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  #21  
Old 30-10-2011, 03:06 PM
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Originally Posted by RickS View Post
Would love to see that link about binning the KAF8300, Greg. Did you forget to include it?

Thanks,
Rick.
Sorry Rick.

Here it is:

Correct, but in practice there are limitations. It is dependent on the
charge capacity (full well) of both the pixels in the output shift register
and the output node into the digitizer. When binning, you clock multiple
pixels into a single pixel in the output shift register. If its well depth
is not N * imaging pixel well depth (N is vertical binning factor), then the
pixel can be saturated (clipped), even though the individual pixels binned
into it are not. Same holds for the output node - when multiple horizontal
pixels are clocked into it, clipping can occur. Every chip is different in
this regard - most do NOT have 2x well depth in these registers, so the
bright stuff (>50% full well) will generally be saturated.

Kurt
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  #22  
Old 30-10-2011, 03:14 PM
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Originally Posted by rcheshire View Post
Wow! Thanks Greg. You have summed up a good many questions that have been revolving around my head. I keep coming back to FLI Microline, which is slightly more expensive than other makes as I recall. As you say, as an all rounder FLI seems to have good characteristics in several important areas.

I think given my skies (it has been raining for weeks now) and AP opportunities QE is important. I just need to feel satisfied that the pixel size is appropriate.

Thanks again. I'll keep chipping away at this.

EDIT: I see that the KAI 4050 is 5.5um.

EDIT: and available in Apogee - not FLI - which is my next choice behind FLI.

Rowland.
I am sure FLI could do a Microline with the 4050. They must have just missed that one.

FLI Microline would be better than Apogee Ascent as Ascent is only 30C cooling or thereabouts whereas Microline is more like 60-65C. But Ascent is quite a bit cheaper.

I had an Apogee U16M camera and it was a great camera. Just the slow cooling plus the cooling could have been stronger but I would image at -25C whereas with the Proline I image at -34C usually. Also the FLI has faster downloads otherwise they are quite similar. Alta is thinner and lighter than Proline. Proline has fast downloads, powerful fast cooling.
Alta with DO9 body has powerful cooling as well just slow and the firmware won't let you hit your target temp if it goes over a preset % of power supply which is also annoying and also adds to the time it takes to get there. Don't know about the Ascent temperature controls. I imagine they are similar but who knows it may have been changed. I think Apogee pride themselves on making a camera that will last for a really long time and they take a very conservative approach based on achieving that.

Greg.
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  #23  
Old 30-10-2011, 03:17 PM
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Looking at the QE for Blue, the 4050 is (approximately) only two thirds as sensitive as the 4022 so, for example, you'd need a 9 minute exposure with the 4050 to capture the same amount of data as a 6 minute exposure with the 4022. That's the worst case. Green sensitivity is the same. Red is lower, but not by as much as Blue.

Only you can decide how significant this is relative to all the other pros and cons.

Cheers,
Rick.

I am surprised the net is not flooded with images of one shot True Sense chipped cameras by now as they have been out for quite a while now. Per Kodak they outperform the Bayer sensor by a lot. The one shot colour imagers should be jumping all over them. They all must be waiting for that one image to hit the net.

The one shot colour of the 4020 with the Bayer matrix still seems higher. I guess the larger pixels is why.

Rowland that could be you mate!

Greg,
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  #24  
Old 30-10-2011, 06:24 PM
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Thanks Greg and Rick. I know where I'm heading now. Definitely leaning in the FLI 4020 direction. For all the reasons stated.
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  #25  
Old 30-10-2011, 06:43 PM
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Quote:
Originally Posted by gregbradley View Post
Sorry Rick.

Here it is:

Correct, but in practice there are limitations. It is dependent on the
charge capacity (full well) of both the pixels in the output shift register
and the output node into the digitizer. When binning, you clock multiple
pixels into a single pixel in the output shift register. If its well depth
is not N * imaging pixel well depth (N is vertical binning factor), then the
pixel can be saturated (clipped), even though the individual pixels binned
into it are not. Same holds for the output node - when multiple horizontal
pixels are clocked into it, clipping can occur. Every chip is different in
this regard - most do NOT have 2x well depth in these registers, so the
bright stuff (>50% full well) will generally be saturated.

