Thanks Greg, Bo, Dunk, Suavi and Colin. All of my imaging mates down here are die-hard monochrome CCD fans, and when you see what such gear can produce, it's persuasive. I like my Nikon D850, but I noticed last night that 40 seconds at 800 (moonless night) on a Zeiss 135mm (attached to a dovetail plate on my Vixen mount) was more than enough to saturate the sensor; 60 seconds was overkill. A ccd would, presumably, take longer before it reached saturation? The QHY 367 is full frame cooled cmos, so I guess that the cooling and maybe one or two other tech tweaks, are what diffentiates it from an unmodded Nikon D850?Don't know.
The QSI 683 or the QHY367 might be the way to go....two very different beasts!
Thanks everyone for your helpful advice. Much appreciated.
Can’t argue with the 367C, quite a beast, but both QHY and ZWO have announced a full-frame mono CMOS sensor for release this year which have pretty interesting specs.
While the 8300 is an old stalwart, there are other chips on the market now with better noise contributions (and thus SNR).
No reason for a mono sensor to take longer than a DSLR, it all depends on what gain is used (ISO is just gain). After all, a DSLR is just a mono sensor with a permanent filter array printed on it. Also, your 135mm is probably faster f-ratio than your scope, so will expose faster. But there’s no way of knowing exactly what the specs of Nikon’s sensor are...whereas astro and scientific manufacturers publish typical figures for their cameras.
Apparently the D850/Z7 has a lower QE than the D810A/QHY367/ASI094 but I get 14-bits of dynamic range which is better than the KAF16803 with 3.1e- read noise.
It’s a good chip
You sure its lower QE? I don't think so.
The D850/Z7 Panasonic S1R/Sony A7rii/Sony A7riii is a slightly modified Sony A7rii and iii sensor which is still the highest rated sensor on DXO Mark. Its BSI, has copper wiring, has refined microlenses and dual gain analogue to digital on chip converters.
The QHY367 is the older 36mp full frame sensor and for sure less QE as the A7riii sensor is backside illuminated with a larger surface area for light to hit as the circuitry is underneath. It also does not have the copper wiring which was a later Sony development.
The latest you-beaut from Sony that is not even in their own cameras yet is the QHY600 which is the next gen full frame backside illuminated (BSI) 60mp super fast readout sensor from Sony. I would expect to see that sensor in the upcoming Sony A7Riv camera probably coming out towards the end of this year or early next year.
That sensor is also available as a stacked sensor meaning they weld a DRAM memory chip on the back of it like in the Sony A9 which gives very fast response time and allows various features none of which would be that useful for astro but perhaps for planetary (60mp though is too large for planetary I would think).
Thanks Greg, Bo, Dunk, Suavi and Colin. All of my imaging mates down here are die-hard monochrome CCD fans, and when you see what such gear can produce, it's persuasive. I like my Nikon D850, but I noticed last night that 40 seconds at 800 (moonless night) on a Zeiss 135mm (attached to a dovetail plate on my Vixen mount) was more than enough to saturate the sensor; 60 seconds was overkill. A ccd would, presumably, take longer before it reached saturation? The QHY 367 is full frame cooled cmos, so I guess that the cooling and maybe one or two other tech tweaks, are what diffentiates it from an unmodded Nikon D850?Don't know.
The QSI 683 or the QHY367 might be the way to go....two very different beasts!
Thanks everyone for your helpful advice. Much appreciated.
Cheers,
Richard
The saturation point is all to do with well depth and at 40-60s it shouldn't even come close to saturation on anything but the brightest of objects even at ISO800.
What aperture were you using on the Zeiss 135mm?
At ISO800 the D850 likely has near a stop of dynamic range over the KAF8300 or ASI1600 variants.
The D850/Z7 Panasonic S1R/Sony A7rii/Sony A7riii is a slightly modified Sony A7rii and iii sensor which is still the highest rated sensor on DXO Mark. Its BSI, has copper wiring, has refined microlenses and dual gain analogue to digital on chip converters.
