Quote:
Originally Posted by strongmanmike
That's not quiiite right, I have an email, direct from Roland himself, confirming that my scope is an oil spaced triplet using FPL53 centre element. I have kept it for provinence  
Here is an excerpt from the email exchange from over a decade ago, when I was asking Roland about my specific scope and how to remove the objective cell and other things:
Me: Out of interest, do you remember what type of ED glass element was used in this lens set, which of the three elements it is and is it an oil spaced triplet?
Roland: It is an oil spaced lens using FPL53 center element. Remove the three large head screws on the front and the lens cell can be lifted out. It is not necessary to mark the exact rotation of the cell because it was properly squared on during assembly by accurate positioning of the countercell (that's the white painted cell behind the lens cell, and it is held to the tube via the 6 side screws). Only if you remove the 6 side screws that the proper collimation is totally lost and you would have to start over again. So, simply remove only the three front screws, and you are in business. ( you would not believe how many people have sent me the countercell along with the lens cell, thinking that this is the only way the collimation is retained).
Roland
Mike |
For those interested here is the complete article on Astro-Physics by Thomas Back (of TMB fame)
https://www.csun.edu/~rprovin/tmb/tmb1.html
Mike, Apologies I didn't mean to be rude by questioning the information in your original post. I am really intrigued with your scope (I am interested in the technical aspects of the top high end APO refractors by Takahashi, TMB, Astro-Physics, Zeiss) and I was trying to place your scope in a build time line but outside the Astro-Physics catalogues the only time line I could find was what was in Thomas Backs Essay. When you mentioned FLP-53 it threw out my estimation on when your scope was manufactured. I gather the reason it didn't rate a mention in Thomas's essay was possible because only two were made so it wasn't by definition a commercially available product but a possible prototype to the 155EDF.
My own classic APO Story
Years ago I purchased a APOMAX 130 f12 so called Super APO but it had a decal on the OTA saying Fluorite APO. I was concerned that the optics in my newly acquired purchase were not original even though it had the unique APOMAX lens cell. I actual wrote to Fred Mrozek who's name appears in Thomas Backs essay as a former friend of Roland whom assisted Roland in the early days before he founded Astro-Physics. Surprisingly Fred replied and gave me some insight to the build of the APOMAX although he wouldn't tell me the material the objective was made out of, I later found out it was FLP-52. I subsequently came across the Astro-Physics article by Thomas Back which I found a fascinating read. I still don't know why the previous owner or the owner before them put the decal on the OTA .. the only material that I knew was confused with or incorrectly termed fluorite was FLP-53. Ok .. Rant over. Sorry for hijacking your thread.