If Celestron state that the CG5 is ST-4 combatable then it should comply with the standard SBig used with original ST-4 pinout.
As far as autoguiders are concerned, I would ask myself what my photographic ambitions are, meaning, do I start off with an autoguiding system that MIGHT be OK or do I go with a dedicated autoguiding system. As one would appreciate, there is a significant cost difference.
As far as entry level systems go, possibly using a Toucam, LPI, DSI or NexStar coupled with free guiding software like GuideDog or Guidemaster or, for a cost K3CCDTOOLS.
For a more advanced system, ST-4 (if you can get one), STV (I think they are no longer available) or one of the cheaper SBig cameras, the major problem is the cost here.
Each has it's advantages and disadvantages and if you are limited to a budget, the Toucam, LPI/DSI or nexStar is the way to go. I did significant tests using an LPI -v- ST-4 and, obviously the ST-4 came out on top BUT that was before Guidemaster had the LPI long exposure support, the downside of using the LPI is that to get long exposure mode you have to install .Net 2 and DirestX 9.0 and above. The biggest problem I found was that you needed to get a fairly bright guidestar for things to work properly.
On top of this, one has to consider how it is to be all connected.
Hope this helps a little.
Cheers
JohnG
