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Meade 10" SN LXD75
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I have always been a "refractor man" in my choices of telescopes. Why am I now reviewing a Meade Schmidt-Newtonian telescope, you might ask. Has he finally lost his marbles? No! I purchased this telescope in anticipation of an upcoming trip (June 2005) to the desert Southwest: Hovenweep National Monument and Mesa Verde National Park, in particular. After measuring all the components of my TMB 175 APO, I realized that it simply would not fit in my vehicle without major modifications (i.e. removing the tailgate of my Dakota). I also didn't relish the prospect of being "rear-ended" in the telescope transport case! Ergo, buy something that will fit the space available. The desert environment, although dry and with dark skies, is also a pretty "gritty" place; I also didn't relish exposing my valuable APO optics to a situation I couldn't control.
After reviewing just about all the existing possibilities, I settled on the Meade LXD-75 SN-10AT as the largest aperture scope that was NOT an SCT on a fork mount, and that would still fit in my midsize pickup truck. As an aside, I have a weakness for Schmidt-Newtonians ever since I had my little Celestron "Comet Catcher" back in the 1980's.
The author is not an employee of Meade Instruments, nor was any compensation offered to or received by the author for preparation of this instrument review.
Description and Specifications:
The Meade LXD 75 series telescopes are all mounted on a Chinese manufactured, Meade designed equatorial mount; the SN-10 AT mount is "Autostar" controlled from a handbox controller. Meade's well-known "Autostar" suite is provided on a CD along with the Lunar and Planetary Imager, which allows the user to generate custom star charts, and also to control the telescope from a PC as an option. The OTA is assembled in China using optical components that Meade advertises as being made at their U.S. facility in Irvine, California. Below, I have reproduced, in an abbreviated form, the specifications listed in the user manual provided with the package:
Meade LXD 75 SN-10 AT (UHTC) 10" f/4 Specifications
Clear aperture: ------------------------------------------10" (254 mm)
Focal length: --------------------------------------------1016 mm
Focal ratio (photographic speed):-------------------f/4
Resolving power:---------------------------------------0.45 arc seconds
Coatings: ------------------------------------------------Meade Ultra-High Transmission Coatings (as option)
Mounting: -----------------------------------------------Die cast aluminum
Input voltage: -------------------------------------------12 volts DC
Alignment: -----------------------------------------------German-type equatorial
Tripod: ---------------------------------------------------Variable height field tripod
Net telescope weight: ----------------------------------30 lbs.
Net tripod (mount) weight: ----------------------------55 lbs.
Summary of Methods:
My method of testing and evaluating telescopes is rather simple, since it is extremely pragmatic. Because I am the one paying for the instrument, it must perform well in the arena that I have chosen. I enjoy observing globular clusters, brighter and more detailed galaxies, planetary nebulae, double stars, and other interesting deep sky objects. Therefore, we are dealing strictly with a "use test", instead of a quasi-scientific "star test".
Many of the classes of objects listed above are pretty demanding of the optical system, and resolution of globular clusters is one of my criteria for good optics. Double stars also provide a fine test. In both of these classes of object, sharp, pinpoint stellar images are mandatory for a telescope to be deemed satisfactory. On the fainter globular clusters and galaxies, decent contrast is also needed. In order to explore the limiting magnitude of the telescope, I used the photograph of M3 from Observing Handbook and Catalogue of Deep Sky Objects, (Luginbuhl, C., and Skiff, B. ; Cambridge University Press , 1989) that shows the visual magnitudes of many stars in the cluster, as my guideline.
In testing the Meade LXD 75 SN-10AT, I have selected objects from my graded lists of double stars and globular clusters, increasing in the difficulty of resolution, and with progressively fainter component stars. I have selected several galaxies I have observed frequently in other telescopes. Also, I have included my observations of a few other well-known and popular DSOs for a more general range of interests. My double stars have been selected from the list of 100 Double Stars, published online by the Astronomical League Double Star Club, and from lists published online by the s33 website. The galaxies are all listed in either the Messier or Caldwell catalogs.
