Choosing a CCD camera

[Ivor]

As I'm not prepared to modify my EOS 400D and having seen what others have done with cooled CCDs I've come to the conclusion that I'm only ever going to be frustrated by the limitation the EOS400D puts on my imaging. With this in mind I'm now looking to buy a cooled CCD, as I want to get this right I want to make an informed decision before handing over the plastic.

My main scope is a William Optics FLT 110 Triplet APO refractor http://www.williamoptics.com/telescopes/flt110_spec.php it is an excellent scope and both visual views and images are pin sharp. Long term I've also got my eye on 10" Ritchey Chretien so I'd be looking for the CCD to excel with both scopes.

With all these purchases there is the challenge of deciding where to draw the line for quality vs cost, practically there is no point in spending £4K on a camera if it's performance is limited by my sky. At the same time from time to time I get the opportunity to go to some dark sites, so I would like to have a camera which would do well in both situations.

As I find more often than not the good nights are those with a moon I want to do narrow band imaging as well, which at least reduces the options to down to a mono CCD. I've got half an eye on cameras with the Kodak 8300 chip with a full frame of 3326 x 2504, 5.4 microns pixel size and sensor diagonal of 22.5mm it provides a FOV of 122.8 arc mins (3438 x 22.5/630) with my reducer if I've understood the equation correctly.

I'm looking to buy this in February (maybe Astrofest will offer a few good deals) which should give me enough time to evaluate the kit on offer against the limitation of my environment.

I see there was discussion of an imaging workshop back in 2008 that cover the topic(http://forum.orpington-astronomy.org.uk/index.php?topic=3687.msg18203#msg18203) did this happen?

So to start the ball rolling my initial questions are:

What factors should I consider when choosing the sensor?
How do I calculate the limiting factor of my sky?
What are the limiting factors of my kit that I need to consider?

[Mac]

In reply to the first one, the size of the sensor is directly proportional to the depth of your pockets. 
I'll let someone else answer this one.

There is a limit to your sky problems with regard to light pollution, but don't let that cloud the issue. (no pun intended).
you can always get two sets of filters.
1. narrow band filters as this will remove the issue of light polution, even in the middle of central london, as they will only pass the narrow bands, normally HA, Hb & Sii, for red, blue and green.
2 Get another set of just RGB for when you are at the dark skies.

The only problem with this is that with narrow band imaging, the amount of light is reduced considerably, so exposure times go up by the same factor,

I purchased a Starlight H9 and havent loooked back, (even if i only did get out about twice last year)

When i lived in Abbey wood, I went down the route of Narrow band filters, this is now limiting me as im am in a dark site now and need to get a set of RGB.

The limiting factors of your kit, will probably be , Mount & Guiding, so you will need to also look at getting another scope and another smaller camera for guiding,

which then opens up another ball game with software ect.

Mac.

[Ivor]

Like everyone my pockets are only so deep, but I wanted to put that cost issue to the side initially and base the selection criteria on quality; if an extra £500 makes a massive difference it would be worth waiting a while longer to allow my pockets to fill a little further

I've got a EQ6 pro mount and I'm already guiding with a Lodestar via a Lidl 70mm scope using PHD; the new camera might well change the choice of software.

What criteria did you use to choose the Starlight H9?

[Mike]

I also had a H9 and can highly recommend it. It is a superb cameras. However, it's been around a while now and technology has moved on a lot since then.

[RobertM]

Hi Ivor,

There is a lot to mull over for such a big decision.  The H9 and it's Atik equivalent are excellent little cameras; they have a global shutter are very easy and flexible to use.  The only drawback is that Sony chip is quite small and so something more APS size would make better use of the available field on your scopes.  I had a very similar decision to make a while back with the H9 I had - where do I go from here.  Mike is right the chip in the has been around for quite a while but there again most of the others have been too.  There certainly hasn't been the quantum leaps in sensor development I would have expected especially in the monochrome camera world. 

One thing I would say is to ask yourself what you want it to be able to do then write that down as a list and do some investigating.  Questions such as:

Sensor size
Mono or colour
Interline or full frame (global/mechanical shutter)
Do you want to use camera lenses and if so what make.
What size of filters will the camera use and can they all be loaded at the same time.
What are the best filters for your area.
etc...

Hope that helps as a starter
Robert

[Mac]

What criteria did you use to choose the Starlight H9?

At the time it was the best camera that i could afford without the other half noticeing. 

Mac.

[Ivor]

I've umm'ed and arrr'ed about what CCD camera to buy and I've now narrowed down my decision to either the ATIK383 or the SBIG ST8300. I'm inclined to go with the ST8300 (I'm clear on the benefit on the STF8300) as it comes with CCDSoft and TheSky, other than that the 2 cameras are much of a muchness. Is there anyone with experience of either camera or CCDSoft who can give a steer either way?

