From: "Russell Jocoy" 
To: telmor{at}teleport.com, milnecd{at}yahoo.com, atm{at}shore.net
Reply-To: "Russell Jocoy" 


>From: Chuck Dethloff 
>To: "Russell Jocoy"
,milnecd{at}yahoo.com,atm{at}shore.net
>Subject: Re: ATM Truss design thoughts.
>Date: Thu, 24 Jul 2003 11:03:13 -0700
>
>
>>>From: Clive Milne 
>>>***snip***If your scope
>>>still vibrates, I'd wager it's not the truss tubes at fault.
>>>It might be time to take a good hard analytical look at the whole
>>>design from the ground up.  Just because everyone has built them
>>>basically the same way for for the last 15 years doesn't make it right.
>>>It's high time we moved on.
>>


>
>
>At 11:00 PM 7/23/2003 -0400, Russell Jocoy wrote:
>
>>           Here, here.... I agree, How can you blame vibration on supports
>>when you are using
>>primative secondary cages made of wood and rocker boxes of thick Plywood.
>
>
>Guys,
>
>I admit that I am troubled by parts of the above quotes. You know, maybe it
>is time that we quit worrying so much about how others build scopes
>compared to what "we" think is the best way. What has been
done in the past
>has worked very well for a lot of people. So have some of the newer designs
>for others. There ain't one single right or wrong way to design a scope, it
>comes down to pluses and minuses for _any_ design and what goals are most
>important to the individual building the scope. I don't see a
"holy grail"
>of Dobsonian design out there, so lets not pretend that there is one.
>
>And what is adequate structurally comes down to a lot more than calculated
>minimum values in the real world. Engineers have over-designed for many
>years for one very good reason. So that the dang thing does not fall apart
>if the materials weaken with age and cumulative stress, or perhaps they
> made an errant assumption or calculation somewhere along the way.
>Like was obviously made recently by NASA engineers despite their
>qualifications.
>
>Or maybe it is exposed to abnormal abuse on occasion. As an example, a
>couple years ago a good friend of mine had his 20" Obsession tarped up
>outside at my house to protect it from rain between observing sessions. The
>next day unusually strong winds caught his OTA just right (well actually,
>just wrong) and blew the OTA up and over out of the rocker box. It landed
>upside down on its back apparently with the cage hitting the ground first.
>Despite that it only sustained minimal mostly cosmetic damage. That
>happened to be one of those primitive wooden cages Russell. If I was
>wagering, I would bet that a more minimal cage ring and truss assembly
>would have been crushed like an eggshell. Which by the way is also very
>rigid for its mass.
>
>I have looked through a lot of scopes over the years. Many of my friends
>have built ultra-light scopes. I certainly do not want to offend them or
>anyone else who likes a more minimal scope while making my points. But I
>need to say what I honestly feel as well, and my opinions are not based
>merely upon mistaken bias. Nor do I feel they are invalid because I don't
>offer up pages of scientific data in support of my viewpoint. Those that
>only accept that type of evidence are only seeing part of the big picture
>IMHO. My thoughts are rather based upon my experiences and what I see
>through the eyepiece of various other scopes.
>
>Most of my frustrations here are with the insinuations from Clive and
>others on this list from time to time that these old dinosaurs have just
>outlived there useful time. Really? Granted, any scope of any design needs
>to be well constructed not just well engineered to work at its best. But
>regarding strength and rigidity (interpreted from at the eyepiece
>performance), nothing I have seen exceeds the more traditional works of the
>past 20 years if well constructed. And the vast majority of the more
>minimal scopes I have seen are a lot more sensitive to vibration than the
>traditional designs.
>
>Having said that, I am now getting closer to 50 years old and weights that
>I handled easily 20 years ago are more imposing. I can see why many folks
>want lighter and more portable scopes. As a result of this, I am going to
>build my new 24" in a much lighter fashion than I ever thought I would ten
>years ago. And I readily admit that I never would have felt comfortable
>even considering building a scope so minimal if not exposed to the work of
>Mel Bartels, Greg Babcock, Bruce Sayre, Tom Osypowski, and others as well.
>I am also inspired by the work of many of you that I have never met in
>person. As I have worked through the design of this scope I think I visited
>just about every web page out there put up about ultra light scopes. My
>thoughts and design have been influenced not only by scopes I have looked
>through, but also by the work of Stathis Kafalis, Ruediger Heins and others
>that I will probably never have a chance to look through. I feel a measure
>of appreciation and respect to all that have pushed the envelope over the
>years and taught us new ways, including you Clive.
>
>But please don't ignore or devaluate the positives of the past in an
>attempt to enhance the glory of the present. Build what you like and let
>others build what they like without making them feel ignorant or wasteful
>for not building them in the latest fashion.
>
>Chuck Dethloff
>


("atm{at}shore.net")

        Chuck,

            What a great comentary, My initial statement was that ATMer's
use the basic materials available
to them to create their telescopes. Through this we have learned what works
and what doesn't.
The concept of making something that is in the same league as a
professional optical instrument is
a great accomplishment. And at times the optics exceed those
"professionals. I think that we all sometimes
loose the old ATM spirit and get a liitle too technical on the structure. A
good mirror will  look good even
with crummy supports as long as it is aligned in an eyepiece and is
somewhat supported.
           Large bulky supports are good , they don't blow around in the
wind, but they are tough to transport.
   Guess what, make them so you can dissasemble them. Oh yes this has been
done before.
        It seems that the never ending quest for the ultra-light has
problems.  I would think that you would need to add wieght to the
ultralight when you observe in areas that have wind. Am I wrong. If the
scope is
so light as to be feather wieght, what happens when that thunder storm
comes along without warning.
   I would guess that you would be so concerned about the stability of your
scope that you would not leave
it alone and babysit..    Just my thoughts.. I have no problem with plywood,
oak, steel, or any material
used to make a telescope.       Russ Jocoy
("atm{at}shore.net")

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