New sensors from On Semi

[gregbradley]

A few new sensors available now.

KAF16200 26.64mm x 17.76 (APSh) 3624 x 2424 pixels 6nm size. 37k full well. QE is a bit unclear its supposed to be similar or better than KAF8300. It may be a tad as the pixels are a little larger.

KAI8670 also APSh sized 8.6mp 12 electron read noise 7.4 nm pixels.

The 16200 sounds good. QHY are going to release a camera with a shutter like an SBIG. OAG and filter wheel combined for this 16200 sensor.

It could be a good upgrade for those who want a bit more FOV than their KAF8300 gives.

http://www.qhyccd.com/IC16200A.html

Also On Semi have developed a KAI47051 sensor (47mp). It looks to be quite large perhaps larger than the 16803. That could be a nice sensor.

Finally some movement in the CCD sensor market.

Greg.

[Octane]

Meanwhile, Canon has announced a 250 megapixel APS-H sensor.

H

[Slawomir]

That's very interesting, thank you for the heads up Greg.

As for the 250mp camera...19,580 x 12,600 pixels with sensor size 28.7 x 19 mm that gives pixels 1.47 x 1.51 microns promising hopeless sensitivity and very shallow pixel wells...no thank you :)

EDIT: Canon specifies its 250mp sensor to be 29.2 x 20.2mm.

[RobF]

Wow, thanks for sharing Greg.
The new QHY cameras are interesting. Similar integrated format as QSI, integrated OAG, onboard RS232 and USB hub for mount and focus control. Looks like for another $500US they have a model with built in PC if I understand correctly including WiFi that could save having a small format PC strapped to your rig (as some people are starting to do).

Interesting times ahead.

Will be interesting to see the 16200 specs. Size would of APS-H sensor would be really nice to have - about 50% bigger in both dimensions for 135% more area that KAF 8300.

[RickS]

Read noise of 10 or 12 e- is horrible for smallish pixels :shrug: Can't they get it at least halfway towards the RN on the Sony sensors which is down in the 3 to 5 region these days? The effect of read noise increases at its square so it gets ugly, especially for narrow band where you're almost certainly read noise limited.

Cheers,
Rick.

[gregbradley]

I don't know Rick. STL11 was around 12 electrons read noise and there are plenty of great narrowband images from them.

Greg.

[RickS]

12e- is not great Greg, but it's a 9x9um pixel and collects a lot of photons. A 7.4x7.4 um pixel is 2/3 the area so you'd expect read noise of 8e- assuming no improvements in the technology. As I mentioned, the Sony chips do much better. It's not that you can't produce good images with high read noise but it takes a lot more data... and it's not like we get a lot of good weather!

Cheers,
Rick.

[gregbradley]

True! I didn't think of the smaller pixel size.

Sony does do a better job. Its a shame they are shutting down their CCD production in favour of CMOS production.

Greg.

[RobF]

More reading on Cloudy Nights: http://www.cloudynights.com/topic/509358-very-new-dso-imaging-qhyccd-cameras/

Including speculation KAF 16200 might be more like 6-9 e- RN in astro use.

[Peter Ward]

Can't say I'm overly impressed by the new sensor specs...though, have to admit, the ON Semi (Truesense) KAI-47051 is BIG!

...but...interline chips/ low well depth/14bit DA and/or high read noise doesn't seem very revolutionary to me.

I have two (not so cheap) Sony sensor cameras for solar work. The CMOS one looked good on paper, but the (previous model) Sony CCD is far superior.

I suspect the bean counters have already made the call, and for astro-imaging community, these new sensors may be akin to re-arranging deck chairs on the Titanic. :sadeyes:

[SimmoW]

Wow, I better look that up. Hey, can you send me a raw demo file? Just one? Whoops sorry, won't work, the file's too big!!

[RickS]

A friend of mine in the life sciences business gets to play with all the cool low read noise cameras (1e- and less.) Unfortunately, they have small sensors and are stupidly expensive

[gregbradley]

I see there is a new Sony ICX695 is 14.6 x 12.88mm and nearly 80% QE. That's larger than the ICX694 which is 12.48 x 9.98mm. Still 6mp. Same size pixels. Did they space the pixels further apart and use a larger microlense? That's a very tricky way to get a bit more light into the sensor.

Greg.

[gregbradley]

[QUOTE=Peter Ward;1201271]Can't say I'm overly impressed by the new sensor specs...though, have to admit, the ON Semi (Truesense) KAI-47051 is BIG!

I think its more the size. APSh is a bit of a hole in the sensor lineup where you either get fairly small sensors or really large ones.

Just like in the digital photography world APS size is becoming not well catered for anymore.

BTW 6micron pixel is probably the perfect size pixel for the Honders.

Greg.

[RickS]

I can't find a data sheet for the ICX695 but I found another camera vendor who says it is 12.5x10.0mm. That's the same as the result I get when I do the arithmetic. Did you get the info from the QHY site, Greg? Perhaps it is not accurate...

Cheers,
Rick.

[gregbradley]

http://www.qhyccd.com/IC695A.html

Gee QHY have come a long way. Their new line of cameras look to be very sophisticated.

Greg.

