This page takes the form of a presentation that I was asked to give at very short notice (3 hours!) at the Monday evening club night of South Cheshire Astronomical Society. Literally just a few thoughts, ideas and anecdotes for a presentation not to last more that 20 minutes.
Trying to avoid real money discussions as I didn't want to get into a 'How Much?' or 'You can buy it cheaper at another emporium' type responses.
So, making a start...
I always introduce my talks with a brief explanation of what we are going to talk about. I opened with a question ' How many here own a Telescope?' Most people put their hand up. The second question was 'How many people use their telescope regularly?'. Most hands stayed down and a few embarrassed chuckles.
A decent telescope is usually an expensive investment for most people. My view is that first telescopes are often purchased on a whim without any thought of the suitability of the instrument bearing in mind the capabilities of the owner, what the telescope will actually be used for and how practical it will be to use in the owners local environment. I was hoping to get people to think about what they really need before they buy.
My response is to create a check list. Clearly, budget is a factor, but be realistic, once the novelty of the initial purchase has been made just how often and what opportunities will you have to use the telescope to become proficient. While thinking about this, think about obstacles that will prevent you from getting maximum enjoyment or will limit the range of celestial objects that you would like to observe. For example if your garden is North facing with a limited southern horizon, choosing a telescope to observe planets may not be the best idea - unless you are prepared to travel - which in itself would probably be a hinderance to using a telescope. You may need to swap North for South if you are reading this in the Southern Hemisphere.
When you have a good idea what you think you will use your telescope for then you can now think about the specification of the instrument that you would like to buy. I explained a few key phrases that you will come across.
Broadly, my recommendations would be - especially for those will a limited budget:
- Always choose optical quality over aperture.
- Unless you really want to do planetary and lunar observing, then always choose aperture over focal length.
Then see what you can buy within your budget. Stick to the well known names where possible or better, discuss with someone with experience.
Don't forget the mount - I discussed mounts later in the presentation.
Finally - where will you keep your instrument. Ideally somewhere secure, dry but unheated. The telescope should always be kept at outside ambient temperature if possible.
So, lets have a look at the type of instruments that you are likely to come across. I cover each of these options in the next few slides.
These should be mandatory for all beginners. Most households already have a pair lying unused in a cupboard somewhere. Learning to find your way around the sky - especially in typical light polluted areas - is so much easier with a pair of binoculars. However holding a pair of binoculars, trying to keep them steady while not getting severe neck/back/arm/shoulder ache can be a challenge. Easily alleviated by using a binocular mount. Older binoculars may have different fitting types, you will need to check your binoculars before you buy. The tripod should be rigid enough to support the binoculars without juddering every time that you want to move it. Something like this with a long arm to move the binoculars works well. I was asked to suggest a binocular size - 10x50 will enable you to see the four Galilean moons and with a weight and size that is easily manageable.
Moving onto telescopes and starting with Newton type reflectors. In many respects these make ideal starter telescopes with an aperture diameter of about 150mm (6"). Compared with similarly sized Refractors, they tend to be cheaper. I have a 200mm (8") Blue (that dates it!) SkyWatcher reflector - similar to the image, that I have owned for about 25 years (purchased in 2000 or 2001 and funded by a bonus). It's 1000mm focal length and therefore has a F5 focal ratio. I can't see me selling it any time soon. The downside of reflectors is that they need fairly frequent (every few months) collimation. This can be a bit nerve wracking and a challenge for a beginner but with a little bit of guidance it becomes a simple routine maintenance task. They tend to be fairly light weight compared with a refractor. I mainly use mine for Deep Space work but it can also give excellent views of the moon and the planets. One benefit for those who may have mobility issues is that the eyepiece is usually around eye level when standing up or sitting on a high stool.
On to Refractors. These are the telescopes that most non astronomers think about when you tell them you are an Astronomer.
My first telescope was a small Tasco refractor, purchased when I was 11 years old - about 1967. I remember standing out on the patio at my parents house observing Saturn. The image quality was awful but I could see the rings of Saturn nicely merged into the planet.
Lets have a think about Refractors. Providing you look after them, they are essentially maintenance free. However, a decent quality refractor will always be more expensive than a Newton reflector 30% bigger. The reason is that the optics are made of high quality glass, optimised to minimise (never eliminate) chromatic dispersion, the effect of seeing a colour halo around bright point objects - like stars. With modern optics using ED (Extra low dispersion) glass or APO technology (Apochromatic - corrects both chromatic and spherical aberrations) unwanted colour is almost insignificant. Chromatic dispersion is caused by light of the three different primary colours (Red, Green and Blue) that make up white light being refracted differently as it passes though the glass.
They are usually a safe bet if buying second hand - see my caveats later - but can be heavy.