Although the telescope is sold as a package deal, I have emphasized the optical system over the mount in this review. I generally expect a mount to track accurately at the sidereal rate and slew controllably using the hand control keys. I don't normally us "go-to" finding of objects, but all of my mounts have this feature included. I have included several trial runs on some of the targets after following the Meade directions for initialization and training the mount. My evaluation is based on a "Go, or No-Go" result. The desired object is either in the field or it isn't. I have also evaluated the mount's stability in relation to the size of the OTA mounted.
The telescope and mount were delivered by UPS in two large boxes, both of which were clearly marked "Made in China". The packing was very well executed, and utilized fitted expanded polystyrene inserts that exactly matched the enclosed parts. I carefully laid out all of the items and compared them to the list in the Owners Manual. Nothing was missing or damaged; so far, so good!
I simply "followed the directions" in assembling the system, and everything went together smoothly. I then stepped back to view my (and Meade's) handiwork: overall it was a very attractively executed telescope setup. No blems in the paint, and no shipping damage, which presented me with a very favorable first impression. I then moved the whole setup outside to the deck and proceeded to align the finder scope. My next find was not as favorable: the finder scope does not focus-- not good for me, since I observe without my glasses. Therefore, there was no way to sharpen-up the finder for my diopter correction: one instant demerit. As I was finding a tree or rock formation in the distance, I noticed quite a long dampening time for the vibrations I induced by fiddling around with the focuser: on the order of 7 seconds to settle down. This was one of my major concerns about the LXD 75 SN-10 when I placed my order--could this mount handle a 10" optical system? Since I was on a wooden deck without anti-vibration pads I withheld my judgment at this time. Lesson number one: set up on a vibration-dampening surface
The next step was checking the collimation of the diagonal mirror. The Owners Manual is very easy to follow at this point, and includes a "correct" view through the focuser sans eyepiece sketch. There seemed to be no collimation issue requiring any corrective adjustments at that point. I then spent the rest of the afternoon reading the instructions for operation of the mount and putting the handbox arrow keys through several of the examples, in addition to the initialization (date, time, Zip code, etc) of the Autostar program. The next step was to move outside for a first light. This was delayed several days by the "new telescope" weather pattern.
After 5 cloudy nights in a row, I finally had a break in the weather and a chance to try out the new tube. As a DSO fanatic I was disappointed by the presence of an 8 day-old Moon (first quarter), but I proceeded anyway. After the first experience on the deck I moved out into the front yard on soft dirt (still damp from the previous day's rain) for this exercise. I started my setup before dark by using a Magellan GPS to determine true North. Note: the mount lacks a built-in level; a machinist's precision level was used to level the tripod/equatorial mount. I dialed in my latitude on the polar axis scale, mounted the OTA and waited for dark.
I initialized the Autostar handbox and started to slew over to the Moon. I say "started", because I never got there. The mount began making some loud complaints in the form of gear-grinding noises, and then stopped slewing. My first impulse was to throw the whole works back in the box and return it to Meade. My second thoughts prevailed, however. Lets figure this out! I then released the declination clutch and noticed that the telescope was not properly balanced anymore. The OTA had slid in the rings as I began slewing towards the zenith. Lesson number two: with this large optical system on this mount: the balance is very critical; otherwise the drive motors don't have enough torque to slew the system. Lesson number three: make sure all adjustable tension devices are tight, including the spreader bar on the tripod. Things have a way of working loose, it would seem. At this point I took another look at the sky, and noticed that my conditions had deteriorated somewhat. In addition to the bright Moon (NELM : magnitude 4 ), I now had some thin, high haziness (transparency: 6/10). Since this was a "get acquainted" session anyway, I persevered.
I wanted to accomplish several things in the first light session: (1) check the defocused star images for any collimation problems, (2) practice using the slewing controls and check the tracking accuracy, and (3) evaluate the overall sharpness of the optical system. Anything beyond this would be frosting on the cake. I decided to start with some easy to locate, bright double stars.
