Re: [ATM] PlOp PlOp Fizz Fizz oh what a relief it isn't?

["Stars" <rocketmaker@intergate.com>]

Hi Curt.

First -off  I asked for proof that PlOp produced superior results because some claim it did. There seems to be no proof. I can cite the study using another modeling program that was used in the design of the 8.2 meter Keck that validates conventional design both through the Finite Element Modeling method but then by actual interferometric measurement. Then there is:
http://www.cruxis.com/scope/scope1100_mirrormesh3d.htm

And from which I quote: 
Limitations of Plop 
Plop can only handle circular mirrors that are subjected to a gravity load parallel to the mirror's optical axis, and is obviously of no use for anything else.

Which I already quoted and with which I agree. I have given the solution to this site for a 12.5", nine point cell that has worked well for 30 years. What do you have?

If you have mirror that is only going to point staight up then PlOp may just work for you but it is not a superior design tool for conventional optics. On the other hand if you are going to build a telescope that looks at different parts of the sky, I assure you my nine point will not require you to refocus as the attitude of your scope changes. I can also assure you the PlOp design will. Again ask yourself. Nine point cells have been around for more than 100 years. Know of any that failed?

34 years ago I served a president of an astronomy club and Clarke Diggs was my secretary. He lived in Escondido and passed away in 1975. Any relation?

Anyway I don't think you read all of my posts about this. That's OK I haven't read all the replies yet either.
Cheers,
Rick Crockett




----- Original Message ----- 
From: "Curt Diggs" <mokiman_210@yahoo.com>
To: <atm@atmlist.net>
Sent: Monday, November 12, 2007 3:09 PM
Subject: Re: [ATM] PlOp PlOp Fizz Fizz oh what a relief it isn't?


> Could you please provide some information that supports your to claim that "PLOP is useless"? 
>   
>  Your disparaging statements with no supporting analysis or information other than your opinion serves no value or helps anyone on this list. Here and elsewhere PLOP results have been compared to and found to be in reasonable agreement with sophisticated and expensive 3D FEA analysis software. If you think PLOP is a "nonsense piece of software" then PROVE it. If you can produce better results, SHOW us.
>   
>  Curt Diggs
>   
>   
>  >Hi Fabio:
>  >The point is that to many people put to much faith in a nonsense piece
>>of 
>>software. Yhe old tried and true ways were actually correct. The fact
>> that 
>>software could produce a beautiful picture did not infact mean it
>> produced 
>>an accurate one. In fact PlOp is usless. I am not convinced it will
>> even 
>>work for a static mirror pointed straight up but I know it will fail
>> for 
>>conventional telescopes. The thing that gets me is the all for Gospel
>> way it 
>>was accepted by a group that should have known better AND I still
>> haven't 
>>seen actual verification that it works. A hex wrench is the wrong tool
>> when 
>>your driving nails. A broken hex wrench is little good for anything.
>  >You make a good point but I make so many telescopes that there is not a
>> 
>>progression for me. Sometimes I go back but I have developed a new
>> technique 
>>of ultra light constuction including an extremely stiff 1.8 oz 6"
>> mirror 
>>cell. The next time might be something in plywood as I try out a new
>> design.
>  >Best,
>>Rick
>  Re: [ATM] PlOp PlOp Fizz Fizz oh what a relief it isn't?
> 
>       
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