Gemini I Model Building from Michael Herman


Result: all worked properly with very close GoTos. At the end of this email, find a table of the Model parameters as each star was added to the ALIGN in Gemini-1.  
Last night, clear but windy with bad seeing, gave me a chance to test out the Gemini-1 model building in a step by step (or star by star) way.  The model is built after each star is ALIGNed and the manual states the first 3 stars MUST be on ONE SIDE of the Meridian only, which I did follow last night.  

My G11 is quite loaded up with a heavy Meade LX200R-12inch f/10 SCT.  I am using a Gemini-1 level 4 v1.05 EPROM.  

I am using for PC software..these free programs:  

Stellarium-scope by DragonWelch   Stellarium 0.14.3 ASCOM  platform 6 driver for ASCOM

Note about the program settings: You MUST enable (checkmark is on) the selection for "Synch performs additional Align" otherwise PC based skychart Synch commands will not change the Gemini will remain as all 0s!
Here is how I connected to the Gemini-1 to read the “Model” values.

1.       Connect Gemini1 to Laptop using serial port.

2.       Start from cold boot.  Leave hand controller at first Align to Bright Star, but do not do that yet.

3.       Connect Laptop to Gemini1 using Stellarium-scope program.

a.       This uses ASCOM chooser

b.      Choose  See Gemini,net connect to the Gemini unit.  

c.       Also start Stellarium program from here

d.      Settings are for CTL-1 as GoTo and CTL-3 as Synch, and "Use J-2000", Slew default 10001 (will be CTL-1), Synch default 10003 (will be CTL-3), Cancel default 10005 (will be CTL-5).  NOTE that Synch command is interpreted by Gemini as NO CHANGE TO MODEL.  Only the ALIGN command can modify the Model...see below.)

4.       Using the applet:

a.       Click on Setup/Advanced Gemini Settings

b.      Click on the Modelling Parameters button  to get the settings values

c.       Reads all 0s

d.      NOTE: at this stage, shows the “Synch performs Additional Align” set UNCHECKED.
This was incorrect.  We want that CHECKED turned on.

5.       Now use the hand controller to pick a bright star on ONE SIDE of the meridian

a.       I picked the East side, starting with Arcturus

b.      The G11 slewed to Arcturus, with small amount of correction by the handset

c.       Press the handset twice to Synch on Arcturus

6.       Look at Model Parameters

a.       Still all 0’s (Synch does NOT modify the existing model).

b.      Press CTL-3 on Stellarium. This sends a Synch but still results in all 0s

Because I had “Synch performs Additional Align” UNCHECKED.  It should be CHECKED.

7.       Use Stellarium to move to a new star on the SAME SIDE of Meridian

a.       I chose Etamin in Stellarium.  Put mouse cursor on Etamin or Search (F3) for Etamin. Press Spacebar to center and track on Etamin. 

b.      In Stellarium press CTL-1 for GoTo (to Etamin).

c.       Scope slews close to Etamin…it is in Finder scope field, not eyepiece

d.      Use hand controller to center Etamin

e.      On Stellarium (or Hand Controller, use Menu/Align/Additional Align to add this star).  Stellarium shows the scope close to, but not on Etamin (using the Gemini measured position)

f.        On Stellarium press CTL-3 to Synch on Etamin.   If the “Synch performs additional Align” is checked off in, this will change the model.  If left Unchecked, the model will remain ALL 0s. !

Now I checked off the "Synch performs additional Align" and now each star I synch on changes the model values as it should.  

8.       Look at the model params per star alignment (Synch + Align, not just Synch!)        Now we see the model change:

Parameter after:

Cold boot

1st star Etamin

2nd star

3rd star Arcturus

Polar Axis Misalign AZ (A)





Polar Ax Misalign EL (E)





Axes non perp pole





Axes nonperp  equator





Index err hour angle (H)





Index err Dec (D)





Mir flop/Gear play RA (FR)





Mir flop/Gear play DEC (FD)





CounterWt & RA axis flex (CF)





Tube flex (TF)





9.   To do:

I want to know (calibrate):
     what 1 degree of front Elevation knob (say moving the front higher) has on the E value.   
     what 1 degree of back AZ knob rotation (say to the East) has on the A value.

So my next work is to:

a.       Rotate the Elevation knob CW in front by a measured amount of degrees  Clear all the values back to 0, redo the 3 star alignment, and see the effect on the E value. 

b.      Rotate the AZ to the East front by a measured amount of degrees.  Clear all the values back to 0, redo the 3 star alignment, and see the effect on the A value.


Best to all,

Michael Herman
mobile: 408 421-1239
email: mherman346@...