[Shiraz]

do you like this one? >0.7 QE, <2e RN, 120ke Wells, 11micron pixels, 48fps http://www.qhyccd.com/QHY42.html

chip appears to be a native Chinese design? http://www.gpixelinc.com/en/Data/Uploads/file/14310698026412.pdf

[gregbradley]

That sounds on paper to be a superb choice for my CDK17.

Greg.

[Atmos]

The 12 bit output would be its only major pitfall.

[gregbradley]

Not necessarily, as most of the image data is in only a small slice of the normal 16 bits but it could mean posterisation in heavily pushed images in dim areas. Worth knowing and checking for.

Greg.

[Shiraz]

even better if the 12 bits are focused at the bottom of the dynamic range and the ADCs just saturate at a fraction of full well. Then, the main advantage of the deep wells is that they will handle brighter stars without lateral blooming, since I suspect that ABG will be difficult to implement in a back illuminated chip. At 48fps and nearly no read noise, this chip would be usable with very short subs, so lots could be used to get much more than 12 bits of dynamic range.

but we are dreaming - there is no such camera yet :lol:. Though it is refreshing to see something that does not appear at first glance to be based on a pixel design from the last century.

[Slawomir]

After a bit of Internet searching I found that all other manufacturers state that ICX695 is the same size as ICX694. The only difference between ICX694 and ICX695 that I managed to identify is that the 695 has half the maximum frame rate supported by the chip that of 694. The same was for ICX814 and ICX815, 814 being the faster of the two (twice as fast). Not sure what impact that would have on astrophotography, maybe download speed would be slower and thus focusing would be affected?

Curiously, Sony does not have data sheets for ICX695 nor for ICX815.

EDIT: the website below has data sheets for these sensors, and numbers indicate that ICX695 has twice the dark signal of ICX694, and chip sizes are the same.

http://www.matrix-vision.com/manuals/mvBlueCOUGAR-X/Appendix_page_0.html#CCD2758_sectio n_1_1

[gregbradley]

QHY must have posted the wrong measurements.

Oh well the KAF16200 sounds the more interesting of the 2 new sensors.

The KAI8670 at 7.4 microns would be good for medium focal length RCs like an RC10.

Greg.

[RickS]

Another sighting of the 16200 sensor: http://www.flicamera.com/16.html

[Slawomir]

Thank you Rick for the link.

Looks like a smaller and cheaper alternative to ML16803, at least when it comes to resolution. Hopefully FLI will bring read noise down though with the final product.

[RickS]

The two FLI PL16803 cameras that I analysed for use at SRO both had read noise substantially below the sensor and camera specs so I think the chances of a better result in the final product are good, Suavi!

[gregbradley]

NIce find Slawomir.

I have mny eye on this sensor as it on paper would be an excellent match for the Honders at 6 microns and 40K well depth.

Hopefully the read noise comes down and it may with the slower download speed.

The other company talking about this sensor is Atik but I always considered them rightly or wrongly as a low end manufacturer. Perhaps they have come up to a high level. The Atik one is promoted as probably US$3999.

I imagine the FLI version is more like US$6995 then.

It may fill an imaging gap.

Not sure what the gain is over a KAI11002 apart from a better pixel size match for many setups.

Greg.

[RickS]

Looks like the QE might be significantly better than a KAI-11K, Greg, though not as good as the Sony sensors.

Cheers,
Rick.

[Slawomir]

Hi Greg, did you mean QHY?

If Atik was making a camera with this sensor, I would be very tempted. But need to save for a more refined mount first...

[gregbradley]

Perhaps not significantly 51% to around 58% at peak but perhaps the curve is better on the 16200. The main gain seems to be the lower read noise. Nowhere near the Sony's though but then the Sony's all have tiny well depths. Nothing's perfect eh? The 16803 though is a pretty good all rounder.




Oh yes sorry that's right. Its QHY. Are they up to making a high quality CCD?

Greg.

[Slawomir]

That's a good question Greg.

[RickS]

Looks like the KAI-11002 has QE just over 30% at Ha: http://blog.astrofotky.cz/pavelpech/files/2013/03/QE_PBernhard.jpg
Let's say it's 32%. Unfortunately, it's difficult to read clearly from the graph.

The new mystery sensor is more like 46%: http://www.flicamera.com/16.html

A QE of 46% is a lot better than 32%... it's a 44% improvement (no matter what a certain SBIG reseller says ;)) And Ha is a pretty important wavelength to us all!

Cheers,
Rick.

[Peter Ward]

Detecting one in three photons... versus just under one in two.
Fair enough :zzz2:

[RickS]

Or needing 10 hours of data to capture the same number of photons as 7 hours with the higher QE sensor. Sounds significant to me.

[Peter Ward]

Having taken some very deep h-alpha images, I have to say I'm pushed to tell *any* difference between 7, then 10 hours of H-alpha data from the same 'scope.

I'd settle for 4 hours of data with superb seeing, over a slightly higher QE during any imaging session.

