Meade LXD75 AR-5

MEADE LXD75 AR5 Refractor

 

(note: this is a post-weight mod photo. See the review for details)

 

My first telescope was a Sears 2.4" refractor mounted on an alta-azimuth mount and it cost about $60 back in 1967. As the years rolled on, "aperture fever" took over and I successively acquired an Edmund 6"Newt, an 8" Cave Newt, and finally, a 12.5" Telescope World Newt. A big refractor? Who can afford one? Back when I was growing up, a 5 inch refractor would have cost thousands of dollars and for the same money I could get one of those larger-aperture reflectors. And so, I've spent my life viewing with Newtonians but always wishing I could afford a decent-sized refractor. With the advent of the Chinese into the astronomical market place, an affordable large-size refractor is now a reality. Enter the Meade LXD AR5.

 

For under $1000 you can now get a 5 inch achromat mounted on a solid, computerized, go-to mount. I figured that now is the time to get one. I placed an order through a local scientific store and they forwarded it on to Meade - who direct-shipped the scope to my house. There were no shipping costs. The scope arrived about 10 days later in two boxes. It had been raining and both boxes had water-damage on one end.

 

Although it looks horrific, it turns out that Meade shipped this scope with outer boxes AND inner boxes so nothing ended up being damaged. After opening the boxes, here's what you see:

 

The tube box contains the optical tube assembly plus the star diagonal, the finder scope, and the eyepiece - a 26mm Meade Plossl. You can see that some water made it through to the inner box but everything is wrapped in plastic and there was no damage.

 

The other box contains the mount and was packaged equally well. This box comes in two layers. The top layer contains the instructions, the central equatorial head bolt, the eyepiece/spreader tray, the Autostar controller, the battery box, and some hardware.

 

Pulling the top Styrofoam shelf out of the box reveals the rest of the mount.

 

Again, everything is wrapped in plastic. I found it interesting that the tripod was already put together - all that had to be done was remove the plastic wrapper, spread out the legs, and set the mount on the ground. Notice that the AR5 comes with a single 10 lb weight.

 

Using the instructions, setup only required about one hour of careful labor. The hardest part of the assembly turned out to be attaching the equatorial head to the tripod. First, it was somewhat difficult to attach a "C"-clip to the central retaining shaft and then that same shaft has to be engaged to the bottom of the equatorial head once the head is placed on the tripod. Careful reading of the instructions and patience will get you through this step.

 

Once assembled, you end up with an attractive-looking mount. All that's left is to put on the counter-weight and the optical tube assembly and you're ready for "First-Light" well, almost.

 

Adjustments

 

Now comes the interesting part. I've never owned a scope that was "perfect" right out of the box and the AR5 is no exception. Fortunately, the modern world features a new technological marvel called "The Internet" and I was able to identify the problem areas BEFORE I made the purchase by visiting a number of different web-sites. What I was interested in were the reports of problems by users of the LXD55 AR5. These problems are summarized here along with the fixes, if any; Meade applied to the LXD75 model:

 

1. The number-one complaint centered on the tripod. It was way too flimsy to support the weights Meade was loading on this mount. Meade's fix was to use a totally different tripod with 2" stainless steel legs. This tripod is rock-solid. This problem is officially "fixed."

 

2. A drive motor would suddenly stop working because one of the gear set-screws would work loose. Each drive has a gear shaft that associates with the electric motor and a gear shaft that associates with the mount. Each shaft is made out of different materials. The brass-looking shaft appears to be the cause of the problem. The brass is too soft and the set-screw eventually puts enough bite-mark into the material to allow wiggle-room. LXD55 users have solved this problem by one of two methods. One method calls for inserting a hard-metal shim (usually cut from an old hacksaw blade) between the set-screw and the flat-spot on the shaft. This prevents the set-screw from creating a crater that allows "wiggle-room." The second technique is to drill out the space between the flat spot on the shaft and the gear and then screwing in a self-tapping screw to "lock" the whole thing up. Of the two methods, I think the first one is the way to go.

