Parks 12.5-inch

Is this a Park with the fiberglass tube? Fred have you ever observed with one of those? Some people said that they have issues with the thermal currents.

Fred σε κατι τετοια αστροπαρτυ πρεπει να παιζει πολυ επιδειξη εξοπλισμου.

Θελω να πω πως πρεπει να πηγαινουν ολοι για να δειχθουν παρα να κανουν παρατηρηση/φωτογραφιση.

Spyros,

 

The PARKS 12.5-inch reflector shown here has a PARKS fiberglass tube that is 15-7/8-inches ID. That is 15.875-inches inside diameter. The mirror is 12.5-inches in diameter. So, naturally, there is a 3.375-inches (3-3/8-inch difference. The clearance around the mirror comes out to be 1.6875-inches or 1-3/16-inches clearance between the mirror and the tube.

 

As to issues with thermal currents, the embraces a few diferent things. One of course is the thickness of the mirror, another is the cooldown time bwtween the mirror and the outside atmosphere and how quickly the temperature changes. I am certain that you are aware that many people have placed fans behind their mirror mount in order to help with the image quality. I have an article that states that all of the turbulence is relegated to the few inches directly above the face of the mirror and that a fan should be placed perpendicular to the actual surface of the mirror. Therefore drawing the warm curents across and away from the surface of the mirror in a more direct fashion. Placing a fan behind the mirror will of course draw air around the sides o fthe mirror, but it will move the air less as one moves away form the edge of the mirror towards the center of the mirror.

 

Naturally for planetary and lunar observing one wants the best seeing possible. For those really extended objects like clusters, nebula and galaxies, practically any seeing condition is ok-as far as I am concerned.

 

 

Angelos,

 

You are correct, the Riverside Telescope Makers Conference is a great place for the amateur telescope maker to show the fruit of his or her labor. There are awards given out for workmanship. At nightfall the telescopes are all trained on objects in the night sky. A few people will actually do some cdd, comet searching or whatever else interests them. Years ago a member from the San Jose Astronomical association, Dom Machholz, discovered a comet at the event and a marker was placed at the spot where his telescope was set up. There is also the talks that take place from themornig up to the evening with breaks for lunch and dinner.

 

During the day it is a "feeding frenzy". On Saturday morning there is the swap meet where people bring all the things that they want to sell and it gets real crazy. Picture 500 pounds of steak being thrown overboard into shark infested waters.

Thanks Fred I didn t know that Parks have such a big clearance between the mirror and the tube