Afocal photographs - RGB

Evening,

Would you be able to give some advice:
I am taking my first photographs through a telescope and I have found a
problem: The Red Green and Blue components of my pictures are shifted
(see example: http://www.j2l.dsl.pipex.com/astronomy/moon_rgb.jpg). I have
to re-align the channels manually with photoshop.
I use a canon A80, an afocal mount, an Explorer 130M and the eyepiece a 24mm
(which came with the telescope).
Am I doing something wrong or could it be a defect of some sort? My camera
seems OK, "terrestrial" photographs are fine.

Thank you.

Jean-Louis Lamacchia

JLL nous a écrit :

Evening,

Would you be able to give some advice:
I am taking my first photographs through a telescope and I have found
a problem: The Red Green and Blue components of my pictures are
shifted (see example:
http://www.j2l.dsl.pipex.com/astronomy/moon_rgb.jpg). I have
to re-align the channels manually with photoshop.
I use a canon A80, an afocal mount, an Explorer 130M and the eyepiece
a 24mm (which came with the telescope).
Am I doing something wrong or could it be a defect of some sort? My
camera seems OK, "terrestrial" photographs are fine.

It seems like a typical chromatic aberration. The Explorer is a
newtonian reflector, so I would suspect your eyepiece.
Another reason could be the atmospheric chromatism if you took your
pictures when the Moon was low in the sky.

--
Norbert. (no X for the answer)
======================================
knowing the universe - stellar and galaxies evolution
http://nrumiano.free.fr
images of the sky http://images.ciel.free.fr
======================================

"Norbert" wrote in message
r...
JLL nous a écrit :

Evening,

Would you be able to give some advice:
I am taking my first photographs through a telescope and I have found
a problem: The Red Green and Blue components of my pictures are
shifted (see example:
http://www.j2l.dsl.pipex.com/astronomy/moon_rgb.jpg). I have
to re-align the channels manually with photoshop.
I use a canon A80, an afocal mount, an Explorer 130M and the eyepiece
a 24mm (which came with the telescope).
Am I doing something wrong or could it be a defect of some sort? My
camera seems OK, "terrestrial" photographs are fine.

It seems like a typical chromatic aberration. The Explorer is a
newtonian reflector, so I would suspect your eyepiece.
Another reason could be the atmospheric chromatism if you took your
pictures when the Moon was low in the sky.

--
Norbert. (no X for the answer)
======================================
knowing the universe - stellar and galaxies evolution
http://nrumiano.free.fr
images of the sky http://images.ciel.free.fr
======================================

Photoshop CS has a chromatic aberration filter. Might be worth trying.
Viewing in greyscale mode may look better, although that will only merge the
three colour channels.Conversly- why not ditch two of the colour channels
and convert the sharpest one to greyscale.
Good luck.
John

Greyscaling gets rid of the fringing but the sharpness will still be
affected. There's just too much glass in the way, I think.
"John Bell" wrote in message
...

"Norbert" wrote in message
r...
JLL nous a écrit :

Evening,

Would you be able to give some advice:
I am taking my first photographs through a telescope and I have found
a problem: The Red Green and Blue components of my pictures are
shifted (see example:
http://www.j2l.dsl.pipex.com/astronomy/moon_rgb.jpg). I have
to re-align the channels manually with photoshop.
I use a canon A80, an afocal mount, an Explorer 130M and the eyepiece
a 24mm (which came with the telescope).
Am I doing something wrong or could it be a defect of some sort? My
camera seems OK, "terrestrial" photographs are fine.

It seems like a typical chromatic aberration. The Explorer is a
newtonian reflector, so I would suspect your eyepiece.
Another reason could be the atmospheric chromatism if you took your
pictures when the Moon was low in the sky.

--
Norbert. (no X for the answer)
======================================
knowing the universe - stellar and galaxies evolution
http://nrumiano.free.fr
images of the sky http://images.ciel.free.fr
======================================

Photoshop CS has a chromatic aberration filter. Might be worth trying.
Viewing in greyscale mode may look better, although that will only merge
the
three colour channels.Conversly- why not ditch two of the colour channels
and convert the sharpest one to greyscale.
Good luck.
John