KAF8300 CCD Cameras

[OzDave]

Hi,

I have been considering purchasing a CCD camera based on the Kodak KAF8300 chip for a while now. The things that are important to me are:

1. Must work on Mac (out of the box).

2. Manufacturer must provide SDK for custom development work.

3. Monochrome

4. Must have shutter

5. Want filter wheel for narrowband imaging

6. Maybe want built-in OAG, although I have the 9mm TS OAG already.

Originally I was interested in the SBIG 8300 models and would have considered getting the filter wheel and OAG separately. However, I've now discovered the QSI 583 and 683 models which have all this stuff built-in. The marketing blurb around why having it all built-in is a good idea seems to make a lot of sense. But does it really matter that much?

I am thinking that separate components would probably be a lot cheaper, considering that the shutter-only cameras start at £2450 for QSI or around £1500 for SBIG. But the convenience of having it all built-in seems like a good idea. But maybe there is a downside I am not thinking about?

So then I looked at the price tags of the QSI 583 and 683:

583wsg: £2975

683wsg: £3349

Both are pricey, but I started thinking if I am going to spend that much on a camera, should I plump for the extra £376? But I'm not sure what that actually buys me.

So, has anyone got either of these QSI cameras, or the SBIG equivalents?

Is built-in equipment all good and no downside?

What would the QSI 683 give me over the 583?

Any help much appreciated!

Regards,

David

[MartinB]

I have a QSI 532 WS with an additional face plate which turns it into a wsg when required. Some general points about the 5 series. Build quality and design is superb, light proof; rapid, accurate and stable cooling; mechanical shutter works with rapid short exposures (good for flats), no problems at all since I have had the camera.

Having the built in filter wheel keeps everything in one box. Changing filters is a bit more fiddly than a seperate wheel in that the face plate has to come off and you then have to unscrew the wheel. If there was a problem with the wheel the camera could effectively be out of action. As I say, I have not had a problem.

The off axis guider works very well and keeps the optical path as short as reasonably possible. Focusing is reasonably straight forward. Used with a lodestar guide cam you have no worries about being able to find focus. Quite an expensive package though.

As far as the 583 and 683 go, the big advantage of the built in filter wheel is that it is situated close enough to the chip for 1.25" filters to work. This is quite a big money saver. QSI have always worked to minimise read noise and their download times have tended to be quite long compared with some of the competition. I have heard lots of arguments for and against this. The 583 has a download time of over 20 seconds. This is fine if you are doing long exposures but seems a major disadvantage if you are doing short exposures from a light polluted site with limited imaging time due to poor climate. The 683 has refined this to a more realistic 10 seconds without increasing read noise. For me that would be enough to justify the extra expense of the 683.

The cooling has been increased from 38 to 45 degrees below ambient which may be handy in a warm climate. There is also the option of an 8 position filter wheel. This would obviously be very convenient but does make the camera much bulkier and, presumably, heavier.

Personally, if I was looking for an 8300 chip and had the budget I would go for the QSI 683 but stick with the 5 filter wheel. If I was after off axis guiding the QSI wsg set up can't really be faulted except on price.

At this quality point I think the only competitor is FLI (but without the built in filter wheel). SX and Atik fall some way short in terms of light proofing, cooling and shutter efficiency, and their price advantage is diminished when you factor in the expense of 2" filters. I've seen the SBIG version and it seems agricultural in comparison.

[OzDave]

Thanks Martin!

Some excellent points in your reply. I am planning to use my Imagine Source camera as guidecam, which should work since it has the CS back focus of 12.5mm. I assume you just screw the guidecam on and it's in the right position for focus? Or are there also minor adjustment screws or something to tweak the focus also?

With some separate OAGs you can rotate the prism (with the guidecam) independently from the main camera to help find a guide star. I guess with a built-in OAG, the prism doesn't move, so you'd need to rotate the whole camera. I guess that is not too much of an issue.

I agree on the 5-filter wheel. I honestly can't see needing more than 5 at a time. I mean, in a typical imaging session, I'd be doing narrowband say, and I could fit all the filter I'd need for that in the wheel. If I managed to use them all in one night, that would be a good night indeed!

I read a review on the 583wsg, which said that the readout time was 23 seconds and even the subframe readout time wasn't brilliant. In fact, the subframe time depends on where the subframe is relative to the main frame. If it's in the top left, it can be fast, but bottom right means still a 23s wait time. That must make focusing very time consuming. Even the 683 at 10s must be quite painful. Do you happen to know if the subframe readout speed on the 683 is any different in nature to the 583?

Seems like the 683 would be best, just for the readout time, as you say.

I had rejected the Atik cameras because they don't provide any Mac support at all. And SX I rejected early on, basically on price when I was thinking of cheaper prices. I don't know if they have Mac support. And yeah, the SBIG cameras do look a little goofy compared to the rest of the market.

So I think I'm leaning towards the QSI683wsg, but will wait a bit to see if anyone else wants to offer an opinion.

David

[MartinB]

David, you will need to check that the thread on your guide cam is compatible, the Lodestar screws in place nicely so needs to be the same. The focus position depends on the filters being used so does need adjustment. There is a threaded focus adjuster which is held in place by set screws. Seems a bit fiddly at first but works well once you get the idea.

Forgot to mention that the 683 had a dual read noise facility. I assume this is primarily for focuusing. It will allow rapid reading of the chip (the penalty being high read noise which isn't a problem when focusing). Unlike interlaced chips which can read just a sub selection of the chip, full frame cameras have to read the whole chip which can make focusing a pain. I believe the 6300 chip is actually divided into 4 parts which speeds up focusing but QSI are suggesting download speeds as short as 1 second with the fast read out mode. This is a major plus point for the 6 series version. Also handy when framing. You will just have to remember to switch back back to high quality mode at the start of the capture!

[OzDave]

Thanks Martin, in all the 683 sounds pretty awesome. I also had an email back from QSI about their software SDK, which they claim will be updated for 600 series very soon (matter of weeks).

So I think I'm sold on the 600 series!

David