Sony A7s or A7iii for astrophotography

[timwetherell]

I'm not as astrophotographer as such, but am toying with the idea of buying a general purpose dslr that will also double up as a rough and ready astro camera for my 7" f7 refractor. I'm not trying to take wonderful images so much as see things that I wouldn't normally be able to with a relatively limited aperture, such as the moons of uranus or spiral arms on brighter  galaxies. And if I'm going to spend quite a lot of money, it would be nice if it could double up as a good quality general purpose camera too - hence my inclining to the sony's rather than dedicated astro gear. A dslr also offers the advantage of an all in one package. My question though is would the 12mb A7s with it's bigger pixels and higher 400,000 ISO be better than the 24mp A7iii as an astro camera? I'd be really interested to hear if anyone had experience with either or both? Thanks

[happy-kat]

If it is a Sony then check first it is not a Sony with the issue with star eating through over zealous noise reduction which can't be turned off.

[timwetherell]

14 minutes ago, happy-kat said:

If it is a Sony then check first it is not a Sony with the issue with star eating through over zealous noise reduction which can't be turned off.

Yes I read about that! One review said the A7iii didn't have this problem but I don't know about the a7s - that's one of my concerns!

[nightfisher]

How about Canons, they seem popular as astro dslr`s, lots of useful software for them 

[John78]

So you're thing about spending £2k on a DSLR camera, that's not a DSLR to use for a general purpose camera that can also be used for astrophotography that has a reputation for screwing up long exposure pictures by its noise reduction you cant turn off.

I'd be inclined to get a Canon 6D, Mk1 or 2 - which is good for both, or a 5D Mk3+ if you need good video capability, or a dedicated entry level astro camera and a 6D Mk1, and still have lots of change from the £2k.

[timwetherell]

2 hours ago, nightfisher said:

How about Canons, they seem popular as astro dslr`s, lots of useful software for them 

Yes I thought about that as I have a 600D which is a nice camera. But I'm rather drawn to the high iso of the sony because in a way i'd like to use it as a poor man's photomultiplier eyepiece  If I could use a canon in that way too it would be a definite plus!

 

[timwetherell]

49 minutes ago, John78 said:

So you're thing about spending £2k on a DSLR camera, that's not a DSLR to use for a general purpose camera that can also be used for astrophotography that has a reputation for screwing up long exposure pictures by its noise reduction you cant turn off.

I'd be inclined to get a Canon 6D, Mk1 or 2 - which is good for both, or a 5D Mk3+ if you need good video capability, or a dedicated entry level astro camera and a 6D Mk1, and still have lots of change from the £2k.

I'm hoping not to spend anything till I've learnt more about these things   But from what i've read,the A7iii doesn't have the star eating problem but it's about £1600 whereas the £1000 a7s may indeed have that problem - that is one of my concerns. Canon would be a very attractive option for me because I have a few canon lenses already that would work with it. My concern with the 6D would simply be that the maximum iso appears to be 40,000? My 600d is a lovely camera but at its max iso of 6400 is horribly noisey. Perhaps the later model canons improve dramatically on that noise performance? One thing that's fairly important to my particular application is that I'd like a live view that provides greater sensitivity than just my eyes which the sony is reputed to do - but perhaps the canon can too? It's definitely worth a look because £500 will be a lot easier to find than £1600!

[John78]

1 minute ago, timwetherell said:

I'm hoping not to spend anything till I've learnt more about these things   But from what i've read,the A7iii doesn't have the star eating problem but it's about £1600 whereas the £1000 a7s may indeed have that problem - that is one of my concerns. Canon would be a very attractive option for me because I have a few canon lenses already that would work with it. My concern with the 6D would simply be that the maximum iso appears to be 40,000? My 600d is a lovely camera but at its max iso of 6400 is horribly noisey. Perhaps the later model canons improve dramatically on that noise performance? One thing that's fairly important to my particular application is that I'd like a live view that provides greater sensitivity than just my eyes which the sony is reputed to do - but perhaps the canon can too? It's definitely worth a look because £500 will be a lot easier to find than £1600!