Kurt
Thanks, Greg. I don't know if that's specific to the KAF8300, but it's what Tandum mentioned earlier. If the CCD readout registers aren't designed to handle the larger values generated by binned data then binning won't have the desired effect. It's not too hard to test with a lightbox, so I'll give it a go with my camera some time soon...
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  #26  
Old 30-10-2011, 10:07 PM
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Quote:
Originally Posted by RickS View Post
Thanks, Greg. I don't know if that's specific to the KAF8300, but it's what Tandum mentioned earlier. If the CCD readout registers aren't designed to handle the larger values generated by binned data then binning won't have the desired effect. It's not too hard to test with a lightbox, so I'll give it a go with my camera some time soon...
I have imaged with a FLI ML8300 2x2 and it does increase sensitivity. In fact the IC4901 image is binned all 2x2. It worked quite well. The cost is a slight drop in resolution and stars are larger. The gain is more sensitivity.

I would not describe it as 4X but it may be 1.5X or perhap 2X.

I just saw the first image from these newer KAI chips. This one is the KAI8050 chip.

It is one of the most spectacular images I have ever seen:

http://www.cosmotography.com/images/small_ngc6853.html

Also that is the Apogee Ascent which is quite a cheap camera.

A great intro to their new range.

Greg.
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  #27  
Old 31-10-2011, 12:03 PM
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Originally Posted by gregbradley View Post
I have imaged with a FLI ML8300 2x2 and it does increase sensitivity. In fact the IC4901 image is binned all 2x2. It worked quite well. The cost is a slight drop in resolution and stars are larger. The gain is more sensitivity.

I would not describe it as 4X but it may be 1.5X or perhap 2X.
Yep, you will still collect more photons per "pixel" and get lower effective read noise. Just need to be careful about exposure length and saturation.

That's a stunning image of M27!

Cheers,
Rick.
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  #28  
Old 31-10-2011, 07:49 PM
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Damn

I just ordered a fully loaded QSI 683 wsg with 9 position filter wheel and built in oag.

That ascent with kai 8050 is a very nice unit for the price. Does not have built in oag but given how long I am waiting for this QSI to arrive with no delivery date in Sight I am now considering changing my order.

I have already paid deposit though so not sure if I can change my order with opt.






Quote:
Originally Posted by gregbradley View Post
I have imaged with a FLI ML8300 2x2 and it does increase sensitivity. In fact the IC4901 image is binned all 2x2. It worked quite well. The cost is a slight drop in resolution and stars are larger. The gain is more sensitivity.

I would not describe it as 4X but it may be 1.5X or perhap 2X.

I just saw the first image from these newer KAI chips. This one is the KAI8050 chip.

It is one of the most spectacular images I have ever seen:

http://www.cosmotography.com/images/small_ngc6853.html

Also that is the Apogee Ascent which is quite a cheap camera.

A great intro to their new range.

Greg.
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  #29  
Old 31-10-2011, 09:05 PM
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The QSI is well designed. Nicely integrated.
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  #30  
Old 31-10-2011, 09:55 PM
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Humm...wasn't really wanting to weigh into this discussion due my commercial links with SBIG...but lists of "this is better" or "that is better" without some hard data I have to say is subjective at best.

Rowland..can I suggest you have a critical look at the images various users are producing:

1) are the stars round? (accurate guiding is VERY important)
2) for a given image scale, are they sharp? or do the stars look bloated or have weird spikes/artifacts? (AO can and does help here)
3) background noise/gradients...is there salt/pepper, noise or weird colour colour in some part of the image? (this points toward difficult/inconsistent calibration)
4) how integrated are the systems (eg. filters, guiding, adaptive optics?)
5) how does the price compare for the same sensor/package?

