Monday, March 24, 2014

Backyard Learning

Over the weekend, I set up the equipment in the backyard and did some testing of the camera, power, and Gemini.  Here's what I've learned.

  • Power: I made the effort to mimic the power setup that I'd use in the field.  13 V supplied at the car with the telescope and other equipment some distance away.  In the new setup, I put a powerpole splitter near the supply source and ran two extension cords to the scope site.  Both cords were not fully extended.  The heavier cord was used to drive the mount, camera, computer, and dew heaters.  The lightweight cord was was used to drive the peltier cooler and USB power source.  Over the course of several nights I did not have any issues with running the system.  The mount never saw a power drop below 12V based on the LED on the Kendrick distribution box.  Only once was there an issue and that was when I plugged in the Peltier device when the mount was on.  At that time, there was enough of a drop to cause a loss of power.  I think that a capacitor would have solved that issue.

    Power readout at the supply was usually over 13V and a max draw of 8 Amps.

    Will use this setup in the field for now on.  Hopefully the Prius won't run too often with this higher drain.

  • Camera: Continued to wrap the body of the camera in the sock. The camera EXIF temps are stable.  They get to a point and then don't change over the course of the night.  I will install the sensor when they arrive and put the PWM controller on the system.  In the meantime, the camera is cold and the system does work without overheating.  Haven't stacked the images yet to see how much latent noise is still in the system.

  • Gemini: The whole system still has the slow RA issue.  On the last night, I swapped out the G2 for the G1 setup.  Running the G1 on 17V gave much better response to commands than I'd experienced at Calstar.  I understand more about how it works.  Was able to get TheSkyX and PHD to work.  Was not able to get Maxim to work.  Did have some issues with gotos, but that might have been due to bad models.

    I did some PEC training with the G2 with the new firmware.  Here's what that graph looks like:

Look at how the slope of the curve goes downward.  Not good.  There's something amiss.

Happened across a comment online in an old archive that the Ovision worm uses a period of 240 vs the Losmandy standard 239.  This one difference may have been enough to cause the issue of running slow.

Here's what PHD2 looks like when guiding using the mount using the G1:


Note how the scatterplot is skewed to the left.  This is after I've replaced the counterweight from an 11 to a 7 pound version.  There was not much east bias on the mount.  The graph prior to the replacement was the same.  In this case, the RA aggressiveness was set to 75%.

I checked the Ovision spreadsheet that was provided and there's something interesting here:


Looks like there is a 240 second period?  Of course, this could just be rounding.  

Based on the math in the Gemini guides, I should be using a custom Divisor of:
For G1, the RA divisor should be: 56250
For G2, the RA divisor should be: 450000

I don't have the chance to test it tonight as there will be rain coming.  When I can get the gear setup again I'll try the G2 again as the new firmware allows custom divisors to be used.  It also has the ability to train custom rates.  I'll also want to do PemPro with the updated worm period.