A Baffling Ghost Problem to Reflect Upon

I think of a ghost image in the EP of a telescope as several images of a bright object, usually a
planet like Mars or Jupiter. No matter how hard one tries to focus, they persist. One is bright and
the others dimmer, but nevertheless visible. I've probed this problem a little before on the net.
Today I decided to try Google and Harrington's book StarWare, 2nd edition. From my Google
experience, it looks like ghosting is fairly common and the solution is most often attributed to
using a 'better' eyepiece. Ocassionally someone mentions the need to baffle the OTA.

A 1993 article is on the web that appeared on Astronomy magazine on this very subject. The author
praises various eyepieces. I'm not sure that some of them are still made, and several seem pretty
expensive. Harrington talks about a Plossl being quite effective and TeleVue making some of the
finest plossls. I have two TeleVue plossls, 13 and 17mm, and I have no trouble seeing ghosting on
several SCTs I've used it on. Very puzzling. Perhaps the ghosting they are talking about isn't what
I experience.

Can anyone comment on the ghosting problem, and shed some light on it--but not too much or I'll be
seeing ghosts, won't I?

Beyond this I would like a good suggestion for an eyepiece that produces no or very little ghosting
with a C-11 SCT. Something that's not over $150.

--
Wayne T. Watson (121.015 Deg. W, 39.262 Deg. N, 2,701 feet, Nevada City, CA)
-- GMT-8 hr std. time, RJ Rcvr 39° 8' 0" N, 121° 1' 0" W

Remember to drink an adequate amount of dihydrogen oxide each day.

Web Page: home.earthlink.net/~mtnviews
Imaginarium Museum: home.earthlink.net/~mtnviews/imaginarium.html

On Tue, 23 Sep 2003 22:46:51 GMT, Wayne Watson
wrote:

I think of a ghost image in the EP of a telescope as several images of a
bright object, usually a
planet like Mars or Jupiter. No matter how hard one tries to focus, they
persist. One is bright and
the others dimmer, but nevertheless visible. I've probed this problem a
little before on the net.
Today I decided to try Google and Harrington's book StarWare, 2nd
edition. From my Google
experience, it looks like ghosting is fairly common and the solution is
most often attributed to
using a 'better' eyepiece. Ocassionally someone mentions the need to
baffle the OTA.

A 1993 article is on the web that appeared on Astronomy magazine on this
very subject. The author
praises various eyepieces. I'm not sure that some of them are still made,
and several seem pretty
expensive. Harrington talks about a Plossl being quite effective and
TeleVue making some of the
finest plossls. I have two TeleVue plossls, 13 and 17mm, and I have no
trouble seeing ghosting on
several SCTs I've used it on. Very puzzling. Perhaps the ghosting they
are talking about isn't what
I experience.

Can anyone comment on the ghosting problem, and shed some light on it--
but not too much or I'll be
seeing ghosts, won't I?

Beyond this I would like a good suggestion for an eyepiece that produces
no or very little ghosting
with a C-11 SCT. Something that's not over $150.

--
Wayne T. Watson (121.015 Deg. W, 39.262 Deg. N, 2,701 feet, Nevada City,
CA)

It is unlikely that telescope optics are responsible for
the ghosts seen at the eyepiece. Multiple reflection in
an Optical Tube Assembly (OTA) will very likely be very
spread out by the time they reach the focal plane.

One possibility you didn't mention was whether or not you
wear contact lenses. Such lenses probably don't have
anti-reflection coatings. Thus the air-to-glass surfaces
will reflect relatively strongly, and if the eyepiece has
a flat or weakly curved eye-lens (on they observer side),
then ghosts may result. This would account for ghosts
being present in a wide variety of quality eyepieces, which
are usually designed to minimize or eliminate internal
reflections.

There are some eyepieces which have little or no ghosting.
IIRC, these include Orthoscopics and Kellners (MA's ?)
because they have relatively few elements, few air-glass
surfaces, and the facing air-glass surfaces are all convex.

Cheers,
Larry G.

Yes, I wear glasses but I've tried it with and without. The ghosts are there. I've talked with
several people who have observed a similar problem.

Several of the sources I looked at mentioned orthoscopics as best all around EPs. Orion no longer
offers them. I haven't checked elsewhere.

IIRC?

Yes, the OTAs could be the source of the problem but I found little about it on the web. I would
think if it is, then baffling in the OTA would be required.

LarryG wrote:

On Tue, 23 Sep 2003 22:46:51 GMT, Wayne Watson
wrote:

I think of a ghost image in the EP of a telescope as several images of a
bright object, usually a
planet like Mars or Jupiter. No matter how hard one tries to focus, they
persist. One is bright and
the others dimmer, but nevertheless visible. I've probed this problem a
little before on the net.
Today I decided to try Google and Harrington's book StarWare, 2nd
edition. From my Google
experience, it looks like ghosting is fairly common and the solution is
most often attributed to
using a 'better' eyepiece. Ocassionally someone mentions the need to
baffle the OTA.

