Wednesday, June 25, 2014

GSSP 2014 Weather Forecast

Looking pretty soggy for the next 24 hours. I expect to run through some rain on the way up.  At least the car will be clean before I hit the muddy field.  Will be interesting to try to set up the tent for rain.  Still, the chance of rain is fairly low - it peaks at about 33%.


From Weather Underground.

M13 from the Backyard

M13 June 2014

This image was taken under a deadline to get ready for GSSP 2014.

Monday, June 23, 2014

Camera Repair

Problems never cease! 

In working to solve the issue with the trailing as noted on an earlier post, I set up the gear in the back yard and waited for some dark, clear skies.  In waiting, I set up the camera to record darks.

Unfortunately, during these 2 nights of waiting, a piece of the flocking material dislodged and wedged against the shutter, preventing it from opening.  Not an issue for darks, but it meant that the electronics to open the shutter are dead.

The mirror flaps up and down, but the shutter remains closed, no matter the setting. 

There's not enough time to get the camera repaired before GSSP.  Thus, I've done the drastic step of putting a dab of hot glue on the retracted shutter to fix it into the open position.

It works now.  Since the timing of the exposure is now set by the mirror position, short exposures are extremely limited in their ability to properly expose.  Taking flats requires reducing the light level vs changing the shutter speed.

First tests seem to work OK.  The dragging issue is not seen, so it appears that the problem was due to snagged cables.

Thursday, June 19, 2014

JIT Problems

Just in Time for GSSP, I'm beset with problems for fixing!

Last night at MBOSP, I set up the G11 and tried for a basic target M13.  Something was amiss.


It appears that maybe cables snagged?  Maybe something was unplugged, not sure at this point.  The Maxim logs show that guiding stopped after just 15 minutes.  No errors regarding star faded, it's almost as if Gemini stopped running.

The only other clue that I saw was that when I went to shut down Maxim at the end of the evening, Maxim showed that the mount was already disconnected.  However, I was able to issue commands to park via the PC-based control panel.

Will be testing tonight to see if I can replicate the error.  If the problem doesn't show again, I'll assume that it was a dragging cable.

Monday, June 9, 2014

Orion ST80 Collimation

I've been following some tips online regarding tuning up the Orion ST80 budget telescope.
Here are the links I've been following:

Major steps taken:
  • Blackened the edges of the lenses.  Pretty easy, just remove the retaining ring and drop out the lenses.  Darken the edges with a Sharpie.  
  • Cleaned the lenses with microfiber rag with Methanol.  This is my preferred method for lens cleaning.  Does a nice job of removing fingerprints and pollen.
  • When inserting the lenses, I made sure that they were seated squarely by rapping the scope body while holding it upright.  Gravity ensured that the lenses rested solidly against the cell.
  • Collimated using airy ring test with my 7mm Nagler.  Even with two extension tubes, it didn't have enough travel to bring it to focus, so I had to let the extensions out a bit more.  I found that the optics were pinched even though I had them loose earlier in the day.  Temperature is a big factor!


Next major step will be to remove/cut/grind off the screws that protrude into the light path.  When looking at the bahtinov mask image, I can see lots of diffraction "curls" appearing.  I don't have a method to grind the screws, I may try fitting a different screw/bolt or press a dremel into service.

Future work may be to get a GSO focuser to replace the stock unit.  This would allow using a reducer/flattener on the scope, further tightening star images.

Already seeing improvement in star images.

Note how close the FWHM value is to "perfect" for this scope as referenced at http://www.calctool.org/CALC/phys/optics/spot_size

Friday, June 6, 2014

Killing time with the ST80, 85mm lenses, and GM8

Doing some practice work in the back yard as I prepare for GSSP, I've been fiddling with trying to get the most from what will be the film setup.

So far:

