[APML] Re: [ap-gto] OT--help for Takahashi Epsilon series

["Bobby Middleton" <bobm@koyote.com>]

----- Original Message -----
> > I apologize for this OT post on the AstroPhysics list, but I am hoping
you
> > guys are knowledgable enough to give me some answers. I have a Takahashi
> > Epsilon astrograph 130 (no longer made). When I photograph a bright star
in
> > the field, I get a big circular looping arc of a reflection all across
the
> > photograph
>
> As I said in the APML group, the source of your ghost image is most likely
> internal reflections from the lens surfaces, not from the lens edges. The
> cure is to have very high transmission coatings applied, but this can only
be
> done on freshly polished glass. Once a lens is coated, it cannot be
stripped
> and recoated without first repolishing it.

Thanks for the reply Roland. I have posted an image I did that shows the
problem just so we can be pretty sure we're talking about the same kind of
reflection. See it here:
http://www.koyote.com/users/bobm/tak130.htm
This is the witch head nebula area. Rigel would be off to the left; outside
the field of view. The reflection arc appears to me to intersect both beta
Eridanus (center top) and Rigel (out of the frame to left). On brighter
stars in the field of view it's much worse.
I assume your fix above is do-able but probably expensive. And I assume each
surface will need the same treatment. Is Takahashi the ones to check with
about doing this, or are there other options? Of course if I had a Traveller
and 6 x 7 film I could cover this much sky <g>. I'm on the list.
Bobby Middleton


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