There are a vast number of award winning astroimages that have been taken with the KAF11002 hence I find this sort of QE difference to be a bit moot ;)

[Shiraz]

'Fraid the physics is against you Peter - imaging time is inversely related to QE and "award winning" is not a convincing technical measure that suggests otherwise.

there are 2 efficiency terms in the sensitivity equation that are very important - QE and optics efficiency. To illustrate, compare a Ha imaging system with a 30% QE chip (eg 11002) to one with a 60% QE chip (eg 694). Also assume that the system with the 11002 has 87% reflective mirrors (2 off) whereas the 694 system has 98% mirrors. If the 11002 system requires 10 hours to get to a given signal-to-noise ratio, the 694 system will only require around 4 hours*
- (10hrs*(30*.87*.87/60*.98*.98)). That is a huge difference and the 694 system will be able to image more than twice as many targets in the short periods between clouds.

this doesn't mean that 11002 sensors cannot produce fine images - they certainly can, but they will take a lot longer to do it (in both total exposure and sub length). QE is of fundamental importance and there is no way round that.

On this topic, I am surprised that (Kodak... Truesense....OnSemi...) cannot improve the QE of some of their ABG chips, when Sony and (Aptina... Onsemi..) have for years routinely produced chips with >70% QE, even ones with very small pixels.

*For equal aperture, sampling and obstruction,

[Peter Ward]

I'm not arguing the Physics, it's pretty cut and dry, but you can't ignore the seeing component of any imaging session either (I suspect this is difficult to quantify).

While they are not ABG, the KAF3200 has had one of the highest QE's bar some pretty expensive back-illuminated chips, for around a decade now...maybe more :question:..... yet, assuming imaging is the goal, there do not seem to be many world beating KAF3200 based images on the web.

Begging the question: does the theory matter that much given the practical applications of many astro-imagers?

[RickS]

If you think that theory is irrelevant, why did you bother to buy a 16" scope, Peter? Or do you think that some of the basic parameters matter and others don't?

[Peter Ward]

I had a back illuminated +95% QE Apogee camera for a while...frankly I found it to be nearly useless for imaging (instant blooming, , unstable bias, a fixed pattern noise that shifted with wavelength)....sure it was a sensitive sucker, but such a PITA to get clean data from....hence my scepticism about QE being a holy grail....there are so many other factors that need to also be working well.

I've had far more success upgrading mounts and the quality of my guiding (plus optical systems) over the years. The 16" was purchased for its native focal length more than anything else.... Sure the extra aperture is nice, but certainly not the prime reason for the upgrade.

[Shiraz]

none of this has the slightest bit to do with CCD QE Peter.

- Seeing will remain the same regardless of which chip you have and the high QE chips will still be twice as fast in good seeing as in bad
- the 3200 is a great science chip, but it has 3mpixels and it blooms - it is not a pretty pictures chip
- the theory is very well developed in professional circles and underpins all that we do, whether we know it or not. You might not like the implications, but the theory is a very accurate and complete representation of reality. It would be foolhardy to ignore it.

[Atmos]

The application of a CCD does need to be taken into consideration along with everything else. Some of the Apogee CCDs are fantastic for scientific research because of their HUGE pixels, enormous well depth and dynamic range but typically tend to fit within the 0.25-4 megapixel category. Some of those sensors have pixels 3x the size of the KAF-8300, 96% peak QE and don't have ABG. At this point you're tailoring your exposure time to reflect what it is that you're wanting to detect. A 0.5mp 24 micron CCD is designed for a purpose and astrophotography isn't one of them :P To put it another way, the KAF-16803 is on my future wish list but I certainly wouldn't be doing planetary imaging with it.

[rally]

Read noise is an issue silently waiting here.

Extremely low read noise cameras allows us to capture a very wide dynamic range and to capture faint detail (low photon count data) without corruption

I do wonder if award winning Ha data is more a case of being able to resolve the extremely faint detail (aka very few photons) as opposed to resolving just the bright stuff where we have bucket loads of photons to capture - after all - displaying that which isnt always seen, resolved or captured produces the Ooh Aahs.

So the art (both the practice and the finished result !) becomes more about capturing and processing the low photon count regions rather than the bright regions.
Some of that is equipment related and much is skill related.

The chip specs will help of course, but so will everything else help to resolve such fine faint detail. Noise is our enemy and it comes in many disguises - seeing, camera noise, dynamic range of chip and of data collection technique, image processing, optics, light pollution, gradients, atmospheric effects (transparency, extinction etc), focus, tracking, guiding, PE, vibration . . . - its a big list - in fact its almost everything we work towards.

So equating hours of total exposure time to results doesnt necessarily tell us anything about the data or the noise inherent in the process, but then neither does Qe in isolation - there is lots at play.

The ideal camera of course for pretty pictures ignoring physics and finance is a huge well depth with an appropriately small image scale, negligible read noise (less than -1e), Qe as close to 100% across the full imaging spectum UV to IR
Its currently a bit of a dream for amateurs but who knows how much further sCMOS will come.
sCMOS cameras with such low read noise have become affordable for mere mortals.

[Peter Ward]

I'm not ignoring it, I'm simply stating ( as Rally has done quite eloquently) with so many other factors, the hope that a 15-20% increase in absolute QE will result in imaging sessions made in Valhalla is forlorn one in my experience.

I made this very step in going from a Kaf11002 to a 16803 sensor some years ago. There was no signal level revelation, hence despite the extra horses under the bonnet, I found myself working on other aspects of my imaging system much as a motor racing team does eg, better weight, suspension, steering, braking all help to improve lap times, to better take advantage of the extra HP.

[RickS]

You're preaching to the converted there, Rally, and read noise was discussed earlier in the thread. The reason it got distilled down to a discussion on QE was that we were comparing two sensors that both had pretty awful read noise specs compared to newer Sony sensors.



