Gemini Level 3, Version 1.0 Serial Interface Command Description

Gemini Level 3, Version 1.1 Serial Interface Command Description

The Gemini system supports a subset of the Meade® LX200 Command Set. Some extensions that follow the same style of commands but being unique to the Gemini system were added.
Please note: Due to the differences between these telescope control systems, some commands are interpreted in a different manner.
From Level 2 up, most Gemini parameters and settings can be downloaded or uploaded using the native command set described at the end of this page.

Syntax: values in <> are (to be) replaced by actual values. Curled brackets {} show alternative characters.
Upon completion, ASCII characters or strings are returned, if indicated.

Command Returns Remarks

0x06 (ACK char) G# after completed startup or
b# while waiting for the selection of the Startup Mode. Usable for testing the serial link and determining the type of mount (German equatorial).
During Startup, with a "b#" being returned, the PC can select the startup mode by sending a
bC# for selecting the Cold Start,
bW# for selecting the Warm Start and
bR# for selecting the Warm Restart.

Synchronize

:Cm# No object!# or
<object name># The string "No object!#" is returned if the mount is not aligned or no object was selected, otherwise the name of the selected object used is returned.
This command does an "Additional Alignment", (re)calculating the pointing model parameters and synchronizing to the position given.

:CM# No object!# or
<object name># The string "No object!#" is returned if the mount is not aligned or no object was selected, otherwise the name of the selected object used is returned.
The position (RA and DEC) is synchronized to the position of the object without affecting the modelling parameters.

Focus Control

:F+# Focus In

:F-# Focus Out

:FQ# Stop focusing

:FF# Focus Fast

:FM# Focus Medium

:FS# Focus Slow

Get Information

:GA# <ddd>°<mm># Get Altitude (from L1, V2.0 up)

:GB# <n># Get LED Display Brightness Value(from L1, V2.0 up)
n=0: 100% n=6: 6.6% n=7: blank display n=8: test mode (all pixels lit).

:GC# <mm>/<dd>/<yy># Local Calendar Date, month mm, days dd and years yy separated by slashs.

:GD# In High Precision mode:
{+-}<dd>:<mm>:<ss>#
In Low Precision mode:
{+-}<dd>°<mm># Apparent (refraction included) Declination the telescope is pointing to, to the equinox of the date. Despite during GoTo operations, the coordinates are corrected according to the pointing model.
Signed degrees (-90 to +90), minutes, seconds. The degree sign in Low Precision mode is the character 0xDF.

:GE# <hh>:<mm>:<ss># Get Alarm time (from L1, V2.0 up)

:GG# {+-}<hh># Get hours from UTC (from L1, V2.0 up)

:GL# <hh>:<mm>:<ss># Civil Time (UTC time from the internal Real Time Clock + UTC offset), hours, minutes, seconds in 24-hour format.

:GR# High Precision mode:
<hh>:<mm>:<ss>#
Low Precision mode:
<hh>:<mm>.<m># Apparent (refraction included) Right Ascension the telescope is pointing to, to the equinox of the date. Despite during GoTo operations, the coordinates are corrected according to the pointing model.
Hours (0 to 24), minutes, seconds or tenth of minutes.

:GV# <l><vv># Get Software Level l (one digit) and Version vv(two digits)

:Gc# (24)# Clock format

:Gg# {+-}<dd>°<mm># Get Site Longitude (from L1, V2.0 up)

:Gt# <ddd>°<mm># Get Site Latitude (from L1, V2.0 up)

:Gv# N (for "no tracking")
G (for Guiding)
C (for Centering)
S (for Slewing)
Get Velocity (from L1, V2.0 up)

Home Position

:hP# Move to Home Position. The Home Position defaults to the celestial pole visible at the given hemisphere (north or south) and can be set by the user at the Gemini.

:h?# 2: Home Search in progress
1: Home Search done
0: Home Search failed or no home search command was received. Move to Home Position Status Inquiry

Move Telescope Note: the directions mentioned depend upon the hemisphere of the observing site and the side of the mount the telescope actually is. Directions do not change when crossing one of the poles.

:ML# # Move Lock: Slew commands :MS# will be supressed, error code 3 (Manual Control) will be returned.

