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.

Friday, September 19, 2014

The Countdown to Calstar 2014

I plan to make the most of my time at Calstar this year, shooting digital and film.
Evening Twilight is 20:30
Morning Twilight is 05:30


SH2 129 - transits 22:06
Wizard Nebula NGC 7380 - transits 23:41
Continue the work on Sadr region (centered on SAO 49578) - transits at 21:18
SH2 171 - Transits 01:00

Later work might go after the California Nebula or Heart and Soul or Pleiades


Color (E200) at 200mm F5.6 for 1 hour
IC 1396 (transits 22:33)
Summer Triangle including Sadr, Deneb, Veil.  Need at least 3 - 1 hour exposures at F5.6 (transits 21:30)
Heart and Soul with Double Cluster (transits 3:30)
California to M45 Widefield (transits 4:40)

Black and White (Acros) at 300mm F5.6 at 40 minutes to 1 hour
Triple Cave (E nebula or Barnard 142) (Transits 20:35 - too low at 23:00)
Cetus widefield (Center on Zeta Cephus - transits 23:00)
Cygnus widefield (Center on GSC 3155:1976 - transits 21:00)
Perseus widefield (Center on Barnard 5 - transits 4:40 - start no earlier than 2 am)
Taurus widefield (Center on Barnard 213 - transits 5:14 - start no earlier than 2:30 am)

Given the need to center on specific targets, I may re-install the Gemini 1 on the GM8 so that it can be used to slew to a specific region.
If I have any extra time to do a trial run at home before Calstar, it will be to validate the installed work and refocus the ST80 with SSAG.  Once I do this, I may create a series of FITs with the SSAG to act as "bookmarks" for slews.

My plan is to arrive at Calstar 2014 on Tuesday, setup and polar align that first night and get some Acros started.  Wednesday and Thursday night will be all E200.  Friday will have a return to Acros, and Saturday will clean up whatever is left.

Stripping Down the Gear

Reducing the Load on the G11

I've been using a side-by-side imaging setup on the G11 for about a year.  In this time, I've found that while the extra mass helps stabilize the guide movements, the tradeoff with additional weight is a setup hassle.

When I put the water cooling system together, I wanted to put the Orion miniguider to work.  I'd tested it before and once the little telescope is properly focused with a fully calibrated SSAG, it shows a lot of stars, ideal for guiding.  Also, the resolved frame is nearly the same size as the APS-C sensor on the SV4.

Thursday, September 18, 2014

Sadr in Cygnus HaRGB

Taken in the back yard during September while I was testing before Calstar 2014.  Fairly happy with how this photo turned out.

Monday, September 15, 2014

Epoxy to the Rescue

Fixing the DSLR (again)

Smeared Sadr

I had some problems recently while testing in the backyard with the low-temperature hot melt glue inside the Pentax K10D camera.  The old glue decided that the heat of the September sun and the never-ending pictures every night was enough to let go.  Thus, the smearing stars came back.

Saturday, September 13, 2014

Losmandy G11 Gears and Stiction

I've been peeling onions in the backyard these past nights.  Based on some questions from Marek and Carl, they were experiencing strange DEC behavior when guiding near Sadr during August.  I felt that much of the problem was due to tracking through the Zenith where scope balance is most ineffective at keeping DEC meshed.

Since I'd moved onto the problem after handling some of the earlier questions about Gemini systems and getting the camera cooling nailed down, my current target is the same region as the problem area.  I quickly saw similar DEC jumping as bad as what Marek was experiencing.

Friday, September 12, 2014

Upgraded Camera Cooling

Water Cooled DSLR

In the past, I've been cooling the DSLR for astrophotography by using a peltier device with CPU style fan heatsink.  It's been working OK, but I've not been getting the best performance out of the peltier devices because the waste heat simply hasn't been removed fast enough.

I knew that the real performance gain would come from better management of heat.  Also, using a single peltier device does not drop the temperature enough to cool the camera.  Thus, I've been playing with stacked cooling chip.  However, these stacked devices will generate a large amount of waste heat on their own, requiring even more heat management.

I use a water cooling system on my home computer, so I was already familiar with the requirements for fluid flow, pumps, heat sink sizes, tubing, etc.  After doing some more research on the yahoo group for DSLR Modifications, I settled on some hardware.

I started with a collection of parts from FrozenCPU:
Swiftech MC350 pump
120mm radiator and fan and mounting kit
 Swiftech Apogee CPU waterblock
1/2 inch tubing with anti-kink coils

Wednesday, September 10, 2014

Full moon backyard testing

Preparing for Calstar 2014 

I've set up the gear in the backyard to test a few problems.  I set the goal to identify the issue with flexure, to collaborate with Carl and Marek to find and fix the problem experienced with DEC guiding, and to push the camera cooling to the next level.