 

What did Meade do about this problem? As far as I can tell: nothing. I've used this scope for several weeks now and I haven't had any problems with the motors. Examining the drives through the inspection ports shows the exact same arrangements as found on the LXD55 however, and I expect the same problem to eventually show up on my LXD75. If it does, I'll be ready.

 

3. Stiffness in the equatorial head. This is caused by the LXD55 using plastic bearings and lots of grease. Meade's solution: ball-bearings on both axes. The result is a mount with ultra-smooth axis motion. The lack of thick grease is evidenced by the ability to spin the declination shaft like a top. In sub-freezing weather the mount hasn't shown the slightest inclination to freeze into an unmovable mass. Both axes are free-moving with zero play no matter what the temperature. This problem is also "fixed."

 

4. On the refractor models, the star diagonal is cheep plastic junk. Meade has NOT fixed this problem. The supplied 1-1/4 inch star diagonal would be right at home on a dime-store 2.4" refractor. This item will have to be replaced.

 

5. The LXD55 AR5 model used a plastic lens mount that was non-adjustable. The LXD75 was upgraded to an adjustable mount of higher quality.

If you look carefully, you can see once source of irritation that Meade hasn't addressed. There are three screws used to secure the lens mount to the tube and they protrude into the light path of the lens. When you look at an out-of-focus image carefully, you can see these three bumps on the edge of the image. I'm going to leave this alone….for now.

 

 

With these five main problems accounted for there still remain other issues. First off, the LXD55 is designed to accommodate both refractors AND reflectors, so even with the tripod legs fully extended, the equatorial head never gets high enough to allow for comfortable viewing through a refractor. To help smooth this problem over I resorted to three fixes:

 

1. I immediately replaced the finder scope with the right-angle one off my Cave 8 inch. This allows easy and comfortable use no matter where the scope is pointing. The excellent finder that Meade supplied works perfectly on the Cave so this fix cost nothing - for me.

 

2. I use a little foot-stool to sit on while I'm viewing. This allows me to sit down while I view and puts me at the right height.

 

3. I loaded up the focuser rack with almost three pounds of lead weights in order to move the tube assembly upward in the saddle. Any purchaser of this scope should do this procedure so here are the details of how it's done.

 

(WARNING! Before doing this modification make sure you're happy with the scope - and you're not planning on sending it back to Meade under warranty. This modification will probably void the warranty on the tube assembly so check the optics and other tube components before you do the following steps.)

 

For materials, you'll need three items: One tube of Black silicone sealant, a can of flat black spray paint, and lead weights.

The weights I used are of the "pyramid" variety and can be found at any decent sport shop's fishing section. I bought these weights from the local Wal-Mart. Each weight is 2 oz and there are eight in a bag. I bought 3 bag's worth. Each weight needs to be pounded flat on one side with a hammer to allow clearance between the weight and the optical tube wall. The brass eyelet on the end should also be snipped off.

After preparing all the weights, the focuser has to be removed from the optical tube assembly. This is no easy task. There are three screws "holding" the focuser to the tube but even after they're removed, the focuser won't budge. I ended up wrapping a socket drive extension shaft with tape and placing this on the lip of the focuser, I was then able to hammer the focuser off the end of the tube. The reason the focuser seemed to be "welded" on was that Meade had placed a band of white hospital tape around the tube to serve as a gasket. This tape stuck to the focuser AND the tube and caused the whole thing to act like one solid piece.

 

If you look at the focuser assembly you'll see that it already has a counter-weight put into it by Meade. This weight is better than nothing but it's still not enough.

Notice that the assembly is divided into three different areas between the counter weight and the rim that goes around the optical tube. This is the area we'll use to pack the extra lead weights into. Each area will take seven 2 ounce weights for a total of 21 weights. This comes out to 21 x 2 = 42 ounces of counter-weight hidden in the focuser assembly.