You're welcome to state that, Peter, but I didn't see anybody claim that QE was magic pixie dust or the only thing that mattered, only that it was a significant factor.

Cheers,
Rick.

[gregbradley]

What would be awesome but unlikely to occur is a larger Sony sensor with the clean read noise, high QE and deep wells.

Since Sony is putting all its eggs in the CMOS market then it may have to come from an advanced CMOS sensor.

Greg.

[RickS]

Yes, I'll have one of those, thanks Greg :thumbsup:

[Peter Ward]

Fair 'nuff. Perhaps I've read too much into Ray's comment:

"QE is of fundamental importance and there is no way round that"

as my experience has been a 10-15% fundamentally wasn't that important

[Shiraz]

Well I stand by it, QE is fundamentally important - suggesting that it isn't "that important" is a novel approach....

The QE difference between an 11002 and a 694 translates into a difference in imaging time of 2x at Ha. That is to say, you can get the same result in half the time at 60% QE (eg 694) compared to 30% QE (eg 11002).

I don't know what your 10-15% figure refers to, but the sensitivity change on going from 30% QE to 60% QE is:

DOUBLE,
TWICE,
TWO TIMES,
2x

- not really sure how else to put it.

Also, you can get this performance advantage even after doing all the optimisations that Rally noted. This is nothing to do with "Valhalla", it's nothing magic - it just seems to be a tiny bit of commonsense. Why would you not want to double the number of targets that you could image in any given time?

And then there is read noise .....

[rally]

Good one Ray,

Yes - I know I am preaching to the converted

But its still possible my point is missed - especially when we are talking about faint detail in low photn count areas of our images

If we have for simplicity -10e read noise and the levels of faint Ha signal is only from very low (say 1e) through 10e and say up to -20e
Then the signal to noise ratio goes from 1:10 (meaning no useful data) through 1: up to 2:1 - add shot noise, dark noise, and all the other possible noise its still a fairly sad situation for useful data . . . - but this is using up the first 4 to 5 bits of our 10-14 bits of data !

Now if we have a -1e read noise camera (and all other things being equal) then the situation becomes 1:1 through to 10:1 and up to 20:1
This is vast improvement improvement in signal quality and will thus produce an image that is (at least for the faint data) not just 20% better but more likely 1000% better

So who cares about an increase in Quantum efficiency of 20 or even 40% when these sorts of gains can arise by low read noise cameras.

Anyone care to analyse this better than my rough numbers

[ericwbenson]

I think most amateur astronomers (and some professionals too) are not only interested in just QE. I think they are looking for, and perhaps they don't consciously know it, is what the pros sometimes call 'etendue', the product of system throughput (collected photons) times sky area. Lower QE can be tolerated in a big chip because you don't need four panels to cover the object of interest, Hence the total time spent imaging a big object is actually half for the KAI11002 in your above example.

Regards,
EB

[Peter Ward]

It refers to the change from my KAF11002 based camera to my current KAF16803..... about 30% vs 45% QE in Ha.

But it really made stuff-all difference in my data...the faint stuff was simply a little less noisy.

Sadly Sony don't make overly large sensors, so despite some impressive QE numbers, it would give my RC16 a field of view similar to a drinking straw....hence the 16803 indeed saves me some time in other ways.

[Atmos]

There are a considerable amount of things that need to be considered. It was only about three months ago that I was looking into what camera to get for my first imaging setup. In the end it came down to either a KAF-8300 or the ICX964 and ultimately went with the KAF because it ended up at about half the price.

As some theoretical comparisons however, they have pixel sizes of 4.54 and 5.4 micron. When calculating their absolute efficiency against one another their total area has to be taken into consideration. The KAF has ~41% more surface area per pixel. Comparing peak QE gives 77% vs 56% which makes the ICX 37.5% better at peak (green) but 50% better at Ha. At their peaks the KAF is ~3% better but the ICX is ~41% better in Ha.

So in short the ICX is basically at par or better with ~19% better native resolution. The biggest difference however comes from the read noise where the ICX has about half, 4.5 vs 8-12 (depending on readout speed) and manufacturer). Earlier this week I took my telescope to my dark site for the first time, managed to get a 60s test exposure before the clouds came over :/ From that I got ~ 150 ADU as background. With a gain of 0.389 in my QHY9 that works out to ~ 58e- per minute or ~ 25.67e-/arcsec/minute and this equates to ~ 41 e-/minute or ~ 137 ADU/min on the ICX. The ICX has a QE 37.5% higher so that then becomes ~188 ADU/min.

A while back Ray (Shiraz) wrote an equation for optimal exposure length being (RN*10)*(RN/gain). From this I know my QHY9 needs a background of ~1860 (RN of 8.5e-) ADU but the ICX only needs ~675 ADU. KAF-8300 hits sky limited in 742s where as the ICX964 does it in ~ 215s. Of course on the other hand it appears like the KAF-16803 only needs ~140s. That’s the benefit of massive wells depths (gain of ~ 1.6e-/ADU) even with a read noise of ~10e- and having large pixels. On the other hand the 11002 would require ~ 338s

Pretty sure all that maths stuff is correct, haven’’t double checked but it feels like it is in the right direction. Everything was calculated at peak QE as my initial test was done in luminance.

