Meridian Flip Settings Explained


Don W
 

Hi All,
The settings in SiTech /ChangeConfig/MountParms concerning GoTo's and Tracking vs the Meridian are very straightforward (they do exactly what they say), but are still confusing to some users.  In particular, the use of a "bent pier" allows a GEM to rotated mostly without "hitting the pier".  This means the telescope can be pointed at the sky while the counterweight shaft is pointed UP (above the horizon).  This just means that SiTech can track (and image) a target starting well east of the meridian and continue all the way to the West horizon without a meridian flip.

OK, how do you setup to do this???
First lets define the terms and what they do.
1. These are only for a GEM, so GEM must be selected.
2. There are two check boxes, one for Auto Flip and another for Auto Track.  These boxes control whether the mount will Flip or Stop when the mount gets to the limit.  That is IT!, there is no other option.
3.The key to tracking without a flip is the setting for Track Past Meridian in the lower left of the window.
4. The limits are set in the wide boxes for 'Over Pole and Under Pole.  These limits are in degrees-minutes-seconds of arc, FROM THE ZENITH!  The angles are measured positive in the direction of the limit.  So +10° for the west limit is toward the west, and +10° for the east limit is toward the east.  Both of these limits can not exceed 90° (the horizon).  Now with 095M and later versions, these limits CAN be set to a negative angle, which allows the limit to be set BEFORE the meridian.

The same methodology applies to UNDER POLE, so the settings are angle from the meridian - directly Under the pole is 180°.  so if you set for 2 degrees after the meridian, set 178° or -178°.

I have said you should not use Under the Pole unless you are very far north latitude (or south latitude), like Canada or northern Europe.  Any DSO will be above the pole for at least 6 months of the year.  OK, if you are doing science measurements of double stars orbits or variable stars then you want to make measurements all year long - That is what Under the Pole is for - targets of opportunity.

I live and observe in southern California at latitude 32° so I don't ever use "Under the Pole" so I don't have any experience using it.

Meridian Flips are not caused by Platesolves!  Platesolves simply initialize the mount to the local sky, either Looking East or Looking West.  when SiTech is not initialized, and you do a platesolve, now it is initialized, and if SiTech is connected to any other ASCOM program, once initialized SiTech will report via ASCOM where it is pointed.

If SiTech is NOT initialized, then any motion via the handpad WILL NOT BE REPORTED to any ASCOM program like SGP.  Once SiTech is initialized SGP will have all mount motion reported.  If you don't understand this, then you WILL have unexpected results.

Don W

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