 

Load the weights into the focuser by first applying a thick line of silicon sealant to the side opposite the side you pounded-out earlier as well as to the sides of the weight. The pounded-out side gets NO silicon sealant applied. Start by gluing the first pyramid in pointing downward and pressed up against one of the three tabs the Meade counter-weight is bolted to. The side opposite the pounded-out side should be pressed up against the Mead counter-weight. The next pyramid weight is placed with the tip pointing up. Continue this pattern until all seven weights are in place and fill the available area. Do the other two areas in the same fashion. The finished product will look like the picture below:

 

Let the silicon sealant dry for at least 24 hours before you paint the whole setup flat black. If you examine the first photo of the focuser, you'll notice that the inside of the draw-tube was originally painted flat black but in the act of adding light-baffles, Meade scratched up the inside of the tube and left shinny parallel marks leading up to the shinny baffles. This won't do. Since you have this assembly out and you're in painting mode, go ahead and re-paint the inside of the draw-tube.

 

Allow the paint to dry and then you're ready to re-assemble the focuser to the tube. If you just put the focuser on to the end of the tube and use the three screws to secure it, you'll discover why Meade used that hospital tape to act as a gasket. The whole assembly has a wiggle to it no matter how much you tighten the screws. You'll need to make your own gasket. Use a high-quality tape, like white medical tape, and wrap the end of the optical tube with about 5 or 6 turns. The focuser needs to slide over this with some resistance… but don't overdo it or you'll be reaching for the socket extension and the hammer the next time you need to remove the assembly. Once you find the right amount of gasket, you can go ahead and secure the unit with those three screws. You should have NO movement if you've done everything right.

 

There turns out to be one problem with the added weights in the optical tube assembly. Meade sent just one 10lb counter weight and its just barely adequate for an un-modified AR5. Once you add the extra weight, all bets are off. I found that you can pick up a cheap 7lb counter weight that fits the LXD75 from Orion. There are other places that sell counter weights but I've found Orion to be the cheapest. If you make this modification, get the extra counter-weight.

 

Operation.

 

The LXD75 operates off of a 12v DC source. Meade supplies a plastic battery holder for 8 D cell batteries. I actually use this arrangement since I happen to have 8 D cell nickel metal hydride rechargeables. At 8500 mAmp-hour each, there's plenty of power to run this scope over several viewing sessions. If you don't have rechargeable batteries, I'd see about getting a 12volt power supply. Just make sure it's rated at around 5 Amps or more. The slewing motors will draw about 1-1/2 amps while going full blast and you don't want to be caught short.

 

I've seen on other web-sites how LXD55 users use bubble-levels to make sure the equatorial-head is dead-level. I don't bother. I first take the mount out and point it to the pole using the polar alignment scope and the handy-dandy built-in mount adjustment controls that move the equatorial head up and down and from side to side. I DO NOT point the cross-hair at Polaris. I point it at the offset from Polaris where I know the true pole to be. Once this is done, I go fetch the optical tube assembly and secure it to the top of the head using the dovetail bar and the two locking screws. Meade changed the LXD75 by having the polar home position marks cast into the metal… where they won't come off. I line up these marks, lock-down the axis and press the "on" button.

 

The first time AutoStar is started it has you enter in your location but once that is done, you'll only have to answer questions about the date and time in order to start the unit up -unless you change locations by a number of miles. After initializing, AutoStar wants to do an "Easy Align." Pressing the Enter key causes AutoStar to select a star (that you have the option to approve) and slew to it. You center this star in the telescope and then press Enter and AutoStar repeats the process for the second star. After that, a message displays saying that alignment was successful (I've never had it fail). In the month or so that I've used this scope, I've never had AutoStar fail to place a selected object within the field of view of the supplied 26mm eyepiece. I'm very impressed.

 

Once an object is acquired, the AutoStar hand-paddle lets you move the scope using arrow keys. You can also tell AutoStar how fast to slew by pressing a numeric key - the higher the number, the faster the scope will slew. The fastest slewing speed still sounds rather loud but the other speeds are quiet. In normal sidereal tracking mode, the RA motor is very quiet.

 

How accurate is the RA drive? I haven't hooked up a CCD camera yet for deep-space photography, but on one evening an object centered in the field of view was still centered after over an hour of in-attention. I suspect that periodic error will not be unacceptable, but I have yet to prove it.

