My new G11 – Modelling Parameters

[browndog (Ian)]

Having recently purchased a G11/Gemini, I am still attempting to set it up correctly. As I am using it mainly for astrophotography work I would like to optimise as much as possible, without any additional expenses. I am hoping that a good understanding of this information will help to improve my setup.

According to GCC the Modelling Parameters for my setup are:

Polar Misalignment
Azmuth: 333
Elevation: -682

Non-Perpendicularities
Pole: -529
Equator: 851

Index Error
Hour Angle: -909
Declination: 729

Mirror Flop / Gear Play
Hour Angle: 3391
Declination: -29

Flexure
Counterweight:30
Tube: 0

Can anyone help to explain the “Modelling Parameters” for the G11/Gemini?

Based on this information are there some simple things that I should try to correct to make the mount work optimally?

[tlgerdes (Trevor)]

Sounds like you are seriously misaligned.

3.5.3 Modeling Parameters

Gemini models the following mount and telescope parameters:

•

Azimuth misalignment from the pole

•

Elevation misalignment from the pole

•

Axis non-perpendicularity at the pole

•

Axis non-perpendicularity at the equator

•

Gear play

•

Mirror flop

•

Index error in hour angle

•

Index error in declination

•

Counterweight flexure
You can examine each of these parameters immediately after an additional alignment. The azimuth and elevation misalignment (A and E) are displayed right after the “Additional Align” is executed. You can also use the “Show Information” menu item to display the other parameters: NP = non-perpendicularity at the pole, NE = nonperpendicularity at the equator, FR = gear play (in RA), FD = mirror flop (in Dec.), IH = Hour Angle index error, ID = declination index error, and CF = counterweight flexure. All values are given in minutes of arc. These values give you valuable information about your alignment, your mount and your telescope.

[browndog (Ian)]

It has been reported elsewhere that the numbers reported by Gemini Control Centre (GCC) are in arc seconds.

So based on my results , my polar misalignment in arc minutes are:
Azmuth: 333 / 60 = 5.55 arc minutes
Elevation: -682 / 60 = 11.3 arc minutes

This means that I am about 12.6 arc minutes from the south celestial pole.

I am not sure what an acceptable result in polar misalignment is but given that I see field rotation in images - I guess it needs to be better than this. It has been reported that a misalignment of; A: <3 arc minutes & E: < 3 arc minutes is needed... (or about 4 arc minutes from the south celestial pole.)

Does anyone have any figures for an acceptable polar misalignment?
(Can you achieve 0 arc minutes?)

[multiweb (Marc)]

If within 30' on each axis from the pole I'm still ok with 10min subs for an image scale of 2-3asp. Your PA value I'd say are excellent compared to what Trev commonly refers as the "Aragnou Alignment". But then again I'm always on the move. That's my excuse anyway

[allan gould]

Did you use either of the twp polar alignmnet routines for the Losmandy? Or do you have a PAS?
I generally use the PAS and then the PAC routine for polar aligning followed by drift aligning if I'm going to do astrophotography.
Its all in the manual.

[Octane (Humayun)]

I've had A and E numbers of 0, respectively, before.

H

[tlgerdes (Trevor)]

Originally Posted by Octane

I've had A and E numbers of 0, respectively, before.

H

Yeah, but you're SuperHuman, or should that be SuperHumayun.