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Old 17-07-2017, 03:07 PM
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graham.hobart (Graham stevens)
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new full frame camera advice (OSC)

With the arrival of my new scope I am in the market initially for a full frame OSC . I haven't been keeping up with the new cameras and as such know little about what is available. My 5D mark II is showing its age and I am using my cooled 60Da on my fs60cb. I Want to know a little more about the colour sensors out there. My friend has an A7 which looks good but I heard something about the software being a bit star unfriendly. I have also noted the existence of backyard Nikon so wouldn't rule out a Nikon. Any suggestions ?
For use with 106N.
Graham
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Old 17-07-2017, 03:27 PM
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alocky (Andrew lockwood)
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The Nikon D810A and the FSQ Seem to be a very good match. I'm very happy with the results.
I think the same sensor is now available in a cooled Astro-friendly body, so the would be better again.
Cheers
Andrew.
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Old 17-07-2017, 03:30 PM
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Atmos (Colin)
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If you only want it for astro work then I would suggest a QHY367 which has the same sensor as the Nikon D810a & Sony A7R? It is a cooled 36MP FX camera dedicated for astro.

If you want to use it for general photography then there is the standard D810.

Most of the Nikon cameras use Sony sensors, until very recently Sony had a noise reduction that kicked in for exposures longer than 30s. It is better than it was but I think there is still some star water going on.
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Old 17-07-2017, 04:30 PM
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gregbradley
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Hi Colin,

The Sony star eating algorithim is essentially the same as the one Nikon was using until a few years ago. It was actually fixed by a non Nikon hobbyist engineer Marianne Oleund.

Basically its an algorithim designed to remove hot pixels which are defined as too bright a pixel (compared to its neighbours within an 8 pixel section due to RGGB filters) that is within a 2x2 pixel grid.

It has not been improved really. A7, A7r, A7s have it where it kicks in in bulb mode (ie beyond 30 seconds) since about firmware 3.3 for A7r2 it kicks in earlier at any exposure longer than 3.2 seconds.

My A7r2 is running firmware 3.1 and should only be kicking in during bulb.
But the recent image I did with 5 minute ISO640 exposures did not show any evidence of star suppression - hard to tell when its a field full of stars.
From examples I have seen it mostly diminishes or erases dim stars in a field. So longer exposures may overcome it.

http://www.pbase.com/gregbradley/image/165750987/large.

The thing about Sony A7 is the high QE sensors and low read noise.

Sony A7r QE is 50% read noise of 2.3 electrons full well depth of 49714

Nikon D810 is QE 47% read noise of 1.3 electrons and full well depth 78083

I am not sure how Nikon coaxes such better full well and read noise out of the same sensor as the A7r.

A7r2 sensor data is not available but it would be substantially better than A7r.

Canon 6D has dark current suppression technology, so does 7D mark 2 which has high QE and low noise. The new 6D2 has much the same dynamic range if not very slightly worse as the older 6D.

My opinion is go for at least 45,000 full well. My experience with CCDs is that full well depth is an often overlooked stat of a sensor and one that affects the image quite a bit.

The Sony A7s stats are crazy good, 65% QE, 0.4 read noise and 155,000 well depth. If not for the star eater it would be perfect. But there are plenty of good images around from those using one so perhaps that should be the go. There is currently a lot of pressure being put on Sony to correct the star eater algorithim. So perhaps within a year it will be corrected but not yet. A recent firmware upgrade improved it marginally in the green channel.

A full list of camera's performance is here:

http://sensorgen.info/


Greg.
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Old 18-07-2017, 07:50 AM
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graham.hobart (Graham stevens)
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best full frame

The Sony A7s looks good - what about computer control of the thing? Anyone doing any software for it yet?
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Old 18-07-2017, 10:47 AM
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SimmoW (SIMON)
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Fun decision Graham!

Look back to my Sony A7s pics in Flickr, go here, the last Pic taken with it - https://flic.kr/p/DhtW9E

Never noticed any star eater issues with it, maybe the firmware is too old? Aint upgrading it!

I've started using it again with my new 10 inch scope and am very determined to get it working after seeing the early results. From my light polluted BY it grabs a heap of data in 2 mins and 4 with a 6nm ha filter.

But, and this is a big but- Sony's ASK is incompatible with any of the astro control software. I have to use 2 free bits of software to control and schedule it. And am currently trying to work out how to use my guidecam as the focus control cam, since I can't use autofocus software with it. No news about improvements in compatibility yet. Idiots.

If you get it modded, use an expert provider and be sure to that they maintain ability to do terrestrial and Wide-field shots, bad guys will fail that and the cam wont get focus for these targets at infinity.

Good luck!
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Old 18-07-2017, 10:58 AM
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I've been using the CentralDS Astro A7S for the past 2 years - it's a cooled mod of the A7S. The star eater algorithm for the original A7 series (pre II) kicks in at bulb as mentioned before.

It really depends on what focal length you're using - i.e. what scope you have. I use my cooled A7S on the Takahashi Mewlon 250CRS (2500mm focal length) and exposed as long as 35 min subs and no star eater issue.

However on my Pentax 125SDP with reducer (600mm focal length) and it's readily apparent in subs however is worked around by drizzling.

So, I pair my cooled A7S with the Mewlon 250CRS, and my D810A with the Pentax 125SDP.
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Old 18-07-2017, 12:01 PM
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Oh, be careful with pixel scale with the a7s, while adequate it might not be to your liking, around 1000mm fl seems to be it's sweetspot . If my images look ok to you, youll be happy. If you can put up with the software niggles
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Old 18-07-2017, 01:00 PM
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graham.hobart (Graham stevens)
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OSc choice

exciting stuff. Nikon D810A - I wonder if centralds will cool that one down (has more Ha response than the normal 810- )
I wonder if Gama will get the QHY camera in.
I wonder if it will rain for the next two months
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Old 18-07-2017, 11:34 PM
AnakChan (Sean)
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Quote:
Originally Posted by graham.hobart View Post
exciting stuff. Nikon D810A - I wonder if centralds will cool that one down (has more Ha response than the normal 810- )
I wonder if Gama will get the QHY camera in.
I wonder if it will rain for the next two months
CentralDS does offer their D810 cooled mod but not much point giving them a D810A to cool since they'll take away the filters off the D810 anyway which will be more Ha responsive than the D810A.

I guess one benefit of sending in the D810A to CDS cool mod is to take advantage of the D810A firmware vs the regular D810 firmware.

http://www.centralds.net/cam/?produc...led-nikon-d810

Last edited by AnakChan; 18-07-2017 at 11:35 PM. Reason: Adding link to CentralDS D810 cool mod
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