Meddling little beasts...
Wednesday night with testing, the raccoons finally got a little too curious. They managed to pull out a USB extension cable and disconnected the on-telescope hub, bringing down the cameras and focuser. I wasn't sure what went wrong when the software started complaining - I was using the VNC connection when the connection went bad. After restarting software, then restarting the machine, I went outside to diagnose the hardware issues, heard the scramble of raccoons quickly running away, found the cable break, and put some gaffer tape on the connection. Now it will not fail. Goodness! What hilarity. Glad that it happened now vs on another time when I couldn't catch them in the act.
Tuesday's thought experiments suggested that the Lodestar was set to an incorrect focus distance.
In looking at some articles on Cloudy Nights about star shapes and flatteners I found that the description of star shapes that show arcs vs points was very specific to my situation. I knew that when the main sensor on the QSI is focused, the stars appearing in the field of the Off Axis Guider were streaks. Originally, I considered that these were because of size of the corrected image image circle. After thinking a bit, I figured that a test of how the star images look at different focus position would be a good test if there could be flatness at such a great distance from the image sensor.
I tested this theory by first focusing the main camera on the LP filter. This showed that the focus adjustment for the guider was about 120 ticks off perfect. I tightened the WGS Focus Ring assembly by turning it clockwise 1/4 of a turn. The star image when using the guider no longer has the long, arc-like shape. Instead, it has a much smaller football shape. When readjusting focus for the different filters, the star image shape seems smaller, tighter, and easier to auto-select. The total range of filter offsets from Ha to Blue is about 100 steps, so I may yet have to tweak to find the best compromise across the range.
As a benefit of a smaller star shape, data assessment is showing less star elongation on the 1200 second subs. Also, I saw that the guiding graph showed less slewing in the axis of the elongated guide image. I think this is something important to note.
I found another annoyance: the exposure for autofocus wasn't long enough for SII. I will have to go into the settings in CCDAP to increase this filter's default values.
I've started working on the Owl Nebula (M97) in narrowband. That will be a fine project to last until next month, as I continue testing the proper focus distance for the guide camera for optimal shape. Haven't looked at the subs yet, it's possible that OIII at 1200 seconds might be too long for this bright object.
At this time, the weather is going to be cloudy until next week -- which I'm pleased about so that I can finally get some needed sleep.
Wednesday night with testing, the raccoons finally got a little too curious. They managed to pull out a USB extension cable and disconnected the on-telescope hub, bringing down the cameras and focuser. I wasn't sure what went wrong when the software started complaining - I was using the VNC connection when the connection went bad. After restarting software, then restarting the machine, I went outside to diagnose the hardware issues, heard the scramble of raccoons quickly running away, found the cable break, and put some gaffer tape on the connection. Now it will not fail. Goodness! What hilarity. Glad that it happened now vs on another time when I couldn't catch them in the act.
Tuesday's thought experiments suggested that the Lodestar was set to an incorrect focus distance.
In looking at some articles on Cloudy Nights about star shapes and flatteners I found that the description of star shapes that show arcs vs points was very specific to my situation. I knew that when the main sensor on the QSI is focused, the stars appearing in the field of the Off Axis Guider were streaks. Originally, I considered that these were because of size of the corrected image image circle. After thinking a bit, I figured that a test of how the star images look at different focus position would be a good test if there could be flatness at such a great distance from the image sensor.
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| Using the QSI Focus Ring |
As a benefit of a smaller star shape, data assessment is showing less star elongation on the 1200 second subs. Also, I saw that the guiding graph showed less slewing in the axis of the elongated guide image. I think this is something important to note.
I found another annoyance: the exposure for autofocus wasn't long enough for SII. I will have to go into the settings in CCDAP to increase this filter's default values.
I've started working on the Owl Nebula (M97) in narrowband. That will be a fine project to last until next month, as I continue testing the proper focus distance for the guide camera for optimal shape. Haven't looked at the subs yet, it's possible that OIII at 1200 seconds might be too long for this bright object.
At this time, the weather is going to be cloudy until next week -- which I'm pleased about so that I can finally get some needed sleep.
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