[RickS]

Here's the KAF-16200 data sheet:
http://www.onsemi.com/pub_link/Collateral/KAF-16200-D.PDF

It's a shame they don't have any data on how read noise varies with clock rate.

Cheers,
Rick.

[Somnium]

so, when are some of the big players such as SBIG, FLI etc going to jump onto this. seems like the 16200 would fit well in the STXL body, making use of the self guiding FW and AO-X

[RickS]

FLI is doing one: http://www.flicamera.com/16.html

[Slawomir]

Thank you Rick for the specs.

Read noise is stated at 14e-, so in an astro camera I would not expect anything near the read noise of the latest sensors from Sony. Nonetheless it should be an interesting option for astrophotographers.

[RickS]

My pleasure, Suavi!

I'd expect at a lower clock rate the read noise will be less. Probably not as low as 4e- or 5e- but hopefully down into the single digits at least.

Cheers,
Rick.

[Slawomir]

If the read noise will be on pair with KAF8300, then it could potentially become a quite popular sensor among astrophotographers. It is over twice the size and twice the resolution of the venerable 8300 (but hopefully the cost won't double!) also with good pixel size.

[Somnium]

oooo any word on pricing or availability before i shoot off an email to them ?

anyone know if SBIG is looking into it? i am considering a new CCD and this fits my spec needs perfectly but i want the SBIG AO option

it looks like the well depth is not stellar ... 39k at 6 microns

[RickS]

Updated FLI specs here: http://www.flicamera.com/spec_sheets/ML16200.pdf

Read noise 7e- @ 3MHz and 11e- @ 12MHz.



$6495 USD for grade 2 sensor, $7495 USD for grade 1. Dunno about availability.



Question for Peter Ward?



About what I'd expect. The area of a pixel is about half that of the KAF-16803 and the well depth is scaled similarly.

Cheers,
Rick.

[gregbradley]

I think you are downplaying the advantages of the extra QE. I noticed the 16803 being more sensitive in Ha straight away.

I understand that it may not seem like a lot but you'd have to add up how much exposure time you now need to take to get a clean and solid Ha image.

The difference with the Sony sensor with Ha and O111 is much more dramatic. Its obvious that you can get a solid Ha image in half the time than using the 16803.

For example I could see the main jet off NGC1097 from the Trius on the Honders in a very pushed 10 minute 1x1 image. That's the QE and the F3.8 at work.

To get a similar image using a KAI11002 would take probably twice as long perhaps even more.

It becomes obvious when imaging dimmer objects like dimmer galaxies not something usually done in the burbs but if you did then the difference is plain to see.

Greg.

[gregbradley]

FLI ML16 Availability is soon. Perhaps within a week or so from an email I got.

It could be a very good sensor. 39K wells is fine. The KAI11002 is not much more than that and I have never noticed an issue with wells with that.

Well depth is a bit of an overblown issue. Although in my personal experience 20K well depth is starting to become a problem with faster scopes.

What I see as the main advantage of well depth is stars are much more robust from a deep well camera compared to a small well camera. Stars can become easily damaged in processing from a small well camera and can lose colour more easily and get fluffy /furry edges/halos.

Greg.

[Atmos]

I am still considering the upgrade to a SX964 and possibly throwing in the AO in for kicks. Of course, all comes down to when funds are available :)

[Peter Ward]

I make no bones about it, I am, as having used a 95% QE sensor which gave terrible results for all sorts of reasons, I did not find the extra QE to be worth all the pain associated with that particular sensor.

But signal can also be gained in many other ways.

My AOX regularly delivers and extra 15-20% of detected flux....across the entire spectrum....and sure in an ideal world I'd have a 36mm x36mm Sony chip as well a large aperture AO.

But sadly it does not exist and is unlikely to do so anytime soon.

[Shiraz]

no it doesn't Peter. Under some conditions, an AO may possibly increase the peak pixel flux on stars, but on things of actual interest, (extended objects like galaxies, nebulae etc) it will always slightly reduce the average signal. Sorry, but AO is not a substitute for QE :)

However, part of your ideal world is already here - the latest SX AO has a large 60mm aperture, which is plenty big enough for all Sony chips, the KAF16200 and anything else up to full frame 35mm. As for wanting big Sony chips, I don't give two hoots who makes my CCD, but I simply cannot understand why ONsemi is still producing their large pixel CCDs with such low QEs, when Sony and Aptina can routinely get above 70%, with full ABG, low thermal and read noise and all using small pixels - I don't get it.

[Somnium]

talking about the chips themselves ... what would be the recommended filter for the 16200, you would probably need 50 mm round or square filters. it would be a good candidate for for the FLI 2-7 or 5-7. or is there anything smaller you can get away with, i suspect not.

[RickS]

With a 34.6mm diagonal on the sensor 36mm filters aren't going to cut it. 50mm round will be the cheapest option.

[Peter Ward]

I have never found an AO to make things worse...and agree it's not the same as QE....nor is tracking or focusing the telescope accurately ( to which AO is a much closer analogy)....

I was thinking more of the overall system.

QE is detected vs actual fux.

I really don't give a toss if I have a 100% QE sensor attached to a system that simply disperses light across the entire field without actually bringing it to focus....sure the light is being detected by the sensor...but the stars are simply not seen above the background soup in that absurd conclusion...hence making the system's QE effectively zero.

