ASTRO-PHYSICS GTO KEYPAD Addendum - Pagina 5

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Horizon Check in the Servo

Command:

Response:

A●bug●was●found●in●the●servo's●internal●horizon●check●in●the●E1●and●KE1●microcontroller●chips●for●the●GTOCP1●and●

GTOCP2●control●boxes.●●The●bug●existed●in●all●prior●versions●of●the●chip.●●Later●versions,●beginning●with●F●and●going●

through●R●partially●addressed●the●issue,●but●it●will●be●version●S●(in●beta●testing●as●of●1-14-10)●that●will●fully●solve●the●

problem.

Since●most●planetarium●software●and●the●Astro-Physics●keypad●firmware●all●perform●their●own●horizon●check●calculations,●

this●command●is●rarely●activated.●●The●horizon●check●was●included●in●the●command●set●for●people●who●may●be●writing●their●

own●control●software.●●

At●this●point,●we●recommend●that●NO ONE SHOULD USE THE HORIZON CHECK in●the●servo.●

Variable Tracking

The●following●text●replaces●the●text●for●these●commands●on●page●87●of●the●v.4.12●keypad●manual●dated●March●7,●

2008●(Appendix●B).●●It●applies●to●GTO●servo●microcontroller●chips●version●G●through●R.●●In●addition●to●a●more●thorough●

explanation,●please take special note of the difference between the northern and southern hemispheres for these

commands.●●●●●Also●note●that●the●command●operates●the●same●in●both●hemispheres●starting●with●version●S.

Command:

Response:

This●command●sets●the●tracking●rate●in●the●RA●axis●("RR")●or●DEC●axis●("RD")●to●sxx.xxxx.●●The●rate●is●expressed●in●terms●

of●multiples●of●the●sidereal●rate●and●can●be●positive●or●negative.●●●●Note●that●earlier●published●text●on●this●command●had●

three●digits●to●the●left●of●the●decimal.●●●This●was●incorrect.●●●Only●two●digits●(not●counting●the●sign)●are●allowed●to●the●left●of●

the●decimal●point.●●●●You●can●use●up●to●four●digits●to●the●right●of●the●decimal.●●●The●format●above●is●correct.

For●the●Right●Ascension,●the●rate●is●added●to●or●subtracted●from●the●default●sidereal●rate●of●1.0000x.●●●If●you●had●the●mount●

set●to●a●different●rate,●like●lunar,●this●is●irrelevant●to●the●command.●●●It●will●always●be●implemented●in●terms●of●the●sidereal●

rate.●●●

This●command●operates●differently●depending●on●the●hemisphere●you●are●in.●●●

● ●

In●the●northern●hemisphere,●the●rate●is●added●to●the●sidereal●rate.●●●For●example,●●●●:RR●+0.1#●●●would●result●in●the●

mount●tracking●10%●faster●than●sidereal●(●1.0●+●0.1●=●1.1●).●●●●:RR●-1#●●●would●stop●tracking●(●1.0●+●(-1.0)●=●0●).

● ●

In●the●southern●hemisphere,●the●rate●is●subtracted●from●the●sidereal.●●●●●Using●the●same●examples●above,●●●●:RR●+0.1#●●

would●result●in●the●mount●tracking●10%●slower●than●sidereal●(●1.0●–●0.1●=●0.9●).●●●●●:RR●-1#●●●●would●result●in●the●mount●

tracking●at●twice●the●sidereal●rate●(●1.0●–●(-1.0)●=●2.0●).

● ●

Starting●with●version●S,●the●command●operates●the●same●in●both●hemispheres●and●follows●the●convention●used●for●the●

northern●hemisphere●above.●●●Also●note●that●Rev,●S●and●later●add●another●digit●to●the●right●of●the●decimal●to●increase●

the●fine●resolution●of●the●command.●●●The●command●is●therefore:●●●●●●●:RR●sxx.xxxxx#

The●variable●Dec.●rate●works●from●a●mechanical●perspective.●●●With●regard●to●the●commands●in●the●servo,●●:RD●+xx.xxxx#●●

will●cause●clockwise●rotation●of●the●Dec.●axis●when●viewed●from●above;●●●:RD●–xx.xxxx#●●will●cause●counter-clockwise●

rotation.●●●●The●pier●side●makes●no●difference,●nor●does●the●hemisphere.●●●●●It●is●better●to●think●in●terms●of●the●mechanical●

rotation●of●the●axis●because●it●is●consistent.●●●●Remember●that●in●the●northern●hemisphere,●on●the●west●side,●clockwise●is●

south;●●on●the●east●side●clockwise●is●north●and●just●the●opposite●holds●true●in●the●southern●hemisphere.●

As●with●the●Right●Ascension,●versions●S●and●later●add●another●digit●to●the●right●of●the●decimal●in●declination.

:ho#

:hq#

(none)

:RR sxx.xxxx#

:RD sxx.xxxx#

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