With my ST-8XE, CFW-9, and AO-8 the 0.12 sec minimum exposure of the internal off-axis tracking sensor is pretty slow and it being an internal sensor means that it is affected by narrowband filters reducing the brightness of guide stars, so I want to use an external tracking sensor. What is the fastest recommended correction rate of the AO-8? In other words, what's the highest practical frame rate to run an external tracking sensor at to help guide the AO-8?
The minimum exposure time is shorter than 0.12 seconds. That is the limit imposed by the camera's mechanical shutter, which is not used while AO guiding. The following paragraph from the user manual is relevant:
I'm aware that is the limit imposed by the mechanical shutter, but any attempt to reduce the exposure time further is ignored and it still feeds me a 0.12 second image to guide off of. I don't really understand why though, since while exposing the main sensor the shutter is open constantly. So based on what you're saying, does this mean that if I set the exposure for the tracking CCD to be 0.05 seconds (for example), then the initial image I select the guide star on is the only image that is limited by that 0.12 second exposure time, and subsequent guiding images will use that 0.05 second exposure time?
You should be able to set the exposure time you want prior to start of tracking. Are you using CCDOPS? Please note that software is no longer under active maintenance.
Yes I can set the exposure time of the imaging sensor and the tracking sensor, but I cannot set the exposure time of the tracking sensor any lower than 0.12 seconds to give myself a higher refresh rate on the AO-8.
I'd suggest getting MaxIm LT. It's a "light" version of our MaxIm DL Pro software, and it fully supports all modern SBIG cameras (and a lot of the old ones, too). There is a demo version of the full MaxIm DL Pro software, if you'd like to try it out before buying. There is a comparison table on the web site, and in the user manual, that explains the differences between the product levels. You would need either MaxIm LT or MaxIm DL Pro to run your camera. See: https://diffractionlimited.com/maxim-dl/
