Strange spikes

Today, back on Easter vacations from Crete, I've finally finished aligning
my Apogee 20x100 and my 60mm/700mm Tasco with the new EP's also from Apogee.

I tried to give the Tasco tube to my precision engineer to cut it a little
shorter, but I ended doing it in a machine shop next door. The focuser ended
up aligned ok, after the sawing, so everything looks ok.

I am getting a strange internal reflection with the new (zoom) EP, however.
On Venus, as well as on relatively bright but small objects, I am getting
two horizontal spikes emanating from Venus for example and extending almost
all the way to the edge of the EP.

I tried rotating the main lens, the spike direction stays the same. I
rotated the EP, but the spikes remained horizontal. I rotated the entire
telescope and the spikes rotated along with it, so finally I rotated only
the diagonal along with the EP and bang, there it was.

The spikes seem to be aligned to the direction of the 45 deg diagonal from
Apogee. Specifically, they seem to be normal to the plane generated by the
45 diagonal's axes.

Does anyone know what are these two horizontal spikes on bright objects? Is
it a sign of a low diagonal quality? They don't seem to be related to dirt
or anything.

Thanks in advance and happy observing.
--
Ioannis Galidakis
http://users.forthnet.gr/ath/jgal/
------------------------------------------
Eventually, _everything_ is understandable

Does anyone know what are these two horizontal spikes on bright objects? Is
it a sign of a low diagonal quality?

45 degree diagonals are used mostly for low power terrestial viewing. They
essentially take the image apart into two pieces and then reassemble it as best
they can back into one... If you look closely you should see a line do the
middle of the prism.

A 90 degree "star" diagonal is what is commonly used in astronomy for this
reason (and others.)

jon

Does anyone know what are these two horizontal spikes on bright objects? Is
it a sign of a low diagonal quality?

45 degree diagonals are used mostly for low power terrestial viewing. They
essentially take the image apart into two pieces and then reassemble it as best
they can back into one... If you look closely you should see a line do the
middle of the prism.

A 90 degree "star" diagonal is what is commonly used in astronomy for this
reason (and others.)

jon

The spikes seem to be aligned to the direction of the 45 deg diagonal from
Apogee. Specifically, they seem to be normal to the plane generated by the
45 diagonal's axes.


Hi:

Spikes and other similar artifacts are almost inevitable with 45 degree
diagonals. Solution? Get a decent 90 degree model.

Peace,
Rod Mollise
Author of _Choosing and Using a Schmidt Cassegrain Telescope_
Like SCTs and MCTs?
Check-out sct-user, the mailing list for CAT fanciers!
Goto http://members.aol.com/RMOLLISE/index.html

The spikes seem to be aligned to the direction of the 45 deg diagonal from
Apogee. Specifically, they seem to be normal to the plane generated by the
45 diagonal's axes.


Hi:

Spikes and other similar artifacts are almost inevitable with 45 degree
diagonals. Solution? Get a decent 90 degree model.

Peace,
Rod Mollise
Author of _Choosing and Using a Schmidt Cassegrain Telescope_
Like SCTs and MCTs?
Check-out sct-user, the mailing list for CAT fanciers!
Goto http://members.aol.com/RMOLLISE/index.html

Ï "Rod Mollise" Ýãñáøå óôï ìÞíõìá
...
[snip]
Hi:

Spikes and other similar artifacts are almost inevitable with 45 degree
diagonals. Solution? Get a decent 90 degree model.

Thanks, but that's not an option the way I've mounted the binos and the
telescope. Can't be viewing straight with the binos and @90 deg with the
telescope both of them aligned and side by side.

It's a relief though to know that it's not related to low quality.

Learning something new (even me) evey day :*)

Peace,
Rod Mollise
Author of _Choosing and Using a Schmidt Cassegrain Telescope_
Like SCTs and MCTs?
Check-out sct-user, the mailing list for CAT fanciers!
Goto http://members.aol.com/RMOLLISE/index.html
--
Ioannis Galidakis
http://users.forthnet.gr/ath/jgal/
------------------------------------------
Eventually, _everything_ is understandable

Ï "Rod Mollise" Ýãñáøå óôï ìÞíõìá
...
[snip]
Hi:

Spikes and other similar artifacts are almost inevitable with 45 degree
diagonals. Solution? Get a decent 90 degree model.

Thanks, but that's not an option the way I've mounted the binos and the
telescope. Can't be viewing straight with the binos and @90 deg with the
telescope both of them aligned and side by side.

It's a relief though to know that it's not related to low quality.

Learning something new (even me) evey day :*)

Peace,
Rod Mollise
Author of _Choosing and Using a Schmidt Cassegrain Telescope_
Like SCTs and MCTs?
Check-out sct-user, the mailing list for CAT fanciers!
Goto http://members.aol.com/RMOLLISE/index.html
--
Ioannis Galidakis
http://users.forthnet.gr/ath/jgal/
------------------------------------------
Eventually, _everything_ is understandable