Sony have some new 2nd Gen Pregius CMOS sensors which are starting to make their way into commercially available cameras. In particular, the IMX250/IMX264 looks good - 5MP, QE of about 70% and very low read noise (looks to be about 60% lower than the 1st Gen Pregius IMX174).
I wonder if ZWO, QHY etc have plans for an astro version of this sensor. Combined with active cooling i think it would be a good contender to apply to deep sky luck imaging at shorter focal lengths of say 1m.
Although these two new CMOS sensors have higher QE than ICX694/ICX814 (CCD), but I think pixel size (3.45 micron), limited dynamic range (due to 12bit ADU and small pixels) and in particular sensor size (11.1 mm diagonal) are altogether too limiting for many amateur astrophotographers.
However, if these sensors are cheap, then maybe some manufacturers will implement them in their 'budget' astro-cameras?
well the pixel size is not that dissimilar to the cooled ASI178 and ASI1600 cameras (2.4 and 3.8 micron respectively). The FOV of the IMX264 matched with my 200mm f4 newt would be similar to that of my current KAF3200 / VC200L @ f6.4 combo, so I don't see FOV as a huge issue either.
As described by Ray in this thread, 12bit ADU is not an impediment when the read noise is as low as this. Lucky imaging with the 12 bit ASI174 seems to be working in this deep sky image of M64, using 1s subs (yes, 1 second).
The FOV of the IMX264 matched with 200mm F/4 scope would be quite limited really (37' x 30') and sampling at circa .89" per pixel will require longer exposures to capture faint signal, and that's where 12 bit ADU and small pixels will have an impact on the data, in spite of low read noise.
While the result with 1s exposures is quite impressive, nonetheless I do not think that a sensor with these parameters will lure many manufacturers to implement it in an astro camera, with the exception of budget ones. That's how I see it anyway
EDIT: I just checked Emil's DSO gallery - I should eat my words! LOL
I am not sure 12 bit is too much of an issue. Your average astro image at 16bit only takes up a tiny slice of the available histogram hence the need for levels and curves to boost the areas of the histogram where the data actually is.
Modern DSLRs are usually 12 or 14 bit. They were 8 bit not that long ago.
Some are 14 bit but switch to 12 bit in some uses (Sony A7 cameras when switched to bulb mode or some other specific features).
I am not sure 12 bit is too much of an issue. Your average astro image at 16bit only takes up a tiny slice of the available histogram hence the need for levels and curves to boost the areas of the histogram where the data actually is.
Modern DSLRs are usually 12 or 14 bit. They were 8 bit not that long ago.
Some are 14 bit but switch to 12 bit in some uses (Sony A7 cameras when switched to bulb mode or some other specific features).
Greg.
Case in point: this image, captured with my cooled 12bit Canon 1000D
As I understand it, whether the stars are clipped or not will depend on the full well depth, and not on the quantization. If the well is full, then it doesn't matter whether you have 12 bit or 8 bit or 16 bit.
thanks very much for the info Richard - just when I had almost made up my mind.
I agree that the 12 bit quantization is not an issue - that's all the (single sub) dynamic range there is anyway and you can boost it back to any desired value by combining large numbers of short subs (and you can do short subs because of the low read noise).
Ray - I emailed ZWO regarding these sensors, and they responded with:
Hi Richard
we don't think the new sensor is better than ASI290 for planetary
and they are not better than ASI1600 for DSO
so we may not have interesting to build a new line for them
Best Wishes
Sam
ZWO Co., Ltd.
At the moment the only vendor I can find for this sensor is Point Grey, who have the IMX264 in the (uncooled) Chameleon3 usb3 format for $735 USD. Maximum exposure is 12secs according to the product specs: https://www.ptgrey.com/chameleon3-50...ion-sonyimx264
Update - i've taken the plunge and placed an order for the Point Grey Chameleon3 IMX264 mono, with the intention of applying it to both lunar and deep sky lucky imaging. The smaller chip size means I can use it with my existing 1.25" filters without vignetting. Data storage should also be more manageable than the alternative ZWO ASI1600MM. Read noise should be just as (if not more) favourable than the ZWO camera, and the dark frames I have seen suggest that amp glow is minimal.
Once I have received the camera I will conduct some tests of read noise and dark current vs gain and share the results here for those who are interested.
A couple of first light images from my new Point Grey Chameleon 3 IMX264 equipped camera. Note that this camera is (currently) uncooled. I plan to fit a small peltier cooler to the camera body in coming weeks.
NGC5139 - 100 x 5 secs subs, gain 15 dB, Astronomik R filter (clouds prevented capture of a full colour set)
M20 - 200 x 5 sec subs, gain 15 dB, Astronomik L filter
scope = Long Perng 80mm f6 achromat, no field flattener used (FOV is small enough that i gambled on not needing to use one)
sensor temp ~ 28 C
Captured with Firecapture v2.5.05. No processing apart from a histogram stretch. Processed with PI.
Am currently trialling some other gain/sub exposure combos, and will post results for those interested.
Short subs are where its at. Ultimately my plan is to use this camera on my 200mm f4 newtonian, for high resolution imaging. I expect that dark noise will be reduced substantially with active cooling, and my preliminary tests suggest that read noise may be sub 1e at high gain, although (like the ASI1600MM) this comes with the trade-off of saturation capacity. Exciting times !
Interesting post Richard. Also the links on specs and images - fantastic result that Emil achieved - It's what Im hoping to attempt with imaging from the burbs, short subs but plenty of them !
You have a very vast knowledge of cameras and their specs, capableness etc!
Ill try keep in checking out your 8" F4 results - in deepsky I assume !
Good Stuff to read !!
Thanks Bob. Yes the plan with the 200mm f4 is for deep sky. I expect that this camera will also be a lunar/planetary killer too, so will be trying that out with my 200mm f6 and x3 extender in due course also.
Yeah Keool, the good of both worlds with one camera.
apart from dslr, ive only had the qhy10 c. tho now starting out with Zwo asi cool colour, really small pixels, not as much dynamic range, but thinking in LP, why attempt the hard to gather faint stuff,. The small 2.4um pixels should suffice with bright galaxies. even with the bayermatrix the four combined pixels in these is a still small 5.76um.
Maybe blend some short subs with longer subs.. Sounds feasible ?
