Dave's DS-90 EC Page
last updated 11/28/2006. version 1.23
My name is David Myers and I'm a recent owner of a Meade DS-90EC telescope. As far as I can see, very little has been written about this particular scope and its capabilities. It's the largest refractor in Meade's Digital Electronic Scope line, a series of inexpensive refractors aimed at, well, the low cost mass market crowd. On a scale of 1 to 5, Ed Ting (7) rates this scope a 2-, barely acceptable. On the other hand, refractors are known to be well collimated out of the box, it weighs about one half to one third of what a 6-8" dob would weigh, and to be totally honest, it was partly an impulse purchase. More so, it's the biggest scope I've ever owned.
I believe optically the scope delivers nicely. The things I see compare well to the descriptions of observations made by scopes of similar size (4,5). I do my observations in a suburb of Atlanta, Georgia, and viewing here is not good. Most stars of magnitude 4.5 or so are lost in sky glow, and there are a lot of clouds. Fluffy, or thin, or pollution-induced haze all affect the seeing in this city.
One major reason for buying the scope was to explore the capabilities of the Autostar computer control system. Initially, a combination of bad skies and endemic power supply connection problems (1) left me using the Autostar as a motor speed controller. Using Sylvain Weiller's fix and either (a) sticking to the AA battery pack, or (b) using either of the recommended battery power cords mentioned below, has enabled me to align and use the scope's GOTO capabilities. It's not perfect yet, as I can lose alignment in the vertical dimension. There is a leather washer fix mentioned on the Meade-DS mailing list archives that helps reduce this problem (2).
A good portion of the DS-90EC is plastic. Depending on how you feel about plastic, you may have better or worse feelings about the DS-90. The focuser is plastic as is the holder for the 6x30 finder. The tripod is also plastic, broad grey triangular legs that come down to black plastic "feet" tipped in rubber. Watch for the rubber pieces at the end, they sometimes fall off. The dew cap comes off, and you can place a dust cap over the 90mm lens. Dust caps also cover the star diagonal. The large dust cap is fragile; it cracked in use after a couple days. A plastic tray comes with the DS-90 attaching to one of the legs. This tray has pre-cut holes for 3 1.25" eyepieces, and 3 .965" eyepieces.
For those who may not know, this scope is a 90mm achromat with multi-coated optics. The focal length is 1000mm. Effective useful maximum magnification is probably about 180x in good seeing conditions, though the eyepiece I like and use the most right now is a 40mm plossl. On bright objects in my kinds of skies, there will be some chromatic abberation around objects. Mars occasionally displays a green edge and bright stars may have a blue halo at high power. The highest power I have used is the 200 power delivered by a Vixen Lanthanum 5mm. This eyepiece I have for the occasional moments of superior seeing.
I find in use that the 6x30 finder view gets blurry quickly. Atlanta is amazingly humid, and dew (or sweat condensation) can be a limiting factor in viewing. In Joe Robert's review of the Meade 4500 4.5" reflector, he recommends making a dew cap for the finder. He then goes on to say that a toilet paper tube can make a dandy dew cap for the Meade finder scope.
The optical tube assembly (OTA) can be removed from the tripod and carried separately. This is easier for me than carrying the unit as a whole. Two thick plastic half circles hold the tube to the mount, and these are easily removed and set back on when needed. Two large metal screws lock the tube in place; about the only thing to need to do with the tube is find the approximate center of gravity and place that point in the holder. I've done this with or without my viewing eyepiece in place, it doesn't seem to make a lot of difference.
One thing that is a concern when you port this scope is the attachment of the drive motors. They're attached by knurled knobs, and the plastic threading isn't the best plastic work I've seen. For one, they're very easy to misthread and it's a little difficult to know when they're properly attached. They will pop off if the scope falls (though this behavior is better than having the motor snap off, to be sure).
The DS-90EC comes with two eyepieces, a MA-25 (25mm focal length) and a MH-9 (9mm focal length). MA stands for Modified Achromat and I'm told this is Meade's version of a Kellner eyepiece. I've had good viewing with this eyepiece in this scope. The MH is a Huygenian eyepiece. This much I can say, I bought a 9.7mm series 4000 Meade plossl with this scope, and the difference in the size of the aperture of the plossl, as compared to the MH-9, is so substantial I've never been inclined to try out the MH-9. Other users of the DS-90EC, who actually used the MH-9, report it as a less than acceptable eyepiece. Huygens eyepieces have poor eye relief and about a 30 degree field of view. It should be replaced with a good Kellner minimally, or perhaps an orthoscopic or plossl.
