Re: ATM Dumb refractor question.

["Bob May" <bobmay@nethere.com>]

Better that you sit down and look at the specs for the different lenses.
Longer FL lenses tend to have higher specs than the short FL ones.  Short FL
lenses tend not to be really diffraction limited over the color range as
well as the longer ones do thus they tend to be done to a different
tolerance level and accuracy point.
In reality, the longer FL lenses, if they use the same materials as the
shorter ones do, tend to use less material (the lenses all start out as
rectangular blocks) and can be blocked up into larger blocks (gentler curves
tend to allow for more lenses in one tool) if desired.
I'll also note that comparing lenses from different manufacturers isn't very
valid as different makers have different price schedules for their work.
Bob May
http://nav.to/bobmay
bobmay@nethere.com
NEW! http://bobmay.astronomy.net