I purchased a SvBONY 80mm refractor about 4 years ago. This is my first choice everyday telescope, it has ED optics and fits well on a EQ-5 Equatorial mount. It goes with me whenever I travel (in my car). I use the telescope about 250 days every year. Although not cheap (it cost me about £450 at the time), it is far and away the best value instrument in terms of usage that I have ever owned.
By Hybrid I am talking about Cassegrain derivatives that use glass 'correctors' to simplify the very complex construction of a traditional Cassegrain telescope. The most common variants are Schmidt Cassegrain (SCT) or Maksutov Cassegrain (MAK) types. The advantage of these telescopes is that due to the light path, they pack a long focal length in a very short tube. The downside is that due to the optical complexity, they can be expensive and also very heavy. When I returned to optical astronomy 4 years ago, I treated myself to a Celestron Edge11HD as a retirement gift to myself. (Along with a second hand Orion EQ-G mount). For planetary and lunar work it is superb but it really needs a permanent observatory mount to get the most out of it. This is something for discussion with your (my) household chief planning officer.
I have two equatorial mounts, an EQ-5 that came with the 200mm Reflector that I mentioned earlier and the EQ-G (similar to an EQ-6) mount that I bought second-hand. Being totally honest, the EQ-5 is too small for a 200mm reflector, The tripod is fine but the equatorial head is not really rigid enough for a telescope of that size. However, I managed to cope with it for over 20 years but it was very frustrating at times.
Most beginners/starter type telescopes are supplied with a tripod and Alt/Az (Altitude (tilt) and Azimuth (rotating around a vertical axis)) fork mount with the telescope tube (also known as an Optical Tube Assembly) sat within the fork. There is nothing inherently wrong with this type of mount except they tend to be a bit too flimsy. If you are considering a telescope with a mount like this, check that it is stiff enough with the legs extended. It really shouldn't move or flex at all when you move or focus the telescope.
Our club has a 200mm SkyWatcher Reflector - a bit more recent than mine with a Dobson mount that is in my care at the moment. It is so easy to use, I can set it up within a minute and be observing. With a low power eyepiece, image drift is not a problem.
The downside of a normal hand powered Dobson is that it is not really suitable for astrophotography unless the exposure is very short - for example, lunar or solar observing. However, some users cope remarkably well with this limitation.
A Dobson mount is inherently very rigid. It is an excellent mount for casual observing and also learning to navigate around the celestial sphere. A nature of the design is that they can only be used with Newton reflector type telescopes.
My anecdote about mounts is perhaps more of a lesson learned. When SkyWatcher released their 'Black Diamond' series of telescopes about 18 years ago, I decided that I would buy a SkyMax 180 Maksutov telescope. It was a beautiful looking instrument and I duly mounted it on my EQ-5. It was totally unusable. The MAK180 was far heavier than the 200mm reflector and the mount simply couldn't cope with the additional mass. I eventually sold the MAK180 at a loss and really felt quite peeved about the experience.
There is no point buying a mount that is not strong enough or rigid enough to support the telescope. It is the quickest path to disillusionment there is. Always go one size bigger if that is an option and you can afford it.
Buying Second Hand. Undoubtedly, there are some very good deals on the second hand market. However, there is also some rubbish out there. I do buy second hand, but, unless it is something low cost, I stick to established Buy and Sell sites that specialise in Astronomical equipment like the (UK) Stargazers Lounge and UK Astronomy Buy and Sell websites. You will be buying from established Amateur Astronomers who will be very concerned about their reputation. Again, stick to well known brands - unless you are taking sound advice from a local experienced amateur.
My anecdote for buying second hand is also not a good story. I purchased an Orion Optics OMC-140 Maksutov telescope about 20 years ago from that well known internet auction site. It wasn't cheap. I asked for evidence of optical quality - I was sent photos of Saturn showing the Cassini division. It all looked good. "Buy now" was duly pressed and I excitedly waited delivery.
The telescope arrived a few days later, wrapped in a single layer of thin bubble wrap - which had come undone. It was left on the doorstep. Although there was no visible damage it was clear that the optics had been damaged or knocked in transit. The optics were dreadful. I had no comeback, the seller had arranged delivery and because there was no visible damage, I was 'stuck with it'. I passed it to an experienced friend of mine who declared 'there was something wrong' but couldn't say what. I took it to Orion Optics (the manufacturer/supplier) and they charged me £70 to look at it and declared it was irreparable but they also couldn't say specifically what was wrong. I tried to collimate it but got nowhere and eventually sold it for spares back on the some auction site. Read my guidance above and take heed.
And that was that, apart from a few questions.
Presentations like this make you think. I hope that this page will be of use to any newcomers out there.
Enjoy your Astronomy.