Vela SNR Mosaic Version Two

[avandonk]

Here is a better version. FOV is 11.8 X 11.2 degrees.


Small 4MB

http://d1355990.i49.quadrahosting.com.au/2010_03/mos2S.jpg

Medium 6MB

http://d1355990.i49.quadrahosting.com.au/2010_03/mos2M.jpg


Bert

[Moon]

Bert
That is simply stunning.
James

[Bassnut]

Wow, thats a huge effort Bert. Endless zooming renders perfect focus, guiding and stunning detail. umm, that would be a DM entry ? ;-).

[gregbradley]

That is a super image Bert. A real winner.

Greg.

[DavidU]

WOW alright !

[mill]

What could i say ? All the above :)

[AlexN]

I'm continuously astounded by your work Bert... This is an epic task you've set yourself.. Vela is a massive region of sky, with many different objects, all of which are considerably dim, and usually hard to process out against the sea of stars behind them...

If ever someone was to rise to the occasion.. This is it. :)

I'm blown away.

[CometGuy]

Bert,

Definitely APOD stuff there!

Terry

[avandonk]

Thanks for all the kind comments.

Over the last few years I have been tweaking my system to improve my data collection.

The mount is guided by a 1250mm FL Mak even when doing wide fields. Since I built the observatory my polar alignment is and stays about as good as drift aligning can get it.

The signal to noise is very good due to two factors the fridge cooling the camera and dithering between exposures. A futher refinement is using an aperture in front of the Canon 300MM F2.8L lens. An extension on the lens light shield also helps especially for the faint stuff. This even improves narrow band data.

Combining full colour and narrow band data was the trick to getting a 'natural' looking image of a very faint extended object such as the Vela SNR. I used a method that is quite unorthodox.

All the other images I have done were just practice and training for this one.

I will go on practising and one day may get it closer to perfect.

The one thing that really helped was enough nights of clear skies while Vela was at or near the zenith. In the past I have had mosaic interruptus more often than I would like.

Bert

[multiweb]

Absolutely superb. :thumbsup: All your hard work and dedicaton paid off and it certainly shows. I'm amazed at the sharpness of the details for such a widefield. How do you focus?

[avandonk]

I use a computer controlled stepper motor to focus the lens. The lens is held at a constant temperature by thermostatically controlled dew heaters. Focus is attained by taking test images 1000 steps apart (1000 steps is 0.15mm of focus ring movement). Once best focus is set not only does it not change for the night it is still at best focus for many nights as long as the lens and camera are equilibrated to their set temperatures. Typically 18C and -10C.

There is a reason for heating the lens body as it stops the filter in the lenses rear filter holder getting condensation due to the camera body being at -10C

Bert

[avandonk]

If you liked the previous versions this one is better as it is bigger.


Extra large 19MB

http://d1355990.i49.quadrahosting.com.au/2010_03/mos2XL.jpg



The original data is about twice this size in pixels!


Bert

[avandonk]

The other processing trick is because of the random dithering between exposures the stacked exposures if done at x1.6 times the native pixel size of your sensor you effectively more than double the size of your sensor in pixels. This is completely mathematically valid to a factor of the square root of two ie 1.414.

The sensor on my Canon 5DH has 8.2 micron square pixels. When sampling the image produced by the 300MM F2.8L the dim or faint stars are about at best three pixels across. The 300mm F2.8L has far better MTF than this. Another complicating factor is the anti aliasing filter on all one shot colour camera's. This filter stops Moire effects where the fine detail interferes with the sampling interval. This filter intentionally blurs the image so no Moire fringes are produced.

I will stop now.

Bert

[multiweb]

Amazing vista. :eyepop: Will have to check tonight on a 46" flat panel.

[avandonk]

Marc you mean yours is bigger than mine!

Bert

[h0ughy]

Bert - simply breathtaking. It is a work of Stellar art

[multiweb]

:lol: No, I have a 46 LCD upstairs with my PS3 and your pic is waaay too big for my flimsy PC monitor here. ;) Need a big screen to take all the picture in, in one go.

[AlexN]

Marc - Not to ruin the suspense for you, but its AMAZING on my 52...

[avandonk]

David I am glad you like it. When you have your observatory fully set up, you too can think more about imaging rather than being a pack horse carrying equipment in and out.

Bert

[avandonk]

I think APOD are a bit like Nature they want exclusivity.


Bert

[multiweb]

Story of my life! :sadeyes: I need a pier something fierce. :) I got donkey's ears growing a bit more everyday....

[strongmanmike]

Bert this is a great (almost incredible) image.

The image sharpness for a 300mm FL is fantastic

Combining narrowband and colour is most difficult, especially if your aim is to get a good colour dynamic range.

As I have said before you really need to get that lens out under a dark sky for a multiple night image run, I am sure your gradient removal work is a lot of your issue. If you were to do this I think you would be astounded at what that lens could reveal :thumbsup:

I think it is well and truely DM awards entry material, colour aint everything...sole ;)

Mike

[gregbradley]

Superb Bert absolutely superb. I like this version much better as it shows more vibrant colour which this area abounds in yet you've captured the delicate hues it also has in abundance.

As you may already know the bright detail in this zone is in the O111 images.

If you PM I can give you my secret recipe for combining the various narrowband and colour images. It needs to be done with layers - I don't think you could do it any other way and retain enough control. It is easy for it to go out of control combining narrowband and colour.

I am not sure your image needs any tweaking though as you have hit a very nice balance here and sometimes you need to take your hands off the computer and say that's it when you've arrived.

Greg.