Further request for CCD camera advice.

[rcheshire]

Hi. I've been researching CCD cameras, learning CCD theory, asking questions and generally reading as much as I can, in deciding whether to upgrade. From what I can tell an OSC is the best choice for my application.

Other than price, the basic criteria seems to be QE, noise (including electronics), cooling and ease of use. So far, FLI and Apogee are of interest with KAI 8050 sensors 5.6um pixels which is the correct pixel size at 200mm and 400mm with 2x2 binning.

EDIT: This is derived from an online pixel size calculator.

Another option is the KAI 4020, 4.2mp interline transfer sensor 7.4um. These seem to have a good reputation, although pixel size is not quite right for the focal length I'm using.

EDIT: 7.4um is somewhere in the middle between 200 and 400mm.

Is pixel size going to be an issue as far as a visible difference in an image taken with a 4.2mp vs 8.3mp at the short focal lengths I'm using. I think not, but that's just a guess.

Does anyone have experience with these criteria to say one way or the other.

[Poita]

What scope is it going onto, and what are your likely targets?

[Hagar]

Just one thing to be aware of. A OSC camera uses a bayer mask in front of the CCD to capture and distinquish colour. Using a OSC camera at 2 x 2 binning or anything higher than 1 X 1 makes the images just black and white.
There are plenty of options out there so the end choice is yours alone. b You might find a cheaper alternative is a camera with either a Mono or colour KAF8300. This CCD has proven itself as probably the most sucessful, best priced CCD available today.

Good luck.

[LightningNZ]

Just don't hope to bin with KAF8300, you won't gain anything much. If you have a long focal length then there are better chips out there. Why would you want to bin 5.6um pixels with a focal length of only 200 or 400? At short focal lengths small pixels work out better.

Cheers,
Cam

[cventer]

Why should you not bin a KAF8300 ?

[marki]

What scope has a 200 mm FL besides a finderscope???? I think you have made a mistake somewhere? What is the scope you plan to put it on?

Mark

[marki]

No reason if it is a mono, only affects OSC as Doug stated in post # 3. 2 x 2 bin is good for collecting colour quickly with the mono chip as you dont need resolution just signal. The stars saturate quickly and the end product is only 2MP but does the job. I have never tried to make up for long FL by binning the KAF8300, better to buy a camera with bigger pixels and deeper wells.

Mark

[RickS]

I have heard a couple of people suggest that binning a KAF8300 doesn't appear to give a significant increase in effective well depth. I haven't ever tried binning on my SX H18, but I might have a play with a light box on the weekend (if it's cloudy) and see if I can test this hypothesis.

Cheers,
Rick.

[Tandum]

It uses non active standard pixels as a buffer to readout the image from the sensor so at 2x2 it sums 4 image pixels into one for readout.

[rcheshire]

I've tried to be more specific. Maybe what I'm asking is not clear, perhaps the answer is obvious, either way I'm using Canon lenses - no plans for a scope. Yep, I'm imaging with a finder scope and want to attach an expensive CCD to it. Is anyone else using camera lenses?

Thanks Doug, the binning issue is not something I understand as far as OSC's are concerned. I'm working on the assumption, pretty much, that there's not a lot of difference between 5.6 and 7.4um, except that the KAI 4020 is 7.4 has a great reputation, even at 4.2mp.

I'm not sure which way to go - the bigger pixel or more pixels, I think it's coming down to that, as a compromise across the two focal lengths. I'm not sure I have a complete grasp on the science yet to make an informed decision. It's not like I'm selecting football team.

[marki]

On a OSC chip it is best to think in groups of 4 pixels in a square. What the manufactures do is use dyes (RGB) which they carefully place over the individual pixels in a set pattern (eg RGGB) to act as a filter for each colour similar to the way we do on mono cameras. When you download an image in 1 x 1 bin the ADU count for each pixel is stored in the file. With astro cameras these are often 16 bit images in the FITS format. These images are grey scale and need to be debayered in a suitable program (eg MaximDL, DSS or simlar) to retrieve the colour information. When you bin 2 x 2 that information is lost and the image cannot be debayered hence Dougs comment about grey scale images.

