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Typical Configuration



Initialization Sequence

Starting Up

When the SHC is powered up an "OnStep w/Teen Astro" splash screen will appear for a few seconds then it'll tell you it's trying to connect.  At this point the SHC presents a signal to OnStep on it's ST4 port to indicate that a SHC is present.  After a couple of seconds OnStep reconfigures the ST4 port lines for synchronous serial comms and the SHC will start displaying the RA, Dec, and status information.

Button Functions

North when tracking or Scroll Up while in Menu's

East when tracking or Back while in Menu's

Short Press = Scroll Information screen, Long Press =  Main Menu, Double Click =  Feature Menu

West when tracking or select current option while in Menu's

South when tracking or Scroll Down while in Menu's

 Decrease currently selected Feature

 Increase currently selected Feature


Note: The Center button [ + ] on recent models is now a 5-way switch that, in addition to a normal switch

function, duplicates the [ N ], [ E ], [ S ], & [ W ] button actions.


Key functions:

  • When at the main info display page, pressing [N],[S],[E],[W] guides in that direction at the rate selected (see below).
  • When at the main info display page, a click on [+] cycles through the display of RA/Dec, Alt/Az, Time, and (optionally) ambient conditions.
    • When doing an align, a click of the [+] key instead accepts the align star once you've centered it using [N],[S],[E],[W]
  • When at the main info display page, a double click on [+] brings up the Feature key selection menu where you can scroll to among guide rate, reticle light, utility light, focuser, or rotator for the [f] and [F] key action. Pressing the [W] key at this point makes the selected menu item the Active Feature.
    • Pressing the [f] (decrease) or [F] (increase) keys then adjusts the selected feature
    • When doing an align, a double click of the [+] key instead allows selecting a different align star (after the goto to the prior align star completes).  Also, during an align, the [f] and [F] keys work only for guide rate selection.
  • A long press on [+] brings up the menus
    • The [N],[S] keys then move up/down the menu selections.
    • The [W] key selects a menu item.
    • The [E] key navigates back to the prior level.


Alignment Star #1

Alignment Star #2 (#3 thru #8 not shown)

Alignment Star #9 (last possible)

Telescope is at home position. Tracking is OFF

Unknown error. Tracking has stopped

Telescope position exceeds user defined Meridian limit. Tracking has stopped

Telescope position exceeds user defined RA limits "Under Pole". Tracking has stopped

Telescope position exceeds user defined Azimuth limits. Tracking has stopped

Telescope position exceeds user defined Declination limit. Tracking has stopped

Telescope limit sensed. Tracking has stopped

Telescope position exceeds user defined Horizon or Overhead limit. Tracking has stopped

Motor fault. Tracking has stopped

East side of pier. Declination is between 90 and -90

West side of pier. Declination is between 180 and 90 or -90 and -180

PEC, paused

PEC, recording

PEC, playing

Telescope is slewing

Lunar Tracking rate is selected

Solar Tracking rate is selected

King Tracking rate is selected

Sidereal Tracking rate is selected

Sidereal Tracking, refraction compensated (RA-axis only)

Sidereal Tracking, refraction compensated (Dual-axis)

Sidereal Tracking, refraction and pointing model compensated (Full)

Sidereal Tracking, refraction and pointing model compensated (Full, Dual-axis)

Tracking is OFF

Telescope is guiding

Park failure

Telescope is slewing to park position

Telescope is parked

Menu structure 3.x

The following is a map of the menu structure of the SHC as of version 3.x.

  • Words that are in a normal font appear on the screen exactly that way (in the English-localized configuration).
  • Anything in square brackets provides information that does not appear on the screen and is an interpretation of what the function means.
  • The indentation level is intended to reflect the submenu nesting.

Main Menu [center button long press]


[Due to a memory size constraint the Teensy 3.2 based SHC has compact versions (lower coordinate precision) and subsets for all catalogs]


Bright Stars [408 stars brighter than 4th magnitude]

STF** [Struve The Father (Friedrich) double stars]

STT** [the other Struve (Otto) double stars]

GCVS~* [General Catalog of Variable Stars]

Deep Sky

Messier, Caldwell, Herschel400, Collinder, NGC, IC

Solar System

Sun, Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, Moon


[Select from up to 16 user catalogs uploaded through SmartWebServer or Sky Planetarium interface]


[Define filters for catalog objects displayed on 'Stars' and 'Deep Sky' menus. If the selection as displayed is prefixed and suffixed by a small dot it means a filter has been set for that property. Initially, the 'Above Horizon' property is the only one set]

