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Tube optical out of aluminium. Achromatic
objective of 80 mm diammeter out of glass ED in an aluminium cell.
Focal distance 600 mm. Crayford focuser 2"and 1.25".
Weight 2,5 kg.
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I wanted a second instrument, easier to transport
than the telescope newton. An instrument which I can put in the car
with the family. Or to observe between two cloudy passages or
for one hour. Moreover I wished a refractor which I can use in
parallel on my telescope, (thus limited weight) and powerful for the
photograph. I wanted to also enjoy in visual observations, in spite
of the inevitable concessions due to the diameter. The ORION 80
ED corresponds well to this schedule of conditions.
Then I needed a mount. The
first tests on foot photographs did not satisfy me, especially with
the binoviewer . I wanted it light, but rigid, with soft
movements, balanced, dismountable for transport. I am very
satisfied with the result. Stability is excellent even with the
bino and I like this refractor which supplement
very well my Newton 200. I had two sources of inspiration:
http://www.cloudynights.com/mounts/homebuilt.htm
http://home.comcast.net/~bberg100/Astronomy/ATM/alt-az.htm
Why build?
There are small equatoriales mounts not expensive.
Their weight is at least as important as my mount and their
disastrous stability. The weight of my mounting is 6 kg without
counterweight. I can use it without counterweight with only one
eyepiece.(without bino or camera). The counterweight
weighs 2 kg and the counterweight on tube 1 kg. I
arrive thus at a weight comparable with the weight of azimuth
mountings "stable" of the trade which uses much aluminium. I
will have been able gained in weight by optimizing the thicknesses of
wood but I had already some plywood. I think that CP of 12
or 15mm would have is enough for the fork. A mount able to
support approximately 4 kg of material without problem is worth in the
trade several hundred euros. Moreover one handyman always
have a plywood fall and two or three cleats in the content of its
garage. In more it is very easy to realize. Longest it is
the reflexion, because I left with a vague idea what I wanted, and I
adapted so that I found. To reproduce with identical that must
be able to be spread out over two or three weekend according to the
motivation and capacities. I did not put
dimension, because that can adapt for other refractors but I am at your
disposal. All that I can say it is that the movements are of a
perfect softness and sturdy as a rock even with the bino.
Conclusion: it is stable, of a reasonable weight, not
expensive, not complicated. I advises you highly the reading of the article Cloudy
Nights link above. And like David Novoselsky:"Never judge says
it has book by its cover indeed! " | |
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Pictures being better than a great speech, I
deliver to you the secrecies of this concentrate of technology.
Click on the thumbnails... If you want more infos, email.
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Overall picture. The feet are in cleat of pine.
The spacing of the feet on the level of the table ensures a good
stability (thank you P. Bourge!) |
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The fork is made of 18 mm plywood and the cube around
the refractor in 12 mm. The shaft are stoppers of tube PVC
reinforced by a disc out of wooden. Weights of sport and a fitting
of assembly found in store of do-it-yourself ensure a good balancing
for a soft rotation. |
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System with spring to increase the friction, because of
the weak weight of the refractor. |
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The blocking system in declinaison. On the top, the
support of Quickfinder RIGEL. The height of the cube is
calculated in manner that a light tightening of the lid to the hand is
enough to remain the refractor without damage. |
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Pieces of Teflon ensure a soft rotation of the shafts |
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The fork rests on 3 Teflon pieces laid out with
120°. A bolt of 10 is used as axis of rotation. |
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The backhander: a disc, a piece of Teflon and a
nut butterfly |
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The well adjusted cube is papered of baize.
A piece of black plastic acts as reserve of safety |
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A weight (of diving) fixed at a ring(Orion)
ensures balancing in the event of strong load on the focuser like
the binocular one |
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I bought two rings by Kendricks
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