A 1993 article is on the web that appeared on Astronomy magazine on this
very subject. The author
praises various eyepieces. I'm not sure that some of them are still made,
and several seem pretty
expensive. Harrington talks about a Plossl being quite effective and
TeleVue making some of the
finest plossls. I have two TeleVue plossls, 13 and 17mm, and I have no
trouble seeing ghosting on
several SCTs I've used it on. Very puzzling. Perhaps the ghosting they
are talking about isn't what
I experience.

Can anyone comment on the ghosting problem, and shed some light on it--
but not too much or I'll be
seeing ghosts, won't I?

Beyond this I would like a good suggestion for an eyepiece that produces
no or very little ghosting
with a C-11 SCT. Something that's not over $150.

--
Wayne T. Watson (121.015 Deg. W, 39.262 Deg. N, 2,701 feet, Nevada City,
CA)

It is unlikely that telescope optics are responsible for
the ghosts seen at the eyepiece. Multiple reflection in
an Optical Tube Assembly (OTA) will very likely be very
spread out by the time they reach the focal plane.

One possibility you didn't mention was whether or not you
wear contact lenses. Such lenses probably don't have
anti-reflection coatings. Thus the air-to-glass surfaces
will reflect relatively strongly, and if the eyepiece has
a flat or weakly curved eye-lens (on they observer side),
then ghosts may result. This would account for ghosts
being present in a wide variety of quality eyepieces, which
are usually designed to minimize or eliminate internal
reflections.

There are some eyepieces which have little or no ghosting.
IIRC, these include Orthoscopics and Kellners (MA's ?)
because they have relatively few elements, few air-glass
surfaces, and the facing air-glass surfaces are all convex.

Cheers,
Larry G.

--
Wayne T. Watson (121.015 Deg. W, 39.262 Deg. N, 2,701 feet, Nevada City, CA)
-- GMT-8 hr std. time, RJ Rcvr 39° 8' 0" N, 121° 1' 0" W

Remember to drink an adequate amount of dihydrogen oxide each day.

Web Page: home.earthlink.net/~mtnviews
Imaginarium Museum: home.earthlink.net/~mtnviews/imaginarium.html

There are some eyepieces which have little or no ghosting.
IIRC, these include Orthoscopics and Kellners (MA's ?)
because they have relatively few elements, few air-glass
surfaces, and the facing air-glass surfaces are all convex.

Actually, the classical Kellner has the field lens at the focus of the
eye lens, and you can get really strong ghosts that way, though
not a series of them if the elements are aligned properly. I
seem to recall that some problems with one's eyes can cause
these "ghosts", but cannot confirm that. I do know that I was
seeing ghost images of bright lights until I got my eyeglass
prescription updated. Perhaps it is astigmatism??

Hope this will help. By the way, though they do have a strong
reflection, Kellners can be a very good EP if well made and
properly coated. I recall seeing M57 as a globe with Plossls
and even Orthos, but clearly seeing it as a ring with a Kellner.


Clear, Dark, Steady Skies!
(And considerate neighbors!!!)

Orthos are still sold by University Optics, and you can look at these on:
http://www.universityoptics.com/
Helix was also advertising them, but they do not seem to have the link active
any more.
Clear, Dark, Steady Skies!
(And considerate neighbors!!!)

On Wed, 24 Sep 2003 00:45:54 GMT, Wayne Watson
wrote:

Yes, I wear glasses but I've tried it with and without. The ghosts are
there. I've talked with
several people who have observed a similar problem.

Several of the sources I looked at mentioned orthoscopics as best all
around EPs. Orion no longer
offers them. I haven't checked elsewhere.

IIRC?

Internet acronym: If I Recall Correctly



Yes, the OTAs could be the source of the problem but I found little about
it on the web. I would
think if it is, then baffling in the OTA would be required.


No! The OTA is almost assuredly NOT a cause of ghosting.
Baffling might reduce scattered light, and may be worthwhile
in itself, but it will have no effect on ghost, other than to
enhance their contrast!


Cheers,
Larry G.



LarryG wrote:

On Tue, 23 Sep 2003 22:46:51 GMT, Wayne Watson
wrote:

I think of a ghost image in the EP of a telescope as several images of
a
bright object, usually a
planet like Mars or Jupiter. No matter how hard one tries to focus,
they
persist. One is bright and
the others dimmer, but nevertheless visible. I've probed this problem
a
little before on the net.
Today I decided to try Google and Harrington's book StarWare, 2nd
edition. From my Google
experience, it looks like ghosting is fairly common and the solution
is
most often attributed to
using a 'better' eyepiece. Ocassionally someone mentions the need to
baffle the OTA.

