Month: November 2020

Meet the Amateur Astronomers at Tele Vue #2

Tele Vue Optics was founded by an amateur astronomer, Al Nagler, and it is no surprise that amateur astronomers have been drawn to fill the ranks of Tele Vue employees. In this week’s blog, as part of an ongoing series, we meet one of the amateur astronomers at Tele Vue.  

Mahendra Mahadeo
Mechanical Engineer

Our newest employee is a telescope builder and avid astrophotographer who has been busy imaging the night sky with a Tele Vue-85 and Canon DSLR since he started at Tele Vue. “Satesh” as he goes by, graduated with a Masters in Mechanical Engineering, from City College of NY. Al Nagler, who also graduated from City College with a Physics degree, but just a “few” years before Satesh, has enjoyed having a fellow alumnus on our team.

Al Nagler in his City College sweatshirt (left) with Mahendra Mahadeo (right) socially distant while standing with Al’s 12-inch, f/5.3 Newtonian that won first prize for Newtonians at the Stellafane Convention in 1972. The framed photograph on the ground nearest Al is of the Double Cluster. Al took it with this scope: 80-minutes, tracked by hand back in the film days was enough to end his pursuit of astrophotography! (Staff photo).

In his own words, Mahendra describes his journey into amateur telescope building.

Astronomy was not always a specific interest of mine, it was always space exploration in general. When I learned that there are amateurs that build their own telescopes, that all changed because I felt as if space had become a bit more accessible to me. Being an aspiring engineer at that time, the idea of building something as elegant as a telescope was more appealing than buying one. An extra challenge I had was that I had absolutely no experience with amateur astronomy or telescope making and when I say absolutely, I mean I had never looked through a telescope. Luckily there is a wealth of information online about telescopes and mirror making and I read so much that I became confident that I could do it.

Shown is the cover of Mahendra’s telescope building journal. Over the last six years, he’s filled this codex with draftsman-like sketches of mirror grinding machines, pitch laps, Dobsonian mounts, and telescope designs along with copious notes and data on his work in progress. (Staff photo)

I approached mirror making as smart as I could. To prevent astigmatism, I decided not to grind the mirror by hand. Instead, I made a fixed-post grinder that was driven by a hand crank and this ensured that the mirror’s surface was ground symmetric about its optical axis. I documented the process in a handwritten journal in case I encountered any problems during Ronchi testing. I could refer back to my notes and see what caused the problem. That paid off because I encountered almost every problem I read about; zones, under correction, over correction, turned down edge, etc. I fixed all of them and finally, I had a parabolized 6-inch F/6.5 mirror uncoated. I quickly assembled the mirror into the optical tube. In October 2014, I looked through a telescope for the first time when I finally tested my mirror on the sky by observing the moon and star testing on Sirius. The mirror was still uncoated and I hadn’t made the Dobsonian mount as yet. I pointed the scope by propping it up on a chair. By the end of 2014, the mirror was coated and the mount was complete. The entire process took almost a year, from building the mirror grinder to completing the scope.

Mahadeo’s design for a mirror grinder. (Staff photo)

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