In your original post you did not mention you were using a camera lens hence the confusion. The KAF8300 would give you higher resolution at both focal lengths as the pixels are smaller but there would be little difference between the two chips you have suggested. I would go for the one that gives you the greatest FOV as you obviously want to do widefield AP. The KAF8300 is used by many at focal lengths much greater then 400mm so I doubt you would have any problems with either chip in the range you are contemplating. The major consideration would be well depth and sensitivity as you may saturate the stars before getting the fine detail.

Mark

[rcheshire]

Thanks Mark. I understand the Bayer matrix, and now that you explain it the effect of binning is really very obvious. There is no way around that as far as I can tell.

I am happy to forego FOV for image quality if it comes to that. As I remember the KAI 4020 has greater well depth and is more sensitive than its 8mp counterparts.

Given that 3 - 4 minutes is optimal exposure time with a DSLR CMOS under my skies, this would be within any practical limit of an OSC from what I understand, avoiding blooming. Would this be true with anti blooming switched off.

Having cleared up these grey areas, I think it comes down to a sensible decision balancing needs and camera attributes/limitations. Given that the difference in relative QE between the chips mentioned is only a few % - I'm not sure whether that is significant in practical terms - the remaining considerations seem to be resolution and noise.

[marki]

Another major difference is electronic shutter (KAI 4020) vs Mechanical shutter (KAF 8300). The electronic shutters are easier to use when taking flats etc, the mechanical shutter needed for the full frame chips can leave artifacts if you dont have your timing down pat. The electronic shutter is also better for very short exposures like the moon and planets (I would not even try with the KAF 8300) but full fame sensors are better for AP even with the extra complexities introduced by a mechanical shutter. This makes a good read on the differences.

http://en.wikipedia.org/wiki/Charge-coupled_device


The KAF 8300 does have 1000x blooming protection whilst the KAI 4020 has 300x but you would expect this when well depth is 25000e vs 40000e respectively. I have not used the KAI 4020 but the KAF 8300 is pretty clean noise wise at temps below -20 C. The KAF 8300 is cleaner with 16e Vs 25e total noise for the KAI 4020. In short the noise performance is going to depend on the camera you buy. The deeper the cooling the cleaner the result. Good cooling and darks go along way towards minimising noise.

Mark

[rcheshire]

Thanks Mark. There's lots to learn. And I wouldn't be happy making a purchase without a substantial level of knowledge. I think I'm at the stage where I need to see the results of combinations of gear, similar to my set up.

[Tandum]

new astronomy ccd press

Rowland, google search for the above, that tool lets you combine ccd spec and telescope spec to get a fov and arc/sec/pix result. I can't tell you you which is best. It's up to you to decide which one you like.

If I run that code here with a 50mm F4 lens and a qhy10 I get 6.28 arc/sec/pix and 271 arc min FOV.

[rcheshire]

Thanks Robin. I'll have a look.

[gregbradley]

Here's a link that explains it if you can understand it. The writer hasn't bothered to define the unusual words but you get the idea that the way the CCD is read affects the result when binning and it isn't a straight quadrupling by binning 2x2 but there is an increase.

7.4 micron would not be in the middle of 200 and 400mm focal length but much longer.

It comes down to sampling theory.

My understanding of this is the Nyquist theory of sampling which states a good sample requires a minimum of 2X to get a good sample.

In other words you want your pixels to be of a size that will gather enough data to get decent resolution but not too many that simply reduces down too much the sensitivity ie several pixels trying to get the same amount of light - its spread too thin. You don't want it spread too thick (undersampling) and you don't want it spread to thin (oversampling).

One way to work it out on a simple easy to follow rule is 1 arc sec/pixel.

So if your seeing is 3 arc seconds you plug in the focal length, aperture and pixel size of the camera into the Wodaski CCD calculator and you get an arc seconds per pixel number.

I shoot for .66 arc seconds per pixel but what you will find with super short focal lengths is that number will get large even with small pixelled cameras.

Having said that this is just a guide. There are numerous awesome FSQ106 images using 16803 chips with 3.6 arc seconds per pixel.

One way of looking at that is it makes the system less prone to the effects of seeing.

