Safety Limits

Another way to think of the "side" of the pier that your scope is on -- it's the side with the center of the saddle. That seems obvious, but if your scope is long and you are near the vertical with the counterweight shaft, the aperture or opposite end of the scope may be across the meridian (or the object you're pointing at is across the meridian.) The saddle is always clearly in one side or the other. This way, it doesn't matter what you are pointing at in the sky, you're always setting a limit or a model for the side that the center of the saddle is on, not what you're looking at.

Northern Hemisphere


Fig 1. Click on image for larger image.
North Hemisphere East Side
Figure 2. 		North Hemisphere West side
Figure 3.

Fig 1. and Fig 4. show the relationship of the different in limits between the northern hemisphere and the southern hemisphere. The Limits are switched between the hemispheres as far as east and west is concerned, but stay the same for left and right. Left and Right is determined by standing in front of the telescope with you back to your respective pole. In figures 2, 3, 5, and 6, you see the angles that are default for the G8, G11, Titan and Titan 50.

The MI-250 angles are different, and should be 92 for the Left limit and 95 degrees for the Right limit.

Note: the Hemisphere is selected totally by the sign of the Latitude in any of the Gemini hardware versions. Positive for Northern Hemisphere and negative for Southern Hemisphere. No switches to change at all.

Note: changing the mount type from the hand controller or web interface does not change the safety limits that are set.

Note: see Reset SRAM so your changes are stored long term.

Southern Hemisphere


Fig 4. Click on image for larger image.
114D Southern Hemisphere
Figure 5. 		123 D Southern Hemisphere
Figure 6.

WebInterface Set Safety Limits
Fig 7. Click on image for larger image

Fig 8

The Eastern Position, Western Position, and Western Goto Limit buttons do take you to the hand-controller menu pages.

Please Note: changing the mount type from the hand controller or web interface does not change the safety limits that are set. Also please see Reset SRAM

The limits can be set either using the Web interface, on the Mount Selection Page, See Fig 7. or on the hand controller see figure 8. (it is under: Menu-->Mount-->Limits

Note that the Web limits are set for left and right side, while the hand controller uses East and West. If using the hand controller, follow these steps.

  1. Start with the mount at Counter Weight Down (CWD), using either Cold Start or Warm Start.

  2. Turn off tracking by placing the mount into Terrestrial mode. Menu->Track->Terrestrial

  3. Move the RA using the Left-Right buttons to the Eastern Limit. Loosen the clutch in Dec. Make sure you can spin the telescope back and forth as far as your cables will allow, or if no cables are connected 360 degrees in Dec without it hitting the mount, if possible. There are no DEC limits to set, so you have to make sure your Dec is clear from hitting also. Use the Menu->Mount->Limits->"Set Limits Here" button, to set the Eastern Limit.

  4. Move the RA using the Left-Right buttons to the Western Limit. Loosen the clutch in Dec. Do the Dec just as you did in step 3 above. Use the Menu->Mount->Limits->"Set Limits Here" button, to set the Western Limit. You now have set the Limits

  5. The Western Goto Limit determines how far past the meridian that the Gemini-2 will do a flip. It is calculated like this. Note that the Meridian is at 90 degrees. The point of Meridian Flip = Western Safety Limit - Goto Limit. An example is if you have the Western Safety limit set to 100 degrees - The Western goto limit of 2.5 degrees (default) you end up with a point of flip of 97.5 degrees, or 7.5 degrees past the meridian. Any target selected that is past this will do a meridian flip. Any target on the East side (Northern Hemisphere) will not do a meridian flip.