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Equipment Discussions >> Refractors

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stanislas-jean
Pooh-Bah

Reged: 10/22/08

Re: Are achromats enjoying a come back? new

new

[Re: jrbarnett]
#5520481 - 11/15/12 01:59 AM

Jim, you may contact also Airylab in France
http://www.airylab.com/
ask Frederic for your enquiries.
There are few observers and semi-professionnals who are acting in the astronomy fields. They could report about the instruments existing in the country (refractors and reflectors still in activities. They did test investigations on (the Nice 760mm refractor it seems for one).
Stanislas-Jean

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chboss
professor emeritus

Reged: 03/24/08

Loc: Tokyo Japan

Re: Are achromats enjoying a come back? new

new

[Re: stanislas-jean]
#5520495 - 11/15/12 02:45 AM

Jim,

Here is an interesting report of a 1906 Zeiss 300mm telescope that was restored and the optics evaluated. Source W. Rohrs list of optic test reports:
http://rohr.aiax.de/Optikpruefung[1].pdf

This telescope is used for outreach by the Urania observatory in Zürich, Switzerland:
http://www.urania-sternwarte.ch/portraet.html

best regards
Chris

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Astrojensen
Post Laureate

Reged: 10/05/08

Loc: Bornholm, Denmark

Re: Are achromats enjoying a come back? new

new

[Re: jrbarnett]
#5520560 - 11/15/12 04:34 AM

Quote:

By extension, "I simply don't understand this. I'm afraid you've lost me. If I see, on the computer screen [or on NASA's HST web page, etc.], a splendid view of NGC 891 (or whatever), I couldn't care less whether the photons are collected by a mirror or a lens. It doesn't make a scrap of difference to me."

OK, now I'm complete lost. What does astrophotography have to do with it all? Are you saying that looking at the stars visually with a reflector is basically the same as looking at a photography, as in, not looking at it at all?

When I am looking at the stars with a reflector or a refractor, I am looking at a live view. My eye registers photons that has just ended their long journey. If I am looking at a photography of something, I have let a camera do that final detection of the photon. That is different than visual. The choice of telescope makes no difference. The method of detection does. The difference between reflection and refraction in this regard is a philosophical discussion at best.

Why does refractor afficionados so often have to come up with the weirdest, most convoluted reasons and justifications to why they use refractors? Can't they just say that they love refractors? Love doesn't need reason, logic or justification. It just is. I love refractors. If I didn't, I wouldn't own ten of them, would I? But more than love refractors, I love telescopes, because they allow me to observe the universe in far greater detail than with my eye alone.

Or is love just a overused, boring word these days, its meaning diluted and its lustre pale from its constant overuse in the modern pop culture?

Clear skies!
Thomas, Denmark

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Jon Isaacs
Postmaster

Reged: 06/16/04

Loc: San Diego and Boulevard, CA

Re: Are achromats enjoying a come back? new

new

[Re: Astrojensen]
#5520572 - 11/15/12 05:08 AM

Quote:

Quote:

but why would I ever want to exchange a direct view for a reflection?

I simply don't understand this. I'm afraid you've lost me. If I see, in the eyepiece, a splendid view of NGC 891 (or whatever), I couldn't care less whether the photons are collected by a mirror or a lens. It doesn't make a scrap of difference to me.

Clear skies!
Thomas, Denmark

Thomas:

It's just a bit of dogma, light that travels through glass is no more direct light than light that is reflected by a metallic coating. When you think of the tortured path that light travels through a refractor, the light is split apart, each color of spectrum traveling a different route and never really quite being put back together correctly, it's surprising they actually work at all.

You have years of making amazing observations with small long focal length refractors like your Zeiss Telementors. You developed your skills with small telescopes and now combined with the dark skies of a small island in the Baltic sea, you are now using those skills with a large reflector. How wonderful can that be?

Young, great eyes, dark skies, what more could one want? They say youth is wasted on the young but sometimes there are those who are wise beyond their years, how lucky you are.

My suggestion: Just let them have their fun, let them have their illusions.

Jon Isaacs

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Astrojensen
Post Laureate

Reged: 10/05/08

Loc: Bornholm, Denmark

Re: Are achromats enjoying a come back? new

new

[Re: Jon Isaacs]
#5520585 - 11/15/12 05:35 AM

Thanks Jon.

