We've done another round of DPAC testing at John Pratte's optical test shop this weekend. Many tests were of privately owned mirrors of various quality sources and ranged from very good to abysmal.
Included also were a couple of noteworthy samples from Lightholder and Zambuto. These are obviously amoung the highest end mirrors available and the tests show exactly why. The first pic shows a sample of various mirrors from various sources that need not be identified. The DPAC test doubles the errors so these tests are very sensitive to any aberrations.
The next shows a 12.5 inch f/5.9 Lightholder. It is from a New Moon telescope John acquired a while back. It is about the best mirror we have ever tested.
The second is my personal 20-inch F4 Lightholder. I feel very fortunate to own such an amazing mirror made to about the highest standard possible and in an amazing Teeters scope. The optical test report also supports our test pic.
Finally we have a 16-inch F4 Zambuto that John recently acquired. It does show a trace of undercorrection. John measured it to be 1% undercorrected. This is perfectly acceptable given that cooling mirrors tend to overcorrect as they cool. The level of smoothness in this mirror is phenomenal.
These samples are clearly made to an amazing degree of accuracy and smoothness and with absolutely no zones and owners of such mirrors or scopes with these mirrors are VERY fortunate.
Edited by Darren Drake, 06 April 2025 - 08:54 PM.