The QHY367 is the older 36mp full frame sensor and for sure less QE as the A7riii sensor is backside illuminated with a larger surface area for light to hit as the circuitry is underneath. It also does not have the copper wiring which was a later Sony development.
The latest you-beaut from Sony that is not even in their own cameras yet is the QHY600 which is the next gen full frame backside illuminated (BSI) 60mp super fast readout sensor from Sony. I would expect to see that sensor in the upcoming Sony A7Riv camera probably coming out towards the end of this year or early next year.
That sensor is also available as a stacked sensor meaning they weld a DRAM memory chip on the back of it like in the Sony A9 which gives very fast response time and allows various features none of which would be that useful for astro but perhaps for planetary (60mp though is too large for planetary I would think).
Its the direction Sony is going in.
Greg.
I went and re-read this thread on CN and I think I remembered a few snippets but not the context. I do agree with you that the BSI sensor in the D850 should have a higher QE due to the architecture so possibly what was being suggested towards the end of the thread is that the D850 has a lower QE compared to some of the other BSI DSLR sensors on the market at the moment.
The saturation point is all to do with well depth and at 40-60s it shouldn't even come close to saturation on anything but the brightest of objects even at ISO800.
What aperture were you using on the Zeiss 135mm?
At ISO800 the D850 likely has near a stop of dynamic range over the KAF8300 or ASI1600 variants.
Hi Colin. My D850 was simply mounted on a dovetail plate and the Vixen Mount(no telescope) on Friday and I found that with the Zeiss 135mm at f2.8 and 30 secs exposure, ISO 800, the image was overexposed (Rho Ophiuchi)Of course, at f2.8, the aperture would be a whopping 48mm....I looked at your link here to your image of M8. A stunner!
I am still having trouble finding the SCP let alone taking images like that...Maybe I should just hold on to my D850 for a while. I always thought that these CMOS cameras offered greater QE, better fidelity with colour frequencies, etc, but if all I am going to get in a camera like the QHY 367 is a CMOS that's cooled below ambient and is otherwise no better than my D850, why bother?
The saturation point is all to do with well depth and at 40-60s it shouldn't even come close to saturation on anything but the brightest of objects even at ISO800.
What aperture were you using on the Zeiss 135mm?
At ISO800 the D850 likely has near a stop of dynamic range over the KAF8300 or ASI1600 variants.
Hi Colin,
one example of an over-exposed image of Rho Ophiuchi (over saturated) with the 135mm lens at F2.8 is attached here, (apologies it was ISO 1600, not 800 as I claimed); so too, one of my images of the Galactic centre with the Zeiss Milvus 35mm at F2.8 30 secs and ISO 800 (and a feeble attempt at processing the image in LR). My camera was just sitting on my mount which was not polar aligned (no scope and it's hard to polar align with a camera alone; the polar scope was useless). Star trailing is obvious and I guess the white balance setting in the D850 was wrong (I forgot whether it was Auto or something else), hence the ghastly sepia tone of all 107 images I took. Not much to salvage here - but my point is if I were tracking accurately, how much better would any of these images look with 3 or 4 minute subs? Is it cooling the CMOS that is critical? As I have a full frame bsi sensor, would it be better to buy a CCD camera as I cannot imagine the Nikon in its unmodded state, delivering much more image detail, and certainly not the quality of your ASI094 image of Rho Ophiuchi....
I’d speculate that there’d be more similarities than differences between the 094 and the D850, especially in winter. While Nikon undoubtedly had a hand in it themselves, technologically it would have drawn on a lot of the Sony tech.
The cooling isn’t going to make a lot of difference on a cool winter evening. On a hot summer one, it’ll certainly help keep the thermal noise in check (but the influence of this would be limited in 40 second subs). Down in Tassie, you have to consider how much that is worth to you.
