M4 and Antares region - DSLR pic

[Robert_T]

Hi All, last night's efforts attached.

5 x 300sec at 400ISO and 1 x600sec at 800ISO with Canon 40D, IDAS-LPS filter and York Optical ED80 on LXD75 mount using PhD guide software.

I used In camera Noise reduction.

Processed and combined in Images Plus, using star-size reduction, multiple resolution smoothing and sharpening. Shadow and highlighting to bring out some of the nebulosity and various noise reductions (none of which seemed overly effective). Pushing to bring out the nebulosity has brought out the grain.

Comments and advice welcome.

cheers,

Rob

[[1ponders]]

'tis a bit noisy and scratchy Rob. I would think that you'd have a much smoother result with the length of the subs you took.

Being a planeteer you'd have PS hanging around somewhere wouldn't you? After combining in IP pop over to PS to do the finishing off. You could also try mucking around with the Digital Development function of IP. That can bring out some suprising results at time. (and some shockers as well :lol: )

[AlexN]

I agree with Paul, I would have expected it to be a lot smoother after that much data.. especially with most subs taken at ISO400. Sometimes I've noticed ICNR (on nikons) to introduce some noise, and have usually found using post processing noise reduction techniques to be much more effective.

Overall though, Its a good image, you've definitely caught that nebulosity, and the mount tracking/alignment seems to have been very good..

Keep em coming!

[Robert_T]

Thanks Guys, yeh I have pulled this from IP into PS CS3 to finish off. I've applied a lot of tweak and every noise reduction going, but there are just so many settings in IP and PS for this sort of thing I don't know what's what.:shrug:

I played around and could reduce the noise a fair bit, but at the cost of some detail. See attached. I'll give the process another go and leave out the 10min 800ISO run.

Oh well I'm learning stuff... just have that feeling I might be missing somethimnng fundamental:whistle:

[jase]

With improved data, this image would show some real potential. Composition is good showing plenty of interesting objects in the FoV. Look forward to seeing more.

[Robert_T]

Thanks Jase, I'm hoping to capture some more data to add to this to improve it as I do find it a very interesting region with a lot going on.

Would you recommend deeper (longer) exposures at lower ISO, or more pushing the speed (eg 800iso)?

Anyway, in the meantime I've pulled right back on this image below just combining the best tracked 4 of the 6 images and limiting noise at the cost of nebulosity.

cheers,

Rob

[AlexN]

Rob, In my limited knowledge of astrophotography, my opinion doesn't mean much, but from my fairly extensive knowledge of dslr's I'll say more time/exposures at lower ISO's is usually always going to yeild better results.

However, some targets in the sky are very faint, and may not show up at the lower ISO speeds.. I dont know that for sure, but I would assume that as your shot without the ISO800 image included shows alot less nebulosity..

Also, in photoshop, have you tried setting your black point? the black background in that image doesnt seem very black to me..

Do you mind me having a quick play with one of the images?

[Robert_T]

Hi Alex, I thought someone would never ask;) by all means tweak away.

How do you set a black point in Photoshop? I've certainly played with all the background darkness and break points settings in Images Plus before importing to Photoshop. I can get the background a lot darker, but I lose a lot of star and nebulosity detail in the process.

[Robert_T]

Ah, I found the black point tool. Applied it and boosted curves a bit. This certainly gets rid of that ruddy background cast. I think it's improved all round :)

[[1ponders]]

Rob have a look in one of bluescopes most recent posts. I outlined how to get the colour balance happening using colour pickers. I'll see if I can find the post.

EDIT: Here's the posts.

1. Select the Eyedropper tool. Press the caps lock to make it a precision picker.

2. Image|adjustments|threshold. Slide the slider to the right until only one star is left showing. Hold down your shift key and click on the star. This will place a colour sampler point on the brightest point of your image (don't worry if it doesn't appear, it's there). Then slide the slider to th left until the darkest part of the image is the only part showing (ignore the edges that may need cropping). Shift +click another colour sampler there. Cancel the Threshold dialog.

3. Open the levels dialog box and double click on the left hand eyedropper at the bottom. In the new dialog box set the RGB in the bottom left of the right hand task bar to R15, G15, B20. Click OK. Do the same with the right hand eyedropper (white point) only set the RGB settings to around 245,245,245. Click ok to close that dialog.

4. Select the black point eyedropper and click on the background colour sampler of your image. Select the white point eyedropper and click on the star colour sampler. Click OK. You have not set your black and white points for all colours. BTW when your precision eyedropper is in the correct position over a colour sampler it will disappear so you know you are in the right spot.

If you look at your info pane now you will see that the two colour sampler points will show their RGB values. Now whenever you adjust your curves you can pop back into the levels box and reset the points when they start to get too out of whack. This is a very rough and ready process but surprisingly effective.

Works best if using adjustment layers as it's non destructive but you can use it on the original and go back through the history if you don't like the results.

If you don't already know this process I hope it helps.

[[1ponders]]

Here's a comparison for you Rob. RB did the processing on this one (and did a fine job too :thumbsup: ) that I took at Astrofest last year. using the 300D and Canon 135mm f/2 lens, 19 x 300sec @ ISO400 @f/2.8.
(Edit Whoops)
http://www.iceinspace.com.au/forum/attachment_browse.php?a=32325

More data need mate. :thumbsup:

[Robert_T]

Wow Paul, that looks fantastic. Sounds like I should have the same FOV as you (roughly) but yours looks a lot bigger here?:shrug:

Now I guess my next question will be around how come your bright stars are so nice and mine look like big blobs (tell me it's guiding and I need to buy a G11:whistle:)

So a lot more runs needed at higher ISO... I'm also running an IDAS-LPS that I assume you wouldn't have needed at Astrofest so that would have effecively put my images back a stop once again.


Thanks muchly - Rob

[[1ponders]]

Check the edit Rob. I made a boo boo. It was with my 135mm lens @f/2.8 :ashamed:

[Robert_T]

I feel soooooo much better now:rofl:

[[1ponders]]

:lol: So at f/6 and ISO 400 you would need to expose each shot at around 2400 sec to achieve a similar depth. Gowan 'ave a go. :lol:

[[1ponders]]

Here's something you could try Rob. Instead of average or median combining your images try using adaptive add or just plain add (which will probably blow your stars out of the water clipping them). But if you tweak adaptive add you might get more depth.

This a combo of M27 with no processing what so ever, just combined in different ways.

[AlexN]

good to see you found the black point... thats pretty much the way I was going have a play with it, so I wont bother posting what I changed.

Its coming along nicely.. and yes, If you're able to get yourself a f/2.8 lens then by all means go for gold!! :D