:Ml# # Move Unlock: Slew commands :MS# will be executed again.

:MS# 0
1Object below horizon.#
2Telescope is not aligned.#
2No object selected.#
3Manual Control.# Slew to the selected object. Selection is done locally or by sending the Sr and Sd command. This commands will be rejected if the system is in Manual Mode, f.i. Identifying or selecting an object from the internal databases.

:Me# Move eastwards at the selected speed rate.

:Mw# Move westwards at the selected speed rate.

:Mn# Move northwards at the selected speed rate.

:Ms# Move southwards at the selected speed rate.

Object/Observing

:OC# Clears the Observing Log.

:ON<name># Tells the Gemini system the name or identification of the selected object. If this command is not used, the name defaults to "PC Object". Using this command is recommended .

:OR# <log entry># Reads the next line from the Observing Log.

:OS# Points to the beginning of the Observing Log.

:Oc# Delete all User Catalog entries.

:Od<object line># Download a User Catalog entry to the Gemini. The object line consist of
the object name (up to 10 ASCII characters),
a comma ',' as delimiter,
Right Ascension <hh>:<mm>:<ss>,
Declination {+-}<dd>:<mm>:<ss>.
The coordinates have to be given for the epoch 2000.0.

:Or# <object line># Upload a User Catalog entry from the Gemini.

:Os# Points to the beginning of the User Catalog (for downloading).

Precession

:p0# No precession calculation necessary in the Gemini. Coordinates transfered to the Gemini are already precessed to the equinox of the date.

:p1# Precession calculation is to be done by Gemini. Coordinates transfered to the Gemini refer to the standard epoch J2000.0.

Precision

:P# HIGH PRECISION
or
LOW PRECISION Both strings are 14 characters long (there are 2 blanks between LOW and PRECISION). HIGH PRECISION indicates that Gemini expects and sends RA and DEC coordinates in long format, LOW PRECISION that the short format is used.

:U# Toggle between Low Precision (short) and High Precision (long) coordinate mode. The system is in High Precision mode after starting up.

Quit Moving

:Q# Quit all movements mentioned below.

:Qe# Quit movement eastwards.

:Qw# Quit movement westwards.

:Qn# Quit movement northwards.

:Qs# Quit movement southwards.

Rate

:RC# Rate Center. Subsequent Move commands will move at Centering Speed.

:RG# Rate Guide. Subsequent Move commands will move at Guiding Speed.

:RM# Rate Move. Subsequent Move commands will move at Centering Speed.

:RS# Rate Slew. Subsequent Move commands will move at Slewing Speed.

Set

:SB<n># Set LED Display Brightness Value(from L1, V2.0 up)
n=0: 100% n=6: 6.6% n=7: blank display n=8: test mode (all pixels lit).

:SC<mm>/<dd>/<yy># 0 if invalid or
1Updating planetary data#
<24 blanks># Set Calendar Date: months mm, days dd, year yy of the civil time according to the timezone set. The internal calender/clock uses GMT.

:SE<hh>:<mm>:<ss># 1 Set Alarm Time from the civil time hours hh, minutes mm and seconds ss. The timezone has to be set before using this command.

:SG{+-}hh# 1 Hours after (sign +) or before (sign -) GMT. The timezone has to be set before setting the Calendar Date (SC) and Local Time (SL), since the Real Time Clock is running at GMT.

:SL<hh>:<mm>:<ss># 1 Set RTC Time from the civil time hours hh, minutes mm and seconds ss. The timezone has to be set before using this command.

:Sd{+-}<dd>{*°}<mm>#
or
:Sd{+-}<dd>{*°:}<mm>:<ss> 0 if invalid or
1 if valid Sets the object's declination and sets the object status to "Selected". It is important that the :Sr# command has been send prior.

:Sg{+-}<ddd>*<mm># 1 if valid Sets the longitude of the observing site to ddd degrees and mm minutes. The longitude has to be specified positively for western latitudes (west of Greenwich, the plus sign may be omitted) and negatively for eastern longitudes. Alternatively, 360 degrees may be added to eastern longitudes.

:Sp# No object!#
1 if object coordinates wer set. Precess coordinate transmitted by means of :Sr and :Sd to the equinox of the date.

