Thursday, August 1, 2013

G11 Gemini Maintenance

With the weather finally getting nice again, I went back to trying some testing in the backyard to see what I could get out of the system.

Recent successes:
  1. Replaced CR 2354 battery.  Found them at Halted for $1.95 each.  They were loose in a box, so there was no age available.  Tested at above 3 V at the store.  In the G2, the web page shows 3.03 V.  Much better than the previous battery that was dropping fast.  Last night it was showing 2.3V
  2. Replaced and kept the RA and DEC cables loose from each other.  This seems to have helped with guiding.  Since the guiding is much better, I figured that PEC would also benefit.  It did!

    Major lessons on PEMPro that I learned:
    1. Ensure mount is set up correctly, specifically Modulo value was set to 10ms.  This was a low enough number and when I looked at the manual program for the curve, I could see that the modulo limited a fair amount of corrections.  I also made sure that only the 4 major index for the worm period was defined.
    2. Current method was to run the mount at .5 guide rate, capturing at .5 second duration for at least 4 passes of the worm.  Then I made a curve and did linear fitting, enabling only the first 4 indexes.  This gave a smooth curve.  Programed the mount, then did another 4 passes with PEC turned on.  This gave a new data set and I used this value to add to the previous curve.  This second curve just showed a fine, wavy line less than 1 arc second.  The summed curve was then sent to the mount and I did a drift compensation routine.  I believe that the critical bit here was the new cable as well as setting an overlap amount of 50%.  I think that I may rerun someday with an overlap that is higher.  
  3. When I tried to save the PEC data from the previous runs, I ran into some issues.  The Gemini control panel didn't see the older files so I was not able to load values and rename them.  This was really getting annoying as I didn't want to lose the good drifted curves.  So I removed the plate off the G2 computer and pulled the SD card.  Bringing it onto my computer, I could see the files 20130731_07:30:24.pec and others.  The filenames made it impossible to rename or modify because of the colon character.  I loaded up the computer with linux and found that the SD card didn't mount because it was unallocated space!  This very odd, because windows 7 saw the files just fine afterwards.  I may need to reformat the card someday.
  4. When I changed the battery, I noticed that many functions on the G2 were snappy and more consistent.  We'll see if it remembers PEC data and other settings.
 I tried to do the backlash exerciser, but it did not want to stop tracking while slewing in DEC.  I may try pulling the RA cable and try it again.

I also want to try getting good focus with the Celestron guider.  That's something I can do on a photo tripod.

I also want to try using a UV filter on the dslr to see if it reduces the tiny cyan halo on certain stars.

Lastly, I should create a reliable, consistent flat method.  I played with longer duration flats and didn't see any value.  Instead, I saw a color shift towards the brown/reddish color because of the paper used to shift the light.