Above Horizon


[A list of the standard 88 IAU constellation names]


All, Galaxy, Open Cluster, Star, Double Star, Other, Galaxy Pair, Galaxy Triplet, Galaxy Group, Globular Cluster, Planetary Nbla, Nebula, Hii Region, Cluster+Nebula, Asterism, Reflectn Nbla, SuperNov Rmnt, Emission Nbla, Non Existant, Nova, Duplicate, Dark Nebula


[for selections other than All, the magnitude is followed by an estimate of the minimum telescope aperture required to see the object]

All, 10th, 12th, 13th, 14th, 15th, 16th, 17th


[angular distance from current position, does not mean distance from Earth]

OFF/Within 1, Within 5, Within 10, Within 15 [degrees]

Var* Max Per.

[maximum period for variable star filter]

Off, <=0.5, <=1.0, <=2.0, <=5, <=10, <=20, <=50, <=100 [days]

Dbl* Min Sep.

[minimum separation for double star filter]

Off, >=0.2",>= 0.5", >=1.0", >=1.5", >=2.0", >=3.0", >=5.0", >=10", >=20", >=50" [arc-seconds]

Dbl* Max Sep.

[maximum separation for double star filter]

Off, <=0.5", <=1.0", <=1.5", <=2.0", <=3.0", <=5.0", <=10", <=20", <=50", <=100" [arc-seconds]


[You can enter arbitrary RA/Dec coordinates here (e.g. comet or asteroid coordinates obtained from sources like a planetarium program)]

Spiral Search

[New as of version 3.02a. Initiates a spiral search at the current guide rate around the current position. Press any button to stop.]


[Will prompt for confirmation of model clearance. Use N/S to toggle Yes and No (Yes clears the model and returns to the home position, No aborts the Goto Home command). If you do not want to lose the model because the telescope will not be moved since the last alignment you should use the 'Park' function.]


['Stars', 'Deep Sky' and 'Solar System' will sync the telescope to the coordinates of the object selected without moving the telescope. You are expected to have centered the object already]


[Same selections as Goto, Stars]

Deep Sky

[Same selection as Goto, Deep Sky]

Solar System

[Same selection as Goto, Solar System]


[syncs to the last Goto coordinates]


1..n-Star Align

[e.g. '1-Star Align', '2-Star Align', '3-Star Align', etc. 'n' is at least 3 for all processors, faster processors allow more alignment points]

Resume Align

[when an alignment is already in progress, the '1..n-Star Align' selections are replaced with a 'Resume Align' selection]

Show Model

[shows pointing model coefficients derived from the alignment points]

Clear Model

[clears the model]

Reset Home

[sets OnStep position to home after physical telescope movement to home]

Refine PA

[for equatorial mounts, guides through adjustment of mount's polar alignment controls using star offsets]



[move telescope to park position (default is home position) and save the alignment model in preparation for power down]


[when powered up at park position following use of Park command in previous session, restores the alignment model and starts tracking]


[used to define a custom park position at the current axis locations]


Start / Stop

[The following 3 selections set the tracking rate to the standard for stellar objects, the sun or the moon]




[The following five 'Comp' selections are not available for Alt/Az mounts]

Comp Full

[compensate for atmospheric refraction and polar alignment inaccuracies]

Comp Refr

[compensate for atmospheric refraction only]

Comp Off

[turn off all compensation]

Comp Sngl Ax

[apply selected compensation only to R.A. axis]

Comp Dual Ax

[apply compensation to both R.A. and Dec axis]

Rate Reset

[Reset tracking rate to a standard rate]

[use the following to adjust tiny tracking rate errors due to gearing parameter inaccuracies]

Rate +0.02Hz

Rate -0.02Hz


[This option is only displayed if PEC is enabled in the controller]


[Start applying PEC previously recorded]


[Stop applying PEC]


[Delete the PEC recording]


[Record a new PEC buffer or average in an additional cycle]

Write to NV

[Save to non-volatile memory. PEC is not permanent until saved using this function]



[Set local date and time. Questions are asked about whether the time was AM or PM (if the SHC was configured with DISPLAY_24HR_TIME OFF) and whether the time was a DST-adjusted time]


Select Site

[Select one of 4 user-defined sites. If the controller gets site data from a GPS, when received it is always stored in 'Site 1' with the name of 'GPS']



UTC Offset

[this is the inverse of your timezone offset, e.g. +5 for North American Eastern which is defined as -5 as a time zone. Do not adjust this for Daylight/summer time... the stars don't care about that]


Turn off

[Press any key to turn on. That first key press is ignored so there's no worry it will cause a telescope motion]

Contrast [also known as brightness]

Min, Low, High, MAX

Dim Timeout

[dims display after key inactivity interval]

Disable, 30 or 60 seconds

Blank Timeout

[blanks display after key inactivity interval. On the wireless SHC it is advisable to use '1 minute' so that the unit spends the maximum amount of time in low-power mode.]

