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Equipment Discussions >> Refractors

Pages: 1

GeHe
super member

Reged: 08/06/11

Loc: Germany

Oilspaced
#5648182 - 01/28/13 01:29 PM

hi,

ist it nessesary to park an oilspaced refractor vertically ?

thanks for answering

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neptun2
professor emeritus

Reged: 03/04/07

Loc: Bulgaria

Re: Oilspaced new

new

[Re: GeHe]
#5648278 - 01/28/13 02:02 PM

I personally do not see any reason for that. The lens cell of the oil spaced telescopes is sealed and i do not see any reason why parking vertically should better than any other position.

Edited by neptun2 (01/28/13 02:03 PM)

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Roy McCoy
Pooh-Bah

Reged: 10/13/05

Loc: Glendale, AZ

Re: Oilspaced new

new

[Re: GeHe]
#5648304 - 01/28/13 02:14 PM

Hi Gerhard,

My 1986 oilspaced refractor has always been parked horizontally.

There are no issues.

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Eddgie
Postmaster

Reged: 02/01/06

Re: Oilspaced new

new

[Re: GeHe]
#5648604 - 01/28/13 04:15 PM

The space between the lenses in an oil spaced design is generally so small that only a few drops of oil are required to immerse the faces of the lenses when they are put into contact.

Once the lenses are oiled, (typically) a piece of special tape is used around the outside of the lens group to seal the oil into place.

Unless the tape fails (which is not unheard of, but at the same time seems to be quite rare), then the orientiation of the OTA makes no difference.

I don't use my 6" oil spaced triplet hardly ever anymore, so mostly it sits in the saddle on its mount. Never been a problem with it.

Edited by Eddgie (01/29/13 12:08 AM)

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CounterWeight
Postmaster

Reged: 10/05/08

Loc: Cloudyopolis, OR.

Re: Oilspaced new

new

[Re: Eddgie]
#5649150 - 01/28/13 08:12 PM

Same here...(+++ no isues NOT being stored vertically if mine qualifies) except I still use mine for visual and ocassionally imaging.

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jrbarnett
Eyepiece Hooligan

Reged: 02/28/06

Loc: Petaluma, CA

Re: Oilspaced new

new

[Re: GeHe]
#5649444 - 01/28/13 11:03 PM

It wouldn't hurt to store the OTA vertically, though.

I assume you're aware of the story on Astro-Foren.DE about the TEC 160 that showed astigmatism until it had been stored for a bit in vertical position. The bigger the triplet, the heavier the objective group. A little tape around the edges is not going to totally stabilize a very large lens containing heavy low dispersion glass.

I store my 140 oil spaced scope horizontally with no issue, but if I had a larger scope (180 for example) I migt consider storing the OTA vertically.

- Jim

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Mike Clemens
Frozen to Eyepiece

Reged: 11/26/05

Loc: Alaska, USA

Re: Oilspaced new

new

[Re: jrbarnett]
#5649645 - 01/29/13 02:24 AM

I have stored my TEC200 horizontally for five years over 100 degree F temp swings seasonally. The lens looks brand new.

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kevint1
sage

Reged: 04/19/11

Loc: Michigan

Re: Oilspaced new

new

[Re: jrbarnett]
#5650416 - 01/29/13 02:08 PM

Quote:

I store my 140 oil spaced scope horizontally with no issue, but if I had a larger scope (180 for example) I migt consider storing the OTA vertically.

- Jim

Jim, why would you consider storing a larger scope vertically? Just curious.

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Paul G
Post Laureate

Reged: 05/08/03

Loc: Freedonia

Re: Oilspaced new

new

[Re: Mike Clemens]
#5650482 - 01/29/13 02:51 PM

Quote:

I have stored my TEC200 horizontally for five years over 100 degree F temp swings seasonally. The lens looks brand new.

I keep mine in their cases, and the cases are designed to be stored horizontally. Hasn't cause any problems. OTOH, I'd worry about storing it vertically, mainly fear of it being knocked over.

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Mike Clemens
Frozen to Eyepiece

Reged: 11/26/05

Loc: Alaska, USA

Re: Oilspaced new

new

[Re: Paul G]
#5650666 - 01/29/13 04:18 PM

> I'd worry about storing it vertically, mainly fear
> of it being knocked over.

way higher risk if you ask me.. gravity is a harsh mistress

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jrbarnett
Eyepiece Hooligan

Reged: 02/28/06

Loc: Petaluma, CA

Re: Oilspaced new

new

[Re: kevint1]
#5651038 - 01/29/13 07:52 PM

Well, if you put any credence into the findings reported on astro-foren.de, which were pretty compellingly demonstrated with bench data, there is at least a possibility that the flimsy edge tape on a truly large, heavy oiled lens doesn't hold the elements 100% statically, and when stored horizontally, the elements decenter slightly, causing the astigmatism reported.

The conclusion of that report, if I recall correctly, was that when the scope was stored vertically, lens-down, for a period, it bench tested nearly perfectly.

So if you have a big, heavy oiled lens, and put any stock in those findings (which for me have greater credibility than anecdotal claims of "no problems" for horizontally stored scopes, including my own) then there's not much harm in storing the scope vertically with the lens down...unless you're a klutz, I suppose. My TEC 140 stands on the end of its Scopeguard case pretty stably, though it's more convenient for me to put it on a shelf with other boxed OTAs than store it in this manner.