Clear skies!
Thomas, Denmark

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Binojunky
Carpal Tunnel

Reged: 12/25/10

Re: Are achromats enjoying a come back? new

new

[Re: Astrojensen]
#5520613 - 11/15/12 06:14 AM

One could have the best of both worlds, the wonderful world of a fine Mak, get your lens and a mirror thrown in for free, for me anyway I have no preference how light is collected and brought to my eye,all designs have strengths and weaknesses, to put the argument into perspective if like friend of mine you have to get rid of your scopes because of impending blindness due to eye disease then the argument of which is the better way to collect the light is silly and irelevent, be thankfull you have sight, nuff said,DA.

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Astrojensen
Post Laureate

Reged: 10/05/08

Loc: Bornholm, Denmark

Re: Are achromats enjoying a come back? new

new

[Re: Binojunky]
#5520624 - 11/15/12 06:30 AM

Quote:

to put the argument into perspective if like friend of mine you have to get rid of your scopes because of impending blindness due to eye disease then the argument of which is the better way to collect the light is silly and irelevent, be thankfull you have sight,

Well said.

Clear skies!
Thomas, Denmark

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Mark Harry
Vendor

Reged: 09/05/05

Loc: Northeast USA

Re: Are achromats enjoying a come back? new

new

[Re: Astrojensen]
#5520699 - 11/15/12 07:53 AM

I got a question. Why do more APO owners get their scopes tested, as referred to on the last page?
********
Can't they use the scopes by themselves and assess the quality, or is this an angst about test results/numbers???

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covey
member

Reged: 07/02/11

Re: Are achromats enjoying a come back? new

new

[Re: Mark Harry]
#5520715 - 11/15/12 08:13 AM

Because it's part of the enjoyment of the hobby....and they enjoy doing it.

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Sky Muse
sage

Reged: 10/26/12

Loc: De Soto County, MS

Re: Are achromats enjoying a come back? new

new

[Re: covey]
#5521057 - 11/15/12 11:46 AM

"Are you saying that looking at the stars visually with a reflector is basically the same as looking at a photography, as in, not looking at it at all?"

Not quite, just a further regression within the set...

1. Viewing through a refractor is exactly like standing in front of someone. They see you, and you see them, and a conversation ensues, or whatever.

2. Viewing through a mirrored arrangement also amounts to conversing with someone, though not standing before them face to face, instead seeing only their reflection via a mirror, as illustrated within a previous posting.

3. A photograph is even further removed from the living experience, the image being all the more impersonal, thus with #2 and #3 being patent regressions of #1.

And then, there's television...

<Holst's "Mars" playing loudly in the background>
Frank turns from the mirror, takes his Polaroid and snaps a photo.
Bill: "That does it! I'm leaving! Goodnight Frank!"
Frank: "Goodnight Bill!"
<door slams>
Frank walks over to the stereo, turns the volume down and bumps the needle to 'Saturn', thinking, "Wait 'til Marge sees this, his sad expression! She's sure to take him back!"

Cheers,

Alan

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Jon Isaacs
Postmaster

Reged: 06/16/04

Loc: San Diego and Boulevard, CA

Re: Are achromats enjoying a come back? new

new

[Re: Sky Muse]
#5521143 - 11/15/12 12:32 PM

Quote:

1. Viewing through a refractor is exactly like standing in front of someone. They see you, and you see them, and a conversation ensues, or whatever.

Not really...

Looking through a refractor is like looking through a fish bowl and for most us we are facing the ground, not the person or the sky.

With a Newtonian you look through the Sky End of the scope, with a refractor, the dirt end...

Jon

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Sky Muse
sage

Reged: 10/26/12

Loc: De Soto County, MS

Re: Are achromats enjoying a come back? new

new

[Re: Sky Muse]
#5521159 - 11/15/12 12:40 PM

"...to put the argument into perspective if like friend of mine you have to get rid of your scopes because of impending blindness due to eye disease then the argument of which is the better way to collect the light is silly and irelevent, be thankfull you have sight..."

My father, 77, has been plagued all his adult life by cataracts. He now has only one "good" eye, but it nonetheless becomes filled with hundreds of floaters when disturbed. My older brother inherited this unfortunate condition as well, his having had more than one operation. Thankfully, I inherited my eyes from my mother, and escaped it, just barely, and never a day goes by without my reflecting upon it.

Happily, the other night, I was able to show my father Andromeda, and as I explained its particulars, its distance, the fact that you'd have to hop upon a beam of light and travel for two million years before reaching its perimeter. I asked, "Can you see it?" He replied, "Yes", and described it somewhat. Of course, I will never know how well in fact.

