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No *90mm* ED APO (semi-APO) Refractors?

Macavity

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Macavity

Macavity

Posted
Posted

Just thinking out loud! Looking at prices (size / weight etc.) of ED APO
(semi-APO?) ED Doublet refractors, I get a feeling most manufacturers
make 80mm & 100mm but NO 90mm's. Unless YOU know otherwise! :p

Not specific, just thinking general purpose, "slightly upmarket", scope
to play about with! I note one astronomer on CN spoke of 90mm being
a "Sweet Spot" in practice? My notion of this is far more speculative! :D

As a LATE convert to ED Refractors, I have come to *love* my little
Altair Astro Lightwave ED66. But sadly there's no "Lightwave ED90"!
I rather suspect quality-wise: "Wave" > "Lightwave" = "Starwave"?  ;)

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John

John

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The William Optics Megrez 90 was just such a beast. Nice ED doublet using FPL-53 glass as one element.

Out of production now but very popular when they were available new so there should be quite a few out there.

Up market again (but not CA free apparently) there is the Takahashi Sky 90 which has a fast Fluorite doublet objective.

WO also did the Megrez 88 not to long ago I recall.

For a real treat the Tele Vue 85 :icon_biggrin:

Probably others about as well but I can't recall them just now.

 

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Chris

Chris

Posted
Posted
16 minutes ago, Macavity said:

I rather suspect quality-wise: "Wave" > "Lightwave" = "Starwave"?

I'm not 100% sure, but I think the Lightwave series has the better glass out of the two, and the Starwave's were semi apo. Although, they may have improved some of the newer Starwave models.  

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Macavity

Macavity

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Thanks @John for (quite!) a few names to ponder! Probably not
quite into in the "Tak" or "TV" market. lol. But food for thought...

People seem to speak so highly of the Skywatcher ED80's - I might
just go for one of those! I know a bit about the general construction
of SW scopes too! Fairly safe to "fiddle about" (The Who?) with? :)

Nothing TOO expensive for my typical "general purpose" needs! :p

Yes, Chris... @Lockie I think I have managed to somewhat "crack"
the naming code of such things. lol. It is always worth reading the
reviews. A topic is more interesting & intriguing than damning... ;)

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mikeDnight

mikeDnight

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29 minutes ago, ollypenrice said:

Although I haven't checked the used proces lately, I remember feeling that the TV85 was one of the most under-priced instruments around. I'd love one but have not the slightest possible excuse!

Olly

You could claim insanity. It works for me! :icon_compress:

You know you NEED one....

 

tumblr_mtzsut0tAO1sjwg5lo1_500.gif.31f7a271a85f935e06efccd7963e951e.gif

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Macavity

Macavity

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56 minutes ago, Peter Drew said:

Perhaps the question should have been "Why no affordable 90mm ED scopes?".    :icon_biggrin:

Excellent, Pete! lol :D

I also thank "ALL our readers" for this excellent thread! My experience with a 
(humble) ED66 (Altair Astro) was the start of the rot the inspiration for this. :)

Some of the scopes cited are (cheerfully) a tad beyond my (financial) means.
Or maybe not? lol. A somewhat larger ED APO remains on my "Bucket List"! ;)

Now, if only I could give up on these temptations to "modify" things. Don't
worry, I won't be "drilling holes" in an... "Astro Physics" (lol) But I may buy a 
SW ED80 for (legitimate) experimentation! :evil4: Another ED APO "For Best!" :D

Such is not the best way to get (remain) "rich" of course, folks... :p

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Ben the Ignorant

Ben the Ignorant

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Some guy from Astrotreff sells his used Sky-Watcher Acuter 90/900 ED semi-apo. Yes, Sky-Watcher did make 90mm semi-apo's but they were f/10, not sure if you would like the length, but this and the FPL-53 glass helps keep aberrations at the lowest level. It's very nearly a flat-field instrument without the need for a corrector.

Sold with case, rings, Vixen bar, finder and a couple basic eyepieces:

http://www.astrotreff.de/topic.asp?TOPIC_ID=219276

It has been reviewed by a professional optician, and judged excellent:

http://www.davidesigillo.eu/test_acuter.html

The offer has been posted yesterday.

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mikeDnight

mikeDnight

Posted
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Here's Baaders offering in the 90mm range, a 95 mm fluorite triplet, which I've half inched from another thread. It's owner looks mighty pleased with his beautiful scope, but theres a catch, or rather two. 1st, its so popular it is currently unavailable. 2nd, the price. EEK! ?

2017-12-04 18.50.18.png

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Macavity

Macavity

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Thanks for the interesting thread! Seems the "subject" may not be
QUITE as rare as I had thought. lol. Plenty of food for thought... :)
(I worry slightly about disquieting test results on some ED APOs.)

ASIDE: If I am to be TOTALLY honest, perhaps what I am looking
for are well figured Lenses and better constructed Refractors - As
such this might even be a *quality* Achromat! I envisage mostly
"narrow band" experiments -- including even HA solar CaK Solar!
ED APOs tend to be better figured AND of shorter focal length... ;)

P.S. "Getting older now", so tiring of the *chore* of "Fast Newts" 
and (even) MAKs. Quite fancy my notion of ONE SHOT Red/Blue
DSO imaging using my favourite Baader UHC filter! <rambling>:evil4: 

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25585

25585

Posted
Posted
On 17 December 2017 at 11:30, Macavity said:

Thanks @John for (quite!) a few names to ponder! Probably not
quite into in the "Tak" or "TV" market. lol. But food for thought...

People seem to speak so highly of the Skywatcher ED80's - I might
just go for one of those! I know a bit about the general construction
of SW scopes too! Fairly safe to "fiddle about" (The Who?) with? :)

Nothing TOO expensive for my typical "general purpose" needs! :p

Yes, Chris... @Lockie I think I have managed to somewhat "crack"
the naming code of such things. lol. It is always worth reading the
reviews. A topic is more interesting & intriguing than damning... ;)

There is an Equinox 80 you can buy. Better tube, focuser & retractable dew hood compared to standard ED 80. 

Are the TV 85s CA free? Or is an Esprit 80 triplet better?

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