I've purchased 7 eyepieces in addition to the ones that came with the scope. I have 2 Meade series 4000 eyepieces, a 9.7 and a 6.4 mm plossl, and 3 Sirius plossls, a 17mm, a 26mm and a 40mm. If you've never seen a 40mm eyepiece, it's...well, its very big. If I were to curl the fingers of my right hand, without making a fist, it's about as large as those closed fingers. However, in this kind of optical body it gives a good 2 degree field of view (actually, it's more like 1.72 degrees) and that wide view was exactly what I purchased the eyepiece for. I'm satisfied with the Sirius plossls as wide field eyepieces for this scope. I'm still searching for the optimal high field eyepiece.
The Meades can give nice images, but I feel as if I'm "pushing my face" into the eyepiece to get to the sweet spot for viewing. Particularly in the 6.4mm size, it seems a little awkward after a while. It's not as noticeable at 9.7mm. Therefore, I've purchased a 5mm Vixen Lanthanum and a 6mm Celestron orthoscopic. I like the Vixen, as a high power eyepiece with some eye relief, and I'm still evaluating the Celestron. Supposedly, the signature advantage of an orthoscopic (beside a hair more contrast) over a plossl is somewhat superior eye relief. At 6mm, my eyelashes are sometimes brushing the ortho.
Meade plossls are often sold at serious discounts on places like Astromart or eBay. Beware of people selling MH 12.5 eyepieces on eBay. Occasionally you can get orthoscopic eyepieces for $25-35 on these two locations. Plossls can run a little more, though used Sirius plossls are priced around $30-35 on Astromart (avoid buying Televue plossls on eBay; they're usually bid much higher than the Astromart price). Offhand, you're more likely to get the best price on Astromart; eyepieces I've bought on eBay cost me, on average, 10 percent more than the Astromart price. eBay more frequently allows Paypal payment, so you can get your purchases faster.
Other astronomical gear that I've acquired in addition to the scope are a pair of binoculars (10x50, Carson optics, purchased at the Discovery Channel store). Binoculars are absolutely necessary in urban skies. You need these to piece out the layout of constellations and figure out what you may be pointing at. Perhaps in a good dark sky site these would not be as essential, but I think of binoculars and a scope as two sides of the same coin. For one, some things just look better in binoculars. For another, the wide field view is a great preview to anything you may wish to look at in more depth.
Sky maps help, though good software (8) will help ameliorate the need for a book. Still, Binocular Astronomy, by Crossen and Tirion, is something I look at a lot. Turn Left at Orion is also highly recommended. Nightwatch, which a lot of people propose as the best beginners book, is a little too wide and too square to be comfortable lugging out into the field. I have the book, but it tends to stay at home.
If Polaris is out of sight, a magnetic compass helps.
I had a red flashlight I bought from the Discovery store; it fell apart in use within a month. I've made my next red flashlight, from a $5.00 flashlight I bought from Home Depot, a piece of soft red plastic that came from a car key holder, and electrical tape.
If you decide that the 10 AA batteries aren't enough juice for your DS scope, I'd recommend going down to Sears and looking at the sealed portable batteries they have available for jump-starting cars. These things can be had cheaply (ca $35.00) when they are on sale, and can be recharged at home (recharger built in) or recharged while driving to a dark site (with a male-to-male cigarette lighter connection). If you're using a battery, stay away from Meade's 12V to scope power cord. The connection it makes with the mount is unreliable and I cannot recommend it. There are at least two better solutions. The first is from Radio Shack. They have a universal cigarette lighter, that will mate with the Adaptaplug "N" adapter. Combined with a clothesline hook, this provides a cord that never needs to be unplugged, because the universal adapter has a switch in the base of the lighter plug. The best single part commercial solution comes from Scopetronix. They have a power cord that connects a battery to a 12V external plug (ITEM# PCRD). The connector is sealed plastic and solid, and the cigarette lighter plug is fused. The fit to a DS-90EC is tight and without the connect problems that plague the Meade connection.
