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.

Tech – Using Renishaw Absolute Encoder

The search for a LBB

As already mentioned in Tech – First Hardware/Software Test and Tech – The Telescope Mount we plan to upgrade the telescope mount with absolute encoders to increase pointing precision and to get rid of aligning the telescope every now and then, and after every shutdown.

As also mentioned in Tech – Telescope Control, we are planning to use the SiTech (Sidereal Technology) Servo II controller. In this document we found a reference to using absolute encoders with 26 bit encoder resolution. However this reference was more or less a sub clause in the document. It also mentioned a “LBB”, a little black box which is needed to interface with the encoders.

After some research we didn’t find out what this LBB is and if absolute encoders really work with the SiTech Servo II. We had our doubts, since there are no dedicated connection ports for absolute encoders and only this document mentioned them. You even do not find the Box in the SiTech online shop.

Our last hope then was the registration in the SiTech support forum and asking our questions there. Btw., we should have done this earlier, since the SiTech guys are really responsive and the forum in general is really accommodating.

So after a short chat there, we got the info that they do have this ominous LBB and they also sell it.

This box is designed to work with absolute encoders supporting the BiSS-C protocol. However SiTech recommends encoders from the British company Renishaw. On the SiTech controller side it will plug into the RS232 interface of the controller. The LBB is also prepared to directly work with the plugs used by Renishaw on their encoder systems.

The Renishaw encoder system

Now that we knew SiTech indeed supports absolute encoders and we also now knew the encoders to go with, we now started the evaluation on the encoder system we really need.

The main problem there was the fact, that our mount does not have “real” axis as described in the post Tech – The Telescope Mount. So the first important point was found: if we would like to use absolute encoders, we have to go with a system which has ring encoders — other designs won’t work on our mount.

The second important point was also figured out quite fast: the minimum inner diameter of the ring encoders. On the DEC axis we have to use one with minimum of 14cm of inner diameter. The problem is the RA axis, since the ring encoder has to fit around the quite thick neck of the fork part of the mount. Here we, at least need an inner diameter of 38cm. Another important point was the supported temperature range of the encoder rings and read heads.

We found, that the Renishaw Resolute measuring system, in combination with their RESA scale rings, will fulfill all of our needs:

  • It is compatible to the LBB (natively → plug and play)
  • It supports the required 26bit encoder resolution
  • It will support our need of an extended temperature range (-40°C to 80°C, the important value is the -40°C since we can reach temperatures well below -30° at our observation site) with their ETR read heads
  • The scale rings are available in sizes we need
  • The scale rings and read heads are small enough to fit with our mount.
The Renishaw absolute encoder system showing two RESA scale rings and the corresponding Resolute read head. (Image by Renishaw)

RA and DEC Mounting

The last issue we had to solve when we use absolute encoders, is the mounting of the encoder on the axes.

On RA it was quite easy, apart from using a really big scale ring, since there is enough space. The other thing is, due to its bad shape, we have to replace the RA friction wheel at all. This makes it now possible to lathe the encoder mounting directly to the RA wheel during remake.

Here you see the current RA friction wheel with the neck towards the fork. The RA wheel will be replaced by a new one including the mounting ring for the encoder scale ring. (Upper blue part = fork, lower gray part = pole block, marked section = RA friction wheel + neck) (Photo by Erich Meyer, 1999)

For DEC it is a little bit more difficult, since the free space is quite narrow. But also in DEC we plan to redo the friction wheel and the bearing cover plate. The bearing cover plate is then an ideal point to mount the encoder scale ring. For this purpose, the cover has to be remade including the mounting ring.

The silver disk is the current bearing cover which will be remade a little bit bigger and with the encoder mounting. (Photo by Erich Meyer, 1999)



Tech – Alignment & Guiding (Take 3) – Fail

We continued with our Hard and Software test regarding the telescope controller and the control PC. Since last test was quite successful (just the small problem with the guide cam and the pointing model) we didn’t expect much troubles ahead. — Oh man were we wrong!

First Fail

We tested the guide cam, a ZWO ASI120MM-S, previously and it worked as intended. It worked also with the actual control PC and its virtualized Windows.

As we tried to fire the thing up on the test site in Davidschlag, it suddenly didn’t work. The cam managed to acquire some images, but it randomly lost connection to the PC.

This was so often, that a guiding via PHD2 was simply not possible. PHD2 lost its guide star constantly.

We are now a little bit concerned  if the problem is related to the telescope control server. It seems that it s USB hubs are faulty and quit working when a lot of USB devices connected to them.

Second Fail

As already mentioned in Tech – The Telescope Mount, the friction wheels are quite corroded, which results in a quite bumpy ride for the telescope.

In our first tests this was annoying and caused position errors, but we were able to move the telescope to the positions we want.