As is my custom with a new telescope, I went to Mizar (zeta Ursae Majoris). Again, I had to stop and readjust the counterweight position to smooth the tracking, which was still pretty jerky. I started the observing session using the eyepiece furnished by Meade: a series 4000, 26mm Ploessl, which yields 39X. I immediately noticed that the focuser was a real pain to use. Unlike any of my other telescopes, the Meade focuser has threaded inserts for the different eyepiece diameters, and the extension tube is also threaded. It is not real convenient to use while wearing gloves and in the dark! Achieving a sharp focus was neither smooth nor easy. The focuser was (1) very stiff, (2) very sloppy and prone to backlash, and (3) felt pretty flimsy for holding my heavy eyepieces. Also, I had to remove my gloves to make sure that the focuser brake was disengaged and get a good grip on the focuser knob. It took a while to get something resembling "sharp focus". At 39X, Mizar was resolved, but the image seemed awfully "mushy". Alcor at the edge of the field exhibited quite a bit of coma until I tweaked the focus a bit more. This adjustment reduced the coma, but it was not completely eliminated. I then switched to my TMB 25 aspheric-orthoscopic, the eyepiece I consider the sharpest in my set. With this OTA it should yield a magnification of 40X. I could not bring this e.p. to a focus, due to the large "in-travel" required. I skipped over this one, since I didn't want to fiddle with unscrewing the extension tube from the focuser at this point. Instead, I substituted a Nagler 17 type 4, and a magnification of 60X. Changing from 1.25" eyepieces to 2" eyepieces also requires unscrewing an eyepiece holder and screwing in another one. Another negative is the eyepiece holder lacks a compression ring, using two finger-tightened setscrews to do the job. This eyepiece gave a much sharper image and cleanly resolved this easy double. I noticed that the coma seen previously with the Ploessl eyepiece was greatly reduced. Since I was experimenting at this point, the next eyepiece on my agenda was an SMC Pentax 10 XW at a magnification of 102X. At this point, I simply used my Televue drop-in adapter for the 1.25" diameter barrels. The stellar images were also greatly improved in this ocular. I proceeded to Cor Caroli for my next stop, and essentially repeated the sequence of eyepieces. Again, the Meade Ploessl gave only a marginally acceptable image, in contrast to the Nagler and Pentax oculars. Since all of this messing with the focuser took some time, I began to notice a distinct improvement in the stellar images in the compound eyepieces. It had been just about 2 hours from sunset to this point; just about enough time for the optics to have finally reached thermal equilibrium. I moved up to Algieba (gamma Leonis), which is a tighter (4.4 arcseconds separation) and more challenging double star. The optics of the telescope finally began to show off a bit--Algieba was very pretty and cleanly split by the Pentax 10 XW at 102X. Both stars of the double appeared to have a golden hue to my eyes. It occurred to me at this point that I had noticed no color fringing in any of these observations. To further test this hypothesis I slewed over to Sirius. After centering the star I carefully defocused the image slightly to check the collimation of the optical train. I was treated to nice round diffraction disks, both inside and outside focus. Also, there was no hint of any false color halos either side of focus.
In spite of the bright moon I decided to have a look at M41. This is one of the brighter open clusters in the entire Messier catalog, and one with which I am intimately familiar. The view in the Nagler 17 type 4 was truly excellent; there are 2 brighter orange stars near the center of the cluster, which stood out from the other blue-white stars. The colors of the stars were very easy to determine using one of the premium eyepieces. Encouraged by this result, I proceeded to Orion and M42/Trapezium. I was surprised to see the "wings" of nebulosity that curl from the "fish's mouth" around towards the Trapezium even in the bright moonlight. Using the SMC Pentax 10 XW, I observed the "Trap" for a while, and while all 4 of the brightest stars were extremely sharp and very well resolved, there was no trace of either theta-1-E or Theta-1-F. I surmised that the glare from the Moon and a bit of haze that as now forming prevented any observation of these fainter and more elusive components of the cluster. As the final objects for the evening I selected sigma Orionis and Mintaka (delta Orionis). By now I had developed a liking for the Pentax 10 XW eyepiece in this OTA. It seemed to be a "sweet spot" of magnification, and showed no "seagulls" or flare. On the other hand, I came to rather dislike the Ploessl that came with the package, since it was astigmatic and hard to focus. Sigma Orionis showed all 4 components in the Pentax 10 XW eyepiece, and Struve 761, a fine triple star, shared the field of view. Mintaka is generally regarded as an easy double, when it is in fact a triple star. The "C" component is not at all easy to see at magnitude 14, but I caught a glimpse of this faint companion as the haze had thinned out momentarily during my final observation of the night.
