Does anybody know...?

[FlashDrive (Poppy)]

Hi Fellas....I have commited myself to purchasing a Meade Series 5000 80mm
APO Refractor ( Triplet ). Meade uses the finest Japanese FCD1 ED (Extremely Low Dispersion) glass.....What I want to know is...Is FCD1 ED the same as FLP-53 Glass. There is FLP-51, FLP-52 and FLP-53. I have read that FLP-53 is the best glass......I just don't know what quality or rating the FCD1 ED is. I have " Googled " it but can't seem to find a proper answer to my question. Can anyone shed some light on this...Thanks for anyone who can help.

Best Regards.....Colin...( FlashDrive )

[Ian Robinson]

See

http://translate.google.com.au/trans...%3Den%26sa%3DG

http://www.activenet.ru/storage/astr...hara/FPL51.pdf

http://www.activenet.ru/storage/astr...hara/FPL53.pdf

If you can find the Abbe No and n , you can compare.

Hoya say "Extremely Low Dispersion Glass: FCD1
Low change in refractive index with different wavelength of light minimizes focusing error caused by the varying wavelength output by laser diodes"


According to http://www.cdgmglass.com/glassreference.asp FCD1 is equivalent to FPL51.

Just have to use the right key words and be prepared to drill.

Guess Meade's claim of "highest quality" is hype unless you are looking at Meade's APOs. Will be a very nice bit of kit nonetheless.

[chris lewis]

FCD1 glass from Hoya has the same optical properties as Ohara FPL-51 glass. The abbbe number [how they measure CA] of FCD1 / FPL-51 is 81 while FPL-53 is 95 - almost the same as pure Fluorite. The FPL-53 does get 20 odd percent better CA correction then the FCD1 / FPL-51 [all things being equal]. However a lot depends on the tolerances, machining, quality of build and esp. the mating glass. A poorly made FPL-53 scope will do worse then a well made FCD1 / FPL-51. Don't forget the Meade 5000 80mm is a triplet design which also helps CA correction. Visually you may not notice the difference between a triplet Hoya FCD1 and a Doublet FPL-53 - maybe some more minor spurious colours on bright objects being the difference - with AP it could be more noticeable. The reviews for the Meade 80mm appear to be good.

[FlashDrive (Poppy)]

Thankyou Chris and Ian for making this much clearer to me. Would have liked it to have been equalivant to FLP-53...but in this hobby,reading reviews and doing a little research is necessary to find the scope of your choice...especially when handing over the $$$....once you've got it...it's yours.

Best Regards.....Colin