And that idea isn't a fantasy anymore and it also isn't expensive -- assuming you have the GOTO mount & telescope. And the setup also isn't complicated. The list of ingredients is short and can be inexpensive
  1. GOTO-mount, often has a RS232 plug or comes with a RS232 adapter cable -- IMO those should be free of charge but some vendors don't use standard RS232 connectors and gauge customers to pay extra for that adapter cable
  2. You will need a USB-to-RS232 adapter unless you have kept some old PC with a built-in COM port alive. These aren't expensive
  3. PC/MAC software to send the commands to the telescope mount -- choose from freeware to $$$ bundles
  4. There are some WIFI doohickeys, often combined with proprietary cell-phone apps that also can control telescopes. If you like that, go ahead.
    My preference is a PC (or even MAC) based solution because I will do more than just send slew commands and because I want to see a bigger map than a 4" screen can offer

Here I'm not going to discuss option 1) -- if you have a mount, you may find this cable in the list of included accessories. Other times they will charge you extra. Latest generation of mounts have added USB plugs instead.

Selecting 2) isn't difficult either but there is one pitfall I have noticed : some RS232 adapters have screws, some have threads. Look at the cable you have and pick one that matches. Or pick a combination of cable + USB-adapter that matches.
Some users swear by cables with FTDI chipset -- I have used different cables & chipsets with success. Another "unavoidable" problem stems from the combination of USB, RS232 and sloppy implementation of drivers. As a result, if you use the same RS232-adapter but plug it into a different USB port of your PC or use a hub, the COM-port number keeps changing. This is very frustrating because you either have to look up the current COM-port number and enter it in the program or you have to go to the control panel and override that value -- I choose the last option.

And now on to 3) -- the software to control the telescope. There are a number of useful tools available for free to help you navigate the sky and they will track and show your telescope's position as well as give you the option to take control.

Option 4) is my least favorite because proprietary apps on cell phones aren't very helpful when you want to combine tools (running on a MAC or PC). Also WIFI isn't always available and prohibited at some starparties (interference, lack of bandwidth).

Many of you readers will know, I like STELLARIUM and you too may have used it. Stellarium has an excellent visual presentation of the (night) sky and has BASIC SUPPORT to control a telescope mount. Newer releases have eliminated some of the useful keyboard shortcuts and you can only connect to a telescope via COM-port -- Stellarium doesn't support ASCOM-standard
==> Stellarium is nice to monitor a telescope's position and for simple point & click commands but it lacks even simple features like move the telescope left/right or up/down. To me, lack of ASCOM support is a big obstacle because it means no other tool can communicate with the mount unless you close Stellarium

Another tool some of you may have received "for free" is Starry Night SE. It isn't really free but Orion bundles it with many items they sell and if you bought a mount or camera, you likely have a free copy. Or you know a friend who can spare a free copy. And since Starry Night isn't solely targeted to a viewing audience (like Stellarium), it has much better telescope related controls, including the 4-way key-pad. The map presented by Starry Night is good but it isn't as photorealistic and has fewer option than Stellarium. If you want to connect to the telescope, that isn't those aren't the most important features. Starry Night receives more frequent updates on comets & satellites. Good visual presentation of the sky map plus ASCOM connectivity and a usable emulation of the handcontroller interface are very positive. Not sure if I would spend $80...$250 on this, but the "free" SE-verion does a good job.

Everything you always wanted to know 'bout "Air Mass" (but were afraid to ask) A program with no photorealistic sky map is AstroPlanner -- and instead of focusing on amazing sky simulations, AstroPlanner provides tons of information, gathered & displayed in large tables full of numbers. This clearly caters to astronomers and not to casual stargazers. Once you get the hang of it, you see that AstroPlanner can be a very useful tool and has quite a number of unique features. It is SHAREWARE -- you can use it unlimited for free but get a nagging screen and one feature is disabled.-- IMO a fair way to try it. And buy it if you use it often. As the name indicates, the focus is on planning and logging your observation, including managing a list of different locations & equipment combinations, estimating the camera's plus off-axis guider's FOV. ASCOM mount-controls are included.