:Sr<hh>:<mm>.<m>#
or
:Sr<hh>:<mm>:<ss># 0 if invalid or
1 if valid Sets the object's Right Ascension and the object status to "Not Selected". The :Sd# command has to follow to complete the selection. The subsequent use of the :ON# command is recommended.

:St{+-}<dd>*<mm># 1 if valid Sets the latitude of the observing site to dd degrees, mm minutes. The minus sign indicates southern latitudes, the positive sign may be omitted.

:Sw<n># 1 if valid Sets the Slewing rate for the Move commands

Gemini Native Commands

<<id>:<checksum># <parameter value><checksum># Get Value(from L2 up)

><id>:<parameter value><checksum># Set Value(from L2 up)

Id's and possible values in Level 3, Version 1.1:

Id Possible Values Description and Remarks

0, 1..5 1: GM8
2: G-11
3: HGM-200 or MI-250
4: CI700
5: Titan
6: Titan50 Mount Type. 0 can be used for requesting. Titan50 supported from V1.1 up.

10, 11..13 11: Use Encoder
12: Test Encoder
13: Ignore Encoder
Encoder State. 10 can be used for requesting.

99 Decimal sum of
1: Telescope is Aligned,
2: Modelling in use,
4: Object is selected,
8: GoTo operation is performed,
16: RA limit reached,
32: Precess coordinates from J2000.0
to the equinox of the date. Status Inquiry.

100 {+-}2048..32768 Encoder Resolution in RA.

110 {+-}2048..32768 Encoder Resolution in DEC.

120 20..2000 Manual Slewing Speed.

130, 131..137 131: Sidereal
132: King Rate
133: Lunar
134: Solar
135: None
136: Closed Loop
137:Comet/User Defined Tracking Rate. 130 can be used for requesting.

140 20..2000 GoTo Slewing Speed.

150 0.2..0.8 Guiding Speed.

160, 161..163 161: Visual Mode
162: Photo Mode
163: All Speeds Handcontroller Mode. 160 can be used for requesting.

170 1..255 Centering Speed.

180, 181..182 181: Alarm Off
182: Alarm On
Alarm Mode. 180 can be used for requesting.

200 0..255 TVC Step Count.

201 {+-}0..65535 Modelling Parameter A (Polar Axis Misalignment in Azimuth), in seconds of arc.

202 {+-}0..65535 Modelling Parameter E (Polar Axis Misalignment in Elevation), in seconds of arc.

203 {+-}0..65535 Modelling Parameter NP (Axes Non-Perpendicularity at the Pole), in seconds of arc.

204 {+-}0..65535 Modelling Parameter NE (Axes Non-Perpendicularity at the Equator), in seconds of arc.

205 {+-}0..65535 Modelling Parameter IH (Index Error in Hour Angle), in seconds of arc.

206 {+-}0..65535 Modelling Parameter ID (Index Error in Declination), in seconds of arc.

207 {+-}0..65535 Modelling Parameter FR (Mirror Flop/Gear Play in RA), in seconds of arc.

208 {+-}0..65535 Modelling Parameter FD (Mirror Flop/Gear Play in Declination), in seconds of arc.

209 {+-}0..65535 Modelling Parameter CF (Counterweight & RA axis Flexure), in seconds of arc.

211 {+-}0..65535 Modelling Parameter TF (Tube Flexure), in seconds of arc.

220 Set Safety Limit to the actual (hour angle/east or west) position. The Get function delivers only a hash mark.

311 0..15(63) Feature Port Status. 4 bits (0..15) can be used for setting input/output bits, 6 bits (two additional pure input bits, 0..63) are available for input.

411 256..65535 RA tracking rate divisor. The RA timer runs at 1.5 MHz, using this divisor the tracking rate can be adapted to the (mount dependent) speed of an object to be tracked.

412 {+-}0..65535 DEC tracking rate divisor. For DEC, no special timer is available, the divisor refers to the number of RA steps to be done for one step in DEC.

