MEADE ETX-70AT COMMENTS
In March 2001, Meade loaned me an ETX-70AT and Standard Field Tripod (the current bundle).
I first unpacked the tripod. This tripod is for mounting the ETX-60AT and ETX-70AT in Altitude/Azimuth orientation only. It comes with a nice carrying case with a strap and a pocket for the accessory tray.
The tripod has adjustable leg heights and an accessory tray with an Autostar holder. The tray can also hold 4 1.25" eyepieces. I was surprised that there were no leg spreader supports for stability. But as it turned out I had no stability problems when in use. I did notice that without the spreaders the legs will fold up somewhat when the tripod is picked up. So, you have to be careful when you set the tripod back down again as the legs may not be in the correct positions. I later discovered that the leg tips are soft rubber and act as effective vibration suppression pads. Nice touch.
I then unpacked the ETX-70AT. It comes with an Autostar #494 as standard, a manual, a 25mm eyepiece (yielding 14X) and a 9mm eyepiece (39X), Star Navigator CD-ROM (used to control the Autostar from Windows if you have a #506 cable), some information on Meade accessories for the ETX-60AT and ETX-70AT, and a Meade catalog. There is no finderscope included. One nice feature of this model which I hope gets included in the ETX-90EC and ETX-125EC models is that the battery compartment is on top of the base instead of beneath it. So, you do not have to unmount the ETX-70AT from the tripod to change batteries. The 6 AA batteries are contained in a slide-out cartridge. Upon power up I noticed that the Autostar was version 10El. It contains some 1400 objects. The Autostar itself has no keypad; all entries are done using the up/down/left/right keys. At first I was concerned that this would be cumbersome but in actual use I found it surprisingly simple and straightforward. The only physical problem I noted with the telescope was that the Declination setting circle was not correctly aligned to the zero position. As with other ETX models, this was easily corrected by loosening the DEC lock knob and rotating the scale until it showed the proper setting.
I then proceeded to read through the manual. It was actually pretty good. One thing that struck me was that Autostar Drive Training is almost an "emergency procedure". The manual states that it is not necessary unless GOTO or tracking problems become evident. I was anxious to put this to the test!
On the first clear evening after receiving the telescope I took it outside to view a thin crescent Venus. The telescope/tripod combination is lightweight; I could carry it outside by holding it in one hand. Setup was extremely easy. The HOME position for this model is: level the telescope (base and tube), point the tube to the North, and power up. Since the control panel is on the top part of the base, there is no cord wrap to be concerned about and hence no hard stops. So, unlike the EC models, you do not have to rotate to a hard stop and then reverse back to pointing North. On powerup, the Autostar goes through the same initialization steps as other Autostar models. You get told about the Sun, get some onscreen help, and then enter the current date/time/etc. If you have not entered your location before now you should do it before first use. The alignment options are the same as with other Autostars; I picked two star and accepted both as centered (the sky was still too bright to see these stars).
I then did a GOTO Venus and it was placed in the 25mm eyepiece field-of-view! (Guess I'm getting pretty good at the blind North pointing!) This was when I noticed the vibration suppression pads on the tripod. There was no vibration from the tracking motors and other vibrations quickly damped out. Venus was pretty small at 14X, certainly not as impressive with the ETX-70AT 350mm focal length versus the ETX-90 1250mm focal length. (More on the focal length differences later.) But I could detect that it was crescent shaped. It was much nicer in the 9mm eyepiece, which yielded 39X. Image quality with either eyepiece was good, with minimal color fringing evident (refractors are more prone to this than other telescope designs).
It is nice that there are two eyepieces supplied with the ETX-70AT as you won't see too many details at 14X. But when you change eyepieces you are in for a real pain. Literally. The standard focus knob is very small and is in a very cramped location on the back of the ETX Optical Tube Assembly (just like on all ETX models). It is so close to where the flip mirror is housed that you can not rotate the knob a full turn. And it takes many full turns to change focus for the 25mm eyepiece to the focus for the 9mm. You end up rotating the knob about 45 degrees at a time. I found this the worst part of the ETX-70AT design. The focus shaft should have been extended further back from the end of the telescope to allow a better grasp on the knob and more rotation. As it is, I found my fingers cramping while changing the focus position. This really cries out for a Scopetronix "FlexiFocus" or electric motor.
The next night out I did some extended GOTO-ing and observing. I started out by doing a two star easy align. After the first star was selected, I realized that I should have extended the tripod legs to their full height so that I wouldn't be hunched over the eyepiece (I left my observing chair inside). So I picked up the telescope/tripod in one hand, slide the legs out, and set it back down with Sirius (the selected star) in the 25mm eyepiece. The next star was slightly outside the field of view but I could easily identify it. Then it was GOTO Saturn: nearly perfect slewing. GOTO Jupiter: almost exactly centered in the 25mm eyepiece. As to the views of Saturn and Jupiter, at 14X both will be a disappointment to most viewers. You can tell Saturn is not round but that is about it. At 39X you can see Saturn's disk, the Rings, and the gap between them; and Jupiter's moons (the brighter ones) and a couple of cloud bands.
I successfully used my #126 2X Barlow Lens with both eyepieces (yielding 28X and 78X). A yellowish cast was visible when the Barlow was used with the 9mm eyepiece. I'm not certain what was causing this. I also tried my Meade #932 Erecting Prism but could not reach a focus with it. There is a different model erecting prism for the ETX-70AT available from Meade.
The "creep after slew" was noticeable at 78X so apparently this Autostar version also suffers from it. It was not seen at lower magnifications, due to the wider field of view and lower magnification.
I then asked the Autostar for a "Guided Tour". All objects that were not behind obstructions or lost in the glare along my northern horizon were easily seen and nearly centered in the 25mm eyepiece. Even M31 was nice in a less than dark sky to my Northwest. The Double Cluster in Perseus was very nice. The Pleiades looked like diamonds on velvet with the entire expanse visible in the 25mm; beautiful. M42 in Orion was also nice, even when I attached a Light Pollution Filter.
Where the ETX-70A (and probably the ETX-60AT as well) really stands out is as a wide-field telescope. I can't wait to try it out on views of the central portion of the Milky Way.
After the Moon reached a waxing crescent I decided to compare the views using the lowest magnification standard eyepiece supplied with each of the ETX models I currently have. The photograph was taken using through the 25mm eyepiece on the ETX-70AT. I made drawings of the view through the 26mm eyepiece on the ETX-90RA and the 26mm eyepiece on the ETX-125EC. I then cropped the image to show the view (the images are just an approximation of the view through the eyepieces). This really demonstrates the change in focal length, hence magnification, with each telescope.
ETX-90RA (1250mm focal length) with 26mm eyepiece (48X)
ETX-70AT (350mm focal length) with 25mm eyepiece (14X)
During all my sessions with the ETX-70AT the only problem I have had is with the focusing knob. As I noted earlier, it takes many turns to change focus when switching between the two supplied eyepieces. But when the scope was pointed at the Zenith I could not even reach the focus knob to change the focus! And my hands are not that big! Focusing while wearing gloves is definitely out. This is the only drawback to an otherwise fine telescope (when used for its intended purpose). It is a nice addition to my "ETX family"!
I have posted some comments about wide-field Milky Way viewing on the 6/17/01 update to the "Update Autostar using a Mac" page.
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