What did I learn from this session? First, the OTA requires more time than my APOs to thermally equilibrate. Second, that the optics are quite good, and are capable of delivering excellent, pinpoint stars when using high quality eyepieces. Third, the drive tracks well enough, provided the tube assembly is properly balanced. Slewing and tracking will be discussed in greater detail after testing the "go-to" feature of the mount. Finally, the focuser is probably the weakest point of the entire unit and should be replaced/upgraded by any serious observer. I also planned to replace the finder scope with one that can be focused.
My next observing session with the telescope came a lot later than I had hoped, but my replacement focuser arrived just a day before the weather and Moon cooperated. Due to my dissatisfaction with the Meade supplied focuser, I'd ordered an NGF-55 in the non-motorized form from JMI. It took only 10-15 minutes to install. After playing with the adjustments in the house, all that was left was a use test under the stars.
It came 3 nights after a full Moon, so the glare problem was absent until about 11:15 PM. My first move was to find a bright star in order to check the collimation of the entire system, and Rigel was available. Unfortunately the optics had not yet thermally equilibrated and the star test was a real mess. I went inside for a while to get my charts, red flashlight, binoculars, and dress a lot warmer.
My second try at the collimation showed that the system
was still in pretty decent adjustment--at least nothing that I considered
worth fiddling with.
Since the skies were reasonably clear and stable (NELM: 6.5; seeing 7 <1 to 10 scale>), I decided to try a fairly challenging double star, 31 Orionis. Even though the separation is 12.7", and is not considered a "difficult" split, the magnitude difference is significant: A: magnitude 6.0; B: magnitude 11.0. Even with the new focuser installed, it was difficult to focus the Meade 26 mm Ploessl eyepiece without seagull-shaped stellar images unless the object viewed were dead center on the field of view. As before my SMC Pentax 10 XW gave the only truly aplanatic (i.e. coma free) view of this beautiful magnitude and color contrast double star. The primary is peach colored, while the secondary is pale blue. I considered this as an adequate test of contrast for the centrally obstructed optical system of the Schmidt-Newtonian design. Just for fun, I continued on my double star quest, and included eta Cassiopiea and 93 Leonis. Neither is really a test piece, but eta Cassiopeia is an extremely popular target for beginners. Both doubles were very nice in the 10 mm Pentax XW eyepiece. I had plans to visit Struve 712 in Orion, but the breeze was now picking up and the telescope was starting to wiggle A LOT! The mount is O.K. for visual use in calm air, but it certainly is wishful thinking on the part of Meade that the LPI (Lunar and Planetary Imager) supplied with the telescope could ever be used under any but perfect conditions!
Before I called it quits for the evening, I slewed to M51 and it's companion galaxy NGC5195. Even though the finder scope gave me fits, I had little difficulty centering this fine DSO. I decided to skip the Ploessl eyepiece because the weather was deteriorating rapidly, and I wanted at least a peek at the "Whirlpool Galaxy". I started out with a Nagler 17 Type 4 at 60x magnification. Image brightness was excellent, and was an invitation to higher power observing. I immediately switched to the Pentax 10 XW and 102X. Too bad the winds were picking up and the telescope starting to jiggle around, or I would have attempted a drawing. With a stable image, I believe I would have been able to trace out both of the spiral arms and the "bridge" between these interacting galaxies. As it was, the moments that the wind dropped, I was able to detect the spiral arms, and the bright central cores of both members of these interacting galaxies were distinct. Image brightness was such that going to 143X with my SMC Pentax 7 XW would have been the next step. When looking for detail in these faint galaxies I use as much magnification as necessary to pick out details. Mother Nature finally won the battle, and I retreated indoors and away from the now-gusting 15-20 mph winds.
