Telescope Reviews: Need 101 instructions on autoguiding Celestron CG5

Richard,

I'm going to expand a bit on the good advice you've already received.

Your mount has two connectivity options for autoguiding ...
1)Guiding via the hand controller or
2)Guiding via the ST-4 (autoguider port) interface

To do #1 you need the Celestron serial HC cable (#93920). This is the same cable used to allow PC based planetarium type applications to control the mount. Since your laptop has a serial i/f you'll also need a serial extension cable (the Celestron cable is only 3' long).

For #2 you have a couple of options ... if you are going to use one of your webcams as an autoguider then you'll need a parallel or USB to ST-4 adapter (like the Shoestring GPUSB). This will give your computer the ability to control an ST-4 compatible interface (the autoguider port on your mount). The other option also comes up if you are not going to use one of your existing imagers for autoguiding and instead a dedicated autoguiding imager (like the Orion SSAG) that has an ST-4 interface built into it. With one of these imagers you don't need a specialized ST-4 interface like the GPUSB.

Now that we have a physical connection between the PC and the mount we need some autoguiding software. Here there are a few more choices ... PHDGuide, GuideDog, MetaGuide are some of the more popular ones. There are also some imaging applications that also include an autoguiding capability. For now it really doesn't matter which one you pick. The autoguiding application has to talk to the autoguiding imager. This is usually done via a USB 2 interface. You likely also need a driver for the specific imager that you are using (if you're going to use one of your wecam based imagers then you've likely got the drivers take care of). The autoguiding application now also has to be able to send commands to the mount to move the mount. If you go with the connect via hand controller (HC) option you'll also need the ASCOM platform (s/w to create a standard method of talking to a telescope mount), and the Celestron mount driver for the ASCOM platform (so ASCOM can talk directly to the mount).

Your choice to use either connectivity option #1 or 2 will come down to price and whether you are also going to use some planetarium software to control the mount (selecting objects to image from the planetarium program rather than from the HC directly). If you are using one app to control the mount and another one to autoguide you open the possibility of inference between the two apps. Using the ST-4 interface is an older and more direct method (it's an electrical interface with no commands to interpret) that is often preferred by folks who've been imaging for many years. The ST-4 interface is effectively dedicated to the autoguider application.

So to use some specific examples ...

Assume you have both the C8 and C80 on your ASGT and the C80 is in 3 point rings. The SPC 900 or NexImage is connected to the C80 and the USB interface goes back to your laptop. Your XSi is connected to the C8 and it's USB connection goes back to another port on your laptop. You really want these two imagers on separate USB ports on your laptop ... they each needs lots of bandwidth. Depending on where you place your laptop you may also need USB extension cables.

ASCOM and Celestron driver loaded, PHDGuide s/w loaded. Serial interface connected to a long serial extension cable, then to the Celestron serial HC cable and then connected to the HC itself via the small 4 pin connector at the bottom of the HC.

Focus both imagers, select an object and slew to it. Preview the object and center it (or orient the object the way you want to on the XSi). Select a suitable guide star with PHDGuide (may need to re orient the C80 in it's 3 point rings to find a suitably bright star). Start autoguiding. Re check your focus on the Xsi. Set your imaging/camera control app to take the appropriate number and duration shots. Start your exposures. Yes this is a bit simplistic, there are other steps depending on what software you're using to guide, image, control the camera, etc.

--------------------
Mark

C11, C6, APM/TMB115, and AT80ED - Tandem mount CGE and CG-5A, WO EZ-Touch and AT Voyager
25x100s and 8x56s, T-Mount Light, Mark 1 eyeballs - Modded 350D, DSI-P, SPC900, Mallincam

Just because you can doesn't necessarily mean that you should