Celestron Nexstar 102 SLT Computerised Telescope

I've wanted a telescope for the past decade, and I recently decided that it was now time to splash out and buy one so that my children (oldest is 6 years) could explore the Moon and planets with me. When it comes to astronomy and telescopes I am a complete novice and so I did a lot of research before settling upon the Celestron Nexstar 102 SLT. Here is what I have learned...

Firstly, a telescope is like a mechanical eye that collects light and focuses it onto an eyepiece. The bigger the aperture of the telescope, the more light it can collect and the fainter the objects it can see - so big is good. Imagine that in the dark, the pupil in your eye has a diameter of 5mm that allows light into your eye where it is focused by a lens. That means your pupil has a surface area of almost 2 square cm to gather light. The Nexstar 102 has an aperture with a diameter of 102mm, giving its lens a surface area of over 800 square cm - meaning that it can focus over 41,000% more light onto its eyepiece than you can with your naked eye. This means that it can gather light from very faint sources, such as distant stars and galaxies.

Secondly there are two main types of telescope, reflectors and refractors. Reflectors use a curved mirror to bounce the collected light into an eyepiece, whereas refractors use a glass lens. Generally mirrors are cheaper than lenses, are not so heavy and can be made bigger (remember, big is good) but mechanically reflectors are more fragile than refractors and need regular calibration (called "collimation"), whereas refractors are more robust. So reflectors and children might not mix as well as refractors and children. The Celestron Nexstar 102 SLT is a refractor.

Next, I wondered what I would do with a telescope once I had bought one. Being a novice, I can't read star maps, so being able to pick out anything in the night sky with the exception of the Moon is simply wishful thinking! And pointing a telescope at an interesting looking object, whilst telling my children that I had no idea what it was that I was showing them, was not the educational experience that I was intending. So, the third thing that I learned was that I needed to buy a "go to" scope, that would point itself at objects of interest in the sky and tell me about them. The Celestron Nexstar 102 SLT does exactly that, and only requires a very simple alignment routine that even I can do. The computer keypad even has a "tour" button, which will automatically point the telescope at items of interest and then tell you all about them. Very clever. And it will also track objects through the sky, keeping them central in the eyepiece automatically. This is very useful, and you might be surprised to see how quickly the Earth's rotation causes an object to move out of view when this feature is turned off.

The last thing I needed was a telescope that would allow me to take photographs. The Celestron Nexstar 102 SLT has many optional extras, one of which allows the connection of a digital camera. Great.

One important thing that I learned is that you can spend as much money as you like on equipment, and so I set myself a budget of £250 (telescopeplanet were selling the Celestron Nexstar 102 SLT for £249). On the negative side, there are very few things to really call out as criticisms, given the (budget) price of this telescope, but... this is a lightweight telescope (it has to be I suppose, because it is motor driven) which takes a few seconds to stop wobbling if it gets knocked; the "enter" key and "up arrow" on the keypad are very close together; and manually driving the scope to an object is not intuitive to the novice. But these are minor irritants.

All things considered, this is an excellent first class educational telescope that is ideal for the beginner, amateur and interested child. It has features that I'm sure would have only been found on professional telescopes only 10 or 20 years ago, and I am sure that it will give me and my children decades of viewing pleasure.

I spent around 6 months investigating which telescope to get, I had pretty much settled on this one or the equivalent product by skywatcher. After this telescope got the Sky at Night Magazines best beginners scope in 2009 I desided to go with this one.

Although this is a goto scope and setting up is fully automated, occasionally it doesnt work and then having an idea of your constellations is helpfully. Sometimes I am better at working out what the scope is pointing at and use one of the less advanced alignment modes.

I also use the optional extra RS232 cable nd hook it up to my PC, this allows me to create tours of objects the to view the day before and then control everything form the PC rather than the handset. I also find an ipod or other mobile device running a star guide program most useful.

I went for the 102mm refractor rather than the similar priced 130mm reflector because I wanted to take pictures and because refractors are less hassle to maintain. Although as the mount is not an equatorial type it wont track as well for longer exposure photographs.

For the price and ease of use as a first telescope I give this product 5 stars. A more advanced user would want a more expensive mount and scope but that would cost much more.

The Hand Control just displays "Transmit Data..." when connected to the telescope base. Celestron website says that the Hand Control is stuck in programming mode and need to be flashed by downloading the latest firmware and update it via the special RS 232 cable which connects using PC COM port. I tried many times but it just won't work. I am still unable to control the motor. One possibility is that the HC version is not compatible with the motor and hence connection cannot be established. The HC might be too old or faulty and need to be replaced. This is what Celestron support people told me.