astrodeb@charter.net wrote:

Don't you need a flip-mirror to find a guidestar with the ST-4? I mean isn't it harder to find a guidestar without one?

General statement: You can use one. I even bought one to experiment with but in the end decided it was easier to not use one (which is why I also have a flip mirror for sale...). But more specifically: If you are going to have the ST-4 looking straight through the scope and do your imaging with a camera mounted piggyback on the scope then the flip mirror might be ok. However, if you are planning on shooting through the scope I'm guessing you'll be using an off axis guider body with the camera looking straight through the scope and the guider looking through the guider body's side port. Adding a flip mirror to that probably would not work very well. In the latter case, I first compose and focus the image through the camera and then lock down the RA and Dec so nothing moves. Then I put an eyepiece in the off axis guider body's (OGB) side port and using the OGB's adjustments I move the port around (without moving the scope) until I find a guide star. Rarely is a bright guide star available so sometimes you have to be dark adapted and use averted vision but if you can see a star the ST-4 can lock onto it. Then, again using the OGB's adjustments, I center the star, remove the eyepiece and replace it with the ST-4's guider head. Wondering about focus? Once the image is focused in the camera you can't mess with telescope's focusing knob so focusing the ST-4's guider head is done by moving it in and out of the OGB's side port. It's a bit tricky the first time you try it but once you've established focus you mark the position of the head and use that same position each time. So, is it hard to do all this? Yeah, the first time it's a pain. But like so many other things, once you know what you're doing it's not hard at all. Patrick