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Title: Remote Telescope Operation

Purpose: To be able to fully control my telescope remotely from inside

Status: Complete and operational!

Imagine it is a cold winter night and you are outside with your scope...wistfully looking at the warmth of the fire inside...wishing there was a way to control things from in there. Or it is a hot, humid, summer day and you are sweltering outside with your solar scope...wishing there was a way to get in to the air conditioning, yet still see get some shots of the sun.

The purpose of this project was to allow for the remote operation of my telescope, including the mount (slew, etc.), telescope focus, and imaging. Although the write-up will be specific for my particular hardware and software, the concept is easily reapplicable.

Early Failures
I promised to share successes and failures in my journey, so I will start off this Project with two early failures.

Attempt #1: Wireless Control
Controlling all of your telescope equipment via computer is pretty easy (see details for my system later in this report). The hard part of remote operation is controlling things across the distance from the inside to the outside. My initial research on this led to wireless technology as a popular candidate. The concept is as follows:

  • Stick a computer (usually a laptop) outside near the telescope
  • Wire all of your control equipment to that laptop, usually via the USB port(s)
  • Connect your outdoor laptop to your home network via a wireless router
  • Use a computer inside to connect to and manipulate the computer outside via your network and software such a Remote Desktop or VNC ("virtual network computer")

My first attempt at remote telescope control used this exact concept, with a fast wireless router and RealVNC software to communicate between the inside and outside PC's. This approach does work, but I had two significant problems:

  1. The outdoor PC was subject to the elements; in the summer taking solar images it got very hot (even after buying a small umbrella to shade it), and in the winter I got frost on the screen and keyboard. To be robust, I really needed to build some sort of enclosure to protect the outdoor PC.
  2. Despite having a high speed router, the communication speed across wireless/VNC just was not satisfactory. It worked fine for stationary viewing, but trying to manipulate mount slewing and watching images like the sun (which moves slightly all the time due to atmospheric disturbance) was painfully slow.

Attempt #2: Wired Control
My second attempt was pretty much the exact same as above, except I bought a 100' category 6 ethernet network cable ($11 from Amazon) and used it (instead of wireless) to directly connect the outside PC to the inside router.

This did significantly increase the speed of communication between my PC's, but I still detected some lag when viewing images (again like the sun) that are constantly moving. More importantly, this solution did not resolve issue #1 above, in that the outdoor PC was baking during the summer days and freezing during winter nights.

Final Solution: USB Extender Cable
USBcableNormal USB cables are limited in length; typically about 10-15', which is far short of what would be needed for a remote telescope application. However, there are now reliable "repeater" USB cables which conform to USB 2.0 standards and vastly extend the possible cable length. Shown here, I purchased a 64' USB 2.0 extension/repeater cable from Amazon for about $35 (at the time of this writing).

Rather than providing a direct link (since items on Amazon no doubt move around over time), here is the exact description of the cable, which can be copy/pasted into a search engine to find it: "PTC - 20 Meters (64 Feet) USB 2.0 Active Extension / Repeater Cable A Male to A Female - Supports High Speed USB2.0 480 Mbps".

USBhubBecause some of the the telescope control devices draw power from their USB connections, and given the length of this cable, I also bought via Amazon a powered 7-port USB 2.0 hub to be placed at the end of this cable, outside near the telescope. By providing power to the hub itself, the telescope control devices can draw the power they need from the hub rather than trying to pull it across the 64' length of USB cable from the indoor computer.

In my testing so far, this connection solution works perfectly, and it has the following huge advantages:

  1. Only 1 PC is required, and it sits inside protected from the elements.
  2. The connection speed across the USB is lightning fast. I have detected no difference in speed between having the PC sitting right next to the telescope (short USB cable) vs. sitting inside with the 64' USB cable. Even the download speeds of RAW digital images are fast and reliable.

