Re: Re : ATM Prime focus

[Bratislav Curcic <epabcc@epa.ericsson.se>]

First I'll apologize if something similar to this message already
appeared. My mailspool kicked bucket while I was sending the reply, and
I have no idea whether mailtool managed to deliver the message or not.

John Maxwell wrote :

> My understanding of "prime focus" is that it's more of a mechanical
> engineering term than an optical one.

So what is 'mechanical prime focus' for a SCT ? What is 'mechanical 
prime focus' of mine (or yours) Newtonian ? Or Herrig's convex primary,
double-pass TCT ?

I am NOT disputing someone's desire to call place where you sit in a
large telescope 'prime focus'. In an instrument with so many possible
configurations, it makes sense, or I'd even say it is required to make
distinction betwen prime, Cassegrainian, Nasmyth etc foci.

What I _am_ disputing is someone challenging us calling the intended
(and in many cases the ONLY) focus of our non-interchangeable telescopes
as PRIME focus.

But this is getting into a war of opinions, and I have no desire
to take part in that. Anyone can call foci of their telescopes any way
they like it, I will do the same.

If weather holds tonight, I may try some TERTIARY focus imaging. You
see, the strong oblate mirror in my telescope produces horrible images
at PRIME focus. So I may add a corrector. And a diagonal flat, as my
head is too big and blocks all the light so I can't focus.

Or should I call it simply "imaging at the Newonian focus of the oblate
primary corrected by Schmidt-like corrector" ?

Bratislav