M42

[Adreneline]

My first attempt at combining different exposure images in PS.

This is 20x15s + 20x90s using an unmodified Canon 70D with an SW-ED80DS-Pro.

Pre-processed in PI and ColourCalibration and ArcsinhStetched in PI plus the usual noise reduction and detail enhancement using MLT.

I tried unsuccessfully to get the HDRComposition to work satisfactorily in PI hence the move to PS using http://www.astropix.com/html/j_digit/laymask.html

I also took 20x30s and 32x60s but I am not sure if there is any great value in adding those to this image.

Any comments, observations or advice would be most welcome.

Thank you for looking.

Adrian

 

[gorann]

You got great detail there and your short exposures have clearly saved the core from being blown out. Next step would be to get more long exposures, like 300 s at ISO1600. That would give you much more of the surrounding nebulosity and dust, and it is plenty of it around that object. Right now you have only about half an hour of data and if you get, say, two or three hours, you would be able to produce a stunning image.

[Adreneline]

1 hour ago, gorann said:

Next step would be to get more long exposures, like 300 s at ISO1600.

Thanks Goran for the advice on where to go next. Even at 15s I seemed to get some clipping on the star cores, in fact I had a major problem with 'pink' cores which I've not had before and had to address by separating out the RGB channels and using a soft brush in PS to address the problem on each problem core before recombining the individual channels; there may have been a much better way to fix it in PI but the recommended Repair HSV Separation script produced some wild results! A thread on CN seemed to imply it was a problem with the interpolation from 14 bit to 16 bit and resolving clipped signal levels; I really don't know enough to comment.

ISO1600 will definitely require a moonless night so fingers crossed for a couple of weeks time from now   - I might even try and grab NGC2024 at the same time - or is that asking too much?

Thank you again.

Adrian

[gorann]

When I started on AP, which was not that long ago (2.5 years) I was target hopping a lot, and it was fun and gave me an idea of what was out there, but now I would never spend a night on more than one object unless it dissapears behind something. Data is just so important to get a great image. With the moon out like now I do not even bother with trying AP since I know my images would not be even close to what I could get on a moonless night. So, the moon and clouds are our main enemies - unless you image the moon of course. This is what I got out of M42 after 2.3 hours (most of it a 300 s) at ISO1600 on a Canon 60Da. Your camera will be a bit less Ha sensitive but you will still capture a lot of surrounding dust. I also have a 60D and the difference between the 60D and 60Da is not that big:

https://www.astrobin.com/276118/F/

[Adreneline]

11 hours ago, gorann said:

This is what I got out of M42 after 2.3 hours (most of it a 300 s) at ISO1600 on a Canon 60Da.

That is certainly a very impressive and beautiful image Goran; even if I collect that much data I am not sure i have yet achieved the processing skills necessary to achieve that sort of result. In one respect I quite like the 'isolationist' image of the nebula against a dark'ish background but then I also like the full drama of the complete nebula and surrounding nebulosity. I have seen dramatic images of M81/M82 with surrounding IFN but then also like to see them set in solitary isolation. I guess you pays your money and you takes your pick. My biggest battle at the moment is ensuring the image is in focus and that I treat the noise reduction sympathetically / correctly / appropriately, etc. etc.! Noise is my nemesis!

And have you noticed how cloudless nights and full moons always seem to go together? What's all that about!?

Adrian

[Rico]

I think you've done a really good job with the core.

M42 is truly an amazing subject. I remember the first time I saw this on the back of my DSLR ... my jaw dropped. There's such a wide dynamic range in that object that you can easily get away with imaging this in a short stint. Just look at what you managed to capture with just half and hour worth of data ... on a DSLR! Amazing.

As @gorann suggests though, if you really want to get the most out of this object get some longer exposures in to capture some of the surrounding dust. 

[newbie alert]

13 hours ago, Adreneline said:

Next step would be to get more long exposures, like 300 s at ISO1600.

Wouldn't 5 mins at iso 1600 overexpose?

[Rico]

It depends on your setup, your sky background, the brightness of the object and a number of other things. I shoot with a modified 700D/SWED80/FR/Astronomik CLS filter and 5 mins is the minimum I would shoot, at ISO1600, to get some of the faint nebulosity. Some of the stars, will end up over exposed and with an object like M42, the core will be completely blown out, but that's the nice thing about using multiple exposures. Some of the faint stuff is so dim, that the exposure needs to be sufficiently long enough to pad the left side of the histogram.  Otherwise, it'll be hidden in a sea of noise. I guess an other thing to consider, is artefacts from over exposed stars. Some chips and scope setups generate awful patterns which simply get worse with increased exposure times. I guess most if is down to trial and error. Try it, if it works, great, if doesn't, fix it and tweak it until you get it just right.

[ollypenrice]

I like it. The decision on how strictly to control the core is a personal one. You could certainly hold it down more using the shorter subs but it has an honest look as it is. There's no right answer to this. (I think Jerry Lodiguruss' method gives a far better result than the very artificial looking HDR wavelets method, by the way.)

I like long exposures and entirely ignore the fact that I white clip the stellar cores. I simply can't go deep enough without doing so. You don't have to apply the clipped luminance cores in the final image and restoring nice colourful cores is not very difficult in post processing.

Olly

[gorann]

23 hours ago, Adreneline said:

That is certainly a very impressive and beautiful image Goran; even if I collect that much data I am not sure i have yet achieved the processing skills necessary to achieve that sort of result. In one respect I quite like the 'isolationist' image of the nebula against a dark'ish background but then I also like the full drama of the complete nebula and surrounding nebulosity. I have seen dramatic images of M81/M82 with surrounding IFN but then also like to see them set in solitary isolation. I guess you pays your money and you takes your pick. My biggest battle at the moment is ensuring the image is in focus and that I treat the noise reduction sympathetically / correctly / appropriately, etc. etc.! Noise is my nemesis!

And have you noticed how cloudless nights and full moons always seem to go together? What's all that about!?

Adrian

Yes, we all have noticed how the moon and clouds are conspiring against us. In fact, they have managed to do it quite well here this weekend. I agree, too much dust can be distracting and there is nothing stopping us from making several versions of our data with more or less dust.