Remote Operation - Overview
With the trickiest part of the system now resolved, the system for remote telescope operation can be described as follows:

  • Install a computer inside with the control software necessary for the telescope and accessories.
  • Run a long USB cable from that computer to the telescope outside.
  • Connect the USB cable to a powered USB hub, to both distribute the USB connection and provide power to the devices outside at the telescope.
  • Connect the various telescope control equipment to the USB hub. In my system this includes:
    a. Interface with the mount for directional control and feedback to/from the computer
    b. A "game pad" for manually moving the mount while outside near the telescope
    c. A focus controller connected to a motor which can focus the telescope remotely
    d. An imaging device, such as a USB connection to a DSLR or astro "webcam" imager

The following schematic depicts this system, and each element is described in more detail below:

(click on the schematic to

The following are brief descriptions with links where appropriate for the elements numbered in the diagram above:

Bullet1 Computer (inside):

The computer used for controlling the system does not need to be particularly powerful; my rig uses an HP Pavilion portable PC which is several years old and still running on Windows Vista. A few key criteria, though are:

  • Windows-based will probably have less software incompatibilites than Mac-based
  • Must have a high speed USB 2.0 port
  • Sufficient HD space to install the needed software (planetarium, imaging, editing, etc.) and have plenty of space for storing images (which in RAW mode can get quite large) or avi (also can get quite large) files.

The core software packages I am using in my system are:

  • MaxIm DL (Diffraction Limited)
  • Canon EOS Utility (for capturing images remotely when using the Canon T2i)
  • IC Capture.AS (Imaging Source capture software for their imager)
  • Adobe Photoshop Elements (for manipulating images)
  • Registax (for manipulating .avi's and stacking them into pictures)

Bullet2 64' USB Active Extension/Repeater Cable

This is described in detail earlier in this report. This actually was the most critical component for making my remote system work properly, with high speed and a single computer (inside)!

Bullet3 Powered USB Hub

This also is described in detail earlier in this report. I am not 100% sure that a powered hub is necessary, but with 4-5 USB devices all connected to a single (long) USB cable coming from inside, I am fairly sure that power for those devices at the telescope would be an issue without the hub itself providing some power. Besides, the cost difference for powered vs. not is trivial, so the choice was easy.

Bullet4 USB-Serial Adapter

Most laptop these days do not have a serial port on them any more, as the technology has migrated to USB. However, many telescope control adapters (including mine) require a serial port. The solution, of course, is a USB-serial adapter. Not all adapters are created equal...I went through two of them before finding one that works well with my computer (and operating system). I use a TRENDnet TU-S9 (here is their main website; search on the model), and it has been very successful for me.

Every time you move this adapter to a different USB port, your operating system will assign it a different COM-port number. This can get very frustrating when you try to launch your mount control software, because you have to constantly reconfigure it for the correct COM-port number.

Always plug the 64' USB cable from outside into the same USB port on your PC, and always plug this USB-serial adapter into the same USB port on your multi-port HUB outside. In my experience, when I am consistent about these port connections, my operating system always assigns it the same COM-port number, so my mount control software can easily find the mount every time without having adjust the port configuration.

Bullet5 EQDIRECT adapter for GoTo mount interface

Having solved the problem of communication from the PC inside to the equipment outside via USB, the next most critical step was the actual remote control of the mount itself. Many mounts come with PC interfaces, often via ASCOM ("Astonomy Common Object Model") software/drivers. The ASCOM website has a wealth of valuable information, including the current platform download, drivers for many mounts/devices, and links to key support websites.

My particular mount (Orion Skyview Pro with GoTo) happens to be compatible with EQMOD, which is an ASCOM compatible software package that provides outstanding mount control via the PC (including the remote gamepad interface, listed in #7 below). On the EQMOD website, you can find the list of compatible mounts, download links for the software, and a lot of outstanding "How To" documentation. This should be your #1 stop if you want to learn more about software control of your mount; they even have handy tutorials for how to set up and align your mount to begin with!

My mount has a SynScan hand control which does allow for Direct PC control. However, the EQMOD team recommends replacing the SynScan hand controller with an adapter to directly connect your PC to the mount (and bypass any "interpretation" the SynScan hand controller might do). The EQMOD website has instructions for how to build one, but the easy solution is to buy it from one of the vendors named. For my system, I bought an EQDIRECT adapter (pictured in the system schematic above) from Shoestring Astronomy (part # EQDIR at the time of this writing).