However, that, too, is beside the point.

Cheers,

Alan

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Sky Muse
sage

Reged: 10/26/12

Loc: De Soto County, MS

Re: Are achromats enjoying a come back? new

new

[Re: Jon Isaacs]
#5521166 - 11/15/12 12:44 PM

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Sky Muse
sage

Reged: 10/26/12

Loc: De Soto County, MS

Re: Are achromats enjoying a come back? new

new

[Re: Sky Muse]
#5521179 - 11/15/12 12:54 PM

The lens of an eye is just that, a lens, a "fish bowl", and just as a refractor's objective.

Sir, you dare question the design of the Maker?

Cheers,

Alan

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Astrojensen
Post Laureate

Reged: 10/05/08

Loc: Bornholm, Denmark

Re: Are achromats enjoying a come back? new

new

[Re: Sky Muse]
#5521309 - 11/15/12 02:14 PM

Quote:

never a day goes by without my reflecting upon it.

Did you just write that?

Clear skies!
Thomas, Denmark

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Astrojensen
Post Laureate

Reged: 10/05/08

Loc: Bornholm, Denmark

Re: Are achromats enjoying a come back? new

new

[Re: Sky Muse]
#5521320 - 11/15/12 02:19 PM

Quote:

The lens of an eye is just that, a lens, a "fish bowl", and just as a refractor's objective.

Sir, you dare question the design of the Maker?

There are actually at least one species of fish and, I believe, one of squid, who use reflectors in their eyes for collecting light. Their eyes strongly resemble Schmidt or maksutov cameras, have an extremely fast f/ratio and are very large, compared to the animal. These animals live deep in the sea, where there is basically no light, save for faint bioluminescence.

Clear skies!
Thomas, Denmark

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Sky Muse
sage

Reged: 10/26/12

Loc: De Soto County, MS

Re: Are achromats enjoying a come back? new

new

[Re: Astrojensen]
#5521332 - 11/15/12 02:24 PM

You caught that, eh? So did I when I wrote it, and then left it.

Cheers,

Alan

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csrlice12
Post Laureate

Reged: 05/22/12

Loc: Denver, CO

Re: Are achromats enjoying a come back? new

new

[Re: Sky Muse]
#5521382 - 11/15/12 02:59 PM

"One should always exchange mirrors for lenses, but never the other way around."

Like anything else, use the proper tool for the job. Wanna look at Jupiter, Globular Clusters?--get a refractor

Want to see faint nebulas and galaxies--Get a Dob/Newt

Want to see everything--get both.

Neither a reflector nor a refractor can do it all. Neither is "better" then the other, just different. They both have their advantages and disadvantages.

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Sky Muse
sage

Reged: 10/26/12

Loc: De Soto County, MS

Re: Are achromats enjoying a come back? new

new

[Re: Astrojensen]
#5521388 - 11/15/12 03:01 PM

Then, there you have, in the animal kingdom, rare, living, extant inspirations for Newton's, Schmidt's and Maksutov's designs, though no doubt unbeknownst to said gentlemen at the time. I always suspected some organic reason or other for the origin of those optical designs. However, I have, as points of reference, the eyes of the vast remainder of the animal kingdom, including human beings.

Incidentally, we are not fish or squids, but human beings.

Cheers,

Alan

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csrlice12
Post Laureate

Reged: 05/22/12

Loc: Denver, CO

Re: Are achromats enjoying a come back? new

new

[Re: Sky Muse]
#5521389 - 11/15/12 03:03 PM

Quote:

Jason,

Yes, this one...

http://www.chuckhawks.com/celestron_XLT102.htm

With Celestron, and with the optics coming out of China being of surprisingly very good quality nowadays, I've considered it myself, and as a replacement for the Parks 80mm f/11 achromat I had before the Tak. Back in the early 90's, I got a Meade 90mm refractor/alt-az setup. The optics were bad, very bad, and were made in Taiwan at the time. After I returned it, I got the Parks, made in Japan, and it was much better.

I think the Celestron Omni XLT on the CG-4 mount would make a great replacement. It comes with a 25mm ocular, and would need, say, a 10mm in addition at least to cover a wide range of viewing. The 10mm plossl that came with my Orion StarBlast 6 reflector is also surprisingly good. A lot of people have rated their plossls favorably.

Regards,

Alan

Getting the 102XLT w/CG4 mount for Xmas. It will make a great combo with my 10XTi. Of course, now i gotta learn how to use an EQ mount--and for some reason, I look forward to it.....

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