We will use a colour system:
bad attention standard good highest level
We will not show the first 2 categories; you will only miss the Information.
Sun Telescopes
They have to have a special sun Telescope with a diameter of minimum 90 mm. The best has 100mm and an air pressure tuning. The biggest problem of a sun telescope is it works in the sun and getting hot. The air inside will get an overpressure and this will kill the quality. Air pressure tuning is a valve witch you open once an hour and the telescope is good for the next hour! If they using night telescope with simple filter to observe the sun, don’t go; you will only see the black spots of the sun. If you like to know what is possible with a 100mm Lunt solar telescope with air pressure tuning see this Video.
Night Telescopes
In
Type: Telescope with Lens
A Refractor has a colour problem; you will see a rainbow around the stars.
An ED-Apochromat has more and better lenses to correct this problem. They seem to be the best telescope, but 1 inch more is always double price. So the big ones are expensive and not in use in an tourist observatory
Telescopes with mirrors (1 and 2 ways)
All mirror telescopes have a problem. The main mirror is in the back and the second mirror is in the way of viewing. So the main mirror has to look around the 2nd one. Only the outside circle of the main mirror is in use. For this they have a problem called coma or speed. The result is, the stars in the centre of your view are clear and in the corners looking like lines pointing to the centre. Depend of the system and the way inside (witch makes a multiplication of the diameter and the result is the magnification) of the telescope they need a smaller or bigger coma corrector. This is a lens system with the same colour problem like the lens telescopes. We will tell you coma corrector or full coma corrector.
The quality of the mirrors makes a big different. Standard is Pyrex, more brilliant and contrast has Sitall and Zerodur.
But the quality will be killed if the mirror has a different temperature than the air around. You will have a turbulent air over the mirror until “phantasmal effect”. Good telescopes have a ventilation system to cool the mirror down. Carbon tubes are not so heavy; you easier can store them inside, heavy ones need a dome.
Some Telescope companies using terms like ACF and UHTC. These are no common technical terms and mostly cover standard level.
Mirror Telescopes with one way system
The 2nd mirror is in a 45° position to the main mirror. The point of view is at the top of the telescope. For the bigger ones you have to climb up stairs for to view. They don’t have a goto system for to help your guide to find the star (Dobson) or he has to rotate the telescope that the point of view is in a comfortable position for you. This is time without observe. A group of 15 Person with full computerised goto 2 way systems will have the same time of observation than a group of 10 with a one way system.
Dobson: A
Maksutov-Newton: smaller 2nd Mirror/Prism with less problems of coma.
Astrograph: A optimized
Mirror Telescopes with 2 way system
The 2nd mirror is parallel to the main mirror. The point of view is at the backside of the tube. This is very comfortable for viewing. Mostly all Telescopes have a full computerized goto system.
Schmidt-Cassegrain: big resolution; but also big problems with coma.
Maksutov-Cassegrain: smaller 2nd mirror/prism; less coma problems.
Dall-Kirkham and Ritchey-Crétian: high- Tec mirrors with more parabolic form. The result is a more effective use of the main mirror. Some 10 inch models can easily beat a 14 inch Schmidt-Cassegrain. Normally they are coming with full coma corrector.
