Tech – LBB (Biss-C protocol converter)

As mentioned in several prior blog posts (Tech – The Telescope Mount, Tech – First Hardware/Software Test, Tech – Alignment & Guiding (Take 3) – Fail, Tech – Telescope Control (Part 2) and Tech – Using Renishaw Absolute Encoder) we plan to use absolute encoders on our telescope mount.

As we found out, the Sidereal Technology SiTech Servo II supports absolute encoder we decided to go for it. To be able to connect the 26bit Biss-C compatible Renishaw Resolute read heads to the SiTech Servo II (which speaks RS232 and not Biss-C) we needed to obtain a small interface box provided by Sidereal Technology: the so called LBB (Little black box).


Essentially it is a prtocol converter which converts the Biss-C protocol electrically and logically to the RS232 interface of the SiTech controller.

Therefore you find some level converters and a small microcontroller inside this box.


So what’s next?

We now have to order the correct sized encoder rings and read heads (in our case the 413mm diameter ring for the RA and the 200mm diameter ring for the DEC axis) and once we got them adapt the mount to be able to mount the rings to it. The main problem here will be to find a suitable and easily adjustable read head mount (the tolerances here are quite narrow). But let us discuss this in another post.



Tech – Dome Improvements

As mentioned in Tech – The Dome and Under Construction – The Dome, we are using a ScopeDome 4m dome to house our telescope.

The stock dome itself is quite well made, but we identified some points to need some improvement – mostly related to the harsh conditions we face in the winter (high snow, fast winds and low temperatures).

The first issue we will solve is related to the shutter mechanism. This was identified through a small incident: we had some very strong winds a few weeks ago, and the wind managed to lift the shutter a little bit so that the drive gear jumped out of the gear rack.

The detached gear. (Photo by Rudi Dobesberger)

We are currently investigating on how to improve this situation. The Problem is, that the shutter has too much play, and therefore it is possible that the gear jumps out of the gear rack.

We think that in this case the wind entered the dome through the several gaps at the shutter and at the gear rim.

To prevent that the wind pull through the dome in the future and to prevent drift snow to enter the dome, we installed a rubber lip at the shutter.

The ready installed rubber lip, which should prevent drift snow and wind inside the dome. (Photo by Joe Stübler, 17.11.2018)
Detail photo of the installed rubber lip. (Photo by Joe Stübler, 17.11.2018)
The right hand part of the rubber lip. (Photo by Joe Stübler, 17.11.2018)

We also plan to install similar lips inside and outside the gear rim, to prevent that insects have easy play when entering the dome.

Another improvement dedicated to the gear rim, was to exchange all screws with stainless steel screws. We also reworked all gear rim mounting holes to make sure, the rim is 100% even and therefore the dome can run very smooth and the driving gear doesn’t get detached from the gear rim.


Star Park Hohe Dirn – Impressions 2

On November the 10th 2018, we had another work project to do (Under Construction – Electrics (Part 2) ) at the KRO. So we left the fog in the valleys behind us and enjoyed the perfect weather on the mountain tops.

Below you’ll find some impressions of this day.

At such days the peak of the Hohe Dirn is quite crowded and it was quite difficult to take some shots without hikers on the road. Another side effect is, that we have to constantly explain to tourists what we are doing here.

Under Construction – Electrics (Part 2)

As installing all the electrics is quite some effort, we had to spend another day installing them.

This day was entirely dedicated to install all power sockets in the engineering room and the dome itself.

Installing the power sockets in the engineering room. (Photo by Robert Mayrhofer, 10.11.2018)
Installing the power sockets in the dome. (Photo by Robert Mayrhofer, 10.11.2018)

There are still a lot of things open, we have to do in the near future:

  • installing all switches
  • finalizing the switchboard
  •  installing the lights

Some of the tasks are currently blocked by the carpenter. He has to finish the ceiling and the staircase to the dome. After this, we can install the lights and switches (some of them will be mounted directly on the staircase).

But these things are subject matter for another post, and day, dedicated to electrical installation.