Regards,

Jim

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JJK
scholastic sledgehammer

Reged: 04/28/08

Re: Oilspaced new

new

[Re: jrbarnett]
#5651262 - 01/29/13 10:07 PM

Quote:

Well, if you put any credence into the findings reported on astro-foren.de, which were pretty compellingly demonstrated with bench data, there is at least a possibility that the flimsy edge tape on a truly large, heavy oiled lens doesn't hold the elements 100% statically, and when stored horizontally, the elements decenter slightly, causing the astigmatism reported.

The conclusion of that report, if I recall correctly, was that when the scope was stored vertically, lens-down, for a period, it bench tested nearly perfectly.

So if you have a big, heavy oiled lens, and put any stock in those findings (which for me have greater credibility than anecdotal claims of "no problems" for horizontally stored scopes, including my own) then there's not much harm in storing the scope vertically with the lens down...unless you're a klutz, I suppose. My TEC 140 stands on the end of its Scopeguard case pretty stably, though it's more convenient for me to put it on a shelf with other boxed OTAs than store it in this manner.

Regards,

Jim

Jim, if the tape starts to fail, and is the means to keep a lens centered, keeping it oriented vertically may not help. When the scope is moved from the vertical orientation (i.e., when used) the lens might decenter anyway. If the lens is going to decenter, it likely won't do so over months or years. It would happen pretty quickly, unless you're suggesting that the tape fails because it is separated from the objective, rather than fail due to aging.

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timwetherell
sage

Reged: 09/03/10

Loc: A Land Down Under

Re: Oilspaced new

new

[Re: Mike Clemens]
#5651359 - 01/29/13 11:16 PM

I have to store my TEC200 vertically and yes, gravity is a worry. It sits on a trolley with the top attached to the wall with a safety tether just in case!

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Paul G
Post Laureate

Reged: 05/08/03

Loc: Freedonia

Re: Oilspaced new

new

[Re: jrbarnett]
#5651649 - 01/30/13 06:22 AM

Quote:

Well, if you put any credence into the findings reported on astro-foren.de, which were pretty compellingly demonstrated with bench data, there is at least a possibility that the flimsy edge tape on a truly large, heavy oiled lens doesn't hold the elements 100% statically, and when stored horizontally, the elements decenter slightly, causing the astigmatism reported.

The conclusion of that report, if I recall correctly, was that when the scope was stored vertically, lens-down, for a period, it bench tested nearly perfectly.

So if you have a big, heavy oiled lens, and put any stock in those findings (which for me have greater credibility than anecdotal claims of "no problems" for horizontally stored scopes, including my own) then there's not much harm in storing the scope vertically with the lens down...unless you're a klutz, I suppose. My TEC 140 stands on the end of its Scopeguard case pretty stably, though it's more convenient for me to put it on a shelf with other boxed OTAs than store it in this manner.

Regards,

Jim

I wonder if the problem isn't really the cell design instead of the tape. Seems to me a refractor that loses its figure when it's not vertical wouldn't be very useful for observing away from the zenith.

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Jon Isaacs
Postmaster

Reged: 06/16/04

Loc: San Diego and Boulevard, CA

Re: Oilspaced new

new

[Re: JJK]
#5651725 - 01/30/13 07:43 AM

Quote:

Jim, if the tape starts to fail, and is the means to keep a lens centered, keeping it oriented vertically may not help.

When the scope is stored vertically, the forces are uniformly distributed in the direction of the optical axis. When the scope is stored horizontally, the weight of the objective lens are now in the direction that favors decentering. If there is any tendency for the tape to change with time, the horizontal storage would seem to be more vulnerable because there is a constant non-uniform force on the tape.

Whether this is a real issue or only an anecdotal incident for one particular instrument of one particular design, I have no idea.

Jon

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jrbarnett
Eyepiece Hooligan

Reged: 02/28/06

Loc: Petaluma, CA

Re: Oilspaced new

new

[Re: Paul G]
#5652046 - 01/30/13 11:00 AM

Paul, my sense isn't that the movement of elements relative to one another is all that rapid. As the scope slews through the sky, the forces on the elements will change direction and, unlike extended horizontal storage, not stay in one location long enough for gravity to gradually shift the elements off center.

Given the radii of curvature of these oiled triplets, vertical storage would ensure that the elements float and gravitate to a centered condition.

You're right that it could be cell design, and I also suspect that lens mass is a major factor. We've seen other makers have issues with large cell designs. The initial batch of TOA 150s, for example, was recalled for a do-over on the cell, because the original design wasn't up to retaining centering during transoceanic shipping.

Regards,

Jim

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Paul G
Post Laureate

Reged: 05/08/03

Loc: Freedonia

Re: Oilspaced new

new

[Re: jrbarnett]
#5652222 - 01/30/13 12:27 PM

You're right, the TOA had that problem. A redesign of the cell solved it.

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Mike Clemens
Frozen to Eyepiece

Reged: 11/26/05

Loc: Alaska, USA

Re: Oilspaced new

new

[Re: Paul G]
#5652646 - 01/30/13 04:08 PM

> I wonder if the problem isn't really the cell design
> instead of the tape. Seems to me a refractor that loses
> its figure when it's not vertical wouldn't be very useful
> for observing away from the zenith.

My TMB152 air spaced lens was tested on horizontal and vertical interferometers back in 2004. It had differing amounts of astigmatism based on the position. The lens was best pointed straight up.

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