Orion Nebulae

[mickyjd]

I know this isn't a brilliant picture but thought i would put it on the site and invite any comments good or bad. Hopefully some of you will be able to advise me on where i go from here. To be honest i am still a little confused when using DSS and still haven't got the hang of it and should have used more images. With this picture i only used about 10 and never added any darks or flats? These were taken with a Canon 350d on an 8" celestron with exposure times of 40 seconds.

Cheers in advance

Mick

[Starbabe]

Gradient removal?

[Black Knight]

I'd probably try 15 sec exposures, around 30 minutes worth so you don't over-expose the stars in the core, together with darks and flats. M42 is a very bright object, so if the core part over the nebula is still over exposed, you may want to reduce the exposure time further still (the last time I did M42, I took 15 second exposures, and it was still too much).

Darks are pretty easy tbh, just put the telescope cover on and take a bunch at the same exposure as your light frames.

Flats can be a bit scary and can be a little tricky to get right. I use a laptop screen with the laptop running Notepad maximised, and a T-shirt over the telescope to diffuse the light. Aim for about 30-60% saturation on the histogram and they should be fine.

Obviously, don't make any changes to the optical train when taking your flats - i.e. don't change the camera orientation or focus etc.

There is a thread on here (which I can never find when I'm looking for it ), which describes some good DSS settings to use when imaging with a DSLR. I'll try and find it.

[Black Knight]

Mickyjd, take a look at this thread: http://stargazerslounge.com/imaging-image-processing-help-techniques/150121-dss-problem-ngc7000.html, in particular a post #9 by AndyUK. Very useful .

HTH

[mickyjd]

Cheers Andy

Never really thought to reduce the exposure time obviously i have been over exposing the object all the time as i keep trying to get longer exposures in the hope i would get more detail.

[Black Knight]

The only problem with that is you end up burning out the core. The thing is, M42 is very bright for a DSO, a bit like the Andromeda galaxy. The ideal approach would be to take a series of short (say 15 sec) exposures, and a series of longer exposures (maybe up to several minutes) to tease out nebulous detail, and then combine them in say Photoshop, so that the core isn't overcooked. I'm not an expert on that though, I've never done it . Hope to this year though! .

What you need to do is to try adding many more subs to improve your signal. Try for 30 mins worth (or more), at a shorter exposure and see how it goes.

[Zakalwe]

That's a pretty decent image. Yes the core is blown, but you could take some more short exposures and blend them in GIMP or Photoshop.

Have a look at this tutorial...it's superb to get you used to DSS.

[Black Knight]

That's a pretty decent image. Yes the core is blown, but you could take some more short exposures and blend them in GIMP or Photoshop.

Have a look at this tutorial...it's superb to get you used to DSS.

... ^^^ and here's a tutorial to show you how to do it!

[rfdesigner]

I had a crack at this last year with different length exposures.

I stacked the short exposures together to make one image, and the long ones together to make another. I then made a mask from the long image by identifying all the pixels that were above a fixed (near bleached out) level. (using a clip command)

I used this mask to cut stars from the short image and then aligned them onto the long image... scaled for the different exposure times.

I did find that I was hitting my head against the 16 bit processing ceiling though. I'll have another go this year using with a better camera and probably use something like Astro Art to stack as that's 32 bit.

Derek

[mickyjd]

Thanks for the advice guys i have checked out the tutorial and hopefully understand this a bit better now? Unfortunately i think you've lost me there Derek lol.

Mick

[rfdesigner]

Don't worry.. it's certainly 'off piste' processing, and I'm still to perfect it.

Derek

[ollypenrice]

The best High Dynamic Range tutorial of which I'm aware is this one;

Compositing 2 Different Exposures via Layer Masks

My own M42 used this method and I think it's very well explained by Jerry Lodigruss.

http://ollypenrice.smugmug.com/Other/Nebulae-and-clusters/M42CCBOV2010/1100345185_HHd4m-X3.jpg

Olly

[Black Knight]

I love that M42 Olly