But in this night, the ride was even bumpier, and constantly caused the SiTech Controller to go in “Blinky-Mode” — a failsafe mode which causes the telescope to immediately stop the movement. So this time we were completely unable to point the telescope to any position at all.

We were quite puzzled what happened, but after some thinking we identified the Problem: Temperature.

Our last tests took place in quite warm weather conditions, this one however was during a quite cold night (in comparison to the last test nights). This causes the metal of the mount to contract and therefore we ended up with different pressures on the friction wheels. This seems to interfere with the bad friction wheels a lot more than in warm weather conditions.


We now decided to stop testing and therefore disassemble the telescope and start with the refit and repair tasks. This means to update the telescope with new friction wheels, additional absolute encoders and motorized mirror/corrector shutter.

However, we obtained some nice images during the last tests, which we plan to present here in this blog and on our other social media channels during the telescope downtime.

If you like it like it 🙂 …

Of course we will keep you up do date on the repair tasks.

Tech – Software Part 1 (SiTech Servo II)

This post should be the prelude to several posts dedicated to the software we are using. The first software we want to discuss is the command and control software of the SiTech Servo II telescope controller.

The software is split into two more or less independent parts:

  • Sidereal Technology Servo Configuration Utility
  • telescope control (sitech.exe)

Servo Config – Sidereal Technology Servo Configuration Utility

This tool is dedicated to configure the controller with all sorts of parameters needed. E.g. motor speeds, encoder ticks, backlash settings and so on.

Servo Config tool main dialog. (Screenshot taken from the SiTech Servo Config manual)

The program is a little bit colorful, but it nicely sums up all relevant information in the main screen. You can easily see the status of both axes (motor status, encoder status) and you can also see other controller settings below.

You also have a little virtual hand pad, which is quite handy when one is fiddling around with parameters and want to test them.

On the left side you’ll find a menu where you can access the settings. The most important menu item is “Edit Parameters” which takes you the parameter setup screen:

The first tab of the “Edit Parameters” screen, where you can change motor parameters. (Screenshot taken from the SiTech Servo Config manual)


SiTech.exe  main window.

All in all the basic setup is/was done quit fast and straight forward. The most difficult part was to determine the actual values for the parameters to set. Some were found in the config files of the old DOS based control software and some were found by trial and error – but with the help of this tool and its documentation we were able to do the whole setup in one day. Seeing the motors moved by the new controller was quite satisfying.

For further in depth information check the documents provided by Sidereal Technology:

SiTech.exe – Telescope control

The more complex part of the SiTech software bundle is the actual command and control software, called SiTech.exe

First of all, you can configure the pointing model there, which as you can read in Tech – Telescope Alignment & Guiding, was not so easy to handle.

The SkyView and InitPoint dialog from SiTech.exe are sufficient for their Task but for Day to Day operation something more widespread will be used.

The basic handling of the scope, e.g. unparking the scope and other stuff can be handled directly from the main screen.

For pointing to object, SiTech.exe also have a full planetarium subprogram included. At this you can easily find objects and point the telescope to them, however we will not really use this part of the program since it is a little bit clunky to handle and pointing to objects through Stellarium is far more comfortable – so we decided to use Stellarium instead. The good thing is, due to full ASCOM support of SiTech.exe, this is quite easy to do.

Connecting Stellarium to the SiTech.exe (Via StellariumScope & ASCOM) makes pointing the Telescope quire easy, at least on the Software side.

So we basically use SiTech.exe as interface to the controller itself. We also use it to configure the pointing models and park/unpark the scope. Perhaps we also use it as main script controller for automation tasks.

SiTech.exe also provides powerful ASCOM scripting extensions. A documentation of them can be found at this web page (SiTechExe ASCOM Extensions Help as of Version 0.91Xe).

In upcoming blog entries regarding software, we will discuss Stellarium, which we use to point at objects and AstroArt which we use for acquiring images.



Project presentation in Linzer Wissensturm

On Monday (22.10.2018) we presented the current project status to LAG club members and the interested public. The event took place as part of LAGs monthly public talks in the Wissensturm¹ (Wissensturm web page) in Linz.


Markus Hoflehner and Günther Truhlar from the KRO team. (Photo by Robert Mayrhofer, 22.10.2018)
(Photo by Günther Truhlar, 22.10.2018)

You can download the slide set presented here: Monatsvortrag_Wissensturm_22.10.2018 (German)

Also in this monthly talk, our LAG colleague Harald Schmidt, presented his aurora borealis pictures, taken this year in March on a cruise in Norwegian waters.

Harald Schmidt from the LAG. (Photo by Peter Lagler, 22.10.2018)

For additional information about our monthly talks please visit our LAG main website.

The upcoming talk will take place again in the Wissensturm and will have the topic “250 Jahre Meteoritenfall von Mauerkirchen” presented by Herbert Raab. (Date: 19.11.2018, 19:30)

¹ rough translation of Wissensturm: Tower of Knowledge