Ad Astra Observatory

My autoguiding isn’t as straightforward as it used to be. I have a lot of new gear that I’m trying to figure out; G-11, Gemini, ASCOM, ST-4, MaxIM. Each of these adds a little bit of uncertainty to the mix.

Of them, the ST-4 (which guides the mount via 4-way relay switches) is the equipment I’m most used to and comfortable with, so all other things being equal, I try to stick to using the ST-4 relays to do the guiding job; they’ve done great for me for years.

However, I’ve noticed that when I’m using the ST-4 standalone with the Gemini, I get long strings of 0 and 1 corrections (that’s as much as 1/5 of a pixel, or ~1.5”), followed by a 5, then a -5, then more 0/1s. So it feels like there is some overcorrection that is happening. To help with this, I set the ST-4 to average about 3 frames, so a 5 usually turns into a a 1 or 2, but I maybe do a couple of them.

When I added MaxIM into the mix, it handles this with “aggressiveness”, which essentially sends a percentage of the asked-for correction. I never really found that aggressiveness and the ST-4 relays worked all that well together; it seemed like the aggro settings were not having much effect.

So I switched over to using ASCOM; ie the ST-4 takes the photo, MaxIM parses it and decides on the correction, and then MaxIM sends the correction directly to the mount via a RS232 connection. After some initial hiccups, I think I have this working pretty well. I set the aggressiveness to 3, and that seems to be enough to keep things more or less in check. I’m not sure why. I think that the ASCOM control might be able to tell the mount “just slow down” or “just speed up”, rather than “go left” or “go right”. I’m not sure about that, but … shrug.

One problem that I’ve been seeing is that tracking works great for 45m or so and then starts getting worse and worse. I have no idea why.

I tried turning on the relays the other night, to see if the 45m problem was related to the ASCOM stuff, but that was a mistake. The relays made things go haywire. At this point, the ASCOM settings are tuned, so I am going to stick with them.