Asymmetric Fuzzy Zone

A German Equatorial Mount requires that the scope be flipped when viewing objects on opposite sides of the Meridian.  In the stepper version of Mel Bartel's Scope program, GEMFlipped Off is defined as the state when the scope is on the East side of the pier and objects are being viewed in the West.  That is, objects with Right Ascensions less that the Ra at the Meridian.

Figure 1 shows a telescope in the GEMFlipped Off state where the scope is on the East side of the pier.  The vertical line represents the Meridian.   While in this state, the scope is normally pointing West but it's possible for the scope to point slightly East before hitting the pier.  This situation is allowed when the configuration parameter AutoGEMFlipOffFuzzDeg is set positive.  The scope cannot point further East of the Meridian than the value of AutoGEMFlipOffFuzzDeg.  For objects on the Celestial Equator, the range of view is (Ra at Meridian + AutoGEMFlipOffFuzzDeg/15) to (Ra at Meridean - 6 Hours).

The zone shown in blue represents the Fuzzy Zone that the scope can occupy in either the GEMFlipped Off or GEMFlipped On state.

Figure 1

The opposite situation occurs when there's an obstruction near the pier that prevents the scope from even reaching the Meridian.  This is shown in Figure 4, where the red represents a Safety Zone that can't be entered when in the GEMFlipped Off state because the tail of the scope cannot move further West than the line representing AutoGEMFlipOffFuzzDeg.

The obstruction on the East side of the pier may not prevent the scope pointing partially or all the way into this Safety Zone when in the GEMFlipped On state.  

Figure 2

Figure 2 shows a scope in the GEMFlipped On state with a positive value of AutoGEMFlipOnFuzzDeg.  In this state, the allowed viewing range becomes, (Ra at Meridian + 6 Hours) to ( Ra at Meridian - AutoGEMFlipOnFuzzDeg/15)

The blue zone allows the scope to point slightly West.

Figure 3

Figure 3 is a simplified drawing combining Figures 1 and 2.  The pier has been removed and the two Meridian lines merged.  This is the situation when both FuzzDeg terms are positive.  The scope can enter the Fuzzy Zone in either state but in both states, it cannot move beyond the line representing the AutoGEMFlipxxFuzzDeg for that state.

When a slew is requested, the scope will request a GEM Flip if the destination is beyond the Meridian and outside the fuzzy zone.

Figure 4

Figure 5

Figure 5 shows a situation where the Safety Zone in the GEMFlipped Off state is partially covered by the positive value of GEMFlipOnFuzzDeg.

In Figure 5, the sum of the two FuzzDeg terms is negative, so there's a Safety Zone where no object can be viewed.  A request to slew to this area will result in an error message and tracking will be halted.

If the sum of the two FuzzDeg terms is zero or positive, no Safety Zone exists and the entire area around the Meridian can be accessed.

AutoGEMFlip

If the scope is in the GEMFlipped On state and tracking an object, a GEMFlip will be initiated when the Current Ra becomes less than (Ra at Meridian - AutoGEMFlipOnFuzzDeg/15).  

This can lead to a situation that should be avoided.  If you're in the GEMFlipped Off state and initiate a slew to an object that is very close to but East of the above point, the object may move beyond the line during the slew.  If this happens, an automatic flip back will be called for.  If the configuration is that shown in Figure 5, an error message will be given and tracking halted because a flip into the Safety Zone is now being requested.