65535 Reboot the Gemini controller software.

Using the native commands:

The Identification tag is interpreted as an integer value, leading zeros are ignored.
The checksum for the native commands is calculated by a bytewise XOR operation of the transmitted characters, including the Get/Set command sign ('<', '>'). The highest significant bit of the result is cleared (modulo 128 operation) and 64 is added.
Undefined Id's are ignored in Set operations. For Get operations, only a hash mark will be returned.
In Debug Mode, the expected and the received checksum are displayed whenever a discrepancy is detected. The command with the wrong checksum will not be executed.

Examples

Get the Mount Type: "<0:v" and "<00:F#" are equivalent.
"<1:w#" and "<2:t#" and "<3:u#" will deliver the same result, f.i. the string "1q#" if the mount type is set to GM-8 or "2r#" if G-11 is selected.

Meade® is a trademark registered by Meade Instruments Corporation, California, USA.

Command	Returns	Remarks
0x06 (ACK char)	G# after completed startup or b# while waiting for the selection of the Startup Mode.	Usable for testing the serial link and determining the type of mount (German equatorial). During Startup, with a "b#" being returned, the PC can select the startup mode by sending a bC# for selecting the Cold Start, bW# for selecting the Warm Start and bR# for selecting the Warm Restart.
Synchronize
:Cm#	No object!# or <object name>#	The string "No object!#" is returned if the mount is not aligned or no object was selected, otherwise the name of the selected object used is returned. This command does an "Additional Alignment", (re)calculating the pointing model parameters and synchronizing to the position given.
:CM#	No object!# or <object name>#	The string "No object!#" is returned if the mount is not aligned or no object was selected, otherwise the name of the selected object used is returned. The position (RA and DEC) is synchronized to the position of the object without affecting the modelling parameters.
Focus Control
:F+#		Focus In
:F-#		Focus Out
:FQ#		Stop focusing
:FF#		Focus Fast
:FM#		Focus Medium
:FS#		Focus Slow
Get Information
:GA#	<ddd>°<mm>#	Get Altitude (from L1, V2.0 up)
:GB#	<n>#	Get LED Display Brightness Value(from L1, V2.0 up) n=0: 100% n=6: 6.6% n=7: blank display n=8: test mode (all pixels lit).
:GC#	<mm>/<dd>/<yy>#	Local Calendar Date, month mm, days dd and years yy separated by slashs.
:GD#	In High Precision mode: {+-}<dd>:<mm>:<ss># In Low Precision mode: {+-}<dd>°<mm>#	Apparent (refraction included) Declination the telescope is pointing to, to the equinox of the date. Despite during GoTo operations, the coordinates are corrected according to the pointing model. Signed degrees (-90 to +90), minutes, seconds. The degree sign in Low Precision mode is the character 0xDF.
:GE#	<hh>:<mm>:<ss>#	Get Alarm time (from L1, V2.0 up)
:GG#	{+-}<hh>#	Get hours from UTC (from L1, V2.0 up)
:GL#	<hh>:<mm>:<ss>#	Civil Time (UTC time from the internal Real Time Clock + UTC offset), hours, minutes, seconds in 24-hour format.
:GR#	High Precision mode: <hh>:<mm>:<ss># Low Precision mode: <hh>:<mm>.<m>#	Apparent (refraction included) Right Ascension the telescope is pointing to, to the equinox of the date. Despite during GoTo operations, the coordinates are corrected according to the pointing model. Hours (0 to 24), minutes, seconds or tenth of minutes.
:GV#	<l><vv>#	Get Software Level l (one digit) and Version vv(two digits)
:Gc#	(24)#	Clock format
:Gg#	{+-}<dd>°<mm>#	Get Site Longitude (from L1, V2.0 up)
:Gt#	<ddd>°<mm>#	Get Site Latitude (from L1, V2.0 up)
:Gv#	N (for "no tracking") G (for Guiding) C (for Centering) S (for Slewing)	Get Velocity (from L1, V2.0 up)
Home Position
:hP#		Move to Home Position. The Home Position defaults to the celestial pole visible at the given hemisphere (north or south) and can be set by the user at the Gemini.
:h?#	2: Home Search in progress 1: Home Search done 0: Home Search failed or no home search command was received.	Move to Home Position Status Inquiry
Move Telescope		Note: the directions mentioned depend upon the hemisphere of the observing site and the side of the mount the telescope actually is. Directions do not change when crossing one of the poles.
:ML#	#	Move Lock: Slew commands :MS# will be supressed, error code 3 (Manual Control) will be returned.
:Ml#	#	Move Unlock: Slew commands :MS# will be executed again.
:MS#	0 1Object below horizon.# 2Telescope is not aligned.# 2No object selected.# 3Manual Control.#	Slew to the selected object. Selection is done locally or by sending the Sr and Sd command. This commands will be rejected if the system is in Manual Mode, f.i. Identifying or selecting an object from the internal databases.
:Me#		Move eastwards at the selected speed rate.
:Mw#		Move westwards at the selected speed rate.
:Mn#		Move northwards at the selected speed rate.
:Ms#		Move southwards at the selected speed rate.
Object/Observing
:OC#		Clears the Observing Log.
:ON<name>#		Tells the Gemini system the name or identification of the selected object. If this command is not used, the name defaults to "PC Object". Using this command is recommended .
:OR#	<log entry>#	Reads the next line from the Observing Log.
:OS#		Points to the beginning of the Observing Log.
:Oc#		Delete all User Catalog entries.
:Od<object line>#		Download a User Catalog entry to the Gemini. The object line consist of the object name (up to 10 ASCII characters), a comma ',' as delimiter, Right Ascension <hh>:<mm>:<ss>, Declination {+-}<dd>:<mm>:<ss>. The coordinates have to be given for the epoch 2000.0.
:Or#	<object line>#	Upload a User Catalog entry from the Gemini.
:Os#		Points to the beginning of the User Catalog (for downloading).

