FPL-51 vs FPL-53 ???

[Robert_T]

Hi Guys, I note some APO/ED refractors with FPL-51 and some with FPL-53 fluorite lens... what's the difference?

cheers,

Rob

[AGarvin]

Hi Rob,

Here's an extract from what appears to be a report on apochromats (http://alice.as.arizona.edu/~rogerc/chapters/Chapter%204a.html):



I'm certainly no expert on this stuff, but from what I've read when one is thinking "apo", one also has to take into consideration the mating element as that is what will make the difference. Here (http://geogdata.csun.edu/~voltaire/roland/ed.html) is an article by Roland Christen (owner/founder of Astro-Physics telescopes) on colour correction. An extract states:



Hope this gets you started (and it's ok to qoute these).

Cheers,
Andrew.

[ozstockman]

Hi Rob,

you can also check this thread (http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/1185928/page/0/view/collapsed/sb/5/o/all/fpart/1/vc/1) on cloudynights forum. It has the same question in the title :-)

cheers,

Michael

[Robert_T]

Thanks Guys, very helpful both responses:thumbsup:

[gts055]

FPL53 is more expensive, than FPL52 or FPL51. You can achieve an equal degree of color correction with all three when given they are matched to suitable mating elements. The difference is that telescope using FPL53, will likely have a shorter focal length. A shorter focal length results in a wider field of view, as desired by imagers. Within each glass type, various grades of quality are availalable. Premium grade of any glass will be guaranteed to a specification regarding striae, bubbles, and clarity etc. Quality comes at a price.
Regards Mark


mmm, my post is late, that Cloudy Nights reference two posts above explains it nicely.