Observatories that I have visited:
Rijeka Observatory, Croatia 2022

Content:

1. The walkway up to Rijeka observatory
2. The panorama terrace and old wooden Newton telescopes
3. The 16" Schmidt Cassegrain telescope
4. The planetarium
5. Old archive photographs

3: The 16" Schmidt Cassegrain telescope

Now we walk to the main observatory and its telescope.

We are now on the floor below the doom which we saw on the Panorama Terrace. The pillar in the middle is the pier to the mount of the telescope. It's not connected to the floor to minimize the vibration which is important when observing at high magnification. We climb up the steep ladder.

Up in the doom, there is a lid to cover the opening where the ladder is. When doing observations it's dark and you don't want any of the young astronomers to fall down here.

This is the telescope, a modern Schmidt Cassegrain telescope. It has a folded light beam to make it compact. Its mirror diameter is 400 mm and a focal length of 4000 mm. still the length of the telescope is less than one meter.

On top of the pier is a wedge, a device that let you direct one of the mounts axis along Earth rotation axis. It make the Earth's rotation much easier to compensate when following an object. The telescope and fork mount is bought new. Other installation here is built by a local workshop, the wedge for example Elio told us.

Backend of the telescope, here is a 90 degree adapter to get the eyepiece in a comfortable position. Two fans speed up the temperature adaption of the mirror inside the telescope. They look to have two focusing devices, the ordinary that move the primary mirror and one extra at the eyepiece. It's all the small details that make the perfect telescope.

Elio opens the hatch that cover the slit in the doom to let in some light.

A closer look at the construction and it looks like they have welded a chain to the inside of the hatch.

Another view of the hatch and its construction. The white wheels guide the hatch in the rails.

To reduce the power of the motor that operate the hatch there are two counter weights that reduce the load.

The dome has a frame welded in steel that is covered with thin steel or aluminum plates. Elio told us that it's constructed and made by the local workshop.

The doom must rotate to have its opening in front of the telescope, it's done by three motors separated by 120 degrees, this is one of them.

The motor and its power controls, it must be safe to operate in a damp climate, water proof.

To have the telescope operate with high precision it must be well balanced, here is two extra counter balances.

To get some idea how big this telescope is.

This telescope has a fork mount, a normal German mount has a need of heavy counter balances and need more space. There are always discussions about what type of mount that is the best. I think they all have some property that fit well dependent of the situation.

Do I look for stars ? No we visited the observatory during the daytime to take photos. But they have observations at night when you can make a visit here.

I show Elio some photos on my smartphone and explain what I have on my homepage.

It was really exciting to come here and see their telescope, normally it is very difficult for us on our travels to get access to the observatories.

We climb down the ladder from the telescope room. Down here is like a classroom, they also have computers here that can control the cameras attached to the telescope. In the background, one of the Newton telescopes I told about earlier.