A little advice on M42 please

[sbooder]

Hi All,

               below is M42 taken 09/12/13, not very good seeing, it was a little moist to say the least and this is only my second attempt at DSOs and I am not too good at the editing bit yet.  This is a stacked image of 10; 30 second images and 10 darks taken ISO 1600.  What I would like to know is what am I looking for in the extremities of the nebula?

To me is seems a little tight and lacks any definition of the outer parts (sorry I am not too technical on the lingo side yet).

I would like to try and get this as good as it can be, so any advice would be most welcome.

Thanks.

Oh yes, I am using Photoshop CS5 if that helps? And the image was taken with no tracking so I do not want to sharpen at all, I find it degrades the image.

[nmoushon]

Thats a very decent start. But with 10x30sec subs you aren't going to get much more than what you currently have. You can try LOTS more and that should add more to your image. But with them only being 30sec your still not going to be getting much more. The farther out you get from the core the fainter the nebulea gets so you will need more subs and longer subs to bring it out. but you've got a good start.

[sbooder]

Thats a very decent start. But with 10x30sec subs you aren't going to get much more than what you currently have. You can try LOTS more and that should add more to your image. But with them only being 30sec your still not going to be getting much more. The farther out you get from the core the fainter the nebulea gets so you will need more subs and longer subs to bring it out. but you've got a good start.

Thanks for the advice.  I thought as much from most of what I read about how others produce fine images.  I tried a few longer exposures after I had taken the subs just to see how far I could push it without guiding...I don't think I have to tell you how they came out?  Yes much more detail but not very sharp detail.  1 minute was...hmm, OKish but 1 min 30 and 2 mins were appalling.

Going back to the subs, should I keep some of the glow that appears at the outer edge so it shows more detail.  I did not know if that was the thing to do or not?

[dkbender]

I saw this M42 image from Anna Morris the other day, from 8 hrs of integration using an unmodified Nikon D7000.   She details her workflow.   I thought that maybe this could give you some guidance.

http://www.astrobin.com/66918/

Click on the image to get the full size.

[sbooder]

I saw this M42 image from Anna Morris the other day, from 8 hrs of integration using an unmodified Nikon D7000.   She details her workflow.   I thought that maybe this could give you some guidance.

http://www.astrobin.com/66918/

Click on the image to get the full size.

Ooo, it's just like mine!

[lensman57]

Hi All,

               below is M42 taken 09/12/13, not very good seeing, it was a little moist to say the least and this is only my second attempt at DSOs and I am not too good at the editing bit yet.  This is a stacked image of 10; 30 second images and 10 darks taken ISO 1600.  What I would like to know is what am I looking for in the extremities of the nebula?

To me is seems a little tight and lacks any definition of the outer parts (sorry I am not too technical on the lingo side yet).

I would like to try and get this as good as it can be, so any advice would be most welcome.

Thanks.

Oh yes, I am using Photoshop CS5 if that helps? And the image was taken with no tracking so I do not want to sharpen at all, I find it degrades the image.

Hi,

I think that you have a pretty decent image even with 30s subs. M42 is very difficult to image properly as it has a very wide dynamic range and ideally you need to have a lot of subs of differing lengths  to process for different parts of the nebula. A while a go I did a series of 10s, 180s and 300s subs of the m42 with a sensitive CCD camera, the 180s subs were the best and the 10s ones were used for the core, as a whole it was quite a decent image. Surprisingly 300s subs did not have much more detail than the 180s ones and in fact they were much noisier ( for a CCD, that is ) so much so that I did not bother using them. last night I fancia quick widefield view of the area around M42 and I did a quick 15 subs of 300s each using my Canon 1000d modded at iso 400, the result is so poor that I did not even bother to try and re process the data. I think that the seeing and transparnecy has a lot to do with this, more than we can realise at times so IMHO there is no point comparing one capture to  another one . My 180s subs of the M42 were taken much later in the early hours of the morning and that is why they were superior to my 300s subs taken on the same night but with less transparent conditions. Try and take a lot of subs of differing lengths and combine them post stack and  see what happenes.

Regards,

A.G

[dkbender]

Ooo, it's just like mine!

Did you look at Anna's frame sequence? 

12x120" ISO200

10x480" ISO200

20x60" ISO200

12x600" ISO200

16x900" ISO200

Image processed in Nebulousity and then PS.   Reported sky was Bortle 6 - 6.5.

Hope that helps.

[sbooder]

Hi All,

            OK, I have been mucking about in PS with a new stack of the same images as used for the last image I posted here and I think I am getting close now.  I have manages to show much more nebulosity but I think the centre is a bit too blown out but I am having fun and learning as I go.  Also I think it is a little bit over processed?

[dkbender]

yes, I'm afraid the core looks blown out to me.   Are you using histograms?   Can you do stretches?

[sbooder]

yes, I'm afraid the core looks blown out to me.   Are you using histograms?   Can you do stretches?

I am just mucking about with stretches.  I think the core is a little blown out to start with so I am having difficulty bringing it down.

[ollypenrice]

Firstly your sky is jet black so I'm pretty sure you're cutting back the black point too aggressively. This is called Black Clipping.

The top histogram is healthy. If applied, the bottom one would remove the flat line to the left of the rising peak. This would be very unhealthy because it would discard precious faint data. When you see an image with a jet black sky you can be sure that the data has been clipped (or that the imager was using a thousand dollar Astrodon 3 Nm Ha filter!)

At F3.9 my longest subs were 10 minutes.

At F7 I used 15 minutes but aim to do a re-run at 30 minutes since lots of the faint data is missing from this version.

I certainly found the long subs essential, though I work from a dark site. I don't think you should have unrealistic expectations if you're limited to short sub exposures. The middle brightnesses are well captured in your image. Just try leaving the histogram with a bit more on the left.

Olly

[sbooder]

Hi Olly,

             thanks for the info and advice.  I have been watching a few vids on youtube and you backed up a lot of what I have heard today.  I am trying again and you are right I was clipping the black end.  I suspect that I will have just to suffer the blown out core but try and concentrate on the fainter details.

[ollypenrice]

I did 10 second subs for the core. You then need to learn about Layer Masks when it comes to blending them.

Olly

[sbooder]

I did 10 second subs for the core. You then need to learn about Layer Masks when it comes to blending them.

Olly

Hi Olly,

              yes I have been mucking about with Layer masks but as you say I need to take some shorter subs for the core.  It is fun though, I have been using PS for a long while but with the type of thing I was using if for I had little or no call to use most of the more powerful tools in PS.

A bit of a learning curve but nothing that is too worrying.