Disable, 1, 2, 3, 4 or 5 minutes

Buzzer [On or Off]

Meridian Flip

[This menu is only available for GEM mounts]


[If a meridian flip is possible at the current coordinates, do it now]


[Should OnStep do meridian flips automatically when hitting the meridian limit when tracking from east to west?]

Pause at home

[When meridian flips go via the home position, should OnStep pause the telescope at the home position to allow the user to verify that no cabling is about to snag? If off, an error will be thrown and tracking stopped when the Meridian West Limit is reached. Requires a button press to continue]


Goto Speed
[Sets the Goto speed to 2x, 1.5x, 1x, .75x or .5x of the configured SLEW_RATE_BASE_DESIRED, respectively]

Fastest, Faster, Default Speed, Slower, Slowest


[sets gear backlash for axis 1 and 2]

Axis1 RA/Az, Axis2 Dec/Alt


Horizon Limit

[Sets number of degrees telescope is allowed to point below the horizon while tracking or slewing]

Overhead Limit

[Sets number of degrees above the horizon that the telescope is allowed to point while tracking or slewing. This is important for Alt/Az telescopes especially because of the 'Dobson hole'. For others it prevents crashing the bottom of an OTA into a pier or tripod.]

Meridn Limit E/Meridn Limit W

[For GEM or FORK mounts, sets how close the telescope is allowed to track to the meridian before a meridian flip is required (tracking stops if meridian flip is not automatic)]

Pier Side

[Sets the 'preferred pier side']

Best, East, West

Firmware Ver

[displays SHC and OnStep firmware version/dates of compilation]


[This menu is displayed only if a camera rotator is configured]

Return Home

[returns the rotator to the zero-degree (middle) position]

At Home

[use to synchronize OnStep's 'at zero-degrees of rotation' with physical reality]


[For Alt/Az mounts only, turns on or off the function that runs the rotator at the appropriate speed to compensate for field rotation]

Move to PA

[For Alt/Az mount only, move the rotator to the parallactic angle - the equatorial coordinate angle associated with the current area of sky]


[For Alt/Az mounts only, reverses the direction of rotation of the de-rotator]

Focuser1 [the '1' does not appear if there is only one focuser]


[For each focuser that is configured a numbered selection is available to set parameters for that focuser]

Return home

[returns the focuser to the home, 'half-travel', position]

At Home

[use to synchronize OnStep's 'At half-travel' status with physical reality]


[compensate for geartrain backlash, if any]

Temp Comp?

[Turn on or off temperature compensation. Controller must have either ambient temperature sensor (e.g. BME280) or TELESCOPE_TEMPERATURE sensor present]

T.C. Coef.

[The temperature compensation coefficient i.e. how many microns (plus or minus) per degree Celcius of temperature change]

T.C. Deadband

[How many microns must the temperature compensation algorithm want to change the focuser position before an adjustment is actually done? This is used to reduce the probability of an exposure being ruined by too many focus changes]


[New as of version 3.02b. A list of the DEW_HEATER and INTERVALOMETER auxiliary features as defined in the controller's Config.h. For DEW_HEATER type features, a submenu allows adjustment of the 'Zero' and 'Span' parameters. For an INTERVALOMETER type features, a submenu allows adjustment of the 'Exp Count', 'Exp Delay' and 'Exp Length' parameters.]

Feature Key menu

[Center button double tap. Select desired Feature [ N ] [ S ] to scroll, [ W ] to accept then press f or F button to alter selected feature. Depending on configurations not all of these selections may be present]

Guide Rate

[Select guide rate between 2x and Max slew speed]

Pulse Guide Rate

[Select pulse guide rate between 1/4x and 1x]

Utility Light

[Off or one of 5 levels]


[Increase or decrease brightness]


[Run rotator CW or CCW]

Focuser1 [the '1' does not appear if there is only one focuser]

[Run selected focuser in or out. Starts at low speed, switches to high speed if held >= 5 seconds]


[New as of version 3.02a. A list of the named auxiliary features as defined in the controller's Config.h. After selecting the feature, if the feature is an ANALOG_OUTPUT type, the 'f' and 'F' buttons adjust the value down or up by 5%, otherwise the 'f' or 'F' buttons turn the feature off or on.]