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Various DSO's unprocessed from Sony A7S

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#26 jimthompson

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Posted 16 September 2014 - 01:22 PM

Dom,

 

The white balancing of which you speak exists but is mearly image manipulation to fool the everyday user into thinking the colours are correct.  The colour temperature setting available on many cameras is a similar form of eye-trickery.  A finer look at images colour corrected this way will show artifacts such as glints (in terrestrial photography) or stars (in astrophotography) that are not white, or relative colour brightnesses that do not represent the true scene.  Using DSP for colour balancing works for everyday consumer level devices but not so much for astronomy.  Note that you can not tweak the red colour channel to make a nebula more visible if there is no signal getting through to the sensor from the nebula in the first place.  This is very evident in the image by jdbastro of M8.  Note how outside the main bright reflection dominated part of the nebula there seems to be simply nothing, just stars.  In reality the nebula fades gradually from center to well outside the object.  A camera that can see Halpha would pick this fainter nebulosity up, but a camera with a typical commercial IR cut filter will not.

 

Best Regards,

 

Jim T.



#27 bwallan

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Posted 23 September 2014 - 03:50 PM

 

Snapped a variety of DSO targets the other night from Mount Pinos, Calif. with the A7S and various lenses. Longest exposures were 30 sec (tracked). Shortest were 1 sec (untracked). All are Jpegs straight out of the camera with all default noise reduction enabled, white balance set to 3500K, 'clear' picture mode.

Here's the album link.


Nice shots!

One question: why does your NGC 6960 image does not have any red color compared to same image taken by bwallan here https://plus.google....148685511342... , considering both images were taken with unmodified A7S?

 

Yupp, it takes a little bit more than one 30 sec shot to adequately capture Ha emission nebulosity with an unmodded camera.  But stack 30+/- 30 sec subs and an unmodded A7S does a decent job.  Actually, the A7R gives much the same results when compared on the same size scale, i.e.: the reduction from 36 MPixels to 12 MPixels does wonders to noise levels!

 

The following is a mosaic of five images off the A7S using the A7 28-70mm kit lens (28mm & f/4.5); 20 sec shots at ISO12800:

 

MW%2BFriday%2BPanorama-1.jpg

 

 

The whole album of A7S images from Alberta Star Party 2014 is here.  Be sure to read the comments to the album.  

 

The A7S is a great all-round camera from noon to midnight!

 

bwa



#28 bwallan

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Posted 24 September 2014 - 05:49 PM

Snapped a variety of DSO targets the other night from Mount Pinos, Calif. with the A7S and various lenses. Longest exposures were 30 sec (tracked). Shortest were 1 sec (untracked). All are Jpegs straight out of the camera with all default noise reduction enabled, white balance set to 3500K, 'clear' picture mode.

Here's the album link.

Why not just set White Balance to Daylight or AWB?  I find Daylight gives very realistic color (whatever that may be).

 

bwa



#29 Relativist

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Posted 06 October 2014 - 12:08 AM

 

 

Snapped a variety of DSO targets the other night from Mount Pinos, Calif. with the A7S and various lenses. Longest exposures were 30 sec (tracked). Shortest were 1 sec (untracked). All are Jpegs straight out of the camera with all default noise reduction enabled, white balance set to 3500K, 'clear' picture mode.

Here's the album link.


Nice shots!

One question: why does your NGC 6960 image does not have any red color compared to same image taken by bwallan here https://plus.google....148685511342... , considering both images were taken with unmodified A7S?

 

Yupp, it takes a little bit more than one 30 sec shot to adequately capture Ha emission nebulosity with an unmodded camera.  But stack 30+/- 30 sec subs and an unmodded A7S does a decent job.  Actually, the A7R gives much the same results when compared on the same size scale, i.e.: the reduction from 36 MPixels to 12 MPixels does wonders to noise levels!

...

bwa

 

 

Can you give some examples of adequately captured Ha emission nebulosity using an un-modded camera? I've seen what some of the dedicated cameras can do with Ha, and it would be nice to compare to what the A7s can do modded after you get it back. (If I remember right your getting yours modified)



#30 DuncanM

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Posted 06 October 2014 - 03:45 PM

I'd really love to see some autoguided, long exposure (5min +) low ISO, images from the A7S. 








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