You know the story. Andy’s sixth birthday brings him Buzz Lightyear, displacing Sheriff Woody. The other toys share Woody's grief until (as always) they confront and surmount the challenges. And they lived happily ever after.
Right now, 14:23 hours 05-July-2026, we are in the trope’s “save the cat” pages of the script.
[Earlier versions of this narrative were posted to Cloudy Nights discussion “New 70mm Maksutov from Spectrum Optical Instruments” started by Jim Riffle on December 3, 2022 in the Cats & Casses Forum. My comments there are #321, #323, and #335.]
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| Back left: white: Explore Scientific 102-mm doublet refractor Front left Astronomers Without Borders 130-mm Newtonian At right: Spectrum Optics Tour Star Pro Maksutov-Cassegrain. |
The Newt Rebellion
June 27: For the past couple of weeks, I have been getting out more with my “tabletop Dobsonian” from Astronomers Without Borders. It is a Newtonian reflector 5 inches (130 mm) in diameter and it comes without a tripod but it does have a Vixen mount for universal compatibility and I put it on a ES First Light Pan-Tilt Mount.
The AWB dob needed collimation (aligning the primary and secondary mirrors) but it was not too far off and it pretty much stayed that way night after night. The time before last, I tweaked it again and made it dead-on to within a gnat's whisker. The next afternoon (June 28), the Spectrum Optics Maksutov Cassegrain telescope arrived from Astronomics and I set it up.
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| Left: AWB 130 on ES First Light Mount. Right: Meade StarPro 70 mm. They got along fine. |
Set-up was easy. I intended to take out the AWB reflector to compare the views. When I looked in the collimation eyepiece, the view was horrific: the entire primary mirror was two-thirds off center, ten times more wrong than it ever had been. I adjusted the three primary screws at the back. That was ineffective. I adjusted the three secondary hex bolts up front. The changes were not the ones I sought. I loosened the main mount of the secondary mirror mount. It only got worse. I took the AWB 5-inch reflector and two cases of small tools into the house.
Unexplained Sightings
June 29. After the unusual failure of the 130-mm Newtonian from Astronomers Without Borders, I took out the Explore Scientific 102-mm doublet refractor. To other stargazers, I identify this as “my grab-and-go.” On its mount, with accessories, the package is 20 lbs (9 kg) and it always works. Tonight, the red-dot LED finder scope would not come on.
Click. Click-click...pause...wait... do it again...
Easy enough, I got another battery. Nothing. Click. Click-click...pause...wait... do it again… Batteries fresh from the pack seldom fail, therefore the LED on the finder must be dead. (Later, I checked the battery and it still had high potential at 3 volts.)
Next, I chose a Celestron 51630 Star Pointer from inventory. With dabs of white-out, I match-marked the On-Off and Up-Down and went out and ran errands. A couple of hours later, I went to the telescope to check the alignment on the red dot finder and the On-Off switch was broken: it clicked Off but rotated fully through On without clicking On. and there was no red dot.
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| Explore Scientific 102-mm refractor. Note at right on the eyepiece mount is a Stellarvue Correcting Prism with fine focus. (I think that taking this off the ES-102 and putting it on the Mak-70 was a point of contention among the scopes.) |
Portland Cement on a Horta
July 3. I filled out a request slip and gave my tool check to the guy at the crib for an AstroTech Multiple Reticle finder the same as I use on my AstroTech 115 mm Extremely-low Dispersion Triplet refractor. Then I found a new base to fit both the ES 102 telescope and the new finder. I settled on the closest match and superglued the plastic bases to each other.
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| Homepage ad from Spectrum Optics At $159 it was very competitive in its class. Astronomics had these for $100. So, I bought five for four friends and myself. |
Right now, the mount for the finder is narrower than the draw of the clamp attaching it to the stand. So, now, I am looking for shims. Passing up scrap aluminum and plastic, I tried folding and rolling paper, then turned to plastic soda straws before cutting to lengths a cardboard stylus for cellphones. To hold the shims, I used SuperGlue gel. It is not a permanent repair but it will work until I get new finders from Explore Scientific. Now, I can use the grab-n-go for all of the deep space objects in my southern skies from 10:00 PM to 2:00 AM and continue to test the Maksutov against the near competitors in my shed.
[Sunday. July 11. 23:30. Like the Official Dog in Eric Frank Russell's "Alamagoosa," the patch failed under gravititic stress. The telescope is back in the shed under wraps "until I get new finders from Explore Scientific."]
[Tuesday. July 14. 16:03. I bought three replacements from Explore Scientific. (I have another 102-mm refractor like this one but longer.) The trees that they are on do not fit the slot in the telescope. I got out the shoebox with new and used finder bases and found a close match. After sighting and aligning on a nearby chimney, when I go out again, I will have to remember that "center" is down and to the left of the red dot.]
The salient problem remains: Why all the failures?
Notes:
Astronomers Without Borders branded their entry-level hobbyist instrument in the name of John Dobson, a problematic Vedanta Hinduist who sought to unify religion and science by building large telescopes from scrap parts and taking them to the streets of San Francisco to show people the skies they did not know.
A Sidewalk Astronomer, documentary film by Jeff Jacobs:
https://www.youtube.com/watch?v= bVbX19kabNc
Tribute by the Planetary Society
https://www.planetary.org/profiles/john-dobson
Wikipedia of course
https://en.wikipedia.org/wiki/John_Dobson_(amateur_astronomer)
Dmitry Dmitrievich Maksutov was serving in the USSR military when he invented this design. Like the Cassegrain and Schmidt, the Maksutov design benefits from a folded optical path, allowing twice the focal length or half the tube size. Moreover, the "negative miniscus" of the secondary optics corrects for spherical aberration. However, the Maksutov design allows aberrations when the diameters of the component mirrors exceed 100 mm (4 inches). So, these tend to be small and lightweight, which is perfect for hobbyists. Moreover, the telescope is sealed: there is nothing for you to adjust.
PREVIOUSLY ON NECESSARY FACTS
National Geographic 70-mm Refractor Field Test