The reasons I mention all the above is the seeing and sky transparency can and does make many "specs" moot at best...urban skyglow will swamp the noise of even a *really* cruddy camera in less than 10 seconds.

One of my personal best images
http://www.atscope.com.au/BRO/gallery39.html was the result of great seeing (infact there was some fog about) and being able to employ adaptive optics.... the latter not always user friendly, but sublime when it works as advertised.

I shoot 99% of my images from a very light polluted Sydney backyard and know my SBIG camera/scope are being hamstrung by the conditions, yet have still produced great results.

I would however single out Apogee as being a manufacturer I would simply not deal with again. Suffice to say, I personally found their software, hardware and subsequent (kiss my a$$) fix from poor to non-existant.
Even more fatal is their shutter design. It's not equi-time across the field so is impossible to flat-field with brief exposures.
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  #31  
Old 01-11-2011, 04:40 AM
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Greg, Rick, etc.,

Forgive me for chiming in.

Greg's explanations here are simply fantastic, so easy for a mere pleb like me to understand.

Could you consider combining this & previous long explanations on modern mid range CCD cameras into an article and post in the Projects & Articles section?

Just this thread alone has cleared up a lot of foggy points.

Greg, again thanks so much for your time and willingness to share a wealth of knowledge with such clarity.

David
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  #32  
Old 01-11-2011, 09:16 AM
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Quote:
Humm...wasn't really wanting to weigh into this discussion due my commercial links with SBIG...but lists of "this is better" or "that is better" without some hard data I have to say is subjective at best.

Rowland..can I suggest you have a critical look at the images various users are producing:
Thanks Peter. I'm glad you responded. I'm just grinding my way through the detail, and no closer to making a choice, attempting to come to grips with the technology. I understand that it is a complex field and wont rush in here and there. But there were a few perception hurdles to overcome.

It is one thing to be informed about the technology, and another to gather valuable insight from people with experience - hence this thread.

I agree the proof is in the pudding and I've spent quite some time perusing. I'm have a healthy degree of scepticism and won't decide easily where this is concerned.

Pool the facts, investigate alternatives, look for options, before operating etc, etc...

That way I can take stock with some satisfaction and joy.

I have looked at SBIG and open to suggestions at this stage. I wasn't quite sure about their cooling.
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  #33  
Old 01-11-2011, 09:31 AM
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Thanks Peter. I'm glad you responded. .............

I have looked at SBIG and open to suggestions at this stage. I wasn't quite sure about their cooling.
Again moot IMHO.

SBIG have a (not often menioned) patent on CCD chamber temperature that allows them to hold it to with 1/100th of a degree of the set-point.

This allows for very accurate dark-sub calibration....which is going to clean up an image way better than a few more degrees of delta-T based on an unstable set-point.

Having used ST, STL and STX versions of their products...that latter having a massive delta-T capability if you choose to run liquid cooling ..I can not say I've not much difference between well calibrated frames from one model to the next.
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  #34  
Old 01-11-2011, 10:20 AM
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That's a strong argument. Again, there is much about the technology and imaging that is only available through informed users. Thanks again.
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  #35  
Old 01-11-2011, 03:33 PM
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Peter makes some good points. SBIG's strength has long been their self guiding cameras, a good range of accessories and good customer service. Their prices generally are reasonable and there are many fabulous images on the net.

I have had 4 SBIG cameras - ST2000XM, 2 STL11's (one shot colour and mono class 2) and an ST402 (I still use).

These cameras are ruggedly built and reliable generally. I was able to take good images with them and the self guiding is very handy when doing LRGB imaging. I particularly liked the STL11's with the integrated filter wheel.

I don't know much about the STX apart from it being a sophisticated camera with many potential and perhaps not fully sorted guiding features.

My main critique of SBIG cameras would be cooling could be a bit stronger in the case of the STL11 (mine did 43C below ambient which is quite strong really). STX on paper sounds to have good cooling.
I understand the point about accurate cooling and callibration and I have seen that effect Peter is referring to myself. Try using a 30C dark on a -35C image with a large chipped camera that requires very accurate flats and you will have big trouble.