ISO is generally a consumer photographer myth, sensors have a sweet spot anything other than that is amplifying the signal and the noise, Sony in particular use hidden post processing trickery to make high ISO images look not noisy.

Take a look at this table and you'll see the best place to use most Canon's (for astrophotography) is around that models default ISO which, when you think about it - makes a whole lot of sense, tune a sensor to do what its designed to do to optimise its S/N ratio.

[Synchronicity]

Are you planning to do imaging with the camera or is it more along the lines of an electronic viewfinder?

Imaging needs low noise to allow faint signals to be brought out during post processing as well as low ISO to avoid saturation.  If you want a decent live view then that's more along the lines of electronic assisted astronomy (EAA) which a number of people here do.  The bottom line is that boosting the incoming signal will always boost the noise so you'll need to decide at what point that becomes unusable for you.

I'd try with the camera that you have set to high ISO and see what you can achieve. If you can connect it to a laptop for live view that also opens up possibilities for taking the image for best performance.

Michael

 

[nightfisher]

Another option to think about is video astronomy, keep the 600D and get a nice video camera

[timwetherell]

7 hours ago, Synchronicity said:

Are you planning to do imaging with the camera or is it more along the lines of an electronic viewfinder?

Imaging needs low noise to allow faint signals to be brought out during post processing as well as low ISO to avoid saturation.  If you want a decent live view then that's more along the lines of electronic assisted astronomy (EAA) which a number of people here do.  The bottom line is that boosting the incoming signal will always boost the noise so you'll need to decide at what point that becomes unusable for you.

I'd try with the camera that you have set to high ISO and see what you can achieve. If you can connect it to a laptop for live view that also opens up possibilities for taking the image for best performance.

Michael

 

Primarily, I'm hoping to create an electronic viewfinder but I'd probably want to take the odd snapshot too. But I'm not trying to capture anything like the fabulous multicoloured images people achieve with stacking and cooled cameras. I've tried with the D600 at iso6400 (its max) and to be honest, it's hopelessly noisy and insensitive - I think because it's an older camera/sensor. I'd need something with an inherently more sensitive CCD to start with because as you say, just boosting signal also boosts the noise. The A7s interested me because its large sensor and low pixel number should theoretically mean bigger pixels and less noisy low light performance. But the star eating noise reduction algorithm is a major concern! If it were fifty quid I'd just give it a bash, but a grand is a different matter  

[timwetherell]

57 minutes ago, nightfisher said:

Another option to think about is video astronomy, keep the 600D and get a nice video camera

Yes, that's a definite possibility. The 600D is a cracking camera for day to day photography but not great in low light. I'd prefer to have a simple setup such as a camera unit with integral screen or camera with an HDMI output to a seperate mini screen rather than have to run a PC and stacking software in the obsy. I have friends that do that stuff and they get great results but I'm more after the immediacy of visual observing - I guess because that's what I'm used to. If I could find a sensitive enough video camera that would work very well. I did see a canon ME20F-SH which has amazing low light performance then I saw the amazing £17,000 price tag - which is so far beyond my budget it would take the light from my budget a million years to reach it

[nightfisher]

£17,000 is a no no unless lotto numbers come up, have a look in the video astronomy section, i bet you could put a nice system together for well under £500 including a monitor, for a nice small screen that runs on lipo battery look at the radio control flyers FPV screens 7-10 inch just right

[nightfisher]

I missed the bit about an obsy, so a 17" pc monitor would be better 

[timwetherell]

2 minutes ago, nightfisher said:

I missed the bit about an obsy, so a 17" pc monitor would be better 

The only thing is that I don't have 240V in the obsy, just 12DC so would have to be a low voltage version  

There's so many possibilities and so many subtle nuances to get my head around I may be on a long learning curve!

[nightfisher]

4 hours ago, timwetherell said:

The only thing is that I don't have 240V in the obsy, just 12DC so would have to be a low voltage version  

There's so many possibilities and so many subtle nuances to get my head around I may be on a long learning curve!

You can hook up to a laptop this would give the option to record as well