Of course, the other advantage to the cooled camera is that you can create a proper set of calibration frames. But again, how much is that really worth for some widefield shots?
So long as you captured RAW data with your Nikon, then the white balance would be irrelevant since it’s usually just a profile for viewing with.
If you had the camera on the tracking mount, the quality of your images are going to be largely dictated by the aberrations of the lens the sensor is peering through.
What you’re dealing with there is the setting of the black point and possibly light pollution. I’ve quickly run it through Lightroom on my phone.
Dropping the ISO down to maybe 200 and using some tracking for longer exposures will make a big difference. As Dunk says, there won’t be much of a difference in winter but during the summer having cooling can make a big noise difference.
I’d speculate that there’d be more similarities than differences between the 094 and the D850, especially in winter. While Nikon undoubtedly had a hand in it themselves, technologically it would have drawn on a lot of the Sony tech.
The cooling isn’t going to make a lot of difference on a cool winter evening. On a hot summer one, it’ll certainly help keep the thermal noise in check (but the influence of this would be limited in 40 second subs). Down in Tassie, you have to consider how much that is worth to you.
Of course, the other advantage to the cooled camera is that you can create a proper set of calibration frames. But again, how much is that really worth for some widefield shots?
So long as you captured RAW data with your Nikon, then the white balance would be irrelevant since it’s usually just a profile for viewing with.
If you had the camera on the tracking mount, the quality of your images are going to be largely dictated by the aberrations of the lens the sensor is peering through.
Hi Dunk,
These photos were taken inner city Hobart, with the city glow directly underneath (east), and facing south, my neighbours' lights were all on too, so I knew it was going to be bad, but the tracking was very poor without proper polar alignment. The Zeiss 35mm is perfection from F3.5 (half a stop down from the 2.8 I used); the Zeiss 135 is close to perfect at 2.8, but at extreme enlargement, some edge aberrations are present. Again, F3.5 is stunning. White balance/temperature can be altered easily in LR, thank goodness, as I hate the uniform dull brown cast of the raw files.
So are you saying that the 084 would not really offer significant gains over my unmodded D850 except perhaps during summer? Food for thought.
What you’re dealing with there is the setting of the black point and possibly light pollution. I’ve quickly run it through Lightroom on my phone.
Dropping the ISO down to maybe 200 and using some tracking for longer exposures will make a big difference. As Dunk says, there won’t be much of a difference in winter but during the summer having cooling can make a big noise difference.
Hi Colin,
You are spot-on about light pollution (as I have just written in reply to Dunk). I had a crack at Rho Ophiuchi in LR but without real success...The 'dehaze' tool is by far the most dramatic in its impact but it adds some sort of surrealistic sharpness here, I guess because, as you intimate, there is not enough data here to work with in the first place. I'll go to our dark site next time and try longer exposures (with correct PA).
The biggest improvement you’ll get with any astro OSC is the higher Ha sensitivity over an unmodded DSLR. It’s the main reason I bought the ASI094 while having a D810. The D810 is my every day camera but lacks the Ha sensitivity.
The biggest improvement you’ll get with any astro OSC is the higher Ha sensitivity over an unmodded DSLR. It’s the main reason I bought the ASI094 while having a D810. The D810 is my every day camera but lacks the Ha sensitivity.
Thanks again, Colin. Will wait a bit longer (ZWO have a new sensor coming out apparently) before I take the plunge.
Have been looking at your amazing images on Astrobin. Fantastic!
I would also go for a mono - and to keep things simple for a start one Luminance filter and one Ha filter - mono images of DSOs can be as beautiful as colour ones
The points you all make are also featured in a video I watched this afternoon from the Astro Imaging Channel : https://www.youtube.com/watch?v=d43vhG5R8xo - which, in my case is appropriately called 'Moving from a DSLR to Dedicated Astro Camera'.