So with regards to noise defects etc the first and most important feature of the camera for a given chip is powerful cooling and clean electronics. Not all cameras have the same read noise - they vary.

The next main thing would be the reliance on a computer for the driver when it powers up. This places too heavy a dependence on the computer. This may not be a problem for most. I found it was an issue far too often. STX again I believe has onboard memory for the drivers (I hope!).

SBIG also seems to have poorer performing electronics in terms of noise. Whilst my STL cameras with the KAI11002 chip would dark subtract well, the images were rather noisy. I thought this would be the same for every camera with that chip as the noise was coming from the chip.

Not so. Mike Sidonio posted a 10 minute dark from his FLI Proline 11002 and I posted my old 10 minute dark same temp from my STL11 class 2. Totally chalk and cheese. The STL was way way noisier. So the readout electronics boards or the analogue to digital to converter electronics vary a lot in quality. As Peter says this dark subtracts out so perhaps not the biggest problem in the world if other factors are good. However I would point out it does place more emphasis on accurate darks.
Both my Apogee and FLI cameras were quite clean in their electronics and dark subtraction is far less important.

I found both FLI and Apogee to cool to the same accuracy (or at least I think so, they both state a temp readout to 3 decimal places) as my SBIGs. Perhaps the SBIG is a bit more accurate there. I am not 100% certain of this but I can say the darks match the lights very accurately of both Apogee and FLI. My opinion is that the darks matching the lights with these very clean electronics brands is more important with larger chips to get accurate flat fielding (there is always some vignetting) than with smaller chips.

With regard to the importance of cooling. Powerful cooling has several
advantages. Apart from less noise which is the obvious advantage there are less artifacts. With my STL11 it had a vertical line that did not always dark subtract out and would present a problem late in the processing. The line itself is not really a fault of the camera but heavier cooling makes these lines almost totally clear away. Like -35C.

A sealed CCD chamber is also important. No desiccant is needed to be serviced. I believe the Argon gas also helps protect the CCD itself. It also allows a no cover slip option.

I know Peter had an expensive U47 Alta which is a high end ultra sensitive chip known as back thinned (they literally thin the chip so its quite thin and it is mounted back to front and these show the patterns of the thinning process easily). These back thinned chips require accurate flats and are prone to residual bulk images (ghosting). This requires an infrared flash and flush several times before the actual image to fill up the deep substrate where the ghost image gets trapped. This flush stops a ghost image from forming but it means extra noise as this flush leaks out during an exposure. Only powerful cooling handles that. FLI at -35C for a large chip is one of the strongest cooling and technically that is insufficent (-100C is). But it works in practice with slightly elevated noise. Apogee has a ghost image fix (I believe the FLI system is the superior one). Ghost imaging is a problem with KAF Full frame sensor technology and not KAI series chips due to different chip architecture.

One of the best images I have seen on the net lately are done by Wolfgang Promper with a 16 inch ASA Cassegrain (Philip Keller) and a FLI Proline 4240 which is one of these high QE (sensitivity) chips by a company called E2V. 90% QE and those images are routinely brighter and more luminous compared to other images of the same object, often he does this with modest exposure times.

As far as shutters go from Apogee or FLI I found both to be good but yes you need at least 3 seconds for a 20,000ADU flat (ADU is a measure of brightness on a chip) to not show the shutter. That may be very difficult with a back thinned 95% QE chip.
Perhaps with one of those illuminating panels a lot are using where you can control the light it may have been more practical. I use 3-10 seconds for flats and the inside of my observatory is painted matt black and a bit of light comes in from the gap of the wall and roof. I put the
white material over the end of my CDK17 and I can do 10 second flats in the middle of the day. Very handy. Flats work well once flat dark subtracted.

KAI chips have an electronic shutter video output option so you can take really short shots without a shutter.