General – Lets Talk about light pollution

Light pollution – a global problem

80%¹ of  earths human population suffers from light pollution, in Europe and the USA even 99%¹. The animal wild life suffers even more, and also plants are reported to be influenced by light pollution¹.

But what is light pollution? In the past this term was only known by the group of persons which are directly affected by it: astronomers and biologists. But the greater public didn’t know the term. But in the last few years, the problem has grown so big, it has even broached in mainstream media.

Light polluted sky over Linz. Taken 30 km south of Linz near Aschach an der Steyr on 12.04.2013. The light pollution increased since. (Photo by Sternfreunde Steyr, Infos about light pollution and the original image can be found here)

Light pollution basically is the presence of anthropogenic light in the night environment². It is created by extensive use of artificial light, such as street lamps, building illumination, etc.

And what are the negative effects of light pollution?

First of all, the lit night sky affects our very own metabolism and psychology². But not only humans suffer from light pollution, so do the animals. And here foremost the insects. You only have to look at a street lamp — you immediately see myriads of insects buzzing around the light. They get trapped in the light, or burned by the very hot light source or just forget to feed and mate. Another less known fact is, that light pollution also has an effect on plants. Plants also rely heavily on the natural day-night cycle which is interfered by the artificial lights.

And of course we astronomers suffer from it, because the free sight to the stars is taken away from us. The artificial light is so powerful that it easy outshines the very faint objects in the sky. In densely populated areas, it is even so strong, that you struggle to see any star at all!

Star Park Hohe Dirn – a perfect sky

The Star Park Hohe Dirn, the location of the KRO, is luckily (yet) a whole other story. We have all major cities in the north and shielded by a small rising ground behind the observatory. So Linz, Steyr, Wels, etc. are well shielded.

The other thing is the south: There are basically two national parks, the national park Kalkalpen³ and the national park Gesäuse³. So in the south there are just mountains and forests for about 120km (Graz). On the east we also have more or less hills and mountains until Vienna comes up in about 150km.

This geographical specialty can now be seen in a light pollution map of the region:

Light pollution map of Austria. The red circle marks the approximate location of the KRO. You can see, it is at the northern border of the very dark area. (Source:, original map can be found here)

Due to this circumstance we have chosen the spot for our star park and for the observatory.
Another lucky circumstance is the local seeing. Our visual observers with their huge dobsonian newton telescopes (> 20″) have reported seeing values from well below 0.5″! And this not just once in a lifetime — these values are achieved several times in a year.

¹Lichtverschmutzung –
²Light pollution –
³Detailed information on the national park Kalkalpen and Gesäuse can be found on the german Wikipedia pages of Nationalpark Kalkalpen and Nationalpark Gesäuse.


Under Construction – Electrics (Part 1)

Friday 02.11.2018 was the day we began to install the basic electrics in the KRO building. But first we had another task to do:

Installing electrics and drive control in the 4m Dome of the Sternfreunde Steyr

As we already have some experience in getting the dome running (see Under Construction – The Dome, additional info of the dome can be found in Tech – The Dome), we made the offer to our partners at the Star Park Hohe Dirn, the astronomical club “Sternfreunde Steyr“, to also setup their dome. Since they need a custom home position for their dome they had to replace the sliding contact for the rotating parts of the dome. Once this was done, we installed all the electric wiring and dome control. It worked like a charm — first time right.

Working on the dome control system of the 4m dome of the Sternfreunde Steyr. (Photo by Joe Stübler, 02.11.2018)

After this all in all one hour effort we switched to our own dome and observatory.

Electrical installation

We started with the installation of the main switchboard for the whole observatory. We planned to have at least some power sockets running this day — however, we had some other troubles to fix first (sealing the dome, small shutter repair after a heavy storm) — so we managed to only install the switchboard and connect it to the main power line.

The image below shows the current state of the switchboard. Some components, especially the control Raspi and related relays are still missing.

The main components of the switch board already installed. On the left hand side, the relays for remote controlling the power sockets and lights, on the right hand side the main GFC and the different circuit breakers. (Photo by Günther Truhlar, 02.11.2018)

In the coming days we will finalize the switchboard and install the power sockets, the light switches and hopefully the lights itself (this depends on the company installing the ceiling which is currently missing). Also the stairs up to the dome are missing an are hopefully installed in some days.