Precession
:p0#		No precession calculation necessary in the Gemini. Coordinates transfered to the Gemini are already precessed to the equinox of the date.
:p1#		Precession calculation is to be done by Gemini. Coordinates transfered to the Gemini refer to the standard epoch J2000.0.
Precision
:P#	HIGH PRECISION or LOW PRECISION	Both strings are 14 characters long (there are 2 blanks between LOW and PRECISION). HIGH PRECISION indicates that Gemini expects and sends RA and DEC coordinates in long format, LOW PRECISION that the short format is used.
:U#		Toggle between Low Precision (short) and High Precision (long) coordinate mode. The system is in High Precision mode after starting up.
Quit Moving
:Q#		Quit all movements mentioned below.
:Qe#		Quit movement eastwards.
:Qw#		Quit movement westwards.
:Qn#		Quit movement northwards.
:Qs#		Quit movement southwards.
Rate
:RC#		Rate Center. Subsequent Move commands will move at Centering Speed.
:RG#		Rate Guide. Subsequent Move commands will move at Guiding Speed.
:RM#		Rate Move. Subsequent Move commands will move at Centering Speed.
:RS#		Rate Slew. Subsequent Move commands will move at Slewing Speed.
Set
:SB<n>#		Set LED Display Brightness Value(from L1, V2.0 up) n=0: 100% n=6: 6.6% n=7: blank display n=8: test mode (all pixels lit).
:SC<mm>/<dd>/<yy>#	0 if invalid or 1Updating planetary data# <24 blanks>#	Set Calendar Date: months mm, days dd, year yy of the civil time according to the timezone set. The internal calender/clock uses GMT.
:SE<hh>:<mm>:<ss>#	1	Set Alarm Time from the civil time hours hh, minutes mm and seconds ss. The timezone has to be set before using this command.
:SG{+-}hh#	1	Hours after (sign +) or before (sign -) GMT. The timezone has to be set before setting the Calendar Date (SC) and Local Time (SL), since the Real Time Clock is running at GMT.
:SL<hh>:<mm>:<ss>#	1	Set RTC Time from the civil time hours hh, minutes mm and seconds ss. The timezone has to be set before using this command.
:Sd{+-}<dd>{°}<mm># or :Sd{+-}<dd>{°:}<mm>:<ss>	0 if invalid or 1 if valid	Sets the object's declination and sets the object status to "Selected". It is important that the :Sr# command has been send prior.
:Sg{+-}<ddd>*<mm>#	1 if valid	Sets the longitude of the observing site to ddd degrees and mm minutes. The longitude has to be specified positively for western latitudes (west of Greenwich, the plus sign may be omitted) and negatively for eastern longitudes. Alternatively, 360 degrees may be added to eastern longitudes.
:Sp#	No object!# 1 if object coordinates wer set.	Precess coordinate transmitted by means of :Sr and :Sd to the equinox of the date.
:Sr<hh>:<mm>.<m># or :Sr<hh>:<mm>:<ss>#	0 if invalid or 1 if valid	Sets the object's Right Ascension and the object status to "Not Selected". The :Sd# command has to follow to complete the selection. The subsequent use of the :ON# command is recommended.
:St{+-}<dd>*<mm>#	1 if valid	Sets the latitude of the observing site to dd degrees, mm minutes. The minus sign indicates southern latitudes, the positive sign may be omitted.
:Sw<n>#	1 if valid	Sets the Slewing rate for the Move commands
Gemini Native Commands
<<id>:<checksum>#	<parameter value><checksum>#	Get Value(from L2 up)
><id>:<parameter value><checksum>#		Set Value(from L2 up)

