casstony
17-04-2006, 08:03 PM
Sounds like the LX200R optics might really shake up the SCT world according to this review from the LX200GPS yahoo group:
P. Clay Sherrod wrote:
> 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
> Harvard MPC H41 (Petit Jean Mountain)
> Harvard MPC H45 (Petit Jean Mountain South)
> Harvard MPC H43 (Conway)
> Harvard MPC H44 (Cascade Mountain)
> http://www.arksky.org/ (http://www.arksky.org/)
It's interesting watching these companies duel. I wonder what Celestron will pull out of the hat?
-Tony
P. Clay Sherrod wrote:
> 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
> Harvard MPC H41 (Petit Jean Mountain)
> Harvard MPC H45 (Petit Jean Mountain South)
> Harvard MPC H43 (Conway)
> Harvard MPC H44 (Cascade Mountain)
> http://www.arksky.org/ (http://www.arksky.org/)
It's interesting watching these companies duel. I wonder what Celestron will pull out of the hat?
-Tony