Server rack

We also got a server rack donated from our chairman Günther Martello and his company MaG Informationsdesign GmbH.

We transported it already to the KRO, but it needs to be reassembled completely and of course a server is still missing. We are currently on the search for one which suits our needs.

The new server rack for the KRO. (Photo by Joe Stübler, 02.11.2018)


The weather was not that fine, but at least it didn’t rain. We took some landscape photos of the gorgeous place where we build our observatory.

Also a lot of tourists wandered up the mountain to get a lovely view and a good meal at the Anton Schosser hut near the summit. Fun fact: the KRO dome is visible at the very far lower right corner of the webcam placed on the Anton Schosser hut.

Tech – Telescope Control (Part 2)

As mentioned in Tech – Telescope Control the telescope control system was quite aged. It was built in the late 90ies and based on DOS(!). Not even the software was dated, also the hardware. The existing control system relies on ISA-bus cards! So using a new computer system with the dated control electronics/software was not possible. But using the old hardware and software was no option too.

So we searched for a control hard and software and found the solution at Sidereal Technology and their SiTech Servo II controller.

It fulfilled our two main requirements:

  1. to be able to reuse our 24V DC Motors
  2. to be able to reuse our Heidenhain motor encoders

And it gave us the opportunity to improve the current system with adding absolute encoders to the axes, which is also supported by the SiTech Servo II. More Information on that can be Found in our blog post Tech – Using Renishaw Absolute Encoder.

Also the first tests were quite a success as you can read in Tech – First Hardware/Software Test and Tech – Telescope Alignment & Guiding.

But what are the pros and cons (are there any?) of the system now?

The Servo Controller II during the first setup.

What can it do

It is a quite compact motor driver solution which is fully ASCOM compatible. Beside this it also supports a hand pad with basic functionality. The main operation of the controller is intended to be driven by the SiTech configuration/control toolset (Tech – Software Part 1 (SiTech Servo II)).

The controller is capable of handling up to four high speed encoders on its encoder input ports. It is also capable of handling absolute encoders via a “LBB” (Little Black Box) (Tech – Using Renishaw Absolute Encoder), you need to by extra and which plugs in to the RS232 port also present on the controller.

The SiTech Servo II also supports auto guiding with a dedicated auto guide port.

If you follow this link to the Sidereal Technology web page describing the new controller version, you’ll find some other useful features:

  • 4 extremely high speed encoder inputs
  • Above feature allows use of the new “Cascade” telescope encoder mode.
  • Industrial Terminal Blocks
  • 4A max motor current
  • Built In Autoguider
  • USB AND RS232
  • Slim and versatile enclosure
  • Overtravel Limit Switch Inputs
  • PEC Limit Switch Inputs
  • Homing Switch Inputs
  • High speed hardware to support future software features
  • LED’s to show hand pad status and Communication Status

Why it is ideal for our project

As mentioned in previous blog posts (e.g. here Tech – The Telescope or here A project begins – What we want to do) we got a very powerful telescope which we will utilize in this project. The only downside of this instrument was its dated and aged control hard- and software.

Due to its special mechanical setup, we’d like to keep as many components as possible in the drive train (e.g. motors and encoders) and just ditch the electronics. Since we use DC motors, a telescope control for stepper motors (by far the most available ones) won’t work.

And there comes SiTech into play: The SiTech Servo II controller can handle our motors AND our encoders. Due to this fact, setting up the new hardware/software to our telescope was more or less plug and play.

Another point is the possibility to extend the controller with really high end features such as absolute encoders.

The last but certainly not the least point was the software integration. SiTech works very well together with other ASCOM software; and it is fully scriptable → a feature we need for the robotic operation mode.

Were there troubles?

Honestly, no. The SiTech system works quite well for us. If I had to name a con regarding our very own setup, this would be the limitation of 4 Amps motor current per axis. If we’d like to drive faster then 3 degree/sec we exceed the 4A during ramp up and the motors went into “blinky” mode (an error state).

But beside this, the SiTech Servo II is a great telescope controller for mid to high end telescopes.