Meade LX200 FAQ

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OTA Only

[Q] Is it possible to exchange the present 8" LX200GPS OTA by only a new 8" LX200R OTA? Does it fit between the LX200GPS fork arms? [A] Doc Clay: the OTA will indeed fit precisely into the existing fork arms; Meade does not provide any hardware, nor do they include a finder, diagonal or eyepiece with the new "R" OTAs; you will need to pirate whatever you can from your existing setup.

Observatations by Dr. Clay of Arkansas Sky Observatories

I have just completed some testing between both the LX200 SCT and the LX200-R and have found several interesting points; although I am not going to elaborate in depth on any of these at this time for various reasons, I think that you will find the following of interest:

  1. of course, mechanically there are NO changes in the mountings at present; there may be in the future.
  2. field of view: larger by about 15% in the LX200-R over the SCT version, even though both operate at f/10
  3. field of view CCD: using the view supplied by the SBIG STV, the CCD frame via an f/3.3 reducer (OPTEC) reveals the following:
    • Effective focal ratio of SCT - f/3.0;
    • Field of view (16" SCT) - 11.7 x 7.5 arc minutes
    • Effective focal ratio of LX200-R - f/2.9
    • Field of view (16" R) - 13.75 x 8.6 arc minutes
  4. field of view CCD: using the view supplied by the SBIG STV, the CCD frame via an f/3.3 reducer (Meade) reveals the following:
    • Effective focal ratio of SCT - f/3.0;
    • Field of view (16" SCT) - 11.2 x 7.3 arc minutes
    • Effective focal ratio of LX200-R - f/2.8
    • Field of view (16" R) - 12.8 x 8.1 arc minutes
  5. CCD visual diagnoses of corner field vignetting, estimated in terms of light loss: (16" with f/3.3 reducer utilizing photometry of known stars in outer 1/4 of field perimeter)
    • STC - 37%
    • R - 12%
  6. Interesting and related fact to 5) above: in one asteroid field test with a defined star field, the SCT offered 8 stars for suitable lock-on comparison for both astrometry and photometry via Guide8 Charon reduction program; the R image of the identical field, somewhat larger in coverage in equal conditions, yielded 21 comparison stars that Charon automatically and correctly locked onto...this is significant for those doing comet and asteroid studies and variable star fields. This is a result of both the increased field of view, as well as the well-corrected outer perimeter which provides pinpoint stars that are not suitable via the SCT optics.
  7. Limiting magnitude, 30-sec. single exposure, dark framed, no moon, field of view 12 deg. east of Meridian and celestial equator, CCD (STV) using f/3.3 OPTEC reducer: SCT = 17.8; R = 18.4; confirmed increase on a variety of similar target shots.
  8. Comment on OTA configuration: although Meade is now providing as standard the smooth roller bearings in focusing, the three LX200-R scopes that I have seen have considerable focuser backlash (not mirror shift, although the shift in the 16 is significant); this backlash results from the focuser not being properly torqued to the appropriate level, thereby exhibiting wobble and a significant "open space" with poor tolerance between the friction surfaces; without this contact, the focuser "free-wheels" resulting in loss of focus due to mirror weight or gravity.
  9. Comment on collimation: there is a bit more difficulty maintaining collimation in the R series than with the SCT, at least in the early models; not sure why this is the case, but I have found that they are prone to lose collimation (not due to primary shift) as one moves the telescope from one point of the sky to one at an opposite horizon, suggesting perhaps shifting of the secondary mirror collimation system as the scope moves.
  10. Overall.....the star images both visual and photographic are far superior in the new R series than with any SCT I have used; the field of view is larger, somewhat better define due to nearly uniform illumination across the field. In collimation star images exhibit textbook Fresnel patterns and in precise focus a very distinct Airy disk is seen with two very fine diffraction rings. Note that the most obvious impression when comparing star fields is the lack of light scatter from bright stars/objects with the R-series over the SCT; those of you who are used to seeing "fuzz balls" for bright stars are in for a treat.

Fine scope....a big winner over the SCT optics in my opinion. I greatly prefer this model over the RCX telescope. It provides the best of both worlds: dependability of a non-totally robotic system as the RCX is locked into, the beautiful modified RC optics and the closed tube design of the LX200 series....hands down beats every scope in its class.

You likely will be seeing more on this soon.

Dr. Clay

Arkansas Sky Observatories
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