Re: [ap-ug] air.. & oiled objectives


Dec 20, 2000

 


----------------------------

#3487 Dec 20, 2000

Just because someone has an air spaced triplet objective

doesn't mean it will never need maintenance. I've heard

of mold and other gunk collecting between the elements of

air spaced objectives.



Rich



>I am talking about a REALLY long time. Some of these scopes are going to be

>around next century and beyond, like Clarks. Are there any 150 year old oil

>spaced lenses around or is this technique just your recent innovation. I am

>just wondering if the oil will turn to varnish after 75 years and should be

>replaced preventively after X years to head off trouble like having the

>elements bonded together.

>I am wondering if I need to put a clause in my will stating that whoever

>wants to inherit my chewing gum wrapper collection must also agree to have

>the telescope lens re-oiled in 2075.

>Dale

>

>-----Original Message-----

>From: chris1011@... [mailto:chris1011@...]

>

>In a message dated 12/20/00 9:33:49 AM Central Standard Time,

>direland@... writes:

>

>< Does the oil in oil spaced objectives require replacement after a

>specific

> time? >>

>

>Unless something unusual happens to the lens, it should last a long long

>time. Replacing of the oil is easier than recoating a Newtonian mirror, and

>can be done in any clean optical shop. My own Traveler, 5"F6 and 6"EDT

>lenses

>are quite old and show no signs of degradation. Lens alignment is not

>difficult, all it needs is a V block. The lens cells we make now have an

>inner ring that assures the elements are centered optically. This assembly

>is

>then dropped into the cell, where the lens rests on 6 cork pads. No magic

>required.

>

>Roland Christen

>



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#3491 Dec 20, 2000

yes, well I didn't mean to compare or criticize the design just wondering

about long term maintenance. Certainly mold is a bigger problem and destroys

many camera lenses, it also etches the glass. I wonder if storing a scope in

an unheated observatory promotes mold growth due to the higher relative

humidity.



-----Original Message-----

From: Rich N. [mailto:rnapo@...]





Just because someone has an air spaced triplet objective

doesn't mean it will never need maintenance. I've heard

of mold and other gunk collecting between the elements of

air spaced objectives.



Rich



----------------------------

#3493 Dec 20, 2000

Here is a link for a desiccant that will dry the air

to -100F, and it is relatively inexpensive.



www.hammond.thomasregister.com/olc/hammond/home.htm







--- Dale Ireland direland@...> wrote: > yes, well I didn't mean to compare or criticize the

> design just wondering

> about long term maintenance. Certainly mold is a

> bigger problem and destroys

> many camera lenses, it also etches the glass. I

> wonder if storing a scope in

> an unheated observatory promotes mold growth due to

> the higher relative

> humidity.

>

> -----Original Message-----

> From: Rich N. [mailto:rnapo@...]

>

>

> Just because someone has an air spaced triplet

> objective

> doesn't mean it will never need maintenance. I've

> heard

> of mold and other gunk collecting between the

> elements of

> air spaced objectives.

>

> Rich

>

>

>

>

>

> .

> s of

> air spaced objectives.

>

> Rich

>

>

>

>

>

> .

>





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----------------------------

#3496 Dec 20, 2000

In a message dated 12/20/00 12:42:46 PM Central Standard Time,

direland@... writes:



< I wonder if storing a scope in

an unheated observatory promotes mold growth due to the higher relative

humidity. >>



It may. I have fixed some airspaced lenses that were ruined by mold.



Roland


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