Cheers

[Rocket Pooch]

Ivor,

I'd suggest you add up the total cost of ownership with these cameras; I did and the QSI583 was cheaper overal because the filters where cheaper (1.25" not 2" filters). 

Also the QSI is small and very easy to use, the cooling works properly, unlike the Atik.

Chris

[RobertM]

I agree with Rocket, the price of the camera on it's own is one thing but it's a different ball game once you add up all the 'incidentals'.  There are some other things you may want to consider:

1. Filter wheel.
Although it's marginally cheaper to have a five way wheel if you ever look at doing narrow band then you will curse having to keep changing the filters over from LRGB to HaOIIISIIHb.  From that perspective I'd definitely choose an 8 way wheel and 8 way wheels only come in 1.25" (mounted/unmounted) and 36mm flavours (that I've found anyway.
2. Camera weight.
This will affect the amount of stress on the focuser and it won't take much flexure for you to have problems.
3. Filters
At some time you may want to use a camera lens so make sure the filters you buy give you an unvignetted field with the Nikon/Canon/whatever lenses you think you may use.  Canon need the shortest back focus so planning for those will cover most other makes too.
4. Camera cooling/download times
Make sure you're happy that the camera can cool enough in the summer months and that the download time for focusing is reasonable.

The STF8300 looks good on paper but have you seen any real world reports by people without bias (same for all cameras by the way).

Robert

[RobertM]

Just a small note on cooling.

With these KAF chips it's essential that you have regulated cooling and that the camera can hold it's temperature throughout a session.  To hold a camera to -20C in the summer you'll need at least 40C of cooling and to -30C at least 50C (I'm assuming a 20C ambient as happens sometimes).  The cooler the chip the less the dark current will be but -20C is a good figure to go for year round and will save you having to use libraries of dark frames (though that's not too much effort).  In the winter most cameras will get the chip down to -30C so it's only the warmer months you really need to consider.

Robert

[Ivor]

As I haven't found anyone significantly cheaper I'm inclined to stay with my preferred supplier Ian King as he's not steered me wrong yet.

The total package I'm considering includes a filter wheel plus LRGB, when budget permits I'll get the narrow band filters.

He offers

the ST8300 + 7 position filter wheel with LRGB for £2140 http://www.iankingimaging.com/show_products.php?category=110

The same package with the STF8300 would be about £300 more. (Other than quicker download speeds I'm not clear what I get for the extra money)

The ATIK383L + 7 position filter wheel with LRGB for £2140 http://www.iankingimaging.com/show_products.php?category=112

The QSI583 + 5 Position filter wheel £2498 http://www.iankingimaging.com/show_products.php?category=113&offset=10&offset=20&offset=30&offset=0

I seen pictures with for my scope with all three cameras and they all look excellent, in the long term I dream about getting a 10" RCI in the future and he has assured me both the ST8300 and ATIK383  will work with both scopes and the 36mm filter will prevent vignettes and the FLT110 shouldn't suffer with any flexure issues.

There doesn't appear to be a big weight different between the models ~100g between the ST8300 and the QSI583.

Cooling looks the same I'm particularly keen on being able to have set point cooling so I can create a bank of master Dark frames (but maybe I don't need to @ -20c?).

The only factor I've not considered is the camera lens, which I'll ask about.

I'd ruled out the QSI based on price, I've not seen images any better than the others, I've not seen any images from the STF8300 + FLT110 and I can't get too stressed about a couple of extra seconds download.

Anything thing else?

[RobertM]

I can't get too stressed about a couple of extra seconds download.

So picture it - you are focusing the camera and you need 20 frames to reach focus manually...  If you are autofocusing the game is slightly different since you may only need 5 or 10 but it's essentially the same.  It may not matter but I thought I'd raise it anyway.

If you get the SBIG then I presume it'll be with the FW8 ? If you get the Baader NB set (you get Hb for free or very little more) then that is 4 filters + LRGB = 8.

There is an 8 way carousel and housing that going to be available for the QSI 58x series soon but it does add a bit to the weight.

Another thing to consider, since you mention the RC10, is the use of an off-axis guider.  I would consider one of those essential at anything >1000mm (depending on mount).  Check out the prices of the different options and whether they will work with your guide cam.

Sorry I'm doing a bit of a brain dump...

Robert

[Ivor]

All thoughts are good, I'd rather have them brain dumped and not make the wrong choice.

The FLT110 comes with a Digital readout on the focuser so normalyl whenever I return to an object I already know the setting so I'm normally only a few mm out, but I get your point.

I see the advantage of having the 8 position wheel, but as I'm a long way away from the luxury of a permanent setup when I want to change the filter I can do so while I'm waiting for the rest of the kit to settle.

I'd considered an off axis auto guider and all options support it, but that will exceed my current budget.

The only fly in the ointment is whether it is worth waiting for the SXVR-694, it's more sensitive but smaller so I'm guessing it is going to be about the same price but I could be completely wrong there.