I want to describe a problem I had with the mount and computer setup and a problematic "buzzing" sound. I wanted to post this to remind myself of my trouble-shooting and to give folks a sense of the
technical problems that seem to regularly plague astro-photographers.
About a week ago, I connected the "big" AP mount to a 13.8 volt power supply, then connected the computer and dew heater to a 12 volt AGM battery via the 600 watt PowerBright inverter. I instantly heard a buzzing sound from the hand controller. It's not a sound I had ever heard before.
It wasn't especially loud, but it was loud enough to hear from about 2 feet away.
I re-seated the connection to the power supply a few times with no change. I slewed the
the mount around and everything seemed fine. So, I proceeded to set up for a night of
imaging.
One thing I noticed immediately was that the trackpad on the laptop was working erratically.
I couldn't move the mouse cursor anywhere but up and down. This is a problem I had
on the second night of our recent Van Vleck trip. My solution was to simply plug in a mouse.
(Need to order a rugged mouse.)
On this particular night, temps were in the mid-20's F. And I had to battle a 5-30 mph wind
so it felt much colder. I wondered if temps were affecting electronics -- though at Van Vleck,
the temps rarely were generally higher in the mid-30's and there was little wind. Why would
I see this problem at both VV and home under different conditions?
I finally had polar alignment and started to do a test track using the Tak102 and the Orion 50mm guider. The first test guiding session with PHD2 was perfect. I guess since I was having so
many little issues I wanted to make sure things were fine. Feeling confident, I centered the target
in Focus/Framing mode in Backyard EOS and started to re-calibrate the guide.
Normally, PHD2 goes through this routine where it does a bunch of North and South "steps"
to calibrate itself in one axis, then moves to the East-West "steps" to calibrate the other axis.
A good calibration generally takes about 15-20 steps in one direction before returning by going back the way it came. There can be problems when the calibration takes 40+ steps or too few steps.
PHD2 guided the mount 2 steps North, then returned. Then it guided 2-3 steps West before it finished calibration. The whole process normally take 2-5 minutes. It finished in 5-10 seconds.
Uh... What? In addition, I kept hearing "clicking sounds" from the mount. Not good.
So, my first course of action was to stop or "quit" PHD2 on the computer. Waiting, waiting,
waiting... I ctrl-alt-del'ed... Waiting. I finally "Task End"ed twice before it shut down.
I've had random weird stuff happen via PHD2 before and usually quitting and starting back
up has fixed the issue. But this time, PHD2 wouldn't even connect to the camera -- PHD2 was
stuck. So, I ctrl-alt-del'ed. Closed all programs ....waiting....Backyard EOS is not closing either.
I decided to power down the camera, unplug the usb cables, then shut everything down, then
turned off the computer. Is this a problem with temps?
For good measure, I unplugged/reseated the power. And I tried a different socket on the 600 watt inverter. Just to be sure, I disconnected any connection between the mount and the computer. The buzzing sound continued to present itself without any connection to the computer.
Reconnected. Fired everthing back up. Same behavior. During calibration, I watched the calibration (N-S, etc), and I noticed that the calibration steps were quite excessive -- so excessive at times that PHD2 would lose the guide star. I also noticed that I would occasionally lose
the camera -- it would disconnect whenever the slightest touch was applied to the cables. What
the heck!!!
After reconnecting all the cables, closing and restarting again. I fired up PHD2, completely reset the configuration, then tried a different calibration step, then tried to calibrate. I could hear the clicking
as I had heard at each previous attempt at calibration. It only took 2-3 steps and started tracking. When the mount tracks, it shows some data every time it makes an adjustment to the mount.
Normally with my setup, you see something like ".2 pixel, N 90 ms" or ".3 pixels, E 60 ms".
Now, it was showing bizarre numbers like "2 pixels, N .33 ms". ??? But it seemed like it was guiding. Though I could see the guide star move more noticeably. It seemed like this was just a bizarre settings issue.
Though I had setup around 8:30, I wasn't able to start an imaging run until 12:30 -- which meant I had easily wasted 2 hours of imaging time! I let the setup run until around 2:00, then
checked my results in BackyardEOS. It wasn't perfect, the first 15 min subexposure had trailing
stars, and another had elongated stars, but a few of them looked "acceptable" so I let it run
until 4 AM. The winds had died down to maybe 4-5 mph coming from the N to NE. And
every so often, a 15-20 mph gust would whip up so I assumed between the suspicious guiding and the random gust, I was losing good data. Out of the 13 subs, it looked like I only had maybe 6-7 good ones.
What are the possible causes for the problems?
Cold temps?
(causing the AP control box to have problems?)
(causing the computer to malfunction?)
Ground loop problem (buzzing is a symptom)?
Bad connections?
Bad power supply?
Snagged USB cable(s)?
This configuration (power supply to the mount) was new to me. I normally attach the mount to an Optima 12 volt battery. Then I either plug in the computer/camera AC adapter to an extension cord that runs to the shop OR I plug everything to a 12 v battery and 600 watt inverter. The reason for the change was that I thought the power supply might be a better source of higher voltage in colder temps. I never bothered to test either the power supply or the voltage from the inverter. It's quite possible that the cold temps (low 20's) were affecting the inverter or the power supply to the mount.
The following night I completely reverted back to connecting the mount to the 12 volt Optima battery and the computer/camera battery to the outlet. Temps were 10-12 deg warmer. Everything acted and worked normally. I even added a USB hub to prevent USB cables from having to run at 90 degrees out of the computer.
