Wednesday, October 15, 2014

Post-Calstar 2014 Wrapup: Thursday

My Thursday at Calstar was ... a bit challenging.

While it was great to learn to use the bow that Carl brought (no pictures of me doing this as far as I know) and having the clouds meant little heat from the late summer sun, there was not a lot going on.  The day was overcast in the morning and didn't break up until later in the afternoon.

The challenging bit was that I didn't power up the mounts until after dark.  Had I done a bit of testing beforehand, I would have been aware that the Dec motor on the G11 was experiencing an encoder failure.  The symptom was a jerky, incomplete slew that stalled prematurely.  Originally, I thought it might have been due to a tight gear, so I loosened the mesh a bit and that didn't solve things.  I recognized that this was an encoder issue and tried cleaning the optical discs with the puffer bulb and checking clearance.  Nothing worked.  By about 10 pm, I knew that the G11 was dead in the water.  Luckily, the GM8 was plugging away, going through a roll of E200, so there wasn't a total loss of progress.
Prior to failure!

I talked with Rich and Carl about the problem.  I knew that Casey's G11 was a push-to style, so he wouldn't have a spare motor.  Marek's G11 was sitting unused under its tarp.  I was tempted to "borrow" a motor.  We joked about how his gear could be stripped like a car at a chop shop, leaving it up on cinderblocks.  The only thing left would be some cut-rate parts, hanging forlornly at the end of a frayed cable.

It was getting late and the night was pressing on.  I finally made the decision to field strip the GM8, back convert it to the push-to motors, and cannibalize the spare Gemini motors and gear boxes for the G11.  In the dark, I spread out a sheet to catch small parts, and tore apart the mounts.  Surprisingly, the whole job only needed about 90 minutes to complete.  Everything was back to running a little before 1 am.

There seems to be a link between the failed gearboxes and the encoders going bad.  I think there's something about how the old gearboxes split open that allow the motor shaft to move and possibly collide with the encoders.  With all the cannibalism of stealing parts back and forth between mounts, the G11 currently has 2 good boxes and 2 good motors.  I dropped the slew rate on the G11 down to 500 as well, reducing the overall speed at the benefit of a lower noise and possibly a better chance to avoid stalls or gearbox breakage.

I did miss the luxury of using TheSky to point the GM8 to the part of the sky where I wanted the film shot to be.  I found that if I was patient, I could use the red dot finder well enough.

The rest of Thursday night into the wee hours of Friday morning was pretty much uneventful.  The camp got very quiet after 3 am.  At 5 am, the morning twilight was starting and thus I wrapped up the efforts.

Tuesday, October 14, 2014

Post-Calstar 2014 Wrapup: Tuesday and Wednesday

I attended Calstar 2014 from Tuesday to Sunday.

Packing for these trips is becoming more of an exercise.  I only use the Prius to travel and so everything has to fit into the car.  There are a lot of small hiding places all over the passenger compartment.  I try to use every bit of space that I can.  For example, I put 1 gallon water jugs under the front seats.  I can easily fit 5 gallons of water in this space.  All the tarps and sheets for the tent go into the foot space in the back seat and the tent fits across the gap.

In the future, I'd like to get a roof-top pod for the Prius to hold the tent and clothes, allowing better management of things inside the car.  As it is, there is no room for a passenger or their supplies.

I arrived just after Rich Crall and then Carl Larson showed up a few minutes later.  Tuesday was spent setting up, polar aligning, and chatting in the quiet evening.  The skies were the clearest on that night compared to the rest of the weekend.  Super dark, very clear and steady.  I worked on some Acros and a couple of digital targets until 5 am.  The Prius purred every 30 minutes or so, depending on how cold the temperature dropped.

Wednesday morning Carl needed to change a battery on his AstroWagon.  This required dropping the battery box and removing most of the wiring.  The weather was nice, no wind, just enough sun to warm things up so that it wasn't chilly.

Acorns were dropping like bombs -- and they hurt when they hit!  The deer were emboldened because of the acorns and we gathered and tossed the extras to the animals when they got close.

Later in the day, people started to filter into the site.  Marek showed up early to set up his tent and unload the scope.  He wasn't able to return until Friday.  Setting up the gear early saved him a lot of time.  Phil Manela and Peter McKone also arrived on Wednesday.  Dan Wright showed up late that evening with the UHaul van.

Wednesday night was a bit of a bust.  It was super clear earlier, but clouded up shortly after 1 am.  Dan showed up a little after midnight and was able to see a few stars before they went away.  Without the stars, there was little reason to stay awake and I got some extra sleep.

Monday, September 22, 2014

Calstar 2014: Forecast Looking Good

From WeatherUnderground.

Looking pretty good for the goal of taking pictures through the night.  There's a little bit of weather that may come to northern California on Thursday.  It shouldn't effect the night sky.

I'm as ready as I can be.  I was able to test the Gemini 1 system on the GM8.

It's pretty finicky, or, it was.  I've replaced the clutch pads which fixed a lot of the problem of jamming DEC and RA.  The old pads must have been thin enough to lock up the ring gear or shift it too far, causing binding with the worm gear.  I replaced the motor reducing gearbox on the DEC axis.  This seemed to eliminate the whole problem with that axis completely.   The old gearbox was bad, broken either by high torque or by collision.

There are still nagging problems that will either be a non-issue or will make me replace the motors in the field and go back to a push-to configuration.   Also, two motors are bad.  One has a bad encoder and is non-usable.  The other is very weak and pulls a lot of current when in use.  It probably has a short in some coils.  It is too weak to use in RA and is only serviceable in DEC at very low slew speeds.  I've set it to 400 - which is half what the default is for the GM8.  I disassembled the motors to see if I could take the guts from one and put it on the encoder for another.  Unfortunately, I am unable to perform this task.  Once I'm back, I'll have to scrape together the cash to buy two more motors and swap from the G11 to the GM8.  Losmandy is only selling the high torque motors, so I'll put the new ones on the G11 and use the old ones on the GM8.  I'll probably leave the slew speed at 400 to keep things putting along.

I packed the car today excepting the last few clothes, the computers and books, some lenses, and one last Pentax 67 body.  If I keep loading this car so heavy, I'll really need to invest in a rooftop pod.  There's no room for a passenger at the moment.

I've managed to pack 5 gallons of fresh water with two gallons in the freezer to keep food.