HOME

MY OBSERVATORY
( VRANIAE DICATVM )

is located in Gonnet, suburb of La Plata, Prov. of Buenos Aires, Argentina.

THE COORDINATES ARE:     34° 53' 24.85" Lat S.     58° 01 ' 07.62" =  03h 52m 04,51s Long.W.

( Visiting Google Earth, You can see it from the sky ! )

Located in a park with aged trees, of 5000 mq., consists of a very solid  twelvefaced construction of two floors, with a classic hemispheric dome of 2,5 ms diameter.

The base, of reinforced concrete, is 30 cm. thick, and supports on 5 columns of 1.8 meters deep and 20 cm. thick. Eaves have an aesthetic, but also a practical function, being useful for the maintenance of the dome.

The central column in the ground floor is one meter high, and is used for mirror grinding. That one which supports the telescope is in the high floor, and is very sturdy. I considered unnecessary to do a single column, isolated from the floor, being the telescope not excessively powerful.

The construction, anyway, made with bricks, iron and cement, is practically, from the subsoil to the end of the column that maintains the telescope, a true monopad, since the superior column is not simply supported on the floor, but it is part of itself, wich is all one with eaves.

For a better heat insulation, mainly in winter, the internal faces of the observatory are carpeted. In the floors, in addition to the moquette, there is a vinilic coating, soft and easy to clean. The external faces are painted with allegorical figures, representing the twelve zodiacal signs. The reason for the two floors is in the necessity to have more space, but there is also an aesthetic aim.

The dome, made in phenolic plywood of cedar for nautical use, with the thickness of 8 mm, is covered with fiber glass with polyester resin, of 2 mm thickness.

The two windows,  80 cm. wide, allow the use of wide-angle lenses and instruments of greater diameter. For hydrodynamics, aerodynamic and aesthetic reasons, the same ones have a triangular profile.
The opening of the great window allows the observation of objects high in the sky, whereas the small window works in this case as light shade. This can nevertheless be raised until the zenith, to allow the observation of  objects low on the horizon, and serves in this case of ceiling for the instrument, protecting it of the bombings of the doves.

The dome weighs 260 kg. The same rotates on 6 ball-bearings of 90 mm diameter, on a stainless steel track. In order to avoid lateral slide of the dome, other six bearings, mounted on vertical axes, assure its centering. The dome can be rotated with a finger. It was not considered necessary to use conical bearings to avoid useless complications.

The instrument was initially a 150 mm reflector, Newton/Cassegrain/Coudè, home made 1979. The main mirror is made of DURAN 50, with the following relations:

- Primary 1:5.3, f= 800 mm exactly;
- Cassegrain f=2000 and f=3200-3300;
- Coudé (North and South): like the Cassegrain;
- A Nasmith-type configuration is also possible.

The hyperbolic small mirrors are both perforated to facilitate centering.

The flat diagonal mirror is also perforated, which allows to obtain a bifocal Newton, taking advantage of the parasitic light reflected by a interference filter. This second focus can be used for guiding purposes. The precision of the primary mirror (my first mirror) is of λ /12 on the glass, equivalent to λ/6 in the wave front. 
The control is made with the Foucault method with the Program (©) I wrote to such aim.
The main mirror is slightly overcorrected (slightly hyperbolic). This small defect is not cause of any disadvantage in the Newton focus, because it is in the limits of tolerance. However, it becomes a small advantage in the Cassegrain, quasi Ritchey-Chrétien configuration.
Sights of 1 arc second can be easily resolved even in adverse conditions, as for example hanging on the spider a roll of tape !

As the dome, all the telescope is constructed with phenolic plywood of cedar for nautical use. The tube is made of not less than 120 parts and is light and very resistant to the torsion and the flexion.

The polar axis is mounted on ball bearings of angular contact of 90 mm diameter, opposed to eliminate all backlash.

The declination axis is mounted on a bronze bridle and a bearing of 80 mm of diameter. The movements are smooth and perfect. As it is possible to be appreciated in the photo, the distance of the optical tube with respect to the polar axis is reduced to the possible minimum (many manufacturers would have to learn to do that).

Also the mirror cell is of phenolic plywood, and gave so good results, that in the transport of the telescope from Rome to Buenos Aires no decentering of the optics could be observed!

The spider of the telescope, done with 4 steel trowels 0,3 mm thick, is oriented according to the 4 cardinal points, which is very practical in the photography.
For visual observation, an apodizing screen allows to eliminate the sometimes annoying diffraction cross, specially in the Jupiter observation.

To avoid turbulence of instrumental origin, and to facilite the interchange of the secondary small mirrors, the tube, as it is seen in the photos and like to the great telescopes,  is totally open. And here also, not last reason, the aesthetic one!

More recently, as compared with the amazing advances of the technology, I had to face the facts, replacing the optimal home-made instrument by one Industrie-Meade (an 8 inch LX-200 ), totally computerized, despite of the not few advantages that my telescope had on this last one.   
 The base, anyway, I preferred to construct it by myself.

The phrase written around the dome:

"IN GIRVM IMVS NOCTE - ET CONSUMIMVR IGNI"
(we go round and round in the night and are consumed by fire)

is a Latin verse that talked about the butterflies, that are turning around the torches and end up burning themselves; but it can also be referred to the stars.

I wrote it on the edge of the dome because it is a two-faced phrase, that can be read in both directions. On the Internet there are thousands of sites on this verse, but neither the author nor the time are known.

I hope that what I have described can urge somebody to make something similar. 
It is a very special satisfaction to cultivate a hobby like this doing all by oneself.

Specially in a world like this one, where it is not often so easy to obtain in the environment of our own work those satisfactions that one would hope.

Dante, Paradise, XI-05                                      HOME