Other batteries in common use by users of the DS-90EC are sealed lead acid batteries ("gel cells"), available at hobby shops or recreational supply stores. People have used batteries rated from 1.2amp-hours to 7 amp-hours with good results. These are usually supplied for RC cars and the like, but can be easily adapted to telescope use. Other users have warned this voltage is not entirely useful acrosss the Meade line. Certain of the 4500 scopes use a 494 Starfinder controller and they do not function well when voltage drops below 11.5 to 12.3 volts (the actual value seems to vary, depending on the report). In this case, two 7.2 volt batteries in series may be a better option.
If you need even more power, a common alternative is a sealed maintenance free deep cycle battery. These are often used on boats, but can be carried in a small cooler and a 12V cigarette lighter adapted for use.
The Meade telescope comes with a CD, which can install a software package to display the skies and another to drive the telescope. As I don't have a spare laptop to devote to this, I just installed the display software. It works, and works nicely. It also displays the apparent brightness of the skies as you work through various viewing times, something I haven't seen on other packages. It can print skies too, but when it does, the Milky Way obscures all the stars on the printed image where the Milky War is found (that may well be correctable, but...). Because of this print problem and support issues in general, I'm more likely to use Cartes du Ciel (8). There is terrific suppport from the amateur community for this product and the configurability of this software is exceptional.
The number of improvements in the Autostar firmware are substantial, and certainly my Autostar was already obsolete by the time I purchased it. On the other hand, the Meade website has a software package that can be downloaded to bring the Autostar up to date. The current software revision is 22E, and to get the best performance out of your system, making sure the Autostar firmware is updated is essential. Meade sells an adapter cord that connects the Autostar to the PC. It didn't seem to matter much which serial port I used for the connection. When I ran the update software, it found the serial port and the update started pretty much automatically. Now, unless you make a custom power panel for the Autostar (plans are available on Mike Weasner's board), you'll need to lug your mount to your PC, so that the Autostar can have power.
The software update needs to be done in two parts. First, update the firmware to revision 21ek using the "Autostar Update Client Application for Windows". Then, make a copy of your old Ephemerides directory (in case you need it) and then download Roms22er.zip. The data in this package will need to be placed in the Ephemerides directory and the update run again. There are tricks to get this running if your OS is Windows 2000; see Mike's site for details(3).
Sylvain Weiller has a fix to the power outage/line tangle problems that he exhibits on one of his web pages (1). I've just completed a version of this fix, using parts available at Home Depot. You need a clothes line hook, 1/4" x 4 1/4" (this contains a threaded hook and two hex nuts), two 1/4" lock washers, and a foot of 3/8" OD, 1/4" ID transparent vinyl tubing. See Mr. Weiller's web site for the location of the hole you drill in the DS mount. After drilling a 1/4" hole, you can fit the hook to the mount; then remove the nuts and slide on the vinyl tubing. You may have to do this in two pieces, one for the curved hook and a second piece for the straight part. Use lock washers between the nuts and the metal of the mount; I used one on both sides. An 11mm wrench works fine to tighten the nuts. The parts are cheap; I think this cost me $1.88.
Another common line tangle fix is called the "skirt fix" and it consists of a piece of 1"-1.5" OD vinyl tubing bent into a circle, secured in that position with a rod inserted inside the vinyl tubing, and the circle then wrapped around the mount to sit on the legs. The idea is to keep the motor wires from falling into the slots formed by the tripod legs and the mount. This fix is popular and doesn't require a mount alteration. See Bill Brady's document, DS_Skirt.txt, in the Meade-DS mailing list archives, for more information (2).
Another simple fix I recommend, for AA battery power use, is adding additional velcro pads to the scope, one on each leg, so that any leg can be used to mount the batteries. I also tend to loop the cord over the OTA and bring it down to the control panel from above. Doing the Weiller fix and 'over the tube' looping of the power cord has led to multiple sessions without a single power disconnect.
I'm also using a version of Joe Robert's dew cap fix for the finder. I've taken 3.5" of rubberized cloth and taped it into a tube, then taped the tube to the finder using electrical tape. I'm not certain if it's helping yet. Atlanta is amazingly humid.