In summary, my PC-mount interface is as follows:

  1. EQMOD/EQASCOM mount control software running on my PC inside
  2. USB cable to the powered USB hub outside near the mount
  3. USB cable to an EQDIRECT adapter, which is plugged into the hand controller port on my mount

So far my system works well, though I will admit I occasionally lose connection between the PC and the mount. I just have no way to know if this is caused by the mount, the EQDIRECT adapter, the USB hub, the long USB cable, or the PC software. It happens rarely enough for me to just deal with it when it happens.

Bullet6 GoTo Mount

Obviously, in order to control your mount remotely, you must have a "motorized" mount, and these typically are the "GoTo" mounts widely available. As shown in my Equipment page, I have an Orion SkyView Pro mount with GoTo (which is an optional set of motors to control the mount's RA and Declination knobs), which uses the SynScan hand controller and is compatible with EQMOD as described in #5 above.

Other popular mounts which should work just as well in this type of remote application are the GoTo's made by Celestron, such as the CG-5 or CGEM mounts.

Bullet7 Gamepad for remote mount movement

One inconvenience which crops up fairly often in a remote system is the ability to move or nudge the mount/telescope when you are standing outside with it. Perhaps you need to center an object a bit more exactly or just want to do some visual observations before connecting your remote imager. The problem is...the control system for the mount is now connected to the computer....which is inside!

Some mount control software (including EQMOD, which I use) allows you to connect a gamepad to your computer and move the mount with it. But the computer doesn't care whether you plug the gamepad into a USB port inside or via the USB hub outside. So the trick is: Plug your gamepad into the USB multi-port hub outside, and you instantly have a mechanism to slew your mount when you are outside with it (and you can slew it with the on-screen controls when you are inside with your computer)!

There are plenty of choices for USB gamepads. I happen to use a Logitech Dual Action USB gamepad, which works very well in my system.

Bullet8 Remote Focuser

A remote focuser is not strictly necessary, but it is a handy addition. You can point the telescope at any bright star early in a viewing session, focus it manually at the telescope, and then leave it alone while you then operate everything from inside. That said, as the temperature changes, the focus may shift, and some astronomers report that they have some focus drift when they slew to new locations (I have not had this issue, but I am sure it's possible). In those cases, having a remote focuser that allows you to adjust the focus from inside right before imaging is handy.

There are a number of options for this, depending on your telescope focuser and how much you want to spend. I went with a fairly low cost option: Orion AccuFocus Electronic Telescope Focuser (search the Orion site for that name). Note that depending on which telescope/focuser you have, you may need to do some "adapting" to get this motor to fit. Neither of my Orion telescopes was listed as compatible, but I got them both to work with a bit of handiwork on my workbench.

The only problem with this device is that it comes with a local hand controller, not an interface for your PC. To solve this problem, Shoestring Astronomy makes a handy USB interface and software to control this focuser from your PC. Search for the product "USB Focus Motor Controller" on their site (part # FCUSB at the time of this writing). The total for the controller and the Orion focuser is in the range of $160 at this time.

As an alternative, JMI Telescopes makes a whole line of focus motors and remote controllers. At the time of this writing, buying a focus motor and remote controller via this route is about 2x the cost vs. above. They do have, however, compatibility listed for many more commonly used telescopes/focusers. You may be able to offset some of the high cost delta by adapting the Shoestring Focus Motor Controller (listed above) to work with a JMI motor. The Shoestring website indicates they are compatible with JMI motors, and they are charging 1/2 for what appears to be the exact same controller...worth a look!

Bullet9 Imagers

You can plug any USB imager you want into your USB multi-port hub outside, and you are ready to go. See my Equipment page for the imagers I use in my system.

Note: Even with very large RAW files, I have not detected any issue or loss of data when capturing images and transferring them through the USB multi-port hub, then across the 64' USB cable to reach my computer inside. And the imagers that produce .avi movies run at full speed (my Imaging Source normally runs at 30 fps and can get up to 60 fps in some cases) without issue.