Re: [APML] 12" & 14" LX200

[Chris1011@aol.com]

In a message dated 12/18/2002 7:50:05 AM Central Standard Time, kwemail@twcny.rr.com writes:


> Someone over on Mapug gave me the following link to Dr. Clay Sherrod's
> independent review of the Meade UHTC vs. EMC coatings.


Without doing an actual transmission test on a spectrophotometer, the above review is really kind of worthless. The limitation of a transmission test is that all spectrophotometers that I know of cannot test whole optical systems. They can only test small sample pieces, from 1/2 to 1" in size, one at a time. These pieces are normally placed in the coating chamber along with the full sized optic and are later analyzed for transmission or reflectivity. They are called witness samples. In fact, the witness samples really have to be thin plano-plano glass blanks because if there are any curves on them, this will mess up the calibration of the spectrophotometer. So, without going thru a battery of tests in a properly conducted way, all estimates of transmission efficiency are just that - estimates. 

Roland Christen