Does D & G offer mirrors?
We did produce mirrors for many years. We are currently in lens production only, with the exception of our 20" F/15 Cassegrain. We may at times offer reflective systems on a limited run basis.
Does D & G offer APO's?
A number of years ago we did produce a small run of 5.1" F/9 APO units. Due to cost and construction time, we are not currently planning another run.
Does D & G offer shorter focal lengths?
The shortest focal ratio we currently offer is F/12. We do, from time to time, offer a 5" F/10 on a limited run basis.
What are limited runs?
D & G will occasionally offer a product not normally available in our product line. These offerings will be in small limited runs. They are sold on a first come basis. Limited runs will be announced here, at our web site, and/or magazine advertisements.
What is meant by "push-pull" cell?
All D & G cells that hold our lenses are of the push-pull design. The cell can be adjusted to square the optical axis precisely.
What is the performance difference between F/12 and F/15?
In our opinion, performance differences, in regards to resolution and defining capabilities, are negligible. The F/12 units are somewhat easier to handle and transport and offer a slightly larger field of view. The F/15 units offer slightly better eye relief with the same given power, produce slightly less chromatic aberration and are the more "classic" choice.
Does D & G offer a coating service?
We do not currently offer a coating service.
Does D & G offer refiguring services?
We did offer a refiguring service for lenses and mirrors for many years. Since repair work needed on many components sent to us was so extensive, it was not cost effective for the customer nor time effective for us to continue this service. We will continue to offer repair service for optical components and/or telescopes, which are historical or antique in nature.
Can you recommend a mounting that will handle your scopes?
This is a somewhat subjective question, depending on the intended application of the user. In our opinion, for most visual purposes, we believe the following would be suitable. This list should not be considered all inclusive, as there may be other suitable mountings, of which we are unaware.
© 2007 D & G Optical