APO MAX 130 F/12 Refractor

I have been spying an ad for an APO MAX 130 F/12 Refractor, a scope I have been fascinated about for years after reading a positive review on this scope. This scope is reported to be a triplet with FPL 52 Schott glass element. Now I have heard the terms Fluorite, FPL-51 ED and FPL-53 during discussions on APO refractors but I would like to know where FPL-52 fits in. The APO Max has been described as a super APO refractor which has three lens elements that bring four distinct wavelengths to a common focus and also maintains extraordinary control of aberrations. Now apparently an APO can only do this for three wavelengths. So what is the deal with the APO MAX is it a Super APO that has an edge over an APO or is it all a sale hype.

You may have read this but if not it is interesting:

http://www.cloudynights.com/item.php?item_id=897

Larry

Somehow it doesn't seem to me to be a big deal to get great performance from a medium sized triplet long focal length refractor. A well made achromat 130 f 12 should also give excellent performance at a fraction of the price. How much worse could a doublet Apo be than a triplet at f 12? If we were talking about f 7, I could see that there would be advantages to a well made triplet apo over a doublet apo, and especially over an achromat.

It's the law of diminishing returns, isn't it?

James Adams

ApoMax is a primarily a visual refractor, at f/12 any of the glasses that you have listed will produce a decent performer. In the early nineties AP used FPL52 for their smaller F/8 and larger F/9 triplets with very good color correction. As a planetary refractor 130mm aperture is the main issue with this scope, to me the minimum aperture for capturing serious planetary detail starts at 6”, I do not see spending that kind of $$ on a planetary scope with aperture limitation.

Vahe

The design of this scope may have 4 color crossings, but that is not important to the performance. One of the crossings is in the very far infrared, which may be of interest to IR researchers, but does nothing for you visual folks. To get this correction in the IR, the design does allow a bit of violet error, something that may or may not be of concern to imagers who are using modern blue-enhanced CCD cameras.

A super apo can be defined for any wavelength range, visual, photographic, infrared or what have you. In any case, at F12 a 5 inch lens should work exceptionally well no matter where the correction is placed. You will find that for planetary work, the longer lenses have a small advantage over a shorter lens because aberrations such as sphero-chromatism can be better controlled and you can use longer focal length eyepieces with their inherent better optical characteristics.

Finally, I know that the lenses were made to a high standard, they were smooth and well corrected, which in the end is really all you need to know - so forget about any of the other details such as 4 color crossings, FPL52, etc. The important thing is that this lens will perform at the peak of what a 5" can do visually.

Rolando

Hans Tucker said:

I have been spying an ad for an APO MAX 130 F/12 Refractor

That was my ad posted last week...wanted to see what was out there. This had been one of my dream scopes for many years...when I was in 5" and smaller aperture. I was leery re shipping from Germany so passed re Markus' scope. I chatted with a few other owners/offers and did some hard thinking before parting with my cash. In the end decision, greater aperture won out. Kinda figures don't it...when I can finally afford one it doesn't fit well in my plans anymore :S

Well after a 2 months wait the APOMAX finally arrived and to my luck survived intact after the long journey from Europe to Australia, FEDEX didn't disappoint in this instant. The scope is in good condition for 10 years old, the optics could do with a clean but more concerning is that I have notice a fair amount of movement in the 4 inch focuser when moving the tube side to side and up and down, I wonder if this movement can be adjusted out. Also this scope uses Nylon screws, are these still available?

I know that HT Precision Optics are no longer around but is Fred Mrozek ?