Which Telescope should I buy? Shopping advice for astronomers

Recently I friend asked me which telescope he should buy. Sounds to me like you have been trying to take a lot of the right steps. I'm going to try and give my best advice...he made a number of points which I answered in turn. I've not reproduced his original email, but I've posted my reply here, mainly so I can refer to it in the future.

Dealing with your points in turn.

  • Societies. Yup. Lots of them are populated by stiff nosed dinosaurs. Everybody tells you to visit your local society first.. but sometimes this is not the right thing to do. I'd advise looking around some of the internet astronomy communities eg ukastroimaging or one of the yahoo groups. Tons of people to talk to and seek advice. And far more convienant than the local village hall every other thursday evening.
  • Internet.. .well, I stumbled into that one above, but yeah, lots of and lots of things to read. Best places are the ones where you talk to people! If you are that way inclined, poke about on the peer to peer networks and get a copy of some nice planetarium software like Skymap pro or THESKY.
  • Books Philips books are pretty good and worth the money. Books are so much more "absorbable" than the internet. Until they invent a computer which is specifically deisgned to be used in the bath anyway. The most legendary book is Norton. This has lots of handy star charts, and a lot of writing about the basics. Always recommended. And it sits on top of the computer in my observatory as the ultimate "backup".
  • Telescope to buy. Don't buy a telescope for 200 quid. More than likely it will just annoy you. With astronomy its very easy to keep buying the wrong thing, and then trying to solve the problem by spending some more money. And so on, and so on.

    Buy some nice binoculars and a sturdy tripod. A tripod is important for binocs. Stops achy tired arms, and lets somebody else have a look too.

    Also, a simple motorised EQ platform for a camera is quite easy to come by example I don't know what the build quality is like, but it will need a sturdy tripod. This should allow you to use up to 200mm lenses and a few minute or so exposures without too much tracking problems. Maybe better if properly tweaked. Getting to some darkish skies and taking some wide field shots can give quite a lot of "bang" for the "buck". Also gets your brain familiar with the operation of EQ mounts. EQ mounts are extremely werid animals at first, but eventually become as instinctive as driving a car.

    Mind you, actually having a "real" telescope is fun all on its own, and sometimes retail therapy wins the day. The biggest bang-buck ratio is the classic Newtonian - but can be tricky to learn to collimate, and can be heavey and cumbersome.

    Other end of the spectrum for beginners are ETXs. Nice for planets and moon, but a bit slow for anything else.

    the newer budget 80mm semi-apos around the 350 quid are fantastic value for money - I know, I've looked down one. But you'd need a mount too, thus it gets rapidly beyond the suggested budget. I have seriously considered one myself, but then that requires yet another reevaulation of my personal upgrade path.


  • Establishing what I want. Astronomy does cover a massive spectrum of specialities. PLanetary imaging, lunar observing, wide field, hi res, emission lines, spectroscophy etc etc etc. Buying a scope these days can be a serious investment... and you'd better get the right one for your areas of interest. Different scopes have different strengths. Don't get too carried away on lunar/planetary observing/imaging. There is only 1 Moon and 8 other planets.. and only 3 of those give any amateur observable features (plus, argueably, Venus)... You are not going to see much on the planets with binoculars anyhow. You need at least 500mm of focal length for that. Mind you, with a tripoded pair of binoculars you can see the dances of planetary moons and, if you squint, just make out the rings of saturn. (the horny planet as galileo said)
  • Taking pictures. Taking pictures can be very simple or very difficult. To get the drop dead gorgeous images requires a massive amount of money and experience. To poke a webcam up a small telescope and get some nice shots of the moon is easy. A simple Eq mount with a wide angle slr is also fairly easy. In general, get some decent planetarium software on your PC. Get hold of some decent binoculars (we have some very nice ones that cost, I think, 80 quid). Get a tripod for them. Google about and you will find a list of nice binocular targets in the northern hemisphere during autumn/winter. Then learn how to find these things in the binoculars. Learn about how the skies work, how the maps relate to fields of view etc. If you really must image something, try some wide angle shots on a simple barndoor or eq1 mount.

Special mention should also go to Meade's new DSI series of cameras. I've heard a few things about these. Whether these faults have been recified I do not know.

  • It has an IR block filter that cuts out Hydrogen Alpha. IR Block filters can be a good thing, they block the poorly focused IR light leading to crisper images in some situations. However, if they cut in too low - ie cutting the Ha they are a serious problem. Ha is the main "red" light emiited by nebulas.

    This is also the reasoning behind mods to the Cannon 300D family about ripping out its IR filter.

  • It does not properly cool the CCD. The sensor is known to be noisey at the ambient temperature of the DSI

These reasons alone, if they are true and unrectified, make lead me to strongly advise against it.

The LPI (Lunar and planetry Imager) from Meade is also unadvised - it has a low sensitivity CMOS sensor. You will get better planetary and luner results with a stock toucam that has a higher sensitivity CCD chip - a chip than, with skill, can be swapped for a more suitable chip.

Whilst we are on the subject of Meade. They launched the LXD55 several years ago - to a very mixed response. Although the system was quite fickle and buggy, with a bit of tenacity it could get good results. More importantly, it brought GOTO technology to the mass market at an attractive price. Despite many complaints, it really is a landmark product.

The LXD75 was lauched quite recently as a replacement for the LXD55, hopefully ironing out the more obvious wrinkles.

I've not used an LXD75, or met one yet, so I can't comment directly. There are two yahoo groups LXD55telescopes and LXD75telescopes. I have been a member of LXD55telescopes for a long time. I did join the 75 group to see what the reaction was to the new scopes, but there was too much personal crap going on, so I left.

I've heard in the grapevine that they are not gigantically better than the 55, but certainly an improvement.

These comments are, of course, about the mount hardware. The actual optics of the system are supposed to be fantastic - perhaps the best at that price.

My best suggestion is to visit the yahoogroup or the excellant http://www.lxd75.com/ and find out what the story is. I certainly can't complain about the 55 - it does reasonably well for me.

But please bear in mind expectation. No mount on the earth (or at least for less than 5k) is going to track perfectly. Its all down to the machining tolerance. A 1/1000th of an inch at one end of the system can translate to about 1 arc minute at the other end....

Thats currently all I have to say on the subject. Doubtless I will think of some more. ;)

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