These calculations I think are more important for long focal length scopes where small pixels will wreck an image. Larger pixels in shorter focal lengths will still be good but not the other way round.

Take other factors into consideration as well like QE, well depth, read noise.

But recent Kodak chips largely have similar performance one to the next once you get past the 16803. The really large chips tend to have very poor performance characteristics for astronomy. Like the KAF39000, 40000 (one of the better large chips) and 50100. Really low QE, small wells, noise is fine.

KAI versus KAF. As pointed out there are 2 main advantages of the KAI chips - electronic shutter and no ghost images. KAF tend to have higher QE though. KAI only go up to 28.8mp, KAF go up to 50mp.

The KAI series seem to have more of the new True Sense one shot colour matrix with far better low light performance.

If you were doing one shot colour I would try out the KAI4050 before the tried and true KAF4021 one shot colour. Noone has posted an image with one but on paper the KAI4050 should be better as a one shot colour.

Most True Sense sensors are 5.5 microns which is quite small for Kodak and only the 8300 is smaller with 5.4 microns (insignificant difference in size).

I have seen for myself the difference with 8300 in fast refractors. Definitely the small pixels shine. The 9 micron pixels are a good compromise but the small ones take on an edge in APOs as they tend to be fairly short in focal length (given good seeing that is).

I hope this helps a bit.

Probably more important than the chip is the camera itself. A FLI or Apogee and QSI as well as Starlight Express seem to be the current leaders. SBIG has a good range and lots of accessories. Moravian are yet to be proven and perhaps still working out the little bugs.QHY are popular because of price and seem to be good bang for buck so is Atik. How they compare in other areas I don't know. Processing cleans up a lot of the little differences.

The main points to evaluate cameras are:

1. Price/value. No point in looking at a $6000 camera if your budget is $2500. Its a very competitive market these days and the cheaper cameras seem to make big strides forward.

2. Cooling. There is no substitute for powerful cooling and cooling solves almost all CCD problems and if anything no brand cools hard enough. FLI and Apogee have the most powerful cooling, Apogee takes 30 minutes plus to get there plus the firmware takes over so you can't utilise alll of the cooling power available. It is a flawed cooling system with incorrect engineering assumptions. FLI is best, QSI Series 6 is excellent, Apogee is great with small chips (if you're patient). SBIG ST8300 may have reasonable cooling but possibly a bit weak but good enough for 8300 chip.
Professional CCD cameras cool to -100C which is where some chips need to be to fully handle ghost images (more for back thinned chips).

As chips age they get more hot pixels or develop lines. Strong cooling fades these defects away. I noticed I have a vertical line in my Microline 8300. I don't notice it because its only there at warmer temps. At normal cooling it completely disappears. I run it -35C in summer and -40C in winter.

3. Sealed CCD chamber with inert gas installed. This prevents frosting. SBIG uses a desiccant plug and whilst this works well it is just something you have to service from time to time.

4. With the sealed chamber comes the option of no cover slip on the CCD which gains you an extra 2% QE and also no small halos on bright stars in fast systems from the cover slip (minor issue really but its something).

5. Download speed and instant connection. My main dislike of SBIG cameras (STX may not have this problem) is the download of the driver from the computer when it powers up. It makes it lag, sometimes it fails, if the power or any cable is disturbed it stops, and needs to have CCDsoft shut down, repower the camera and then reboot CCDsoft - a real drag. If you have a reliable SBIG camera and reliable cables and power supply this is probably no big deal. I have not experienced that and I estimate I have had to do this 300 times.

I love the instant connection of the FLI and Apogee cameras. They have a built in memory buffer and the driver is on board. Once turned on you can unplug them from the computer and they are still going once plugged back in. You can't do that with an SBIG camera except perhap STX (I assume). For me that is a deal breaker but for you maybe not.

6. Download speeds. FLI are fastest. I think the new QSI series 6 are now fast as well. Apogee is quite a bit slower but fast compared to other brands. My FLI cameras download 1x1 in 1 second. Great for dusk flats etc.