  • Tested polar alignment within PHD2 (2.2.2a) that it works well without an ASCOM mount.  Just point it at the proper parts of the sky, set the approximate values in the Drift Align tool within PHD2 and go.  The rest of the method seems to work.  What's nice is that the way PHD2 now has equipment settings that are savable and selectable, notes from the respective Drift Tool are persistent.
  • I have seen the return of a slow, consistent RA drift.  Considering that I've removed the three-point rings on the ST80 in favor of the clamping rings, I'm thinking that what's happening now is a refraction-based compression and expansion of the scene as the scope points higher into the sky.  Will need to run some math and see what the expected distortion should be and if it checks out.  Also, it would be worthwhile to check in other parts of the sky to see if the apparent movement tracks via RA or via refraction.  Testing near the pole, but low in altitude would be worthwhile.
  • Tightened up the DEC backlash that was causing issues with calibration.  Checked to ensure that the grub screws attaching the motor and worm gear were tight, then watched the spinning gear vs movement in the eyepiece.  Turned out that the backlash problem was irrespective of TVC or motor connection play.  What was the real problem was gear lash between the worm and the ring.  Tightened up this play via repositioning the worm blocks and offsetting the DEC balance.  Now the mount will move in DEC within 5 seconds of a change in direction.
  • Tested the performance of a couple of lenses.  Last year I picked up the smc PENTAX-A* 1:1.4 85mm lens for K mount.  I also had the S-M-C Takumar 6X7 LS 90mm f/2.8 lens.  The K mount lens performs well at F4 - sharp to the corners and minimal fringing once it's in focus.  I tried putting the B+W 486 filter on it to control the fringe, however this introduced star flare.  In reaction, I tried the medium format lens with an IDAS LPS P2 filter inside the adapter.  After a long time attempting to focus the 67 lens using the bahtinov mask, I was disappointed to see that the field flatness of the lens left a lot to be desired!  Also note the red doughnuts visible in the 67 lens image.  This was shot on a non-converted camera, so it seems the unfocused starlight is a problem even before the NIR range.
Upper left corner at 100%

Vega region, near center of FOV
Final testing to complete on the ST80:
  • Continue adjusting lens cell of the ST80 to improve star images for the SSAG.  I will loosen the holding screws on the lens cell and try tilting it to improve the out-of-round patterns of the stars.
  • Test different filters on the SSAG.  I have just a few available in the 1.25'' size.  Baader Moon and Skyglow, UHC, Baader Contrast Booster, Yellow, and Red 25.  The yellow showed some promise, but not as good as I'd like.  I think it was passing too much NIR.  The Moon and Skyglow filter has a built in IR block, so it should work well.

Wednesday, June 4, 2014

GM8 No Longer Goto

I removed the Gemini 1 electronics from the GM8 mount and now it's a simple push-to GEM.

I had to adjust the RA gear mesh and tighten the motor to worm attachment.  Everything is working smoothly now.  I've also removed the 3-point rings on the Orion ST80 in favor of solid rings.  They grip nicely and there's no slop.

There's a new SSAG in the mix (old style).  I did the same maintenance that I'd done to my earlier SSAG; removed the t-thread plate and hot glue the edge of the circuit board to the frame.  This removes any possible flex within the camera.

I'd done some work on the ST80 as well.  I removed the lens cell and blackened the edges of the lens with a sharpie.  I'd also over-tightened the lens cell and there seemed to be some pinched optics.  Also, instead of using a UV-IR filter, I'd opted for a yellow filter!  I've been very pleased with the star images and how well the focus can be made.

With all the work, I set up the mount to track Vega/Lyra.  Note the scatterplot.  The horizontal band is RA and shows the range of the periodic error.  I did turn on PEC training.  


Monday, June 2, 2014

Prep work for GSSP

GSSP is coming in just a few short weeks. 

I've been recently fixing up the gear to try to do a two-mount setup, learning from Calstar where the GM8 with Gemini 1 didn't work well at all.

Went to MBOSP last week and tried out the GM8 with Gemini 1.  It exhibited signs of a fatal error in the encoder chip on the main board.  When the mount powered up, it would slew uncontrollably.  Swapped the cables and motors with spares and replaced the CMOS battery twice.  No signs of improvement.  I've sent a message off to Losmandy about what repairs can be done to this old device.

I converted it back to the digital drive system - the non-goto setup that it had from the factory.  The DDS does not use ASCOM and it has no understanding of where it is in the sky.  Nicely, I've been able to keep using the PHD2 drift align tool so long as it is forced to calibrate each time.

I did see that the conversion didn't go as smoothly as it should - the RA worm slipped and needed to be tightened.

Last night, I went up to MBOSP again and was able to figure out a pretty good power system.  However, I managed to break the Gemini 2 Hand Controller.  One of the tactile buttons stopped working, so I followed the procedure to open up the device.  The LCD shattered in the process.  I've ordered a replacement controller and am asking Losmandy about repairs.

In the meantime, I can still use the G2 without the HC.  It will require a lot of running back and forth to click on buttons on the laptop.  Still, if I'm not able to get a replacement prior to GSSP, I can still use the system.

I'll be practicing again with the old GM8 DDS in the backyard a few days to see if the tracking is good.