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Highlands Astronomical Society

A First Purchase Guide

What can I buy on a limited budget?

by Antony McEwan

So you're thinking of buying your first telescope. A budget of £300 gives you a lot of choices, but it will depend somewhat on what you want to view with it. Are you mostly interested in high power planetary and lunar viewing, or will you be more interested in wide-field, low power deep-sky hunting? How portable does it have to be? Will you be hoping to take photographs through the eyepiece? Do you have experience with telescopes already or is this your first experience?

If you are interested primarily in high power planetary and lunar viewing, I'd suggest a 102mm f10 refractor on EQ3 mount. This would enable you to track the target by turning only one slow-motion control. Currently (Feb 2005) you can get a 102mm f10 refractor on EQ3 mount for £259 brand new from one of the many retailers who advertise in Astronomy Now. It will give very good views of most things, and will even accept 2" eyepieces to give low power wide (-ish) field viewing on the Pleiades, Double Cluster and Orion Nebula, etc. The only drawback is that at high power it will exhibit some false colour fringing when looking at very bright objects like the Moon, Saturn, Jupiter or stars like Vega and Sirius, but that can be filtered out by means of an add-on filter costing about £25. This phenomenon does not affect everybody to the same degree, and most people live with it quite happily.

You can buy a single axis motor drive for this mount for an additional £78, and this would be a worthwhile extra expense, especially if you wanted to take photographs or CCD images. Here's one thorough review of the setup and there are many other telescope review sites on the web.

You can also get the same sort of package for a 102mm f5 refractor at about the same price. This would give wider fields and lower powers with any eyepiece when compared with the f10 version, but will also give worse false colour when viewing bright objects like the Moon and planets.

If you want to get a bit more aperture for your money (bigger light grasp reveals more detail) then a Dobsonian reflector might be better. A 6" or 8" Dob is a great telescope and will show you a LOT of stuff in the sky and will also reveal a lot of detail on the planets and Moon as well as revealing galaxies and nebulae very well. They are a bit cumbersome to transport though, and you have to let them cool down a bit before they give their best views, but they are quick and easy to set up. For more details please read the review and update on the GSO 680 Dobsonian on the Equipment pages. The 8" is available for under £300, is supplied with a couple of eyepieces and now has a Pyrex glass mirror which will cool down quicker than plain old BK glass. Other models are available, including a nice 6" f8 version. You will have to learn the sky for yourself (no computers on Dobs at this price level) which I think is a good thing, and you will have to get the hang of tracking by hand, giving gentle little nudges to the 'scope to follow the object as it drifts through the field of view. Once you master that you will be able to use high powers easily with these scopes, provided you keep the mirrors aligned and in collimation.

If you want to aim a little bit higher in terms of quality, you can actually get an 80mm, 600mm focal length, f7.5 apochromatic refractor tube assembly for £295! They are advertised in Astronomy Now, and are made by Skywatcher. The optics have been compared side by side with much more expensive apos of the same aperture and there was very little difference in them (much to my chagrin as a Televue owner....). This would give you low power wide field views AND be able to zoom up to high power views with ease. Apochromats exhibit little or no false colour when viewing bright objects but they tend to be more expensive due to the exotic types of glass used in the lenses. The drawback is that you would still have to buy a mount for it (EQ3 mounts are available as an end of line product for £99 brand new).

Also, although the optics are first class, sometimes the quality control is not as thorough as it could be. You may have a focusser with a little play in it, or the drawtube may need to be adjusted slightly to be centred, etc. Neither of these problems is serious, just annoying and easily dealt with. I still think they are great all-round scopes but you are a little limited in aperture. 80mm will show a fair bit, but not nearly as much detail as in a 6" reflector. This with an EQ3 mount would cost £400, a little over budget but worth it.

If you are willing to think second-hand, there will be even more affordable choices for you, including Meade ETX90EC 90mm f12.5 GoTo computer controlled Maksutovs. These are quite classy high power oriented scopes with a GoTo hand controller which slews the scope to your target of choice from a database of thousands in the handset. You just align on two or three stars at the start of the session and the computer does the rest. I THINK they'd be round about the £300 - £400 price mark second hand. A Skywatcher 127mm Maksutov on EQ3 mount (probably with motors) could be had for less than £300 second-hand, or £419 brand new, and this would give you a decent bit of aperture, with first class optics, in a small easily portable package. Downside - narrow field of view for first time viewers.

I'd suggest you check out the reviews at Cloudy Nights or Excelsis Reviews and, of course, the member's reviews on this site. It's always a good idea to check with the members of your local club- they will probably have used some of the telescopes you are considering buying, and should be able to advise you. We've all had to go through the process and know the pitfalls, so make use of the experience! It’s also possible that members of your local club may have good equipment up for sale. For example, you can check out the Buying and Selling section on our own message board, and be sure to ask all the questions you seek answers to before agreeing to a deal. A seller should know their product inside out, and be willing and happy to answer any serious questions about it.

With a first class degree in hindsight, for a first time purchase I'd probably go for the 102mm f10 refractor, or the 6" f8 Dob. Both would serve well and perform at levels exceeding their costs.

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