DesertSky

I bet John is eating pop corn and watching now (joking with respect)

I see that became nebula after my responded to STU.... C'mon STU! Help me to become a galaxy. HA!

Dear Proto Star, This is not data but a flood. This is a typical pattern of internet trolls. You have disclosed yourself and your sponsor, I think.

Then you should not say anything if a person says the earth is flat until you visit stratosphere... HA!

No, Sir. I have not experienced or compared LZOS or FPL53 glass before. I proudly own a 80mm doublet scope. An identical version is available at FLO. I honestly believe that I will not be able to differentiate the visual qualities of the glasses FPL51, LZOS (FPL 52 similar) and FPL53 (or FCD100) because I am only a visual hobbyist and not imaging deep sky. On the other hand, I have a strong scientific educational background and I work hard for the money. That helps me to judge the fair market value for a product. I would not pay a price of gold for the silver. LZOS is a marketing phenomenon. If there is someone claiming that LZOS is a TAK, TEC or AP similar product, I want to see the data. not only words. I will be happy to answer if you have any other questions.

This data table below shows the facts. LZOS glass is inferior than FPL53 and its producer Russians discontinue scope production long ago. A German vendor is promoting it like a first class glass by overrating it. I think it is not bad but certainly it is a second class glass. Common Optical Glass Types (from RefractiveIndex.info, LZOS): Glass Type Manufacturer Abbe No. (Vd) Refractive Index (n) Extinct Coef (k) H-FK61 Flour Crown CDGM 81.59 1.497 9.3613E-09 D-LAK5 Lanthanum Crown CDGM 54.9 1.6779 1.4009E-08 K4A Crown CDGM 61.06 1.508 2.3438E-08 F1 Flint CDGM 38.01 1.6034 4.6783E-09 E-C3 Crown Hoya 58.96 1.5182 2.0923E-08 BSC7 Borosilicate Crown Hoya 64.2 1.5168 4.6783E-09 E-F1 Flint Hoya 35.74 1.6259 1.4049E-08 FCD100 Dense Flour Crown Hoya 95.1 1.437 4.6783E-09 FCD1 Dense Flour Crown Hoya 81.61 1.497 4.6783E-09 FC5 Flour Crown Hoya 70.44 1.4875 4.6783E-09 LAC7 Lanthanum Crown Hoya 54.8 1.6516 4.6783E-09 OK-4 Special Crown LZOS 92.04 1.4473 -- K8 Crown LZOS 64.07 1.5164 -- F8 Flint LZOS 35.57 1.6249 -- KF7 Crown Flint LZOS 51.15 1.5176 -- FPL-51 Flourophosphate Ohara 81.61 1.497 0.0000E+00 FPL-53 Flourophosphate Ohara 94.96 1.4387 0.0000E+00 BSL1 Borosilicate Ohara 63.63 1.5101 1.7652E-08 LAL7 Lanthanum Ohara 58.52 1.6516 0.0000E+00 LAFN7 Lanthanum Flint Schott 34.95 1.7495 9.3754E-09 N-KF9 Crown Flint Schott 51.54 1.5235 8.2503E-09 F2 Flint Schott 36.37 1.62 3.7445E-09 K2 Crown Schott 60.41 1.5111 1.0879E-08 BK Borosilicate Crown Schott 63.58 1.5197 3.7786E-08 BK7 Crown Schott 64.17 1.5168 9.7525E-09 Soda-Lime Clear NA 63.97 1.5234 3.8974E-07 Fused Silica - Quartz NA 67.82 1.4585 --

I have read controversial posts about the quality of LZOS glass. Some say they are overrated because they are technically equivalent to FPL51 but not FPL53 or FCD100. Any comments about that?

A barlow and a zoom makes 2 pieces not one Also a good barlow can be costly like an eyepiece. Additionally attaching, removing a barlow and re-focusing is not easier than changing eyepieces. Denkmeier sells a powerswitch that can make it easy but it is not cheap.

If you search keywords like doublet and apochtomatic, FLO will list many TS-optics, Vixen' Tele Vue, Skywatcher and Takahashi products. Pricy ones usually have FPL53 or FC-100 glass but the economical ones have FPL51 or FK61 glass that may be technically slightly inferior but they still satisfy hobbyists.

Astro Tech, Altair and Teleskop Express offer almost identical products. They offer doublets for lower price and triplets for a higher range. Triplets may have a slightly better color correction. They are all good for observing and imaging. I would watch for the First Light Optics's offerings because they have even better products.

You want too much with your limited budget. I would recommend starting observing and learning the sky maps using a 7x50 binocular. For general use, an 8 inch Newtonian or a Dobsonian is great for solar system and okay for deep sky if you do not have light pollution. Imaging is another dimension. You better experience observing first because it will cost you less than 1k but imaging can go easily up to 10k. Clear skies, my friend.

7.7mm-15.4mm is a very narrow range. I have doubts... I would wait for some reviews to be published.