Also self guiding in SBIG cameras gets stopped during downloads. An STL11 takes 26 seconds to download a 1x1 image. That means your tracking has been building up errors and you need to program in at least a 30 second delay for the guiding to catch up before the next exposure.
Not so with STX. Also not with FLI or Apogee or QSI or others as they use a different guide chips.

7. Accessories. SBIG has the best range. FLI has filter wheels and focuser but no guide cameras nor offaxis guiders. Apogee also. Starlight Express has the next best range. QSI also offers the filter wheel and guider in one package which is a fabulous idea and better than SBIG's self guiding as you can guide normally though narrowband filters.

8. Noise level of electronics. This should really be up higher on the list.
I am not sure of the others but FLI, Apogee and Starlight Express have super low noise electronics and you almost don't need darks.

9. After sales service and resale value. Speaks for itself.

10. Futureproof.
The STL design had a flaw in that they made the opening too small. So advances in CCD size meant they couldn't fit the next generation chips in the body. A big and costly mistake. FLI and Apogee have very large openings and will be able to handle any size chip for some time. FLI can put in any chip even the Kodak 50mp monster with no sweat.
QSI 6 series is limited to the KAF8300 at the largest and are working on another body for the larger chips. All the others seem to be able to accomodate up to 16803 at this time. FLI Microline can handle any sized chip. Apogee Ascent only KAI chips and limited to 29mp, Alta body anything. QSI the 8300. Starlight Express offer up to 16803, QHY and Atik I think both offer up to 16803.


11. Reliability. Obvious.

12. Weight:

Here is a loaded one. FLI Proline is arguably the best but its main problem is it is very heavy. I don't know what an SBIG STX weighs but it may well be the Proline is the heaviest of all these cameras. Apogee Alta is a few lbs lighter. But the good news is FLI Microline is lighter and more compact than a lot and can handle any chip. On a 16803 chip apparently the Microline cools to within 3 or 4C of the Proline. That may mean -30C instead of -35C on a 16803 chip. You would get -25C with a standard Alta Apogee or similar with the DO9 body (but that probably makes the Alta the same weight as the Proline).

Weight is a big issue with some scopes. Many scopes can not handle the heavy weight of a Proline, some can. A lens is not an issue as it will not be supporting the camera.

Phew - I did not mean it to be such a long post but there is a lot to take in on CCD cameras and its such a big investment you want to make sure you get it right.

If I were getting another 8300 camera I'd go QSI Series 6 as I like the idea of built in filter wheel with cheaper smaller filters and a built in offaixs guider. I love my FLI Microline though.

If I were getting another large chipped camera I would go with FLI Microline. Its a bit cheaper but mostly because it is way lighter and being lighter like heavy cooling, saves you a lot of problems.


Greg.

[rcheshire]

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.

[RickS]

Would love to see that link about binning the KAF8300, Greg. Did you forget to include it?

Thanks,
Rick.

[RickS]

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.

[gregbradley]

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

[gregbradley]

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.

[gregbradley]

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,

[rcheshire]

Thanks Greg and Rick. I know where I'm heading now. Definitely leaning in the FLI 4020 direction. For all the reasons stated.

[RickS]

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...

[gregbradley]

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.

[RickS]

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.

[cventer]

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.

[rcheshire]

The QSI is well designed. Nicely integrated.

[Peter Ward]

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.

[Brundah1]

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

[rcheshire]

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.

[Peter Ward]

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.

[rcheshire]

That's a strong argument. Again, there is much about the technology and imaging that is only available through informed users. Thanks again.

[gregbradley]

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.

[Peter Ward]

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.

[gregbradley]

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.

[Peter Ward]

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 :)

[rcheshire]

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.

[gregbradley]

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.

[rcheshire]

Yes. Still thinking it over. I've had a look at Sony's Super HAD and Super HAD CCDII technology. Would be good to hear what users think of their Sony chip gear. The CCDII looks promising for video cams.

[Bassnut]

It's funny, thinking of a new cam, I read adds/specs, customer feed back, agonize over hot new features, mega cooling,mega pixels, back thinned hi qe, fast downloads,support, RBI, brand difference, it's a head spin.

So I take a step back and look at my rather limited (sbig only) brand experience,compare it to other brand user posts, what I really want in features in practical terms,and, although it's not a priority ,value for money.

