Sky Engineering Sky Commander XP4 Flash Computer Module

Sky Engineering Sky Commander XP4 Flash Computer Module
  • The Sky Commander XP4 computer can be added to a wide variety of telescopes (both alt-az, like Dobsonians, and equatorial).
  • Once the Sky Commander XP4 is connected and put through a simple alignment procedure, your telescope will be able to "find" up to 30,000 stored objects.
  • The Flash memory of the XP4 allows you to upgrade via your PC and download a large number of astronomical catalogs, such as Messier, NGC, IC, Double Stars, Bayer Stars, Arp Galaxies, and a whole lot more.
  • The Sky Commander XP4 has easy to use six-button control and a large 32 character LCD screen. A RS232 port allows you to plug your PC in and interface with planetarium programs like TheSky, Starry Night & more.
  • Slew your telescope around and objects that match your scope's position are displayed!
  • The Sky Commander XP4 comes with a flash cable & manual. Dobsonians require an encoder kit & cable, and other scopes (which have encoders built in) will require an encoder cable connector.


The Sky Commander XP4 Flash was designed especially for those amateurs who would like to be able to locate and observe celestial objects fast and easily. With the aid of the Sky Commander XP4 more time can be spent at the eyepiece and less time at the finder scope and sky atlas. Objects are located by entering their catalog number using push buttons. A liquid crystal display shows you the scope's position and lets you 'zero in' to objects. With a little practice you can locate even hard to find objects in seconds.

The Sky Commander XP4 is based on the original Sky Commander DSC (digital setting circles) design but with the following important hardware upgrades:

  • 4 times the internal memory space – 512kB vs 128kB, allowing room for many more objects to be stored, up to approximately 30,000.

  • Memory is Flash type – this means it is re-programmable in the unit. No need to physically replace an OTP (One Time Programmable) EPROM in order to upgrade. Flash memory has virtually unlimited reprogramming cycles.

  • Encoder ‘Fast-Tracking’ – This is the first important upgrade supported in version 4.2. It allows use of very high resolution encoders, up to 24576 count without the problem of loosing encoder counts if the scope is moved quickly. It is also useful on very small scopes that can move quickly. This feature operates only while external 12 volt power is applied because it uses more power than an internal 9 volt battery can supply.

  • New custom ABS plastic enclosure with externally accessible battery compartment for easy battery replacement.

  • With the downloadable XP4 Boot-Flash Utility you will be able to upgrade to the most recent version. With this version (starting at 5.01) you will be able to select from a number of astronomical catalogs:

    • Abell Planetary Neb* - An 82 object list of old and ancient plantetary nebulae researched by a well known astronomer, George Abell. As these planetaries are ancient, they provide a nice challenge as most are extended and of low surface brightness.

    • Arp Galaxies - A list of 338 galaxies showing different aspects of peculiarity studied by Halton Arp.

    • Bayer Stars - About 1500 stars cataloged by Greek letter and constellation.

    • Double Stars - A collection of 600 fine double stars provided with permision from the Saguaro Astonomy Club.

    • Hickson* - A list of small compact galaxy groups, which presents a challenge for the observer. This list of 100 groups was compiled by a Canadian professional astronomer, Paul Hickson, for research on discordant redshifts.

    • Messier - The famous catalog of Charles Messier. 110 bright deep sky objects.

    • Named Deep Sky - 135 deep sky objects by common name.

    • Named Stars - 142 stars by common name.

    • NGC - Entire NGC catalog, about 7800 deep sky objects.

    • IC - Index Catalog of 5250 deep sky objects.

    • Barnard - 159 Dark Nebula

    • Berkley - 86 Open Clusters

    • Collinder - 71 Open Clusters

    • Trumpler - 34 Open Clusters

More Information on the Sky Commander...

Many of the basic operating principals and features of the original Sky Commander are carried forward in the new XP4 design, including:

  • Six Button Control – the ENTER, MENU, UP, DOWN, LEFT and RIGHT buttons are used to control the unit. You will quickly master the operation by understanding a few basic principals.

  • Large LCD - 32 character (16 x 2 line) Liquid Crystal Display with adjustable intensity yellow-green backlight. The backlight is soft on the eyes and not detrimental to night vision.

  • RS232 - Serial (RS232) port to connect the Sky Commander to your Personal Computer. Display telescope position on the PCs screen. Many astronomy programs interface to the Sky Commander – The Sky, Megastar, Guide 7.0, Sky Map Pro, Deep Sky Planner, and more.

  • Search & Identify mode – As you pan the scope, any database object that matches the scopes position is displayed immediately. Search is ‘filtered’ by an adjustable magnitude limit.

  • Browse by Constellation – Select a constellation and ‘browse’ the database. Adjustable magnitude limit.

  • User List – Select objects from the internal database and add them to a ‘favorites’ list for easy access at a later time.

  • Special List – Add coordinates of any object to a ‘special’ list. This can be done ‘on the fly’ through the keypad or through the RS232 interface.

  • Realign to Object – Improve pointing accuracy, especially in the vicinity of the object that you realign to.

  • Ultra Low Power – Get about 40 hours of operation from a single 9 volt battery. Battery current is a mere 6mA.

