California Nebula - Work in Progress

[MarkS]

This is a proof of concept for a follow-up night of imaging.  This is very quickly processed just to see what is there.  There are still some residual background gradients but the surrounding dust is beginning to become quite obvious.

90min total exposure in 30sec subs taken between the clouds last night with H-alpha modified Sony A7S on Tak Epsilon 180ED.



Larger version here:  http://www.markshelley.co.uk/Astronomy/2016/california20161005.jpg

I definitely think this warrants a full night of imaging later in the season when it is higher in the sky.

I've hit a new problem with the Sony A7S when stretching the data so much.  The master flat has a lot of concentric rings of coloured banding caused by the compression scheme used by the raw.  It reacts with the concentric coloured banding in the lights in weird and wonderful ways.  I don't yet know how to get around this.  I have quite a backlog of processing waiting for a workaround   This might well be the issue that finally breaks the camera for me.

Mark

[Carole]

That camera is wonderful, but seems there are a lot of technical issues not designed for astro-imaging, i.e. long exposure and stretching of data. 

Looks a great start on the California Nebula.

Carole

[JohnP]

Great Potential. John

[MarkS]

For those who are interested, I finally got to the bottom of the concentric banding issue that I mentioned above.

You can follow it here:
http://www.cloudynights.com/topic/557931-concentric-coloured-rings-caused-by-flats/

Yet another compromise built into the Sony A7S

Mark

[JohnP]

Mark - just read the whole of that thread - I really am amazed at your tenacity to stick at a problem till you find a reason/ answer - You must know as much about the A7S as Sony engineers.. So problems you have found with this camera to date are:

banding due to two part sensor build
<30 secs exposures due to star eating algorithm
& now concentric banding due to ADU scaling factors...

All I can say is despite the faults it/ you still produces amazing images with it.

Thks for sharing,  John

[MarkS]

Thanks John!

Yes you've summed up the problems quite nicely.

Regarding star-eater, there has been a nasty development just this week on the DPReview forum.  Sony released a firmware update for the Sony A7RII with an unannounced change to the way that star-eater behaves.  It now applies in bulb mode and to any exposure over 4 seconds.  I suspect the same crippling "upgrade" will be rolled out to the other A7 series cameras.

If Sony's ultimate aim is to prevent their cameras ever being used for astrophotography then I can't think of a better way to achieve it

Mark

[JohnP]

Well if Sony made dedicated astrophotography cameras and they didn't want to compete with their own products I could understand that.. but to me it sounds like if they made a few tweaks to the A7 they could open up a whole new market. If it wasn't for the negatives you've uncovered and the price I for one would be seriously tempted to get one. I've enjoyed following your analytical approaches to solving the problems you've uncovered.  Cheers. John.

[RobertM]

I read that topic as well, all in all it's very depressing

The only saving grace is that it still produces great images.

Robert

[Kenny]

Amzing, such beauful rich colours and detailed starfield.

[Carole]

I presume the star-eating upgrade will only apply to new models, i.e. not ones already bought like yours. Presume you never have to plug it into the internet or anything.

Maybe what Sony needs is feedback from someone like yourself to tell them the problems for astroimagers and the market they will be losing out on. Then suggest the dedicate one model for the astro market only.

Carole

Carole