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LX200 Telescope

I have a Meade 8" LX200 f/10 telescope which I purchased in 1995. 

The telescope has a light collecting aperture of 8" (203mm) and a focal length of 80" (2000mm), yet by virtue of its Schmidt-Cassegrain Catadioptric design, the telescope tube is only 16" long. Light enters the front of the telescope through a thin "correcting plate" lens of 8" diameter to a spherical primary mirror at the back of the tube, which reflects light to a convex secondary mirror sitting in the centre of the correcting plate at the front, this then reflects the light back through a central hole in the primary mirror to reach focus at the focal plane. The secondary mirror multiplies the effective focal length of the primary mirror and produces a very compact telescope for its aperture. The telescope's theoretical resolution is 0.56 arc sec. Maximum practical visual magnification power is x500, but I normally operate it using eyepieces which give a x77 - x209 magnification.

The telescope tube is mounted between heavy duty fork mounts and DC-servo-motor-controlled worm gear drives on both telescope axes permit high precision in tracking,  guiding and slewing. The telescope has a push button hand control with a red backlit digital readout display which is linked to the telescope's 16MHz 68000 microprocessor main control. The hand controller has a built in library of over 64,000 objects and after alignment, the telescope can be brought to bear on any of the objects with a simple GOTO function.  A series of more advanced functions are also available to achieve high-precision pointing and tracking.

The telescope can be used in altazimuth mode, land mode or polar mode. In the latter mode the telescope is fitted on top of a special Equatorial Wedge that tilts the telescope such that it's axis points directly to Celestial North (a point close to Polaris - The Pole Star - about which the stars appear to rotate, of course it is really the earth that is rotating).

See also
Meade's full description and specification for the LX200 
Doc G's comprehensive mechanical analysis of the LX200 
Doc G's comprehensive electrical analysis of the LX200
(these external link will open in a separate window).

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LX200 Comments

My own experience and comments with regard to the 8" LX200 are in the process of being added here (please check back again soon).  All of the comments are my own. I hope that they will compliment and extend the advice and hints posted by other LX200 users.

• 8" LX200 - Good Points

• 8" LX200 - Bad Points

• Advice and Hints

8" LX200 - Good Points 

• The telescope is highly compact for its aperture.

• The front lens provides protection to the primary mirror (compare with a simple reflecting telescope or Dob where the primary mirror is at the mercy of the elements.

• It comes with a sturdy Tripod (and provides a firm viewing base until the time you can get a Pier).

• The scope allows high precision pointing and tracking.

• The LX200's GOTO facility allows quick access to finding planets and hundreds/thousands of stellar and deep sky objects.

• Periodic error in telescope tracking can be corrected for by 'training'.

• The scope can be controlled remotely from a computer using appropriate software if required.

• There are loads of accessories for the LX200.

• There is relatively large and active user group

8" LX200 - Bad Points

• Image shift whilst focussing the LX200 can be large - and annoyingly so. Whilst mechanical tuning of the focussing mechanism can reduce the amount of shift it doesn't seem to make it go away (use of an alternative focussing equipment - such as the JMI -NGS-F focusser - is considered a vital necessity).

• The stability of a telescope is only as good as its weakest point. The LX200 and equatorial wedge make a pretty stable combination, but play in the telescope's bearing where they attach to the forks seem to be the LX200's weakest point.   Doc G's comprehensive mechanical analysis of the LX200 gives a lot more info on mechanical stability of the LX200 (note: this external link will open in a separate window).

• The telescope's standard ViewFinder  is pretty useless - the cross-hairs can't be seen when viewing a dark sky (very little help for aligning the telescope to a star) and the absence of a right angle-viewer means its very difficult for looking at objects high in the sky. Trying to see Polaris can be a real pain in the neck ! (use of an alternative finding equipment - such as a Telrad Sight - is considered a vital necessity, you will need a 1.25" diagonal however).

• Fitting of the telescope direct to tripod (as used in altazimuth mode) is a highly awkward process. requiring balancing the telescope scope on top with one hand whilst screwing in a threaded rod into the base with the other  (fitting is much easier once an equatorial wedge is used and of course this gives advantages of allowing polar alignment).

Advice and Hints

• Choose your telescope size with care (8",10" or 12")
  Which LX200 scope size is best ? It depends ....
  The larger aperture provided by the 12" scope will generally provide better access to smaller and/or dimmer sky objects  (0.375 arc sec resolution vs only 0.56 arc sec for 8") but it's considerably heavier (telescope tube+fork weight  is 70% heavier than for the 8", 80 vs 41 lbs, tripod 57 vs 26lbs) and it's much more expensive (70% more expensive than 8").    
  Overall I would suggest that the 10" scope represents the best value (0.45 arc sec resolution, and only 15% more expensive than the 8").  
  The telescope's tube+fork mount is however still 40% heavier than for the 8" (58 vs 41 lbs) so if mobility is important (and unless you have a permament housing the mobility difference could mean the difference between using the scope and not using it)  then the 8" LX200 is probably the best buy.   
  It has been said 8" LX200 is a good match for the limited seeing conditions which we have in the UK, I can't comment on that myself, as I've only used an 8" scope.  The Meade specification suggests that the limiting visual magnitude of the 8" LX200 (Mag +14.0) is only mag 0.5 less than for the 10" scope and only mag 1.0 less than for the 12".   

• Try to get your LX200 set up on a permanent pier in an observatory of some form. 
  The pier saves a considerable amount of time at the start and end of each observing session. The observatory protects the telescope when not in use and gives some protection from wind during observing.   The observatory can also help block out the impact of direct light from street and house lights, provide some privacy for the observer and provide extra room for storing accessories & cases. Whilst there is some environmental and security risk to the telescope in keeping storing it outside of the house, I believe there is more risk to the telescope in carrying it outside and then inside again each time its used, especially if it's across any icy patio !

• Try to get the best alignment you can
  Once set up on a pier it is worth spending some time to get the very best alignment that you can.  Finding objects will be a lot more easy.   My original alignment has held up pretty well and for visual observation I can get by without any polar alignment checking at all (I just match to a suitable star and then I'm straight into observing).  However if you're needing high-precision pointing and tracking (eg for CCD astronomy) you will need to check the telescopes alignment more regularly.  

• Reduce the Slew Rate Setting down to 6.
  Whilst the 8" LX200 can slew quickly across the sky (up to 8 deg per second), the Meade drives make a lot of noise, especially on a quite still night.  Slowing down the slew rate using Telescope Option #9, makes a lot less noise. I find that a Slew rate of 6 gives the best balance between speed and quietness. Slew rate needs to be set at the start of each session.  (Slew is the term given to moving the pointing direction of the telescope from one part of the sky to another).

• Regularly check/correct the LX200's clock.
  The LX200's clock has a tendency to loose or gain time between observing sessions.  If it shifts by much the pointing accuracy of the telescope is compromised, so it is wish to check and correct the clock every so often and if you haven't used the telescope for a few weeks.

• Don't rely on compass alignment
  The legs of the Meade Tripod carry some magnetism and affect the compass that comes with the Meade telescope/equatorial wedge.

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