I recently installed an off axis guider ( OAG8300) on my STF8300 camera. I am getting a seriously distorted image from the guider. The stars are small ellipses instead of circles. They also have tails to the right of each star. They look like small comets. All the tails are extended to the right. I have followed the installation instructions with the OAG positioned as shown in Figure 11 in the manual. The image train is a TAK106ED scope , FLI Atlas focuser, Pyxis rotator , SBIG OAG, SBIG FW, SBIG STF8300 camera. The camera is at focus and operating correctly with good images. Please tell me what corrections are needed on the OAG.
Most likely your telescope produces distorted images off axis. Pretty much all telescopes do if you're far enough off axis. You might get better images by moving the mirror inwards, possibly at the cost of more vignetting. All that said, you don't need perfect star images to guide. Give it a try as-is
I did move the mirror inwards which improved the STi image. It is not perfect but it seems to be adequate to maintain the guide star. I am also getting some vignetting but it is manageable. I will experiment with additional movement of the mirror to see if I can reach an optimum position, balancing vignetting with image quality. Thank you for your response.