Speaking of programs with accurate but not photorealistic maps : Cartes du Ciel / Sky Chart is one of them and it too is FREEWARE. I must admit, so far, I have neglected using this one because with the four programs above, I have more than enough options. CDC is after AstroPlanner the only other tool to display the FOV of the imaging camera plus an off-axis camera / guider. That's useful when preparing to ensure there's a bright enough guide star nearby.

The following two programs offer more than simple telescope control : BackyardEOS & AstroPhotographyTool both are kind of "dashboards" to control a couple astronomy tools, including telescope movements -- GOTO & SLEW. Rudimentary map and only a limited list of targets (no updates for new comets etc ...). They aren't intended for visually tracking the scope & camera on a map -- instead they are the workhorses to do your imaging tasks. When combined with another ASCOM-compaible program (or GOTO hand-controller) that may be all you need. Lightweight and easy to use and with a surprising amount of features, these tools are the swiss-army-knife to get your imaging tasks done. Just like a swiss army knife, these tools need someone to give them directions -- for fully automated operations, you have to look elseewhere

If you want more automation, SGP (Sequence Generator Pro) may be for you. Your impression and expectations may vary. The biggest nuisance to me -- especially when compared to APT & BYE -- is the screen layout and multiple windows. On a small laptop with 1300x750 screen, SGP is not as practical to use as APT. That's not to say that SGP has features I don't like. Maybe If I bring along a higher resolution 15" screen, I'd be more happy with SGP. $100 for SGP and $40 for a mosaic tool don't make this a wallet-breaker but are steep compared to the $20 for APT.

The most Rock-Bottom solution to remote control a telescope via PC/MAC is not to use ANY PROGRAM at all and solely use the POTH ASCOM-driver as an extension of the telescope's hand-controller. There's no GOTO at all, but you have the 4-way directional controls and can adjust slew-speeds. It's not much but if you just want to remotely move the telescope mount, there you have it. The ASCOM-driver provides the current coordinates as a feedback


Above software is free or cost < $50 and personally, I favor a more "modular" approach even if I have to pay 4 x $50 instead of a $200 all-in-one package. Very rarely does an all-in-one fit my taste or is compatible & upgradable as I want it to be. If need be, I can upgrade one module instead of paying $$$ to update a big package

There are two big All-in-One packages & combining features can simplify some tasks
Maxim-DL dSLR (no planetarium SW) $399 or PRO $499 -- add more for plug-ins
The Sky : $329 + $199 (camera add-on) -- add more for plug-in options

Another argument are issues related to license keys -- these lower-cost software often have a more flexible licensing approach like install on multiple PCs as long as you use only one copy at a time. I haven't bought The Sky or Maxim DL, but expensive tools often lock licenses to just one computer. A new laptop may require a new license.


