Rick_It

In 102mm f11, nobody I think could spot the difference between and FPL51 and an FPL53 variant. In a 102mm f7 (where we have both the FPL51 and the FPL53 doublets) I think this difference is much larger.

The focuser cannot costs too much, as the same unit is included in the 300€ Evolux 62mm. The difference in price between the two is quite strange. The price of the 62mm ED makes sense: same price as the Evostar 72mm, with 10mm less aperture but a better focuser and retractable dew shield. It's the 82mm price which is strange. In principle, it could eventually be the case that the 82mm is using a better glass (like FPL53 instead of FPL51). But consumers cannot consider that, as SW refuses to disclose this key technical characteristic.

A thing to consider when buying second-hand is the higher probability of getting a lemon. Suppose you buy a new C8: you will be much more likely to resell it if it is a lemon (say 1/3 wave PV) than if it is a fine scope (say 1/6 wave PV). This is expecially true for mass produced scope with some variability in their quality. I'm not talking about a specific scope, I'm referring to the chances of getting a good scope. Of course, this is not an issue for Tak, Televue etc..

IMHO, this is the new ED glass from CDGM, the H-FK71. It is somewhat in between FPL51 and FPL53, but closer to FPL53. I've already seen SW using terms like new or improved ED glass, and this glass is actually new and improved from H-FK61 (the previous "ED" from CDGM). And, from a marketing perspective I can understand that they don't want to disclose this glass, as (i) it is slightly inferior to FPL53 (and FCD100), (ii) it's new-unproven and (iii) not from the traditional glassmakers (Ohara, Hoya, Schott).

The 62mm should have the same glass as the Evostar 72mm ED (323€ on FLO, 10mm more aperture but mechanically inferior).

Italian prices are out, and they are much better than the australian ones. https://www.telescopi-artesky.it/it/skywatcher/rifrattori-apocromatici-/4726-rifrattore-evolux-62ed-skywatcher.html https://www.telescopi-artesky.it/it/skywatcher/rifrattori-apocromatici-/3150-rifrattore-evolux-82ed-skywatcher.html Evolux 62mm: 304€ Evolux 82mm: 760€

You can derive the refractive index and the Abbe number of a glass, but this require dismantling the scope and testing the single lens using professional equipments.

IMHO, when characteristics are not fully declared, it is a safe assumption to assume for the minimum / cheapest specifications. In this case, as the scope is still advertised as ED, I assume HK61 (chinese copy, and slightly worse, of FPL51). Then, if someone tells me that CA is on par with the ED80 (FPL53), I will change my mind. But, if this is the case (and SW is using FPL55 or FC100), then this is really a crazy marketing strategy. If you are using a good glass, why don't you declare it?

For sure it is not FPL53. But what's important is if the glass is FPL53 "like" (FPL55, FC100) or if the glass is FPL51 "like" (FPL51, FC1, HK61). I think a direct comparison (star test at high magnification) of the Evostar 80mm ED with this new Evolux should reveal the truth. The Evolux has almost the same diameter but it is a bit faster than the Evostar. If they are using an inferior glass (FP51 equivalent), chromatic aberration should be noticeable higher than CA in the Evostar 80ED.

The funny thing is that this situation, called natural monopoly, is a standard example of market failure which calls for state regulations. But state regulations are anathema for US and UK policy makers. Sorry for the OT

It depends on the economy of scales of the monopolist 😀

Congrats FLO and Rowan, the mount is a very interesting product. The mount is heavy and quite expensive: I think you could explore the possibility of producing a smaller mount - call it Rowan 50. It should have a payload of about 8-12kg (with/without counterweights), a weight of about 3-4kg, no slo-mo controls (as a cost-saving measure) but still the encoders option (this is what really differentiate this class of mounts).

I had the scope and the diagonal. I confirm the diagonal can be aligned.

Watch out. Encoders seem to be mounted internally in the Rowan 100, but externally in the AZ8. Having the encoder internally mounted (like in the AYO mounts) is better.

Think out of the box https://www.teleskop-express.de/shop/product_info.php/info/p6880_Explore-Scientific-MN-152-f-4-8-Maksutov-Newtonian-Telescope-with-Field-Correction.html