Meade LX200GPS Alt/Az vs Losmandy G-11

[John Carter]

I have two telescopes. One is a 12" Meade LX200 OTA mounted on a Losmandy G-11 with a Shoestring GPUSB interface to the ST-4 port. The other is a stock 8" Meade LX200GPS Alt/Az on a tripod with an Orion Starshoot Autoguider with the on-camera interface to the autoguider port.

When I looked at the PHD2 chart for guiding on the 8", it was well within +/- 1 arc-sec and steady.

When I looked at the PHD2 chart for guiding on the Losmandy mount, it was well over +/- 4 arc-sec and bouncing all over the place.

I then checked the drift align on the Losmandy (for the first time - ever), and saw that the DEC was steadily rising while the RA was jumping around. Wow! And I thought I had done a good job of Polar Alignment with the Polar Scope.

I did a drift align (DEC align only, just to see if anything changes) with the Drift Alignment tool and checked the calibrated guiding again. This time the DEC graph started out all over the place, but settled in to within +/- 2 arc-sec.

So now my job is to get the ASCOM interface going on the Losmandy mount and do the drift align and guiding all over again. The Losmandy is connected to the computer via ethernet, so it should be doable.

The downside of guiding with the Alt/Az is that it is only suitable for visual observing to keep the object centered. Attempting long exposure astrophotography on an Alt/Az mount is an exercise in futility due to field rotation. But it can be done with a field rotator accessory, like the Orion SteadyStar Adaptive Optics Guider with Rotator.

John C

Prescott Valley, AZ

[John Carter]

I managed to get the computer connected to the Losmandy G-11 mount via ASCOM and ethernet.

I took another look at the guiding and it was nearly perfect.

I made one last adjustment to the DEC drift and after a couple of minutes it was dead on.

I checked the RA drift and it was also dead on.

Then I looked at the Guiding Assistant and took the recommended adjustments.

A final look at guiding and it is stable within +/- 1 arcsec.

I'm happy.

What I learned is a lot, but mostly to follow instructions, be patient, and do what's recommended.

[bw_msgboard]

Good to hear!  Thanks for reporting back – hope your imaging goes well.

 

Bruce

 

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[Masa Nagaya]

Hi John,

Could you tell me if your PEC is ON for 8" Meade.

I have 10" but was told that Meade PEC won't work with AZ/Alt.

Wondering if 8" is different.

Regards,

Masa

[John Carter]

I've never done PEC on the 8" Meade - Both RA and DEC PEC are off, always have been. 

A few nights ago was the first time I managed to drift alignment on my 12" Meade.

The guiding graph for the 8" Meade without having to do anything is within +/- 1 arcsec - twice as good as the guiding graph for the 12" after doing the drift alignment, and it barely within +/- 1.5 arcsec. The 8" is Alt/Az and the 12" is EQ.

John