I am however far more interested in an imaging system that concentrates the flux to tight + intense footprints.

I've been using AO's of one sort or another for over a decade and know (despite your statements to to contrary) they help do just that, time and time again, and have the data to prove it.

Higher pixel values by better QE or AO? Sure, not the same, but the higher intensity result is a rose by any other name here.

Sure I'd like a higher QE sensor +AO (as I said earlier, not available), but getting higher values in lieu of a more efficient CCD, via an AO, works for me.

[Shiraz]

interesting point Eric - basic question then is, how big does the sensor need to be? - guess that depends on the targets of interest. I have never felt a need for anything bigger than 6 mp (ie less than 1 degree^2 at optimal sampling in local conditions), but then, I have no interest in extensive nebulas and am not doing survey work. The new chips generally up the ante by providing more pixels in their market segments - as you point out, for other users, a larger pixel count could be worthwhile, even if the pixel design is a bit behind the times.

Another possibility is that more pixels make more sense in really good seeing, so maybe the bigger chips will have more payoff on mountaintops, rather than in Australia?

edit; been thinking about it and, for interest, at equivalent sampling, a 694 could pretty much match the sky area of an 11002 using just 2 panels, so in time/etendue terms, the systems would be almost equal.

[Slawomir]

Good point. I would also like to point out that ICX834 would do just that with one panel and with 1.25" filters. I know pixels are small, but so is the read noise (about 3e- with FLI and QSI) and QE is on pair with ICX694. I have a very positive experience with ICX814 (also tiny pixels) and narrowband imaging and I feel that ICX834 is usually easily overlooked and also quite underestimated sensor by amateur astrophotographers.

[gregbradley]

I agree. I have always been able to tell if an AO unit was used in acquiring an image.
The images have more punch.
Much like a non AO system on night of good seeing.
Greg

[ericwbenson]

It would seem most professional installations are heading towards multi-multi-megapixel cameras..it make sense if you've already invested buckets of money on the telescope/site/support/buildings and all you have to do is change the electronics to get more throughput.



2 panels? For the same telescope the KAI11002 has ~7x times the sky coverage, the KAF16803 10x the coverage (with less read noise, lower dark current, better QE, deeper wells and higher cost than the interline chip).

Regards,
EB

[gregbradley]

Not sure what Ray meant by sky coverage as the 694 sensor is much less than 1/2 the size of the 11002.

There is one point perhaps taken into account with your sensitivity formula and that is a larger sensor collects more light than a smaller one.

Well known in digital cameras. A full frame (35mm sized sensor) DSLR always performs better than a smaller APSc or smaller sensor for nightscapes etc. Its just simply the larger collecting areas. Even more true for CCDs where there aren't really large spaces between pixels like CMOS does.

Greg.

[Slawomir]

Ray clearly stated "at equivalent sampling", so to my understanding his statement is correct, and that's also why I mentioned that ICX834 with equivalent sampling is an interesting (and cheaper) but overlooked alternative to KAI11002.

[gregbradley]

I can't see the 814 being in any way equivalent to the 11002.The KAI11002 is a full frame sensor meaning a massive wide field of view versus a tiny one with the 814. I am not sure what you meant, perhaps you meant that with a short enough focal length they can get a similar field of view as the 11002 on a 3X longer focal length?

But for the 814 to match the 11002 in field of view you would probably have to go down to 300mm lenses on an 814 to match the FOV of the 11002 at 900mm. The 11002 is like 3X the width and height of the 814.

36 x 26mm versus 12mm x 10mm or so for the 814. 50,000 well depth versus 16,000 or so for the 814. Lower QE for the 11002 and higher read noise but 9 micron pixel suits lots of scopes and full frame means more total light collected.

Mind you I like the tiny FOV of the 694 as I use it for my close up, zoomed in camera. The 16803 and 11002 give the wide expansive widefield images that an 814/694 can't unless you do a mosaic which opens the door to all sorts of mismatches and tricky processing.

The allure of these large sensors is the large wide field of view in a single image with a shorter focal length scope (that has a large enough corrected field which is now in the realm of higher end scopes). Or on a longer focal length scope good for galaxies like your RCs, CDKs etc. This is one of the problems of the larger sensors - everything needs to be upgraded. Focusers need to be at least 3.5 inches, corrected field on the scope needs to be around 46mm or larger and no flex, everything nice and square. Reducers no longer work to the corners, you need a flattener on most scopes. Cost goes way up. Everything becomes heavier, the need for a higher capacity mount becomes critical. Stiffer adapters become more important, flex is more likely to be an issue.

Greg

[Shiraz]

This only applies to those who are doing survey work Eric. It all depends on the target and if you are doing a whole sky survey I agree that large etendue is paramount. For high res investigations it isn't and for example, it seems that the Keck2 has a 1kx1k array as its high res NIR sensor. That is enough to cover the isoplanatic patch, so that's all that is needed. In contrast, the ESO has gone to a lot of trouble on the VST survey scope, which has a 256mpix array. At entirely the other end of the scale, I am primarily interested in imaging galaxies and smaller objects at high resolution, so anything much over 0.5 degrees and about 6mpix would be a waste of time and money in my seeing. I don't want images of a galaxy surrounded by an acre of stars, but for someone who wants to image large nebulas, more etendue would be a good thing - but it isn't a goal for all astronomy.



but you wouldn't put a 694 on a 2+m telescope - it would be a heavily oversampled system. If you put it on a 1m scope (ie at the same sampling, as was specified - thanks S), it will cover the same sky as an 11002 on a 2m scope using just 2 panels. eg an 11002 on a 10inch f8 will have the same resolution, sampling, etendue etc as a 694 on a 10 inch f4. However, the 10 inch f4 with a 694 will have twice the Ha sensitivity on targets within it's field of view, due to the higher QE.

