List, Adam and I have been going around on a couple of problems I have with the STF-8300 & Lodestar auto guider camera. He suggested I post here as he's going to be out of the office for awhile. I have two possibly related problems which I will describe. I'm running MaxIm 5.23. Problem 1 The STF-8300 shutter doesn’t always end up in the fully closed position after an exposure. This sometimes causes the shutter to partially block the sensor in the next exposure. If you’re unfamiliar with how the shutter operates in the STF-8300, here’s an explanation. The shutter rests in the closed position. At the start of an exposure it rotates 180 degrees (also closed) and then back 90 degrees to stop in the open position. At the end of an exposure it rotates back the remaining 90 degrees to the closed position. There is a stop both at 0 degrees and 180 degrees to prevent it from moving farther. The “clanking” sound at STF-8300 power up is the shutter hitting the 0 degree stop. I assume this is done to establish a reference position. The shutter should never hit the 180 degree stop. Normal shutter operation is silent. There is no problem with the shutter opening. The problem is that it sometimes stops before it rotates back to 0 degrees from the 90 degree open position. When the next exposure is started, the shutter tries to rotate 180 degrees but hits the 180 degree stop and a “clank” is heard. This sometimes causes the shutter to partially block the sensor. (Actually it’s even more complicated than this but would require pictures to fully explain it.) I’ve run a lot of tests with the camera open and the FW5 filter wheel and Lodestar still connected to observe exactly what is happening. If the Lodestar is connected but is idle, like when taking dark frames, the STF-8300 shutter operates correctly 100% of the time. If the Lodestar is taking guiding exposures, the shutter problem occurs intermittently. I’ve tried a number of different configurations. My normal configuration in the observatory is an old PC running Windows XP. The Lodestar and the STF-8300 are connected via a single USB port and a USB hub. I can run this setup using an iMac and Windows 7 under Parallels. The results are exactly the same. I tried running the Lodestar and the STF-8300 through separate USB ports eliminating the hub. The problem occurs more often. I see no issue with the operation of the Lodestar in any configuration. I looked at the SBIG Universal Driver command list to see how the shutter opens and closes. It’s pretty straightforward. There is one command to open the shutter, set the exposure time and then close the shutter when the time expires. This is handled inside the camera. There is no separate “Close Shutter” command. It seems as though the shutter movement is being stopped somehow even though there is no command to that. I just updated the STF-8300 firmware. There was no change in the problem. Problem 2 When the Lodestar is autoguiding and the STF-8300 is imaging the STF-8300 exposure time is longer than what is programmed. For example, when 600 secs is set as the exposure time in MaxIm, the STF-8300 exposure is actually 614 secs. I see the timer count down in the Exposure tab to 0 and the "Reading" is displayed for 14 seconds and then "Downloading" for 2 seconds. I've been told by Cyanogen that "Reading" means the camera status is "Busy" and not ready to download. If the auto guider is inactive, like when taking dark frames, the STF-8300 exposure time is correct with no additional time added. It turns out that the extra time scales with the length of the exposure. It's about 1.4 seconds per minute of exposure time. A minute exposure adds about 1 sec, 3 minutes adds 4 secs, 5 minutes added 7 seconds and so on. In order to get 600 sec light frames, I have to program the exposure time to 586 seconds, otherwise my dark and light frames don't match. Again, two completely different computers with different OS's have exactly the same problem. Is it possible my camera has some weird hardware problem? I'd like to hear any ideas even though I don't think anyone will have the answer. Chuck
My old Windows XP machine died (not the disk drive) and I replaced it with a new Windows 10 machine. I used it for the fist time last night to run the STF-8300 and Lodestar guider. The extra time added to the exposure has been reduced to 4 seconds. I had to modify my exposure settings to 596 seconds to get 600 second exposures. I did not experience the the shutter problem. I took 30 light frames and none were lost. I did not hear any shutter banging. One night is a bit soon to be sure that the problem is gone but I'm hopeful. I don't understand why these issues exist running MaxIm under any OS. Chuck
