New telescope decision

it is an AC synchronous motor operating at 220V. I had tried Meade (no joy) and one or two specialist shops who recommended a new mount for the OTA.
John

I'm surprised that the actual motor runs on 220 AC and isnt stepped down to some dc voltage in the base of the scope, if it were, it would be very simple to get it working for the northern hemisphere.
I've had a look on the web and see that the LX5 2080 has a north/south switch on the base control panel, does your scope not have this ???
www.grampianstars.com.au/telescope.htm
or is your scope pre 1987 ??

Anway, I'm still trying to figure out exactly what I'm looking at but the PE graph seems to indicate a periodic curve of 7" peak to peak (Which would be amazing if true). However the curve drifts east in a linear fashion by about 8" per revolution of the worm. It may be partly due to differential refraction, I'm not sure yet.

Dave - I get precisely the same behaviour with the AP1200 - except its not the AP1200... The issue is that the optical axis is not staying in line with the mechanical axis - the primary mirror on SCT's move (unless you have a solid mirror lock) as the mount moves. Hence the drift.

Roll on a 20" RC....

The AP software (a special version of PEMPro) actually allows for this drift when programming PE back into the mount - does Guidemaster allow this? If not, be careful when programming the curve back into the mount. Or just leave it 7 arcsecs peak-to-peak - that's great performance.

John (and others) if your heart is set on serious astrophotography, spend the time on the research and think carefully about a 'package' deal. In my opinion there really isn't a sole manufacturer out there producing a 'package' that is good enough out of the box. Most good astrophotography setups consist of a good mount and a good scope - usually from different manufacturers.

That said, you can get a package deal and tweak the mount but you're going to have to invest a fair bit of time tweaking. Of course, if you are going to take the odd photo and do visual observing, I think you'll be very happy with most high-end off-the-shelf solutions.

Unfortunately, AstroPhysics don't sell packages (OTA and Mount) otherwise they would be the best out of the box solution.

Dave

If you mean that the curve drifts 8" over the worm period and then resets, then that's the worm component of the PE (as opposed to the worm-gear component).

If you mean that the curve has drifted 16" after two periods, then that sounds like your polar alignment is off slightly. You didn't say how long your drift alignment went with no movement. Was it at least as long as your worm cycle?

Atmospheric refraction doesn't seem right unless your target was under 20° or so.

Hi Jeff,

Here's the graph;



The period of the worm is 438 seconds so this encompasses two full worm revolutions.

As for the drift alignment, I aligned accurately enough that I could not see any visible declination drift after 20minutes. The software reported a declination error of .8" after that time.

The AP software (a special version of PEMPro) actually allows for this drift when programming PE back into the mount - does Guidemaster allow this? If not, be careful when programming the curve back into the mount. Or just leave it 7 arcsecs peak-to-peak - that's great performance.

Guidemaster doesn't do PEC programming, its just an autoguiding tool. It can measure and log errors to sub-pixel accuracy so I just used it to measure the PEC (with guiding turned off). I downloaded the trial version of PEM-PRO, however there is an issue between it and the CGE mount which I'm trying to work out.

It would strike me that a perfectly good explaination for this 'drift' would be if the sidereal rate is not perfectly precise? The CGE does allow custom rates, maybe I should look into that.

Welcome to the boards Jonn!

I'm sorry i don't have anything to offer to the thread except that!
(I only bought a wee scope this summer)
If you don't mind me asking,
how much are AI charging for that scope & mount?
(not that I'll be buying one amytime soon, but we can all live in hope!)

Dave - the raw data shows some fairly hefty spikes of as much as 4 arcseconds or so. But the averaged curve looks good - 6 to 7 arcsec peak to peak.

Did you have to tell the software your resolution, pixel size etc? And is the chart dervived from you main OTA or guidescope?

As far as sidereal rate goes, I suppose if it was inaccurate that could cause 'drift'. But in the case of the graph below, I'd suspect other issues first - polar alignemnt, mirror flop etc.

HTH

Dave