University Lowbrow Astronomers

The Meade ETX 70 AT.

by Clayton W. Kessler
Printed in Reflections: January, 2002.

This interesting little scope was purchased to provide an airline portable wide field scope to observe with while in Arizona.  I spent some time looking at the alternatives for a “lookin’through” scope to use while my 4” refractor and G11 were working hard taking astrophotos.  I researched many alternatives, 8” dobsonians, 4” f5 short tube scopes, a 6” or 8” reflector mounted on my existing SVD mount.  All of these had something going for them - but also had many drawbacks.  The most common was the physical size.  None of these would fit aircraft “carry on” luggage.  It would be possible to build an 8” or even a 10” carry on dobsonian telescope but it would not be a small chore.  It would take a lot of careful work to craft a scope of this nature.

I was Christmas shopping up at one of the local malls when I drifted into a store that specialized in science and nature items.  I noted that the store was stocking up on Celestron telescopes and the Meade scopes were all on sale.  A little conversation with a salesman confirmed that a “brand change” was taking place.  I took careful note of the 60mm and 70mm ETX style refractors that were on display.  These scopes had an identical focal length (350mm) and while they would never be high powered planetary scopes I suspected that widefield views would be quite nice.  I popped an eyepiece into the 70mm version and took a look at a light fixture out in the mall.  As you would expect the achromat design of this refractor showed color fringing on a bright light source.  On the other hand, the view was fairly sharp across the whole eyepiece.  Hmmmmm.......

I must admit to some curiosity about the mount.  The ETX mount included the “Autostar” computerized controller.  This, if it worked, would make it quite easy to find objects and also opens up the possibility of tracking satellites with this thing.  I have never owned a “GOTO” telescope before and this intrigued me quite a bit.  A couple of weeks after Christmas I stopped by the mall again and purchased a 70mm sample of this scope.

To those of you familiar with the ETX90 the telescope controls are no mystery.  The focus knob is in the back and moves the front lens cell in and out to achieve focus.  This worked well but it was somewhat hard for my fat old fingers to reach in and turn this knob.  Fortunately “Scopetronix” makes a focus knob extension that replaces the stock knob and is very easy to use.  There is a “flip mirror” to allow mounting a camera in the back of the scope.  I think this will work well for terrestrial photography but the mount is not robust enough for astrophotography with this scope.  The computer control works on 6 “AA” sized batteries that are supposed to power the system for 20 hours.

The scope came with a 25mm MA and a 9mm MA eyepiece yielding 14x and 38x respectively.  While these are not Naglers, they offer a reasonable amount of magnification to use with this little beast.  One small complaint, they are not even close to parfocal!  It took many turn of the focus knob to change them.  After the first time I focused with the 9mm and slid the barrel of the 25mm out until rough focus was obtained.  I need to try some parfocal eyepieces with this, maybe some Edmund RKE’s will work well.

On my arrival in Arizona the weather was not the best.  I arrived about a day or two after the new moon and by the time the rains stopped (4 days later) there was too much moon for astrophotography.  For a while I did not think I would get to use this little scope.  Fortunately a night spent at Roger Tanner’s Rita Ranch observatory gave me the opportunity to put this thing through it’s paces.  I borrowed a Bogen photo tripod to set the scope on and it proved to be a very sturdy support for this mount.  The setup of the computer control was straightforward - I just followed the instructions on the hand controller (I don’t need no stinkin’ manual!).  The scope has you center two stars in the FOV.  I thought it was somewhat odd - I had to slew the scope up 10 degrees or so to center each star.  Then I realized I had the “position” set as “Ann Arbor Michigan” instead of “Tucson Arizona.”  I decided to leave this setting alone and see if the scope could cope with this “casual” setup.  I got an alignment complete message so I set the scope to slew to M42 which was high in the east.  The ETX 70 AT is not as loud as the LX200 scopes - but you can tell that they come from the same family.  Once the slewing stopped and the scope “beeped” me to indicate it was finished I peaked into the eyepiece.  M42 was almost dead center.  Even with the bright moon I could see a lot of nebulosity.  A quick change of eyepieces to the 9mm showed the four trapezium stars resolved at 38x.  Not Bad......

Now for something a little harder - a planet.  In order to slew to a planet the scope must know what day and time it is.  This is set as a part of the initial setup.  I told the scope to find Jupiter and after a little growling - presto!  The banded planet and it’s moons.  This scope will never be a high power planetary scope but I could easily see the four moons and the major belts on the planet at 38x.  Saturn clearly showed it’s rings - although Cassini’s division was absent with the supplied eyepieces.

I have to admit being impressed with the performance of this inexpensive GOTO mount.  As an experiment I slewed to M44, the beehive cluster.  I then left the scope to track by itself in Alt-Az mode for about 2 hours while we hunted and killed a “pizza.”  During that 2 hours the beehive barely moved from dead center of the eyepiece field of view.  In fact everything that I asked it to slew to ended up in the field of view.  This included a couple of trips across the sky to look at M31 and the double cluster.  Like the LX200 it is easy to center an object and re-synchronize the mount to refine your alignment.  On this moon washed night the dimmest object that I could see was M104 - the Sombrero Galaxy.  It was just a dim oval patch but it was there in direct vision.  On a darker night I suspect that most or all of the Messiers will be possible with this scope.

Conclusion:

This is looking to be a very nice scope.  The size of this scope is such that it can be placed in a small duffel bag and carried onto an airplane.  I am impressed with the ease of use and performance of the GOTO mount.  As long as one does not expect to use high magnifications this satisfies the requirements for a “grab and go” scope for an experienced observer.  In my opinion this also represents a fine scope for a beginner - as long as one does not expect to use high magnifications.  I suspect that - atmosphere permitting - 100x will be the max usable on this system, and this will be a rare night indeed.  On the other hand I am anxious to try my 7mm and 4.8mm Naglers in the scope.  I suspect they will be very nice at 50x and 73x.  As the weather warms I will try to get out to Island Lake some weekend if anyone is interested in getting some eyepiece time with this interesting telescope.

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Copyright © 2013, the University Lowbrow Astronomers. (The University Lowbrow Astronomers are an amateur astronomy club based in Ann Arbor, Michigan).
This page originally appeared in Reflections of the University Lowbrow Astronomers (the club newsletter).
This page revised Sunday, March 9, 2014 4:30 PM.
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