Id	Possible Values	Description and Remarks
0, 1..5	1: GM8 2: G-11 3: HGM-200 or MI-250 4: CI700 5: Titan 6: Titan50	Mount Type. 0 can be used for requesting. Titan50 supported from V1.1 up.
10, 11..13	11: Use Encoder 12: Test Encoder 13: Ignore Encoder	Encoder State. 10 can be used for requesting.
99	Decimal sum of 1: Telescope is Aligned, 2: Modelling in use, 4: Object is selected, 8: GoTo operation is performed, 16: RA limit reached, 32: Precess coordinates from J2000.0 to the equinox of the date.	Status Inquiry.
100	{+-}2048..32768	Encoder Resolution in RA.
110	{+-}2048..32768	Encoder Resolution in DEC.
120	20..2000	Manual Slewing Speed.
130, 131..137	131: Sidereal 132: King Rate 133: Lunar 134: Solar 135: None 136: Closed Loop 137:Comet/User Defined	Tracking Rate. 130 can be used for requesting.
140	20..2000	GoTo Slewing Speed.
150	0.2..0.8	Guiding Speed.
160, 161..163	161: Visual Mode 162: Photo Mode 163: All Speeds	Handcontroller Mode. 160 can be used for requesting.
170	1..255	Centering Speed.
180, 181..182	181: Alarm Off 182: Alarm On	Alarm Mode. 180 can be used for requesting.
200	0..255	TVC Step Count.
201	{+-}0..65535	Modelling Parameter A (Polar Axis Misalignment in Azimuth), in seconds of arc.
202	{+-}0..65535	Modelling Parameter E (Polar Axis Misalignment in Elevation), in seconds of arc.
203	{+-}0..65535	Modelling Parameter NP (Axes Non-Perpendicularity at the Pole), in seconds of arc.
204	{+-}0..65535	Modelling Parameter NE (Axes Non-Perpendicularity at the Equator), in seconds of arc.
205	{+-}0..65535	Modelling Parameter IH (Index Error in Hour Angle), in seconds of arc.
206	{+-}0..65535	Modelling Parameter ID (Index Error in Declination), in seconds of arc.
207	{+-}0..65535	Modelling Parameter FR (Mirror Flop/Gear Play in RA), in seconds of arc.
208	{+-}0..65535	Modelling Parameter FD (Mirror Flop/Gear Play in Declination), in seconds of arc.
209	{+-}0..65535	Modelling Parameter CF (Counterweight & RA axis Flexure), in seconds of arc.
211	{+-}0..65535	Modelling Parameter TF (Tube Flexure), in seconds of arc.
220		Set Safety Limit to the actual (hour angle/east or west) position. The Get function delivers only a hash mark.
311	0..15(63)	Feature Port Status. 4 bits (0..15) can be used for setting input/output bits, 6 bits (two additional pure input bits, 0..63) are available for input.
411	256..65535	RA tracking rate divisor. The RA timer runs at 1.5 MHz, using this divisor the tracking rate can be adapted to the (mount dependent) speed of an object to be tracked.
412	{+-}0..65535	DEC tracking rate divisor. For DEC, no special timer is available, the divisor refers to the number of RA steps to be done for one step in DEC.
65535		Reboot the Gemini controller software.