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CHAMÄLEON OBSERVATORY A new telescope for Chamäleon
observatory |
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In the fall of 2015 - after returning from Namibia -
we began to considered a new telescope with larger aperture and longer focal
length for our chameleon Observatory.
Based on our excellent experience
with the
17" PlaneWave astrograph at Rooisand Desert Ranch (simple
and stable adjustment and even at full frame a very good image quality) our
choice also fell on a Plane Wave. For reasons of cost and the available space
in the 3m dome we choosed the 12.5" instrument with a primary focal length of
2.540mm and a focal ratio of f/8. |
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Further
advantages for our site is the closed carbon tube that protects the mirror
against dust and sand much more efficiatly as an open truss tube. The telescope
has a large back focus with just 190 mm, so that various accessories can be
connected. For example a large offaxis-guider and a focal reducer along with a
full-frame DSLR camera. And with "only" 21kg weight of the telescope there is
no problem with the 6ADN Mount from Eckard Alt.
The instrument was
tested in Germany in the dome of Paech. The images above show the PlaneWave on
a Astrophysics GTO 1200 Mount. To the left is a test image of the Pleiades (1 x
10 min), taken with a Canon EOS 60D APS-C. All images on
this page can be enlarged by clicking on it..
Available are two
focal reducer, both showing a very good image quality in the far corners of the
full frame. Since the PlaneWave already has a correction system and a planar
field, there are basically only two possible reducers within our reach (nearly
all currently reducers on the market are build for refractors and correct the
curvature of the refractors, when used on the PlaneWave they would distort the
plane field into a curved one).
- TeleVue 0.8x, results in a focal
length of 2.030mm at f / 6.4 and
- Pentax 0.72x, results in a focal
length of 1.830mm at f / 5.8 (if t all, only second hand)
The animation below shows the focal
reducing of both reducers compared to the full focal
length. |
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The
telescope was ordered at Baader Planetarium in February 2016 and shipped by
airfreight to friends in Windhoek who also took care about the customs import.
In mid-April we transported the telescope to Onjala, unpacked and assembled
it. |
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In addition
to very poor weather conditions at the end of April in Namibia we had further
problems. After our arrival, we unfortunately had to see that all the
electronics was more or less defect in the 3m dome. Dome control, telescope
control and light control were completely "dead" and not repairable on site. We
suppose a lightning strike near the dome.
The dome gap we could manually
open and close. But the FS 2 mount control was not usable. While we have a
Little Foot control as a replacement and got the RA motor in operation, but a
decent Guiding was not possible. But the main problem was the often cloudy
skies in the evening and in the few clear hours we had a terrible
seeing. |
For
sure, this will be our final instrumentation in the 3m chameleon dome
- 12.5 "PlaneWave Astrograph
with 2.540mm focal length
- 5 "Astrophysics EDF
refractor with 780mm focal length and a
- 75mm Pentax refractor with
500mm focal length.
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In addition
a larger telephoto lens can also be mounted. The former fixed mounted Celestron
11 with the f/2 HyperStar system is now being used on our CGEM-DX
mount. |
Due to
the above-mentioned technical and weather conditions we were unable to do some
long exposed and tracked images. After all we could take some short exposed
images after the adjustment of the PlaneWave to check the image quality - even
when seeing conditions were not optimal.
» core of Omega Centauri, 20 x 15 sec focal
(full frame, EOS 6D) and »
» core of Omega Centauri, 20 x 15 sec. with Televue Reducer
(full frame, EOS 6D)
Click to load
larger images |
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« « Core of Eta Carinae, 10 x 30
seconds taken at f / 5.8 with the Pentax-reducer at 1.830 mm focal length and a
cooled EOS 700 DA (APS-C format). Taken at poor seeing conditions.
« As above, but with enlarged star images in
the corners with an image scale of 1: 1 (click to load larger
images)
We look forward to our
next stay in Namibia! |
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All Images and all Content are ©
by Franz Hofmann + Wolfgang Paech |
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