Balancing, Alignment and Motor Training
While I've balanced my scope by hand horizontally, there is a train of thought among DS users that the scope should be balanced so that the front of the scope is pointed upward at a 45 degree angle, and that this should be done with your heaviest eyepiece in place. I doubt there is much physical difference between these two points on the DS-90EC, though leaving the scope's "neutral position" at about a 45 degree angle probably makes it easier for the motors to position the scope in the 30-60 degree range.
The documentation that accompanies the DS-90EC states that the scope should be leveled and pointed to the north before the Autostar can begin the alignment process. If you're looking for a level to accompany your scope, small, inexpensive ones can be had at a local hardware store (T. Johnson, model I believe is #125, cost about $3.00 at Home Depot). It's more important that the optical tube be level than the mount, though obviously leveling both cannot hurt. Meade documentation suggests leveling need not be exceptionally precise. Also, the orientation towards North only need be approximate, to within a few degrees. Eyeballing the OTA towards Polaris has yielded acceptable results.
There is a suggestion on Mike Weasner's board that ETX telescopes be motor trained at night using Polaris, and using a slow motor speed (the author suggested a speed of 3), in order to effectively center the star in the eyepiece. The rationale behind this is that it is much easier to center a small star than a larger terrestrial object. I have done this using the DS-90EC and was very pleased with the results. The subsequent point of the scope to Arcturus, as part of the two star alignment process, was well within the finder and close to the eyepiece.
There are techniques for using a laser pointer for alignment developed by Rich Swanson. These techniques should be done in a spare room, inside. In essence, tape a laser pen to the barrel of the scope so that it points parallel to the OTA, and then elevate the scope to about a 45 degree angle. Mark the spot where the laser falls on your wall (Rich suggests taping a paper 'X' to the spot). Then go through the training 'ritual', using eyesight to bring the laser back to your mark The big advantage is that you can train inside and without an eyepiece. Further, laser training can be used to detect bad motors. See the Meade-DS mailing list file archive for details(2).
GOTO capabilities and tracking
In my hands, these are erratic in quality. I get in-the-eyepiece GOTOs only for short hops. Now, to be sure, I'm not motor training every day and often Polaris is obscured, so a certain amount of guesswork is necessary to set up the scope. However, I'm getting two good stars for alignment, and as long as my GOTOs are near my second alignment star, things work reasonably well. On long slews, though, final position is a roll of the dice. The target may be in the viewfinder, or vertical alignment can be off by 10 degrees. If I SYNC locally, afterwards the scope has the sometimes nasty habit of wanting to motor down the field, sometimes about half the apparent field of a 26mm plossl eyepiece. I can't help but wonder if I'm not activating the spiral scan capability of the Autostar by accident.
I haven't tried the leather washer mod yet. That is supposed to improve the ability to hold vertical alignment.
Tracking, once it's stable and not acting flaky, is rather nice. It helps with handling higher magnification and switching from lower power to higher power eyepieces. And with lower power eyepieces, it's much easier to step away from the eyepiece, talk to a passer-by, and be sure the target is still in view.
When you're done, it's recommended that you use the PARK SCOPE option. That tells your scope to move back to the home position, and you can then power down. Shutting down in this way causes the Autostar to remember the current alignment. When power is applied again, the scope will track immediately, without a new alignment Now, that may not be the smartest thing, if the scope has been moved, but it allows for a quick SYNC near the object of interest after powering up again. Further, as Bill Brady has noted, you can align at nightime and later on in daylight, GOTO Venus.
For now, observations will be placed on Alistair Thomson's site (4), under the 90mm section.
Questions or Comments?
You can email me here.
What's New? -- Web Page Changes
1.23 - Converted page to XHTML and added a style sheet.
1.22 - Updated battery comments after receiving Scopetronix's battery cord. Revamped the eyepiece comments. Added note about flashlight.
1.21 - Batteries have become their own section. A paragraph is devoted to balancing, and the value of parking scopes discussed. Comments about the viewing quality of the MH-9 have been added. These additions are based substantially on email discussions in the Meade-DS mailing list.
1.20 - typo fixes.
1.19 - Added the Meade-DS mailing list link. Added information gleaned from the files section of this site. Added the section called "GOTO capabilities and tracking".
1.18 - Amplified some comments in the Dobsonian links. Added the Autostar section.
1.17 - Added the Dobsonian links.
