What is a robotic telescope?
People in the ATM (amateur telescope making) community sometimes talk about building “Robotic Telescopes”. They’re usually referring to a telescope which is permanently mounted in an observatory, and which can be operated by remote control – an important benefit on a cold winter’s night. But there is nothing new or surprising about the technology — professional telescopes at major observatories have been built this way for decades. The operator sits in front of a computer in a heated room, and directs the telescope through a custom interface. The view through the telescope appears on the monitor, and the data is stored automatically for later processing. The astronomer who has booked the telescope for the evening often doesn’t even need to be at the observatory, as the data will simply be waiting for him in his mailbox in the morning.
But what is required to do this on a smaller amateur scale? What technology lies behind these telescopes? Firstly, the telescope itself, comprising of an Optical Tube Assembly (OTA – the actual optics that do all the work) and its mounting. The mount is usually some sort of Alt-Azimuth design, partly because it is mechanically simple and intrinsically more stable and partly because the robotic nature of the system negates the advantages of the more complex equatorial mount.
Second comes sort of guiding and tracking system. This consists of a system of electric motors attached to the mount which can move the telescope to point at any required position, and a computerised control circuit. The computer knows the geographical location of the observatory, along with the date and time. When it is given a set of coordinates, it runs a series of calculations to determine what direction to point the telescope (and then drives the motors to move the telescope into position), and then continues to send tiny adjustments to compensate for the motion of the Earth.
The third component of a robotic telescope is the image capture system. The core of this system is usually a CCD camera (similar to the sensor in commercial digital cameras and webcams), but it is often supplemented with a mechanism to control focus, as well as a system to bring other accessories into the light path (Filters, spectroscopes, etc).
So how do you, as an amateur telescope maker, get so much advanced gear in place and working together? Only a few decades ago the answer was simply “You don’t”, but times have changed very rapidly since the early 90’s. The majority of new telescopes sold are so-called “Go-To” scopes, which have all the control and guidance mechanisms built in – they have a control panel which allows a novice operator to select from a list of planets or deep-sky objects, and the telescope points itself at that object. These telescopes usually have an external interface as well, allowing direct control through various software packages running on a laptop. Similarly, the field of amateur digital astro-photography has exploded in recent years. Cheap high-quality CCD cameras are widely available, to fit all standard size telescopes. These too connect to a laptop, and are capable of producing the sort of breathtaking images that used to be the sole preserve of powerful professional observatories.
So a typical amateur robotic telescope setup is actually quite simple to build: Put a good telescope on a goto mount, and attach a CCD camera. Connect both the camera and the mount to a computer, and write software to provide a common interface to them both. Many astronomers take the final step of extending the cables so that the telescope sits in its observatory at the bottom of the garden, while the computer is in the main house, warm and well lit. It lacks the charm of a traditional manual rig, and you lose the wonder of seeing the universe through your one eye pressed to an eyepiece, but the robotic rig makes viewing so comfortable that it guarantees significantly more use. It’s up to the individual to decide which they prefer.
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