From this session, it was obvious to me that my enjoyment level at the eyepiece had increased by the upgrade of the focuser. Had the weather not interfered, I would have been able to test my TMB 25 Aspheric-Orthoscopic, and my SMC Pentax 7 XW eyepieces. I did gain additional respect for the optics, and was satisfied with the tracking at sidereal rate and the variable slew speeds of the arrow keys. I felt that the contrast of the optical system was far better than I expected, especially on M51. Although this Schmidt-Newtonian was not optimized for double stars by the design, it certainly has performed well enough to impress me favorably.
Two nights later I had extremely clear skies and a chance to view M3. This is one of my key test objects for the overall evaluation of a telescope's optics. The slewing and tracking of the mount continued to impress me with it's accuracy, even tho' it IS a bit noisy. Once I located the globular, tracking at the sidereal rate kept it fairly well-centered at 102X and even at 143X. I finally had a chance to use my TMB 25 AO eyepiece! I used it in place of the 26mm Ploessl for locating objects. On axis, the stellar images were excellent, but alas, it too showed some coma over the outer 25 to 30% of the field.
M3 in the SMC Pentax 10 XW eyepiece was a remarkable sight; upon very close scrutiny, the cluster was a virtual swarm of micro-pinpoint stars. I didn't have my magnitude chart with me at the eyepiece, but I am certain that I was easily reaching magnitude 15 stars by using averted vision. I switched to my Pentax 7 XW and 142X, which increased the resolution across the cluster's face, and increased the image scale. My notes from previous observations of M3 indicated that an ideal magnification for studying detail in this object is something on the order of 125X. I continued observing this beautiful globular cluster for about an hour, taking breaks from the e.p., and doing some strolling around the yard and breathing deeply.
Falling temperatures and dew were putting an early end to this session, but I did manage a quick visit to Jupiter before heading in for the night. I was able to see the equatorial bands even at low magnification (40X), and the darker polar zones were also easy to see. For what is ostensibly a "Rich Field" telescope, it performed acceptably on its foray onto planets.
The mount in all cases performed well, even if it is loaded beyond a realistic point. I did a few brief experiments with the go-to alignment procedure, and I was reasonably satisfied that the mount would do what the manufacturer claims. It IS MANDATORY to do the "Training the Mount" procedure exactly as described, and the telescope MUST be precisely balanced or the results suffer badly.
On the night of 4/12/2005 and the wee hours of 4/13/2005, I made a final series of observations prior to posting this review. I didn't start until the waxing crescent Moon was low in the West (4 days old). This was a night of exceptional clarity and stability. In spite of the Moon I was able to find M13 and I started there. The SMC Pentax 10 XW was used to center the object, and I subsequently switched to the Pentax 7 XW at 143X. The view of the Great Hercules cluster was almost worth the price of admission (i.e. the telescope). The stellar images were strictly pinpoint, and the cluster was a swarm of flickers across the face. I would estimate that several hundred stars were resolved at 143X. I spent almost an hour just looking through the eyepiece, then a short stroll around the yard with deep breathing, and then back to the scope again.
I noticed that Lyra was now well above the horizon, so I shifted my attention to epsilon Lyrae, one of my key test objects in the double star series. At first, the view was not real good. I waited for almost an hour for the stellar system to get up a bit higher, and in the Pentax 7 XW I was able to first see "peanuts", then figure 8's, and finally complete splits flicker in and out of view with the changes in seeing. Epsilon-2 was actually a cleaner split, 2.3 arc seconds, than was epsilon-1 at 2.6 arc seconds. Still, this is outstanding performance from a telescope design that is not optimized for this type of viewing! I also picked up M57, the "Ring", while I was in the area. Unfortunately it was still lower towards the horizon, and was still pretty "soft" or "mushy". And, no, I didn't see the central star. My final test object for thee night was alpha Herculis or Rasalgethi. This is a real popular double; a real nice color contrast (orange primary ,and blue-white or white companion). At 4.6 arc seconds it isn't real challenging, but is extremely pretty in a good telescope.