1.16 - Added a link to Joe Robert's telescope reviews, which
talks about a related Meade scope, the 4500. As the finder on this
scope is the same as the DS-90EC finder, his advice about adding a
dew cap is repeated here. Added links to Joe Robert's page and Tom
Campbell's page as well. Added this section to the web page.
1. Sylvain Weiller's DS tangle fix
I've had a lot of problems with the power supply disconnecting at the wrong time. This is one partial solution to this issue.
2. Meade DS mailing list
It's been relatively quiet as a mailing list goes, but the archives of problems and fixes is a treasure for a DS owner. Odds are I'll end up trying one or two of them, even if I've found some other ways to resolve certain of these issues.
3. Weasner's Mighty ETX Site
Though oriented towards the ETX telescopes, there are plenty of user reports covering the whole DS line, and as well, Richard Seymour prowls these pages and offers a lot of good advice. Some of the best information about alignment can be found on these pages and most anything new and hot about the Autostar (such as converting a 495 Autostar into a 497 Autostar) can be found here. It's often very hands on, with schematics of the various Autostar-oriented cables and electronics.
4. Observing with a small telescope
Alistair Thomson's site has a lot to offer the beginner, with a range of observation reports using anything from hand held binocular to 8 inch SCTs. The focus is on the 6" Newtonian but it's one of the best sites, if what you wish is to get a feel for the skies you see.
5. The Urban Astronomer
Cindy Quek's home page is a joy. For one, she uses smaller scopes. For another, the links on her page are very useful to the beginning astronomer.
6. Cloudy Nights Telescope Reviews
Going just by the name will give you a misperception of this page. There are more than just telescope reviews here. There are a lot of 'how-to' articles on construction of useful stuff, and the scope reviews will often contain extensive discussions of the telescope modifications these owners have implemented. There are at least three useful reviews of eyepieces (not all with the same opinions about eyepieces, either), and in the beginner's section, the article titled "How to start an introductory eyepiece collection for $50" is well worth reading.
7. Ed's Ting's Telescope Reviews
Ed is an amateur of long standing, a president of his local club and has a lot larger budget for astronomy than I ever will. But he has some pithy things to say about the scopes he uses, I think him worthwhile to read, and he covers a lot of ground in the higher-end telescope market.
8. Cartes du Ciel homepage.
Good stuff. This software can plot star charts, calculate the locations of the various planets and other moving objects. It's a star hopper's dream, as you're able to plot the sizes of your eyepieces over a nearby star, and see if it overlaps your target. This was how I found M57. Cartes du Ciel made it easy. Also, don't let the French of this home page deter you. Click on the little English flag to the left, you'll be able to read it then.
9. A history of the telescope
A concise history of the telescope.
10. The Atlanta Astronomy club
Just joined. These are nice folks and well worth spending some time with.
11. Steve Bedair's DS powered telescope mounts
This site reminds me again why computers and computer controls
can be so much fun. You just have to think sideways about the
problems at hand. Steve
is taking scopes with no "GOTO" capacity, and attaching the DS motors and an Autostar to custom mounts, and thereby creating computer controlled scopes.
12. Hans Peter Wallner's page
Another site with a collection of DS driven larger telescopes.
13. Tom Campbell's Amateur Astronomy
I ran into this page when I was browsing Alistair Thomson's site. Tom's observations with a 60mm comprise a substantial plurality of all the 60mm observations recorded here. As he's been through the meat grinder of the department store scope purchase and upgrade, and survived, I think it's a site that all small refractor owners should take a gander at, sometime.
14. Amateur Astronomer's Notebook
Among other things, Joe Roberts reviews his equipment, which includes a Meade 4500 4.5" reflector. The review is worth reading slowly and carefully, as Joe is good at the little details that make astronomy better.
15. Plans for Building a Sidewalk Telescope
I constantly run into people when I observe, and they seem amazed that they could build a telescope of their own. This is the original of these kinds of plans, provided by the Telescopes in Education (TIE) group in NASA. It's here so I don't have to remember their URL. I can give people my URL and point them to this site. Also, I think the owners of DS scopes can get a lot from the ATM crowd. DS scopes aren't perfect out of the box, and the more aware people are that telescopes aren't sacred cows, the more pleasure they'll be able to get out of their telescope.
16. How to Build a Dobsonian Telescope
Another good 'how-to' link. In some respects I think this a more
accessible site than the NASA site..