I would use an SBIG again. Although I have become spoilt by instant and stable connections, 1 second downloads, super low noise, powerful cooling. I think the Proline is quite heavy and can be a problem for some scopes unless they have a beefy focuser. That would probably be the same for STX and Apogee Alta. The FLI Proline also has a minor defect in that some brighter stars have a little diagional spike on them almost like a diffraction spike. The same chip in a FLI Microline does not have these. I personally don't mind them but they should not be there. My ML8300 has no spikes.

SBIG does have a good range of accessories that are integrated and the many fabulous images prove they are good. Non STX models though are getting a bit dated and need a bit of a refresh (cleaner electronics, faster downloads, self guiding that does not get interrupted by downloads, sealed chambers, an image memory buffer, more powerful cooling, a larger and cleaner guide chip) to remain competitive as there are now a lot of camera makers and they all seem to be improving their models each year. QSI seems to be developing their models the fastest and the current go getters. Their range of chips is limited though until they get the bigger model out which could be a while. Then they will need to do the 1-2 year sorting out of issues that arise in the field.

No one camera is perfect for your needs. Some chips give big widefield images others close up detail, some super sensitive others not bad, some one shot colour some not. Like scopes, you end up wanting a few to be able to capture a particular image!

Greg.
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  #36  
Old 01-11-2011, 05:17 PM
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In regard to my U47..... It had all sorts of problems. Buggy drivers. Fan vibration, stupidly slow cooling, non-linear shutter, random bias ripple and a spectrally shifted fixed chip pattern...looked rather like a tartan cloth, that changed shape depending on what filters were being used.

It went across the Pacific 8 times. Apogee simply could not offer a fix. All quite disappointing given it's significant cost.
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Old 01-11-2011, 07:33 PM
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Wow, not good.

Did you do flats for each filter or did it constantly shift?

If you had a drifting bias that would make it pretty hard.

I know Richard Crisp made some mention about doing flats for
back thinned chips. Wolfgang said they look weird but they flat out OK
on his FLI. Given their $25,000 + cost you'd want some certainty.

The slow cooling is an annoying Apogee feature. You are not the only one
who did not like that.

Was that the E2V chip?

Greg.
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  #38  
Old 01-11-2011, 07:59 PM
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Quote:
Originally Posted by gregbradley View Post
Wow, not good.

Did you do flats for each filter or did it constantly shift?

If you had a drifting bias that would make it pretty hard.

I know Richard Crisp made some mention about doing flats for
back thinned chips. Wolfgang said they look weird but they flat out OK
on his FLI. Given their $25,000 + cost you'd want some certainty.

The slow cooling is an annoying Apogee feature. You are not the only one
who did not like that.

Was that the E2V chip?

Greg.
EV chip. Flats constantly shifted and had to be matched for each exposure.

Lord help you if you actually rotated the camera and didn't have a matching flat. Bias was unpredictable.

It was super sensitive, but you simply couldn't capitalise on it .... I actually pushed SBIG to implement a back illuminated camera but they were fully aware of all the above and politely told me it was a dumb idea
(and in hindsight, they were correct)

BTW SBIG quote 9.3e- read noise on their new ST8300's.

I find it amusing that both QSI and FLI quote 8e- (Kodak's KAF8300 Chip spec) on their implementations of the same chip.... apparently their electronics add *zero* noise to the chip readup.... not likely IMHO
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Old 01-11-2011, 08:45 PM
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http://www.optcorp.com/product.aspx?pid=10342

This has a good write up and is of particular interest. Currently <3k, with features that are relevant to my usage and stood out when comparing prices across similar types. I like the features it offer. The more expensive model similarly has a good write up.
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  #40  
Old 05-11-2011, 08:47 AM
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A good chip and that sale is making it all very affordable.

I wonder how that would compare with the QHY10 which is a 10mp one shot colour Sony chipped camera? The Sony chips seem to be very well respected and a few here are using the QHY10. I think its about the same price.

Starlight Express also sell a camera using that same Sony 10mp chip if you wanted their camera.

The KAI4022 is a hot chip and I have always been impressed by the images from that chip.

Greg.
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