Re: optician's trial lens for telescope use?

waz wrote:

>
> Hello!
>
> I have a astigmatism developing in my eyes, -0.50 each eye.
> I also use a telescope. I prefer to observe without my glasses on if
> possible but this is getting to be a problem.
>
> I do not have any test lenses to try, so I have to ask...
>
> In theory, would it be possible to mount an optician's test lens (let's
> say to correct for -0.50 cylinder) BETWEEN the telescope eyepiece and the
> objective and have it correct the view for me?? Could this lens be placed
> somewhere in the barrel of the eyepiece?
>
> (I am sure it would work between the eyepiece and the eye).
>
> Would the distance between the test lens and the eyepiece lenses be
> critical or would a centimeter either way be usable?
>
> If this trial lens (-0.50 cyl) would work for one eyepiece of a given
> focal length, would work for several eyepices of different focal lengths?
>
> I was thinking of trying some "quality test lenses" but thought I would
> ask my question here before I looked into where and how to obtain them.
>
> Many thanks for your thoughts on this.
>
> Waz
>
> wazungy@xxxxxxxxxxxx

I thought I followed up but it doesn't seem to have gone through.
I'll try again...

Thanks for all the input.

It seems the general consensus is that the lens I intend to add should be
placed between the eye and the eyepiece.

I had intended to try to place it between the eyepiece and the objective to
avoid loss of field of view (with short focal length eyepieces) and to keep
the corrective lens clean and eyelash oil free.

While I know a corrective lens between the eyepiece and the eye does indeed
work, it is difficult to get it to fit all eyepiece models which might have
wildly differing widths and bevels.

All my eyepieces have 1.25 inch barrels with threading for filters so this
is the easiest universal fix if it works optically.

I'll try both positions and see if acceptable results are obtained.

Thank you very much!

Waz
.

Relevant Pages

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