Polemaster on a mount without GoTo

[cesco]

Hi everybody,

I put  the QHYCCD Polemaster on my Losmandy G11 mount not equipped without GoTo system and relative quick motors. Since rotations by 30 to 45 degrees take long when moving the scope with 8x speed (the max allowed by the mount), I move the RA axis by hand, gently grasping the counterweight bar and pulling it as smoothly as I can. Moving the scope by hand is strongly not recommended in the instruction manual, as this may disturb the axis setup. In turn, axis disturbance may depend upon RA clutch release, which I can understand... although this is absolutely unnecessary for Losmandy G11. Nonetheless I am afraid that some disturbance  may enter after my hand pull. When the scope gets back to home position, the selected reference star strictly stays on the green track: I would not expect this after some disturbance, as a doubly strayed track should be more probable after forward and back rotation. So I am not that afraid...still a tiny RA drift remains.

Before my first use of Polemaster, I polar aligned the mount by the Bigourdan - or drift - method, and also tryed  the polemaster on the drift aligned mount. The two methods coincided exactly, not as completion time of course (!), but while PH2 rated the drift align as 3 arcsec, the Polemaster instructions claim a precision of "up to 30 arcsec"...tenfold worse?

Anyway, my frames are not affected by such a drift because I take many 30 s exposures in order to take advantage of high frame numbers in order to increase the S/N ratio and reduce the bad effects of light pollution in my observing site. Nonetheless, I have autoguiding facility by use of a SBIG Relay Box, and though not as sophisticated as the Gemini 2 system, I am confident that the drift will be optimized when using both the Polemaster and the SBIG Relay Box.

Does somebody have experience of Polemaster use without the GoTo?

Thank you for advice.

Clear skies,

Cesco

 

[StuartJPP]

A few people, including myself have used a PoleMaster on an AstroTrac. You have to release the clutches on the head and manually move RA by hand. I only did this a couple of times and it seemed to work quite well.

As long as you lock the head in the required positions to similar tensions it should be pretty close.

[cesco]

Sure that's true with AstroTrac, but Losmandy mounts don't need clutches release when moving the scope by hand... this a very comfortable peculiarity of Losmandy mounts.

The fact that the reference star actually follows the green circle strictly when putting back the scope to home position tells that hand motion caused no disturbance to the RA axis set. Rather, I would like to understand whether some additional optimization exists to decrease more the residual error in polar alignement, unless it is the minimum inherent error for that mount.... I should ask the rare manual Losmandy G11 users....though not so many are still around....