to Del Boy). Having said that, my first M42 will always be the one I love the most. "It's a funny old world Pete."