 

Optics

One reason I bought the AR5 was because I wanted a larger refractor and I wanted a reasonable f-ratio. A 6 inch f8 refractor not only cost more, the fast F ratio gave me concerns about unacceptable chromatic aberrations. The AR5 is rated at F9.3 which is still fast for a refractor but it turns out to be a great compromise between size and performance. Viewing very bright objects does bring in the usual blue halo but not at a level I can't live with. I also noticed that the eyepiece being used had a very noticeable effect on the amount of the chromatic aberration. As you would expect, my TeleVue Plossl eyepieces gave the best performance - by a wide margin over the other brands that I have.

Images in the AR5 have the very pleasant "snap to focus" that refractors are renowned for. Still, just how good is the figure in these lenses? I took a picture of Vega both inside and outside of focus using a Starlight Xpress MX5c camera.

The image on the left is inside focus and the image at the right is outside. First off, you'll notice that the alignment appears to be off. Actually, when viewing visually, the image is concentric and the factory alignment is quite good right out of the box.

 

The alignment in the picture is off a bit because the weight of the camera caused the draw tube to flex enough to throw off the image. This gives you some idea about the amount of flex present in the focuser mechanism. Other than the flex, I found the focuser to operate rather well. It has nice aluminum knobs and smooth action.

 

Looking at the rings, you can see that the lens is under corrected but is still operating at around 1/4 wave. When viewing through the scope, the lens is plenty good enough to cause stars to focus down to tiny pin-points.

 

As a first visual test I wanted to see how the AR5 would handle Epsilon Lyra. I was able to get the stars to separate with as little as 66 power (18mm TeleVue Plossl). With a 6 mm TeleVue Plossl I had the best view of the system that I have ever seen. Each star was a perfect pin-point widely separated from its neighbor. No, I wasn't going to be sending this optical tube assembly back to Meade for replacement. It isn't perfect, but it's still pretty darn good.

 

Deep-sky viewing is outstanding - especially on star clusters. Stars in my 32mm Celestron Plossl show perfect pin-points close to the edge. It's clear that the F9.3 ratio is coaxing out the best performance of each eyepiece you view thru. This is the trade-off. Views thru my 12.5 F4.8 Newtonian show more stars, but the coma and the short F-ratio causes the field to deteriorate toward the edges. The AR5 doesn't have this problem. It WANTS to give sharp images right up to the edge. It's up to the eyepiece to deliver the goods. If you buy this refractor, get a GOOD set of eyepieces and you'll be richly rewarded.

 

Bonuses

 

The final reason I bought this telescope was to provide a go-to computerized platform for my 1959 8" Cave Astrola Newtonian. This scope has a mind-blowing mirror but the mount is rather primitive by today's standards. I bought an extra dovetail bar and enough weights to support the Cave and just like that, I've got a modern, 1959 Cave 8"!

One other thing this experiment told me is the weight limit of the mount. The Cave weighs in at 24lbs and I wouldn't want to add anything more. The 10" LXD75 is supposed to weigh around 30lbs so I think I'd be a bit concerned about the stability of such a setup.

 

Summary

I love this telescope. Yes, it needed some tweaking, but it's a terrific value and a joy to use. Here is the breakdown of pluses and minuses:

 

Pro:

1. Solid tripod with 2" stainless steel tubes.
2. Excellent go-to computerized operation.
3. Accurate drives on both axes.
4. Upgraded ball-bearing mount with a very nice finish.
5. Attractive F ratio for a larger-sized refractor

 

Con:

1. STILL being sent out with dime-store star diagonal.
2. Meade never saw fit to provide a place to hold the AutoStar hand-paddle. Most users resort to Velcro strips…just like I did.
3. The tripod is about 10 inches too short for a refractor. This CAN be combated however, using methods outlined in the review.
4. Only ships with one eyepiece.
5. When slewing, the scope still sounds like a coffee-grinder.
6. Straight-through finder scope. This is unsuitable given the short tripod.