Orion Nebula

[GeeM]

Happy New Year folks! Been a while since a have posted.
With lots of people out of town for the Christmas holidays the skies are darker than normal, which allowed me to capture my personal best image of M42 yet. Very chuffed with it. May have over cooked the saturation though.. what do you think?
Prime focus 13 secs ISO 12800 with the gear below.
Cheers,
Graeme

[Somnium]

great shot Graeme! well done from a dob. have you thought of stacking multiple images to build up the signal and reduce the noise ?

[GeeM]

Thanks Aidan. I have tried to use deep sky stacker but can't better what I have been able to in a single shot. I'll have to keep at it though!

[Somnium]

hmmm, if you are stacking images of similar quality then it should come out better. DSS can tend to make your images really dark, you may need to stretch and balance them after stacking

[g__day]

Very good result!

f you are use Photoshop after DSS you may get an excellent lift from combining short and medium and long duration shots together in batches using layers and a mask. There are a lot of examples on youtube showing you exactly how to do this - its about a 13 step process. This allows you to say stitch 10 second, 30 second, 120 second and 480 seconds shots together without blowing out the core. https://www.youtube.com/watch?v=K-PC4Sq0Zho How to process M42 using Photoshop Layer Masks - Astrophotography Tutorial

You can use DSS to combine say 10 - 30 shots of similar duration to create masters for in the above example the 10, 30, 120 and 480 second shots. You open one of these master then map in the data from another master - masking out where the first master has started to blow out - and so on until you reach the core. This dramatically improves your image quality when you have a subject like M42 which has such a high dynamic range!

Example 1 - Letting DDS combine say 3 shots (combining a 4 second, 30 second and 180 second shot together) results in core blown

https://www.facebook.com/photo.php?fbid=942396669168836&set=a.126760794065765.28799.1000019 55346541&type=3&theater

Example 2 - Combine those exact same three shots using layers and masks in Photoshop to integrate them

https://www.facebook.com/photo.php?fbid=943192809089222&set=a.126760794065765.28799.1000019 55346541&type=3&theater

[GeeM]

That's where I get lost. Once it's done it's thing I have no idea how to manipulate it to get the image right. I realise I'll have to learn how to do it. Only so far I'm going to get with a single image. I guess I realise I'm only going to be able to go so far with a dob and an unmodified DSLR. But I'm having fun so that's the main thing for me ATM.

[Somnium]

but if you are getting those results from your current set up, you don't need to change anything to get even better results if you stack. do you have photoshop or some other processing tool ?

[GeeM]

Yes I am using Lightroom. Thanks for the positive feedback gents, you have inspired me to revisit DSS and persevere with it. How many frames do you think I need to take to improve on what I've got so far?

[Somnium]

try to stack at least 10 and see how you go. the more you stack the better but you start getting diminishing marginal returns.

[GeeM]

Will do Aidan. I'll have a look at those links that Matthew posted too.

:thanx:

[g__day]

When you stack in DSS - make sure you:

1. Select the Canon Bayer matrix
2. Try and match your light and dark frame durations
3. Create master darks and then once you have a master .tiff of a set duration just use that to speed things up
4. Select Median combine normally as your default then register and stack your frames using recommended settings:

then

5. In the luminance tab - the curve that looks like a S shaped curve starting low on the right - running through your three colour curves raisese high to teh right is the curve you will normally be adjusting.
6. Shift the light and dark portion of your Luminance curve so the S is fairly flat on the far left and far right of the curve
7. Once the image looks about the right brightness - go to the third tab and set the Saturation between 16 - 19 usually to get the colour raised
8. Make sure your bias frames are the fast your camera can take with the lens of your scope covered (so its the fastest dark frame you can take)

For the Luminance tab I normal set:

1. The top sliders Darkness to 0 and the second slider close to 100 (flattening the slope of the extreme dark)
2. For highlight I leave the six slider where it is but the fifth one I reduce until the curve is flat and level (so I straighten the line)
3. The Midtone sliders are the crucial ones. Shift the bottom one (the fourth slider) until it is just right of the right most colour curve. Play with the mid tones 3rd slider gradually - until fine detail is revealed

If you highlight a small but important area of your picture in a rectangle - the processing commands will only be done on that rectangle - so they will run a lot faster. When you are happy with the result - click outside the rectangle to turn it off - then apply your processing commands to the whole picture.

The colour channels don't have to line up. Expect a lot of red - for Hydrogen alpha - especially with a modded DSLR and Oxygen II colour line is blue. At most bring the colour channels slightly together. You will fix the colour most likely in Photoshop (doing a Level on each channel individually to best drop out the noise and set the best black point).

Finally save the file as a 16 or 32 bit Tiff. Process it in a post processing software suite - like Photoshop!

[dimithri86]

Hey Graeme,

How did you get 13 sec single exposure with a dob?

Looks great. Inspired me to try again after the NSW rain clears.

Dimithri.

[GeeM]

Wow thanks Matthew. The last with the curves was where I got stumped. No matter what I did with those sliders I couldn't make a descent image. I will spend more time on it. Thanks for your info.
Cheers
Graeme

[GeeM]

Well Dimithri, I have a GOTO dob so I do have tracking. It works well for targets close to an arc between East - West. I can get good exposures out 40 sec at times. An object like the Tarantula nebula has to be a lot shorter as the Alt/Az mount can't follow the field rotation near the SCP.
It hasn't been easy though. I have purchased an ankle exercise weight to strap around the base of the scope to balance the camera. It's worth the effort to level the base too before aligning. You definitely require a dslr with good high ISO and low noise performance. It's rewarding when you do get a great image though!

Cheers
Graeme