A 1993 article is on the web that appeared on Astronomy magazine on
this
very subject. The author
praises various eyepieces. I'm not sure that some of them are still
made,
and several seem pretty
expensive. Harrington talks about a Plossl being quite effective and
TeleVue making some of the
finest plossls. I have two TeleVue plossls, 13 and 17mm, and I have no
trouble seeing ghosting on
several SCTs I've used it on. Very puzzling. Perhaps the ghosting they
are talking about isn't what
I experience.

Can anyone comment on the ghosting problem, and shed some light on it--


but not too much or I'll be
seeing ghosts, won't I?

Beyond this I would like a good suggestion for an eyepiece that
produces
no or very little ghosting
with a C-11 SCT. Something that's not over $150.

--
Wayne T. Watson (121.015 Deg. W, 39.262 Deg. N, 2,701 feet, Nevada
City,
CA)

It is unlikely that telescope optics are responsible for
the ghosts seen at the eyepiece. Multiple reflection in
an Optical Tube Assembly (OTA) will very likely be very
spread out by the time they reach the focal plane.

One possibility you didn't mention was whether or not you
wear contact lenses. Such lenses probably don't have
anti-reflection coatings. Thus the air-to-glass surfaces
will reflect relatively strongly, and if the eyepiece has
a flat or weakly curved eye-lens (on they observer side),
then ghosts may result. This would account for ghosts
being present in a wide variety of quality eyepieces, which
are usually designed to minimize or eliminate internal
reflections.

There are some eyepieces which have little or no ghosting.
IIRC, these include Orthoscopics and Kellners (MA's ?)
because they have relatively few elements, few air-glass
surfaces, and the facing air-glass surfaces are all convex.

Cheers,
Larry G.

--
Wayne T. Watson (121.015 Deg. W, 39.262 Deg. N, 2,701 feet, Nevada City,
CA)
-- GMT-8 hr std. time, RJ Rcvr 39° 8' 0" N, 121° 1' 0" W

Remember to drink an adequate amount of dihydrogen oxide each day.

Web Page: home.earthlink.net/~mtnviews
Imaginarium Museum: home.earthlink.net/~mtnviews/imaginarium.html






--
Vote Republican - The Party of 'Spend and Squander'!

On 24 Sep 2003 01:29:59 GMT, Bill Foley wrote:

There are some eyepieces which have little or no ghosting.
IIRC, these include Orthoscopics and Kellners (MA's ?)
because they have relatively few elements, few air-glass
surfaces, and the facing air-glass surfaces are all convex.

Actually, the classical Kellner has the field lens at the focus of the
eye lens, and you can get really strong ghosts that way, though not a
series of them if the elements are aligned properly. I seem to recall
that some problems with one's eyes can cause these "ghosts", but cannot
confirm that. I do know that I was seeing ghost images of bright lights
until I got my eyeglass prescription updated. Perhaps it is
astigmatism??

Well the air-glass surfaces seem more likely culprits.
I've had a similar problem looking through short focus
Orthos - the ghost was a reflection off of the flat eyelens
from the lens of my own eye hovering within a few mm's of
the e.p.


Cheers,
Larry G.

"Wayne Watson" wrote in message
...
Yes, I wear glasses but I've tried it with and without. The ghosts are
there. I've talked with
several people who have observed a similar problem.

Several of the sources I looked at mentioned orthoscopics as best all
around EPs. Orion no longer
offers them. I haven't checked elsewhere.

University Optics has some very good orthos at good prices.

Clear Skies

Chuck Taylor
Do you observe the moon?
Try the Lunar Observing Group
http://groups.yahoo.com/group/lunar-observing/

On Tue, 23 Sep 2003 21:36:13 -0700, "Chuck Taylor" ...reflected:

"Wayne Watson" wrote in message
...
Yes, I wear glasses but I've tried it with and without. The ghosts are
there. I've talked with
several people who have observed a similar problem.

Several of the sources I looked at mentioned orthoscopics as best all
around EPs. Orion no longer
offers them. I haven't checked elsewhere.

University Optics has some very good orthos at good prices.

Clear Skies

Chuck Taylor
Do you observe the moon?
Try the Lunar Observing Group
http://groups.yahoo.com/group/lunar-observing/

Correction: University Optics has EXCELLENT orthoscopics
at EXCELLENT prices.

8^)

Alan, who has the 4mm, the 5mm, the 7mm, and the 9mm, whilst
contemplating the 12.5mm

"Alan W. Craft" wrote in message
...

University Optics has some very good orthos at good prices.

Correction: University Optics has EXCELLENT orthoscopics
at EXCELLENT prices.

8^)

Alan, who has the 4mm, the 5mm, the 7mm, and the 9mm, whilst
contemplating the 12.5mm

Hi Alan,

I stand corrected! (Well, actually I'm sitting while being corrected). I
have the 4, 5 & 6 and love them.

Clear Skies

Chuck Taylor
Do you observe the moon?
Try the Lunar Observing Group
http://groups.yahoo.com/group/lunar-observing/