M20 and M21 - fun with in camera noise reduction

[DJT (David)]

This is a test series of 4 * 20 minute subs at ISO 400 using an unmoddified DSLR with a CLS filter and in camera noise reduction, the image taken in my back yard over 2 nights..No bias or external darks were used but flats were stacked.

http://i1154.photobucket.com/albums/...INSICDRPS1.png

Am still trying to grips with all the discussions on more subs, less subs, SNR, how many darks, use of Bias etc, so I decided to step right back and get back to basics. Basic rule of thumb, less ISO and more signal.

Am pleased with reduction in my usual level of noise and with how well the image held out on processing but would value further feedback as I think that for a DSLR this process seems to be effective. Tweaks in setup needed as slight egg in some stars to the right of the image.


Thanks for looking

[Rigel003 (Graeme)]

Looks good but if anything the nebula looks a little too smooth. I'd turn off the in-camera noise reduction. In post processing you can do it more selectively. You have more control over the amount of noise reduction and have the option of deselecting the brighter stars and nebula and reducing noise only in the dimmer regions.

[DJT (David)]

Originally Posted by Rigel003

Looks good but if anything the nebula looks a little too smooth. I'd turn off the in-camera noise reduction. In post processing you can do it more selectively. You have more control over the amount of noise reduction and have the option of deselecting the brighter stars and nebula and reducing noise only in the dimmer regions.

Thanks for that. Wondering if I overcooked with Noise Ninja rather than this being an in camera dark removal thing. I will go back and check how this looks before applying noise reduction with this.

[jjjnettie (Jeanette)]

I'd not be using ICNR. You are using valuable time that could be used to capture more subs. Once your session is over you can take your flats then leave the camera to take darks.
I don't know if its noise ninja or the ICNR, but your back ground stars are very faint. The image should be sprinkled with golden star.
Otherwise, congrats on getting such long subs. I'm jealous.

[alocky (Andrew lockwood)]

Very nice results - your guiding setup is working pretty well to let you go that long with very little elongation.
I was playing with my own D200 on the weekend and did a little experimenting with best iso numbers too. I found if you leave the long exposure noise reduction on, and set the 'high iso' noise reduction to normal, it works best at about iso800, if you disable the Nikon 'star-eater' by switching the camera off as soon as you close the shutter; that forces it to save the image without taking the dark frame.
I was able to get the attached with 5 x 5 minute subs, 5 x 5 minute darks and processed in deepsky stacker with a tiny bit of horsing around in photoshop. You can see plenty of glow from the amplifiers in the corner of the light frames, but the dark subtraction does remove most of that. ISO 1600 is too much for the D200, but 800 seems like a good compromise.

I mucked the focus up when I tightened the loose adapter on the drawtube without considering that it moved the camera so don't look too closely, the earlier images of the night were much sharper... Scope was a 4" f5 APO and polar alignment was only via the alignment scope, no drift aligning. I was experimenting too, the sky was very dark, and there was a 25" Dob 5m away...
cheers,
Andrew

[DJT (David)]

Originally Posted by alocky

I was playing with my own D200 on the weekend and did a little experimenting with best iso numbers too.

Nice image Andrew. I should update my signature as i am now using a canon 30d

To jjj, I'll redo with the long subs and try external darks.

Thanks for feedback

[alocky (Andrew lockwood)]

Right then - no 'star eater' at work in your camera, and you'll probably find a different iso compromise works best for you too! I wonder if the new D800 has the same 'feature'?
cheers,
Andrew.