  • Standby Mode – Extend battery life and extinguish backlight with a simple ‘double-click’ on the MENU button. Return to normal operation by pressing any button.

  • Battery Monitor – Bar graph indicates relative battery life.

  • External Power – Standard 2.1 mm power jack for use with 12 volt battery or power supply.

  • Display Heater – In cold weather the LCD (Liquid Crystal Display) will be come slow. An internal heater will turn on under thermostat control. This feature requires the use of external 12 volt DC.

  • Equatorial Table Support – Use the Sky Commander with an equatorial table. No need to re-do the two star alignment after resetting the table.

Sky Commander Frequently Asked Questions...

  • What is the Sky Commander?

    The Sky Commander is a small self contained computer designed for the specific purpose of locating and identifying celestial objects with a telescope.

  • How Does it Work?

    The computer ‘reads’ the position of the telescope with the use of two optical encoder modules. The encoders are attached mechanically to the telescope axes in such a way that the encoder shaft turns as the telescope is turned. At the beginning of an observing session, the user initializes the computer by pointing the telescope at two different stars. By sensing the change in position between the two stars, the computer is able to fix on the orientation of the both telescope and sky.

  • How do I point the telescope to an object?

    A six button keypad and LCD display from the easy operator interface. First you select a catalog, e.g. Messier, NGC or Planet. Then you enter the catalog number (four digits). Arrow buttons are used for this purpose. Pressing the ENTER button makes the object ‘current’. The user moves the telescope while watching the LCD. As the scope moves closer to the target object, the display digits roll down to zero in AZ and EL. Arrows are displayed to indicate direction.

  • What does the display show me?

    The Liquid Crystal Display (LCD for short) shows you the position of the telescope in RA and declination, or the relative position of the scope to the target object (‘zero in’ display). It also shows you the current catalog and object number (used for object selection) and some information such as object type, magnitude, and constellation.

  • How do I get it set up on my telescope?

    The Sky Commander works on both Alt-Azimuth (e.g. Dobsonian) and equatorial type scopes. You will need a general purpose encoder mounting kit for Dobsonian type scopes. Since it is a general purpose kit, some modifications may be required to make it work depending on what scope you have. Dobsonian type scopes are by far the easiest to fit encoders because there is generally plenty of room to work with. For other type scopes, the Sky Commander will work with most commercially available encoder setups. A standard encoder cable connector (modular RJ45 also used for computer network cables) is used.

  • What’s the deal with encoder resolutions?

    Angular resolution of the system is determined by the encoders themselves. The Sky Commander can handle a wide range of resolutions. Typical encoders are 4000 step per revolution, but other resolutions are also used, (2160, 4096, 8192, etc). The important thing is that you enter the encoder information into the Sky Commander so it knows how many counts per degree of scope rotation. This information only needs to be entered one time, but can be changed whenever needed.

  • Do higher resolution encoders mean higher accuracy?

    Possibly, but be aware that the encoders themselves have an inherent ‘runout’ error which may exceed the step size, especially for the higher resolution units.

  • What is the RS232 connector for?

    RS232 is a standard for serial communications between computers. In the Sky Commander it is used to tell a PC the position of the telescope so it can be displayed on the screen. In this way the user can tap into the huge resources provided by many Astronomy programs. On the XP4 RS232 is used as a ‘Flash Port’ when updating the software or internal database.

  • How is the Sky Commander powered?

    The Sky Commander is powered from an internal 9 volt battery which will last a very long time (about 40 hours) under normal use. There is also an optional 2.1mm (5.5mm OD) power jack for connection to 12 volt DC.

  • What do I need to buy? – If your scope already has optical encoders installed with a standard encoder cable, you need just the Sky Commander XP4 itself, CMP-XP-4000. If you have a Dobsonian scope you will need to attach stepper encoders to your scope beforehand, and you will need an encoder cable.

Sky Commander XP4 Specifications...

  • Operating Voltage (internal 9v battery): 5.5v min to 10v max

  • Operating Voltage (external 12vdc supply): Regulated 11 to 13.8 volts @ 300mA min

  • Internal Battery Life: 40 hours based on 6.5mA typical current

  • Operating Temperature with external 12v supply: -10 to +30C

  • Operating Temperature with internal 9v battery: +5 to +30C

  • Display Type: 32 Character Dot Matrix LCD w/yellow-green backlight

  • Encoder Resolution: Programmable, 4000 typical, 24576 max with external 12 volts

  • Encoder Speed (internal battery): 1500 counts/sec min

  • Encoder Speed (external 12 volts): 8000 counts/sec min

  • Displayed Resolution: .1 degree Azimuth and Elevation

  • Serial Port: Programmable 9600bps max, 8 data bits

  • Dimensions: 4.2" X 3.0" X 1.7"

  • Weight: 8oz. with battery

Additional Information

Additional Information

Manufacturer Sky Engineering
Warranty 1 Year Warranty

Customer Reviews 1 item(s)

This is one amazing pointing computer
1= Houston, We Have a Problem & 5= It's Out of This World
Review by John Downs / (Posted on 11/2/2009)
Included Items

Included Items

  • Sky Commander XP4 Computer Module
  • Flash Cable
  • Instruction Manual
  • One Year Limited Warranty
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