What is it about the design and execution of newts that makes them so sensitive to collimation. I understand that all telescopes require proper alignment; but, once that is achieved why isn't the mounting system designed to hold the correct collimation indefinitely? Is there a need for the variable mirror cell, or can the mirror simply be mounted in a more riggid and durable cell and tube assembly?
Newtonian telescopes - collimation
Started by n2s-astronomy, 02/09/2009 08:06PM
Posted 02/09/2009 08:06PM
| Edited 02/09/2009 08:23PM
Opening Post
Posted 02/09/2009 08:57PM
#1
Enrique Barrio said:
What is it about the design and execution of newts that makes them so sensitive to collimation. I understand that all telescopes require proper alignment; but, once that is achieved why isn't the mounting system designed to hold the correct collimation indefinitely? Is there a need for the variable mirror cell, or can the mirror simply be mounted in a more riggid and durable cell and tube assembly?
Enrique: Newtonians are the least sensitive of all designs when it comes to collimation. The Newtonian is the only design that uses a single curved surface, this means it is relatively insensitive to collimation errors.
It is this very insensitivity that makes collimating a Newtonian relatively easy which means that the operator/user/owner can be trusted with the task. It also means that the structure can be relatively flimsy and light in weight. Other designs that are more sensitive to collimation require mush more rigid structures.
The OTA assembly of my 16inch F/4.42 weighs less than 60 lbs and can be assembled and collimated in about 10 minutes. If it were sufficiently robust that it held collimation, it would have to be considerably more massive....
Bottom line: The reason that Newtonians need to be collimated is that it is a simple task.
Jon
Posted 02/11/2009 01:13AM
#2
Enrique Barrio said:
What is it about the design and execution of newts that makes them so sensitive to collimation. I understand that all telescopes require proper alignment; but, once that is achieved why isn't the mounting system designed to hold the correct collimation indefinitely? Is there a need for the variable mirror cell, or can the mirror simply be mounted in a more riggid and durable cell and tube assembly?
Three small points:
Roland Christen has pointed out that Tak Netonians were made permanently collimated at the factory, and he recommneded that Newtonians in general should be made that way.
We are told that collimation of Newtonians is relatively simple; no doubt that is why threads on CN explaining collimation rarely exceed 250 posts.
To learn collimation, get an experienced amateur to teach you hnads on. Failing that, consult Nils Olaf Carlson's S & T article, and his web page on myths of collimation.
Bill Meyers
Funding Member
