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Observatories that I have visited:
3.2: the Newton reflector guided tour
After finished the guided tour at the double refractor we walk down to the entrance hall and wait for the next guided tour.
Here we wait for the Newton reflector guided tour. While waiting here, look at the beautiful wall and ceiling.
The time is now 5 pm, the guided tour starts and we walk out through the door. The Newton Observatory building is at another place, about 400 m away.
This time it's Lars-Erik who will be the guide for us.
The main building is big. At bottom floor was a workshop for the instruments, a chemical work shop for development of the glass plates and more. During the 1990s when I study here the class rooms were placed at the upper floor.
We are not many here participating the guided tour. A small trop of 8 persons, isn't it bigger interest for astronomy in Sweden ? We take the walk path to the observatory building for the Newton telescope.
Lars-Erik tells us about the environment here and other buildings.
Newton reflector Observatory:
The Newton telescope building, it's much lower than the refractor building.
We also see another building up the hill, this is the astrograph. I took photos of this and wrote a long article about it many years ago, Astrograph.
In front of the Newton telescope building Lars-Erik tell us more about the work done here in earlier days and the instrument they used.
Observations going on, maybe 30 years ago. I never did any observations with this telescope.
Bottom floor, in center the fundament of the telescope.
A window show us its internal secrets.
A view out through the entrance door, there are two doors and we discussed why it was so. Our conclusion, it made a better look of the building.
Even this dome has electric rails to transfer the power to the dome. These are the spring loaded electric connectors to the rail.
The Newton telescope is much bigger than the refractors we looked at earlier, but at the same time very compact. It's the design with a reflection telescope that let it be that compact. The big 1 meter mirror is at the bottom of the tube to the left.
What a surprise, they use the same Pentax medium format lens as a finder telescope as I used as an astrograph earlier. It's a Pentax 500 mm f/4.5 telephoto lens.
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What use of these two knobs ? There are secret controls everywhere on the telescope.
A reflector telescope can have support on the backside of the mirror. That's one reason why they can built it much bigger compare to a refractor. A center hole in the mirror let the light beam out, then it's a Cassegrain telescope. The telescope can be figured in two ways: A short 5 meters focal length Newton telescope or a long 18 meters focal length Cassegrain telescope. When in Newton mode the light beam is reflected 90 degrees out to one side of the telescope.
More info about reflector telescopes:
Credit: Observatoiet i Saltsjöbaden Digitaltmuseum / Tekniska Museet
An old photo from 1936 tell us how the telescope looked like when it was new. Even this telescope was built by Grubb Parsons & Co Ltd.
On the fundament of the telescope can be read:
Handtaster, kind of remote control. The one to the left control the telescope up/down and left/right in astronomical coordinates.
This window held its interior in secret. Maybe the RA motor is placed inside here.
This must be the DEC motor. DEC = Declination.
Even if the telescope has motors for its positioning there are scales to help to know where it's pointing. This is the RA shaft which is divided in 24 hours. RA = Right Ascension.
More info about Astronomical coordinate systems:
This floor isn't possible to change in height. The telescope is more used to do photography with and then not in need of that. This kind of telescope is also very back heavy, then the height where the photographic plats are doesn't change very much in height (when in Cassegrain mode).
Fully open hatches give a wide slit for the telescope to reach the stars through.
This is the spur gear for the DEC shaft.
I'm not sure what purpose of these mechanics, maybe a focus control or to open and close the protection lid over the mirror.
The mechanics that control the lid over the mirror. A pizza slice design of 8 triangular shields.
The two knobs we saw in the beginning. Now I maybe found the purpose of them, to open and close the lid over the mirror.
RA shaft and an encoder that give the position angle of the axis.
Front of the Pentax lens. In earlier days most problem was solved with mechanics, not electronics. Electronic these days was bulky and fragile vacuum tubes.
Some new attached electronic devices.
It's an open tube design, much lighter and easier to access inside. Thermal equilibrium is also achieved faster with such a construction. If the mirror and other parts are not at the same temperature as the surroundings, thermal air currents arise that disturb the image.
A truss construction like this will be very strong without being heavy.
The dome of the Astrograph that I wrote about earlier had a fantastic wooden dome. This one which is bigger looks to be made of steel, stronger but not as beautiful.
Lars-Erik close the hatches of the dome and the show is over. We have been here many hours and now feel it's time for us to go home.
Thanks a lot Uno and Lars-Erik for the exciting guided tour you gave us !
A page from Stockholm's University and a very old film from 1930s they have found recently from Stockholm (Saltsjöbaden) Observatory: