Astromart

>>I've read that Mak corrector thickness is the main reason Mak type scopes (of whatever configuration) take so long to equilibrate temperature-wise, >>

Yes, lots of folks seem to believe that and it is total myth. Now that you know this is not true, you can laugh every time you read this kind of statement and dismiss it as pure fiction.

Roland Christen

February 20, 2006 09:16 PM Forum: Maksutovs

Mak correctors

Posted By Roland Christen

>>I've read that Mak corrector thickness is the main reason Mak type scopes (of whatever configuration) take so long to equilibrate temperature-wise>>

Let me put it another way. What you have read is plain wrong. The corrector of a Mak-Cass is not to blame for the thermal problems of some Maks. The reason that you believe this is because you read it somewhere in a post or letter written by another person who read it somewhere, etc. etc.

The letter that you have written here will no doubt be read by another couple of people who will in turn relay that on and on. It will never stop. For every one time that I see something like this written, there will be 1000 posts which will say again that thick Mak correctors are to blame for temperature problems. And the plain fact is that not one of those letters and posts will be based on real information, just hearsay. So, please the next time that you post something about Maks, keep in mind what I have told you, and please mention that the thermal thing of thick Mak correctors is a myth (probably perpretrated by some competing Cassegrains that feel deprived).

Rolando

March 31, 2006 02:55 PM Forum: Refractors

orion 100mm ed

Posted By Roland Christen

>>The bright stars seemed to not be pinpoint but like little tiny plus signs>>

+ sign means the image has classic astigmatism. Could be caused by differential temperature, cell pinching the optics, tube currents due to insufficient cooldown etc.

RC

April 1, 2006 04:30 PM Forum: Equipment Talk

Dielectric coatings and distortion??

Posted By Roland Christen

You are falling victim to a marketing ploy. The dielectric star diagonals that we make use a proprietary coating process that does not stress the mirror surface, neither when new, nor years down the road.

Aluminum coatings are fine for general use. For critical planetary viewing they have an advantage because you need a very clean surface on your eyepiece lenses as well as on the diagonal to get the highest possible contrast. Dielectrics have much better longevity and cleanability and lower scatter than any mirror coated with a metallic material.

Diagonals are very prone to accumulation of dirt and dust because one tends to insert eyepiece barrels numerous times during the night. This action drops crud down on top of the diagonal mirror which most often does not come off by simple blowing of air. Shine a flashlight onto your diagonal after only one night's use, and you will see. Dielectric diagonals can be repeatedly cleaned without picking up tiny faint sleeks.

Roland Christen

April 1, 2006 07:27 PM Forum: Chinese Optics Imports

Latest Item-Quartz Diagonals

Posted By Roland Christen

It has no advantage in a star diagonal, other than it sounds sexy and is the darling of marketeers. For primary mirrors in Newtonians or maksutovs, it has some advantages as far as cooldown, but in the 2" sizes of a typical star diagonal there are no cooldown issues. As far as accuracy, for a 2" size, one can put high accuracy surfaces on just about any substrate, be it quartz, Sital, pyrex, and even plate glass.

Rolando

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Dielectric coatings and distortion??

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