Don't get me wrong, I am not advocating that anyone with a large scope change over to the Sony chips - they just came up as real world examples of what was out there in the discussion on whether a change from 30% QE to 60 % QE actually resulted in a doubling of sensitivity, rather than a 30% change - and why Adaptive Optics cannot possibly give 15-20% more detected flux on extended targets. Somehow that whole discussion went down some odd rabbit holes, but that is where the mention of Sony chips came from - they have higher QE than the new ONsemi ones and the question that is pertinent to the thread is - why can't ONsemi achieve similar QE/noise specs on their big pixels?

Greg, the equation for sensitivity is pixel-based - the size of the field of view is not considered.

regards Ray

[Slawomir]

Hi Greg,

I was suggesting that ICX834 (not 814) could be a cheaper alternative to 11002.

And you are right, ICX834 would need to be put at the end of a much smaller telescope to give the same FOV as 11002, but that what I meant - maybe I did not explain it correctly.

Agreed, ICX834 has tiny pixels but read noise in only 2e- with FLI MLx834 - I really think when combined with FSQ106 (1.21"/px) it would be a very capable relatively fast narrowband imaging setup.

KAI11002 would need to be combined with 1500mm fl to give the same resolution, and both setups would have about the same FOV.
Yes, KAI11002 has much deeper wells but also significantly higher read noise and significantly lower QE making it, in theory, less suitable for narrowband imaging, in spite of being more expensive (as you pointed out- larger mount, larger filters etc).

So if someone's on a budget (relatively speaking) and has a smaller telescope, I feel that ICX834 presents an interesting and in theory quite capable option.

[gregbradley]

I totally agree the 834 is an amazing sensor and I have been very impressed with the quality of your images with a modest refractor and your QSI690.

It does emulate a larger sensor when used with a short focal length refractor and reducer and I think the Sony sensors and the KAF8300 have lowered the cost of imaging a lot as you can get superb results from a smallish and modest refractor with these sensors instead of the larger and more expensive APOs and required expensive mounts.

The full frame sensors as I mentioned really add to the cost and complexity of the system and not many scopes can cope with them really. None of them are cheap either. Not many reducers work with them as well without coma in the corners.


Greg.

[gregbradley]

Onsemi bought from True Sense who bought Kodak's sensor division.

Kodak went down an engineering path. My understanding is that these sensor plants are worth billions to setup. So once they go down a path that is it for some time. Canon was/is in that predicament where their sensor plant was (not sure what the current state of play is) behind the times compared to Sony. I read once Canon's plant was running on something like 500 micron size and Sony's at 15 microns.

Sony is the world's largest sensor maker. It also acquires companies that have technology they want for their sensors. That's how the Sony Exmor sensor got such good low light low noise performance - by buying the tech from someone else in CMOS.

Sony also has a technology sharing agreement with Aptina who holds a lot of technology patents for sensors.

I can't see OnSemi changing these sensors. The money involved probably does not make sense to do so.

So its either a future Sony CMOS sensor that is ubeaut or perhaps some new Chinese player (have a look at QHY 42 for example) to bring something new to the table.

Scientific CMOS is one possible future. Sony seems to have left the CCD business to concentrate on CMOS so I take it they believe that is where the demand is (Smartphone camera sensors, digital cameras, industrial vision).

Now we have backside illuminated CMOS as a standard Sony CMOS camera sensor so perhaps just a few more development iterations and CMOS may in fact be more advanced than CCD?

One advantage CCD had over CMOS I thought was less space around each pixel needed for circuitry. CMOS is around 40%. I don't know what it is for Kodak CCDs. I assume very little if any.

Greg.

[ericwbenson]

Hi Ray,

Well funny enough my main interest has also always been small faint galaxies and hence why I was content with an ST7 then an ST8 for a long time. However when it came time to upgrade for various reasons, such as better cooling that I needed in Australia vs Canada, remote operation hence sealed CCD chamber (no desiccant swaps), better image transfer system etc, I also started looking at various CCDs. The good old KAF3200ME had a lot going for it except for it's tendency to bloom easily (high QE, 6.8um pixels, no ABG = PITA for processing), and it was still fairly costly. KAF6303M looks good except again no ABG and lower QE (due to no microlenses) than my ST8XME. So the obvious choice was the KAF16803 which has all the good stuff and decent QE, plus allowed me to use my scope for more than just galaxies, I could actually image nebulas larger than the Horsehead! I don't think the latest Sony chips were available then, they would have been contenders except for the pixel size mismatch.


Changing the focal length to get the same sampling muddies the waters since for constant aperture (hence sky flux) the fratio must decrease for the smaller pixel CCD, and the problems associated with fast optics rear their head - no free lunch.
At constant aperture a bigger CCD is 'usually' easier to use than a small one. Yes it implies longer focal length, but that does not mean longer tube (enter catadioptrics), nor different requirements on tracking (where pixel scale is the only factor), it means slower optics which are generally more tolerant in the making and holding in place, plus longer focus zone.


