About Aperture Fever
Roberto Garza
I want to add my experiences to the assertions on Jack Kramer's article "The Aperture Ailment" which appeared in the August 2005 Night Times.
I started building telescopes in 1992. I built a copy scope at first, then 3 Dobsonians: a 6"F8, a 10"F6 and finally a 12.5"F6. I made at least 3 versions of each. And there's still room for improvement on my 12.5" which I currently use.
The "Aperture Fever" hit me when I compared the image my 6" F8 made of M51, with an image by the club's 10" F5. Both scopes had fairly good optics, but the 10" won "hands down", showing a lot more detail of the galaxy pair. Not long after seeing this, I acquired a 10" Pyrex mirror from Orion Telescope and Binocular Store. I built a two truss open Dobsonian. It accompanied me to big and small star parties around the country and western Canada. I compiled more than 400 objects of all design-nations with it. Everything was fine till I started running out of objects below 12th magnitude. I began to think about "more aperture!".
An opportunity came my way and I built the 4 truss 12.5" using ash wood at first. I took the prototype to British Columbia in 2003 and found many problems to be fixed. The main one was weight. It was hard for me to tuck it inside the cap in the back of my truck while on my knees. I could not achieve the proper leverage without straining my back. This prompted me to build another version with glued pine boards panels, bought at Menards. It was somewhat lighter, but there was still the problem of "leverage". In desperation I came up with the idea of a collapsing system. I eventually got it all in place.
Now the metal legs on the base, all of the walls and bottom of the rocker come apart, as does the primary mirror assembly. I'm working on a collapsible mirror box too; it will be ready before the Star Parties start next year. The collapsible concept allows me to lift and carry piece-by-piece with weights of less than 10 lbs. with the exception of the primary mirror assembly (which reaches almost 25 lbs). It takes some time to set it up, but I think it is worth the trouble. I usually attend star parties of 3 nights or more, so assembly time is not a problem. I haven't seen any object deeper than 13.5 magnitude yet, but then: I haven't encountered the "perfect" night either!
Even though I'm very pleased with the performance of my 12.5" 1/8 wave mirror, I will not discard the possibility of going bigger with the certainty that I would need to find an easy way to lift whatever I build.
My goal is to reach a 1000 object level. After that, I would go back to review the most remarkable ones and perhaps observe them with more power or different eyepieces and filters to see more. Or maybe I will turn into astroimaging, which is "the way to go" now a days, with the ever increasing light pollution and the result of the diminishing dark sites.
Being a "visual" observer, gives me a sense of connection. The feeling that I am seeing something in person so far away and so deep into the past that... it may not even exist anymore!
Published in the December 2005 issue of the NightTimes