It won't surprise you, when I say the choice really depends on your intended usage
  • When it comes to combine visual sky maps with telescope control (preferably) via ASCOM) the "free" Starry Night SE does a good job. It doesn't win in terms of photo-realistic display and the satellite data also isn't up to date but otherwise you get a good sky-map and can slew & fine-control movements.
    It lacks accuracy (or timely updates) when it comes to updates satellites and the default landscape is annoying. AFAIK only the expensive version supports defining multiple custom locations :-(
  • I must say, I wish STELLARIUM would get their act together and put more effort into the telescope control. Removing keyboard shortcuts to move the mount wasn't a welcome change. With no ASCOM-support, there is no workaround to the lack of a (PC) hand-controller. OTOH, it is possible to easily add/download updated information (comets, satellites, ...), and those seem accurate and up-to-date.
  • ASTROPLANNER is growing on me with the useful details it provides -- e.g. simulate obstructions along the horizon. The latest version added ASCOM support. There still are suggestions, I will want to send to the developer. If you are "The man with a Plan", AstroPlanner is the tool for you. For fine-control of the mount, use the ASCOM "handset"
  • APT currently is my favorite tool -- it has a wealth of features to control the mount, the camera(s) and other telescope accessories. I called it a swiss army knife for good reason because it helps you with a hands-on approach.
    For fully automated tasks, APT lacks features like slew, sync, shoot, slew, sync, shoot -- for my mobile needs, this isn't a high priority. To slew to a target I use the handcontroller or another SW tool.
    APT wins against BackyardEOS because of the better support for ASCOM CCD-cameras (including debayer) plus support for motorized focusers & filters.
  • To me, Sequence Generator's most enticing feature is the Mosaic generator and the ability to first pause PHD, slew to a new position and confirm & correct it via plate solver, restart PHD, resume imaging once PHD has re-acquired lock -- I'm trying to get this to work. SGP also support Nikon SLRs -- that's another good argument.
  • Not an interactive tool but very helpul is a good PLATE SOLVER that works in conjunction with your image capture software. I've been using APT + Astro Tortilla for quite a while and am very happy with the results (speed & accuracy). (read /stargazer95050/636937 ) At the time, AT didn't support BYE. SGP can connect to AT (requires some work) or use Elbrus -- I haven't tested either but plan to do so.

Not part of the TELESCOPE CONTROL & SKY-MAP feature but also important is the ability to simulate the camera's or eye- piece's FOV, based on the camera/eye-piece + scope combination you've chosen. Plot the simulated image, based on the observation target. That helps to prepare & choose the suitable combo.
The three -- Starry Night, Stellarium & AstroPlanner -- all have featurs to support this.
Cartes du Ciel might fit in between Starry Night & AstroPlanner. AstroPlanner & CDS also have the ability to place an off-axis guider in addition to the imaging camera.


In the summary I said, I like APT because it combines all the useful functions onto one screen and makes imaging tasks easier. If you are getting started and want to try out your SLR for USB-tethered astronomy shots, there are ways to do that by using "non-astronomy" tools, you may already own. And these suggestions will also work with NIKON camera-bodies.
  • Canon users can pick the "Canon EOS Utility" that comes free on the CD
  • Nikon chargees you for a similar tool "Nikon Camera Control Pro 2"
    At you can find a free & open-source tool
  • several big photo-packages include support for tethered shooting -- you have to check if exposures > 30s are possible -- see Lightroom, PhaseOne, Aperture for details
  • any USB-tethering software can do the job but for astronomy shoots, check if you have complete camera control capabilities, including HDR, intervalometer, time lapse (combined with HDR) and also mirror lock-up or exposure-delay. Useful is the option to choose between on-camera storage and download to PC. Very useful to minimize latency but still see preview is the ability to download small JPG and keep the large RAW on the SD-card.
    Nikon & older Canon models exposure is limited to 30s -- unless you use an external shutter cable
  • dslrShutter is the most rudimentary solution -- but a solution that can break the 30s barrier and perform timelapses & HDR, if you program the sequence. The drawback is the need for an adapter to mimic the shuttr release cable -- see

You don't necessarily need to buy an astronomy-specific software but it is convenient to coordinate the various functions under one roof. Experiment with your current SW to see if you get good results. After that, investing $20...$50 may be worthwhile to add some unique functions, these regular "photography" tools lack.
  • Exposure delay / mirror lockup you might find, but the delay is short -- APT can define arbitrary intervals and I use 6s delay because the focal length is a lot longer and magnifications are higher
  • 30s is a "short exposure" for astrophotographers and therefore astronomy tools have implemented various ways to support longer exposures (it varies depending on camera model, some require a "shoestring" cable + adapter)
  • Accurate focus is critical but isn't easy to accomplish when you have no auto- focus lens and need 5...30s per exposure -- astro tools have functions to help you with that
  • some tools can be a stepping stone and you can continue to use it as you upgrade your camera equipment and that's why I pick tools with ASCOM-camera support.


May 2014 -- updated article, added Sequence Generator & non-astronomy tools
Dec 2013 -- 1st release

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