|
For more than 300 years after the invention of the telescope, the choice for refractors was basically limited to Achromats.
All the discoveries made during this time were made with Achromats.
It's only in the past 60 years that multi element, exotic glass has been available and used to produce the "APO" type telescopes of today.
The long and illustrious tradition of the Achromat should not be forgotten.
Bang per buck they can still do very useful work.
My 2c
|