I see peters experience with the u47 and very few image posts generally with back thinned CCDs, they seem very attractive qe wise, but I've also read there are many difficultys with them and are very expensive, so I keep coming back to a 6303 chip, which despite it age is still the chip of choice for NF NB

So brand. Yes FLI has better cooling and faster downloads, but at what cost, and does it really, really matter (for me).

I don't give rats if download is 2 or 4 secs, or whatever the diff between usb1 and 2 is, and from experience, with accurate darks, I don't much care about the max cooling temp either, I don't have to battle RBI so -10 or 15 Or 20 is fine by me.

So, value for money. Well, I need a 7 pos filter wheel so:

Fli 6303 proline with 7 pos filter wheel total us$10490' SBIG STL 6303 with 8 pos filter wheel $6795 total. (OPT as reference). Mmm, big diff.

Ok, fli has better cooling and faster download, not that I care much, but SBIG has internal guide, AO interface, plug for a very sensitive cooled guide cam.

Support. I don't know about FLI , but when I sent an st10 for an upgrade, it was a smooth reasonably priced experience, and a guide cam in for repair got, I kid you not, a daily report on progress by the repair tech and a full explanation of the problem and what was done.

So, I'm thinking, do I go with what I know is a bullet proof , tried and tested product, albeit a bit behind in unessential specs, but with excellent support and oddly much cheaper with a wider range of interfaces and accessories ( eg AO). or another newer very attractive more expensive brand that may well give the same image result for far more money and less options?

[bert]

Hi Rowland,

You managed to get an interesting thread going....

I have an st4000xcm and I love it. I have used it on a variety of scope and focal lengths. I have it currently mounted on an Astro Physics 130 f6 refractor, but I have used it on a vc200 at 1800 and 1260fl, a vixen fl102 refractor at918fl and a william optics triplet refractor at 480mm. My buddy had it mounted on his rc at 2800fl as well for a while, All worked well.

One advantage of this camera is because it is one shot colour, you can use adaptive optics with the internal guide chip. No OAG needed. I get a -35 delta cooling, dessicant needs charging once a year (this time when I charged it I filled the chamber with argon as well).

It is by no means sensitive, better than some osc cameras, worse than others. A lot worse than most mono cameras though. There is noise, but it is not too intrusive.

It has not missed a beat since in the 2 years I have had it. And I have done a lot of imaging with it, as my observatory is automated enough to do data collection all night unattended.

Check my posts here on iis to see some of the imaging I have done with it.

Brett

[rcheshire]

It seems that SBIG gets a good wrap on a number of fronts including price. Customer service wasn't a consideration when first starting this thread - so let's add that to the list of requirements for an OSC.

Given that there is not a huge variance in sensor technology for OSC's in the price range under consideration and it really comes down to 8mp vs 4mp or even 2mp - resolution vs charge capacity (if I understand correctly) - and to what degree that matters given the manner in which the camera will be used. The considerations in no special order for DSLR replacement are;

Charge capacity (QE)
Electronics (noise)
Cooling (noise) - accurate temperature control.
Simplicity (ease of use)
Easy to adapt to camera lenses
Software compatibility
Customer service
Price

Bonus items are;

In-built guiding chip, preferably using the main optics with no requirement for a separate guide scope.

From what I can see SBIG meets those requirements reasonably well.

Any other considerations:question: that I've missed.

But a list like that may not satisfy purist / specialist requirements.

Alternatively (for my purposes, which are basic), spectrum enhance my 5D MKII and rely on its low noise characteristics as a relatively lower cost alternative. And implement some ideas I have for a sealed, dry air cooling system that retains access to the camera controls.

[gregbradley]

Good post Fred. Yes you raise an interesting point.

SBIG does represent good value at the moment and they definitely do have the accessories and integration.

I thought about a 6303 chip for my CDK17 for a while. A number of posts complained about the blooming. I then realised that basically its more pixel size I needed to match to the optics and the best QE. The 16803 chip is not that different in QE to the 6303 and they are both 9 micron plus it has the advantage of antiblooming. If I crop my 16803 I can get the same image scale of the 6303 (which is what I was mostly looking at).