Rather than "belabor the point", re: evaluating the telescope, I have decided to skip over reporting most of my other observations and "get to the point".
Discussion of results
This telescope system is somewhat of an enigma to me. It seems to be somewhat of "a work in progress", and shows a lot of potential. Many of the components were obviously selected in order to hold down the costs, and that is a real shame. I found the optical performance to be much higher than my expectations when using well-corrected eyepieces of a type that includes a Barlow-type element as the field lens: Panoptics, Naglers, and Pentax XW's. My SMC Pentax XW eyepieces consistently yielded the best views, followed by the Naglers. Coma is nearly eliminated under these conditions, and the resulting stellar images are very sharp.
By far the most irritating feature of the telescope is the focuser. After only one observing session, I started shopping around for an aftermarket upgrade. I ordered a JMI NGF-55 Crayford-type focuser from the several available choices. My decision to install this particular model was based on the "no drilling", and "telescope—specific" nature of the kit. Both William Optics and Starlight Instruments (Feathertouch) manufacture Crayford style focusers that could be adapted to work on the SN-10, so it becomes a matter of economics and personal choice.
SN-10 with JMI, inc. NGF-55 focuser installed
I also replaced the 8x50 fixed-focus finder scope by "borrowing" the Takahashi 7x50 finder from my TOA 130. My eyeglasses have shaded lenses which attenuate the light entirely too much for use at night, especially when searching for faint objects. I discovered that something of a "focus" could be obtained by partially unscrewing the eyepiece from the body of the Meade finder scope, but it became pretty loose with my visual correction. Not really a solution to the problem!
The only other aftermarket item I acquired later was a dew shield from Astrozap. This was an "off the shelf" accessory, and was entirely satisfactory in my area where an unheated dew shield is adequate.
Overall, I was quite pleased with the optical performance. The collimation was quite good when the telescope arrived, and appeared to not require frequent adjustment. I rated the brightness of the stars, and the DSO's as being about 65 to 75 percent brighter than in my TMB 175. This estimate was based on an observation of M13 through my TMB 175 compared to the SN-10 observation of M3; the two objects appeared almost equally bright to my eyes. I used Steve O'Meara's estimates, (Deep Sky Companions ; The Messier Objects; Cambridge ), of the relative magnitudes of these two globular clusters to arrive at the brightness ratio. Also, I was able to split some double stars of moderate difficulty, and resolve globular clusters very well. In fact, I was rather surprised and pleased by these results. Open clusters were a marvelous experience, as was the Orion Nebula.
The mount and tripod were better than I expected, but the SN-10 OTA is right at the limit of acceptable stability for visual observing. I wouldn't even try imaging with this setup under anything less than still air conditions.
Good features of this telescope:
(1) Very good optical components in the OTA
(2) Nice fit and finish on all components (focuser excepted!)
(3) The tracking and slewing of the mount were accurate and smooth
Features that need improvement:
(1) The focuser is disappointing and almost toy-like
(2) Needs an illuminated reticle finder that focuses
(3) A 10" aperture telescope needs a "beefier" mount, especially on the Polar Axis and R.A. gearing. The tracking also "lags" after slewing in R.A., or an over correction is needed when centering objects
(4) A better quality eyepiece would be nice
Although this telescope is priced and marketed as a starter telescope, it has a few "warts" would probably really turn off the "newbies". The optical performance is more what an intermediate amateur would appreciate, and if this package were upgraded accordingly, Meade would have a real winner. I knew what I wanted from this telescope, so I made the necessary modifications. I also already own a substantial number of very high quality eyepieces, therefore my total financial outlay wasn't too bad.
Would I recommend this telescope to a prospective buyer? Yes, but with a few reservations. A prospective buyer/user should be prepared to spend some additional money on a few quality eyepieces, a new focuser, and a better finder scope or Telrad. Even with these few caveats, the Meade LXD 75 SN-10 AT is a real bargain in today's marketplace, and is a remarkable value for the price. I am pleasantly surprised by this telescope.
I plan to post a follow up to this review after some of the Summer deep sky objects have made an appearance.
- shahram and fissauer like this