And I am not certainly advocating everybody go out and buy a KAF16803. I think we actually see things in much the same way, though with slightly different experiences colouring our perception. Frank discussion is always interesting.


This is an aside that could be it's own thread :) IMHO after using an AO8 for 5+ years, amateur AO doesn't provide much boost for big CCDs if the mount is good enough to start with (most PMEs that are not overloaded, almost all Astrophysics mounts if the legend serves to be correct, and any Renishaw encoder equipped mount qualifies). Maybe one day I will use AO again and change my mind, but for the cost+complexity to add to my system it will be awhile ;)
However, that being said, from empirical observation the signal from extended sources such as faint jets or spiral arms can be greatly affected by the seeing conditions. Perhaps it is the faint structures that get washed out diminishing the contrast, or simply the feature being smeared out against the background, not sure, but a single low FWHM subs is always worth many crappy high FWHM subs in a stack.


Perhaps the answer is simple, they don't have the tech, can't afford to develop the tech, and Sony just doesn't give a hoot about the large CCD market segment. Amateur, and to some extent pro astronomy, have always been at the mercy of other commercial endeavours (e.g. medical imaging, surveillance) for CCD development, I can't see how this will change in the forseable future.

Best regards,
EB

[Shiraz]

this is a Really Smart idea Slawomir..

Taking it a bit further, I have just done some back of the envelope calculations and a NB setup using a 180mm f3.5 lens and 834 could possibly even be more sensitive than the very popular FSQ106/11002 combination (will need to do the modelling properly to make sure that is right) and with similar field of view and resolution - nothing budget about it from a performance viewpoint, just a lot lower cost. Very very neat:thumbsup:! Only question mark that I can think of for now would be how the camera lens handled bright stars - the FSQ produces beautiful soft fuzzy balls and a camera lens may possibly be a bit harsher (although that may not be such an issue at NB).

[gregbradley]

Well I could test that out. I have a Nikon 180mm F2.8 ED lens and Nikon adapter for my FLI Filter wheel. My Trius 694 fits into my FLI Filter wheel so I should be able to image with it and focus manually. I have to work out a mount for the lens. Perhaps a lens foot and a Losmandy D clamp and fit it on top of the Honders. I think I may have those parts. A project for the future once I have finished current imaging projects.

A step down ring may help with the sun stars on bright stars that a lens aperture creates. I also have adapters for the very excellent Pentax 165mm 6 x 7 F2.8 which is sharp wide open.

Greg.

[Shiraz]

sounds good Greg. Only issue may be the NB filter - 3nm is too tight for an f2.8 system and will really reduce the signal, although I suppose that it would be OK for an initial test just to see if there are any hidden gotchas.

have done some more careful modelling - results attached. Looks very promising in all respects - Slawomir's 834 + 180 system should be similar to an FSQ106/11002, provided the chosen camera lens can get close to the diffraction limit (the better ones seem to be able to do so in the centre of the field - which is all that is needed). I assumed 5nm NB for the two f2.8 systems and 3nm for the FSQ106, dark sky, seeing of 2 arcsec and RN of 11e for 11002, 5e for 694 and 3e for 834.

[Slawomir]

The data looks interesting, thank you Ray.

I think Alluxa can modify their filters to adapt them for given telescope, so perhaps 3nm narrowband filters with high transmission are possible for fast systems.

One possible advantage of using 3nm (or narrower) filters is that since stars have continuous spectrums, the amount of photons coming from stars gets reduced with narrower filters while the signal from a nebula at a particular emission line remains constant - I found it helps (with 3nm filters in my case) to reduce the effect of shallow pixel wells - saturation point is reached somehow later.

Would love to test such system (ICX834 at f2.8 with custom narrowband filters) - just need a few sponsors to fund the project :lol:

[Shiraz]

I think that the problem is that the outer rays at f2.8 are a fair way off the normal to the filter, so they do not even get through it (the interference stack transmission peak shifts to shorter? wavelengths as the incidence angle increases). 3nm is fairly inefficient at f3 and worse at f2.8. Broader filters are more tolerant to incidence angle and a 5nm should do OK at f2.8. For a system with high central obstruction, the passband can be shifted so that the filter works over the range of incidence angles presented by the light that gets through the input annulus, but I don't think that is a viable approach with an unobstructed system. The alternative would be a full aperture NB filter in front of the lens.....

In any case the 834 system will have more dynamic range than the 11002 system, so operating at 5nm should not be a major problem - there will be more background light to contend with, but that has been accounted for in the modelling and the 5nm 834 is still close to the sensitivity of the 3nm 11002 system.

[Slawomir]

Thank you for explaining that Ray; I have been recently looking at an option for going narrower that 3nm with my f5.6 system and what you wrote has perfectly clarified the concept of the issues with angle of incidence.

[gregbradley]

The narrowband filters I have are 5nm not 3nm so that should help.

Of course a Nikon 180mm ED lens or a Pentax 67 165mm F2.8 lens is not the optical equivalent of an FSQ106ED.

Greg.

[Shiraz]

in a heavily undersampled system and over a smallish field, that probably doesn't matter much. It will be very interesting to see how you get on - particularly keeping the focus in the 17 micron CFZ :thumbsup:.