You do not need a parachute to skydive, you only need a parachute to skydive twice...
Quote:Here's a question to go with that. The AT80ED sold by AstroTech uses FPL-51 I think and the Orion 80ED uses FPL-53. They are both doublet designs and the Orion has a focal length of f/7.5 while the AT80ED has a focal length of f/6.8.
According to these, which would I be better off getting for the best color correction considering they're both near in price and mechanics...?
Quote:Anyone can design a doublet. I've seen the average astronomer (ie. NOT someone who makes scopes) come up with a design in downloadable sofware. Designing a refractor is not a difficult or challenging process that needs 'experts' to do.
Quote:For a FPL-51 doublet to have the same color correction as a FPL-53 doublet it will have to have a FL 20% longer, so a focal ratio of F9. Therefore the orion 80ED will have approxiamtely 30% better color correction than the AT80ED if they use the glasses you mentioned.
Quote:Quote:Anyone can design a doublet. I've seen the average astronomer (ie. NOT someone who makes scopes) come up with a design in downloadable sofware. Designing a refractor is not a difficult or challenging process that needs 'experts' to do.
Coming up with a design is one thing, coming up with a good design is another. Not only does a good design need to control abberations as much as possible (And this gets harder with faster designs) but the design must also be one that is practical to manufacture. There are some designs out there that give great results but have a number of problems associated with them. There is a reason that Thomas Back is able to sell scopes with his name on them; not every design that corrects for Chromatic is going to produce a great telescope.
Mind you, some of the best names in Refractor Design today started as Amateurs. Both Roland Christen and Thomas Back got their starts as Amateurs (if I remember correctly) but they made their names through good designs that maximized the potential of the glasses they were using.
Quote:Now I just need to decide between the AT80 and the 80ED... AND I still need a mount and diagonal to go with it... This is going to be pricy.
Dee space-scientist student violinist Nexstar8i,SV80S,80/9D,FC100,94 Brandon,TMB92SS,GM8 8" f/7 Discovery,12.5" Portaball, PST
Quote:Tom, seeing as you've had experience with them apparently, where do the mechanics on the AT80 excel over the ED80? Obviously the color correction would be better, but is it too minor to be worried about on the AT80? I want reflector-like views, but if the moon is a little warm-hued, I can deal. What I DONT want would be any fringing or obvious discoloration inside the object that distracts the eye.
Quote:As for the suggestion that these units are more "inconsistent" in quality than any others, I think that is unsubstantiated as well. There are many reports on these 80mm and 100mm FPL-53 doublet units, including several with actual interferometric test data, and several others based on side-by-side, same night evaluation by extremely experienced observers.