Your needs are a bit different as you are predominantly narrowband and I am predominantly LRGB with Ha occassionally and NB occassionally.

You should grab that STL6303 before the sale ends - $2000 off is a huge saving.

By the way a fairer comparison would be Microline 6303 to STL6303 (FLI is still more expensive though).

I like my Proline but when I get another FLI Camera I would be choosing Microline as the weight difference is significant yet the difference with the Proline boils down only really to an extra 3 or 4C cooling power and a USB and Power hub built in in the Proline (plus a better shutter which you can also specify in the Microline).

The difference between the FLI and the SBIG in my opinion is that the FLI is the absolute best in all areas but the SBIG gets the job done too. The FLI makes almost everything easier (except for AO units) and foolproof like imaging with a good Tak or AP scope and it all just works everytime. You also tend to get used to whatever brand you have been using. I am now used to FLI. I was used to my STL and it served me well for some time.

Greg.

[gregbradley]

Charge capacity (QE)
Electronics (noise)
Cooling (noise) - accurate temperature control.
Simplicity (ease of use)
Easy to adapt to camera lenses
Software compatibility
Customer service
Price

Bonus items are;

In-built guiding chip, preferably using the main optics with no requirement for a separate guide scope.

Hi Rowland,

You've got a few concepts not right there. QE stands for Quantum Efficiency which means how sensitive the camera is. In other words what % of photons hitting the chip actually get converted to an electron by a pixel that can be measured by the electronics. QE of 60% is good. One shot colour are usually around 23 to 40% depending on chip and what colour (different sensitivities for different colours, green is usually more sensitive). Most mono CCD cameras are 50-60% QE. Anything over 60% is exceptional. 60% is plenty though. 50% is fine as well. 23% is limiting you to brighter objects with faster scopes with larger aperture.

Charge capacity is called well depth. It is not really a measure of sensitivity. It is how many electrons can a pixel hold. It is measured in numbers of electrons. 20,000 electron well capacity is about as low as it goes, 110,000 is about as high as usual chips go. It is not 4022 is medium/low but workable. Small well depth means you may have to shoot shorter subexposures on faster telescopes than long well depth. It means bright stars will end up overexposed and white - no colour- fairly easily and is something you have to keep an eye on.
40,000 well depth or more is what you want. 100,000 is great. You'll get colourful bright stars even with 15-20 minute exposures.

Cooling (noise) is not about how accurate you can regulate it (I think almost all regulated cooled cameras now are accurately regulated) its about how powerful the cooling is. Highly regulated weak cooling still leaves lots of noise and artifacts in the chip. Most CCD chips have noise reduced by half with every extra 6 degrees C cooling. So running a typical chip at -20C versus -35C you are talking about 1/5th less noise in the -35C no matter how well regulated the temp is. Regulated temperature is important and all the major brands do that as far as I am aware. I think Starlight Express did not always do it but Apogee FLI and as far as I know QSI and others do this quite well. It is true accurate controlled temperature is valuable so your darks match your light exposures and do a clean dark subtract.
Weak cooling means you now HAVE to have super well done darks. I often use only 3-6 darks for a master with powerful cooling. Weak cooling would take 16-32. Again not that big of a deal perhap but almost all defects in a chip are reduced by powerful cooling. Some vertical lines in chips do not dark subtract out easily no matter how accurate your darks are. That then gives you a problem processing the images with these little background vertical lines showing up.

Also with better electronics there is FAR less noise in the first place to subract making them more reliable images.

My 8300 chip is as clean as anything at -35C yet I noticed when it was warm it actually has a slight vertical line in it. I don't know what temp it is when that disappears but I think its past -20C. I usually run it at -35 or -40C. So if your camera maxed at -20C that line would still be visible and you would be relying on your darks to remove it. That may or may not work.

Adapters to lenses are available for any camera. Precise Parts will make an adapter for anything so that is not really a difference between brands. I have had lens adapters for my SBIG, Apogee and FLI cameras.

Compatibility with software. As far as I know they are all compatible with the major software. CCDsoft does need a camera plug in to work with non-SBIG cameras. But Maxim DL I don't think does.

