Orion 80 mm ED Apo via Zeiss Telementor 63/840

Hi Everybody

Today I received my first 3 samples Orion 80 mm ED Apos and could
already test them. I would like to receive some feedback from customers
who already owns it.
In almost any review I know of today about the Orion 80 mm ED I read its
colorfree and of high optical quality.

I dont know the telescopes the owners have reported about, I dont know
if something changed in the design and quality now where the production
seems to run, but here is what I found.

My experience with orion 80 ED

1, collimation/lens centering is rather good, not perfect, but good
enough to show a nondistored airydisc and a complete first diffraction
ring with a hint of coma at an acceptable level

2, spherical correction estimated first by my experienced eye ( a
complete interferometrical test will be done next 8 days ):
- thinny central zonal deffect ( not real poor but visible)
- global undercorrection of about 1/3 to 1/4 wavefront p.t.v. Using a
red filter show about similar startest as in white light, using green
filter show even worser startest . The undercorrection is such bad, that
the image does not show a snap in focuse and the first diffraction ring
is as bright/wide as in a good quality Maksutov with 33% C.O.

3, colorcorrection: In defocused image you see one side bright red and
on other side bright green color, infocuse itself you see a white
airydisc, soroundet by a mixture colored red/white diffraction ring
soroundet by green straylight due the spherical aberration.
My Carl Zeiss Jena Telementor, a standart douplet airspacest achromat D=
63 mm f=830 mm ( r-tatio f/13.3) show by same 250 power nearly no color
accept very very little deep purple .
To find out how the colorcorrection is against a achromat, I took now a
Skywatcher Achromat 102F/1000 and made several masks. Doing a Mask with
60 mm , the Skywatcher offers a bit better colorcorrection, doing a mask
with 80 mm the Skywatcher was a bit worser.
The best matched the Mask of 70 mm , than my eyes saw about same level
of colorcorrection as in the 80 mm ED. This means estimated by huma eyes
the colorcorrection in the orion 80F/7.5 ED Apo is about equal to a 70
mm F/14 achromatic refractor.Such level of colorcorrection was called by
Zeiss Jena Semiapo as they have had in here AS Types.
For a cheap chinese made douplet ED Apo 80 mm the level of
colorcorrection is not bad and the pricerelation is rather good, so we
can say you get what you pay for.

One thing confuse me very much. Almost any report about this 80 mm ED
Apo I wrote stated zero or nearly zero color even at high power, but hey
there is quite some visible color even at lower powers.How such reports
can come up ? Or did the manufactor changed something in the production
run ?

All in all I would say you get a very good value for your money if you
want a short 80 mm Telescope , but if you want a good Planetary
Telescope I personaly would prefer the maybe not more expensive Vixen
80F/1200 real achromat which show way higher quality and not less ( or
at least not much less ) good colorcorrection but way better spherical
correction.
What I found is far away from the Top Notch douplet ED Apos , like Tele
Vue 76 or Tele Vue 85 .

If you like to do CCD Imaging, low power wide field deep sky observing
and looking from time to time to the planets, than the orion 80 ED is a
good purchase.

If you looking for a real high quality apo in the 80 mm range, you need
to look elsewhere ( or I received 3 lemons today, which is another but I
think rather small possibility)

clear skies

Markus Ludes




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