I thought I would clarify those points.

SBIG self guiding is handy for sure but it is useless for Ha or Narrowband so you end up needing an off axis guider or guide scope anyway. Self guiding is a brilliant idea but its weakness is the guide camera looks through the filters. Guide exposures are usually a few seconds or less. But to get a guide star through a Ha filter may require 30seconds to a minute to see one. I don't know of a mount that will handle 30 to 60 secod guide exposures and get round stars at long focal length. Not even a Paramount ME would do that. If you only do colour and no Ha (and there goes all your nebula shots) then its not a problem.

So you see there is no simple work around these laws of Physics we are up against when imaging.

Greg.

[rcheshire]

Thanks Greg. I remember now - appreciate correction on those points.

Amending the list without actually typing it out there are some items to reconsider. The picture is clearer for sure, but after all I'm not sure that the limited opportunities for AP that present themselves warrant the expense. I have a much better understanding of the technology, which has educated me fairly well as what to expect. Time to consider - decision making time I think.

[Bassnut]

Hey Greg (sorry for the hijack Roland). At 656nm (Ha) the16803 is 45%Qe and the 6303 is 65%. ok there's not much in it for lrgb as you say,But for me that makes the 6303 more attractive for NB, it's the difference ( roughly) between a 16 and 20" aperture for the same image result.

The 16801 on the other hand peaks at 68% Qe (nabg version) at Ha, which is very interesting, but much more expensive. I can't find any astroimager user pics, mmm, wonder why ?.

Another thing, the 16803s dark noise is 0.08e at -35c, but the 6303 is 0.0005e at -45c, several orders of mag lower, yet I often hear the 6303 is a noisy chip? Thats got me stumped, unless the cooling on the SBIG is the problem, in which case the FLI then becomes far more attractive with deeper cooling, what do you think?.

[rcheshire]

Be my guest. It's a very interesting and educational discussion.

[gregbradley]

I haven't seen any 16801 images either. I see what you mean, another 20% QE in Ha is pretty attractive but its less QE at 550nm (52% verus 60%). That would be relevant for LRGB so yes the camera is best used for NB. Also the chip direction Kodak seems to have taken it would seem this sort of performance will be a thing of the past from them. They are going the small pixel platform more megapixel type direction and have settled into 50% QE as being high.

I just looked at the Kodak Spec sheet. They are not the same criteria from one sheet to the next (I don't know why they do that). But it shows readout noise at 15 electrons for the 6303 and 9 electrons for the 16803. I am not sure that is the correct measure for what you are asking.

Best ask Steve Crouch about noise performance in the field in an STL body as he is the only one I see using one here. I don't see noise in his images. So like any camera you just match the darks poperly and you'll be fine.

I think it would be a nice change from the ST10 which is a legend of a camera but the 6303 is more real estate.

Greg.

[bert]

I use both the 4022 chip and the 6303e. Not much difference in noise, the 4022 does show vertical lines more in bias, but they dark subtract well.

The 6303 is on another planet with its well depth and crazy sensitivity. They are completely different to process because of the dynamic range of the 6303.

Brett

edit: the 4022 is in a st4k osc, the 6303 is wrapped in an stl body.

The stl cooling is faster than the st series, and has a better cooling delta.

[Peter Ward]

Beg to differ. :)

I often use the internal guide chip for NB.... it just needs a bit of planning (via a sync to TheSky with an instrument rotator, guide stars are pretty easy to find.)

Better still is using SBIG's Adaptive Optics a remote guide head with the AstroDon MOAG....you can get some incredibly tight stars with AO guided narrow band.

.... In short SBIG's system integration is in my opinion, the best available.

I must admit STX secondary systems have been slow to come to market, but am confident differential guiding etc. will pave the way for some very impressive images in the not too distant future.

[gregbradley]

I must admit I'd love it if my FLI had self guiding sometimes. It is extremely convenient. I did like the fact the STL was so self contained.

I'd like to see more of those features in the STX. But aren't they not needed though if you are using a MMOAG and are useful if you are using a guide scope? (which you sometimes use even if you have a MMOAG like me - CDK reducer does not allow enough backfocus for a MMOAG).

Greg.