Tech – First Hardware/Software Test

As mentioned in previous posts, the telescope for the KRO already exists. It is located in a observatory north of Linz, quite easily accessible for us. So we can test most of the modernized functions already there.

What was the goal of the first test:

  • controlling the telescope with the SiTech Servo II
  • testing the myFocuserPro2 (a DIY motor focuser)vand the autofocus mode
  • testing if all works with Astroart (image capturing, filter wheel control, auto focus control and telescope control for fine adjustments
  • using Stellarium (and StellariumScope) to find and GoTo to the desired Object (you can find a German document pointing out the usage of Stellarium with a telescope here, by Johannes Stübler
  • Remote control (remote connection to the telescope server)
  • test of the underlying ASCOM layer (ASCOM POTH)

First of all, the test went really well, all components worked together and we ended up needing just two programs to do the job of finding objects and take images of them. The underlying ASCOM, SiTech system doesn’t concern the user and therefore the user do not have to deal with the complex lower layers. Users only have to deal with Stellarium for finding the objects and pointing to them and of course the image capture software Astroart.

The test setup: in front the remote notebook PC from where we perform the observation, in the back the telescope server which is connected to the scope via SiTech controller and on the left side behind the notebook, the telescope itself. (Photo by Günther Truhlar, 18.09.2018)

The software is preconfigured and ready to use. So the first thing is to locate and GoTo the desired object. For this the we only have to open Stellarium and open the telescope dialog.

The telescope control and GoTo dialog in Stellarium. (Screenshot by Johannes Stübler, source)

Once the we hit “GoTo” (in the image above “Schwenken”) the telescope will point to the desired object and we now can switch to the image capturing tool.

The first step there is to focus the camera. For this Astroart supports an auto focus feature which is compatible with our ASCOM motor focus:

The autofocus dialog in Astroart. The small rectangle in the main image window shows the region or the star which Astroart should use to focus. You can see the star then also in the small focus window. (Screenshot by Günther Truhlar, 18.09.2018)
The test setup of the motor focus hardware. In front you can see the motor driver DRV8825 , on the left the rotary encoder for manual focus adjustment and in the back the display and the controlling Arduino Nano (right beside the display).And you can also see some sweets we brought with us for motivation 🙂 . (Photo by Günther Truhlar, 18.09.2018)

After a successful focus procedure, we only have to select the desired filter and trigger an image acquisition (either single mode or as predefined sequence or as predefined script).

Test image with M33 in the center and filter select dialog on the right. Currently the green filter is selected.  (Screenshot by Günther Truhlar, 60sec, 18.09.2018)
Another test image, in this case the bubble nebula NGC 7635, with the clear filter and 30sec exposure. (Screenshot by Günther Truhlar, 18.09.2018)

We demonstrated that the basic user interface and telescope controls are working quite well together and it is already now possible to control the scope fully by remote connection.

We plan a second test session, discussed in a future post, where we focus on the 16-point alignment to increase pointing accuracy, reading out PEC-Data (to be able to compare before/after absolute encoders) and enabling auto guiding via PHD2. Perhaps we can shoot the last pretty picture on the old telescope location.

Once the tests are completed, we will disassemble the telescope on its old observing site, rework it, add the additional absolute encoders and rebuild it at its new observing site on the “Hohe Dirn”.



Tech – The Telescope Mount

Each telescope needs a mount. In our case, this is a self-built equatorial fork mount. It is called “Österreich Neu” or ÖPFM, and was developed by Rudolf Pressberger.  He also developed the telescope housing which is an integral part of the complete mount. This makes the mount very stable and effective. The downside is, you can’t use other telescopes with it.

Only a few of these mounts are produced till this date, and the LAG owns two of them: the public telescope in Linz located at the Johannes Kepler Observatory and now the KRO telescope.

The KRO telescope on its old location (Observatory Davidschlag) shortly after mobilization in 1999. The Photo shows (from left to right) one of the owners, Erich Meyer, the developer of the mount/telescope, Rudolf Pressberger and the second owner Erwin Obermaier.
The telescope (50cm f/10 Cassegrain telescope) at the Johannes Kepler Observatory in Linz during a public viewing. (Photo by Herbert Raab).

What is now so special regarding this mount? Basically it was designed to be built by one self – surly with some skill in welding and general metal works – and for precision.

Pressberger developed two versions, one more conventional one, with worm gear drive and rolling contact bearing and one refined version with friction wheel drive and special Teflon ball joint bearings. The second version is the one we use for the KRO and the Johannes Kepler Observatory.

The basic advantages of the version 2 mount are:

  • The special ball joint bearings are superior in terms of friction compared to really high quality pendulum rolling contact bearings. A nice side effect is, that you can easily make them by yourself.
  • There is no conventional RA axis, with its usual big and expansive rolling contact bearings, attached to the fork. The big friction wheel itself will become a part of the bearing. Therefore, you do not have the usual eight-part cantilever strain of the RA axis.
  • The weight distribution of the mount and tube is optimized for low vibration.
  • Friction wheels are generally not so easy to handle, but in combination with the special bearings mentioned above, they can be used successfully.
  • The necessary contact pressure of the drive shaft on the friction wheel is applied in RA of the weight of the fork and the tube. Thus, the remaining cantilever load of the hour axis is used meaningfully.


The 50cm telescope of the Johannes Kepler Observatory during construction (around 2000). It is similar in construction to the KRO telescope. Only the fork width and mirror cell are a little bit bigger in the KRO since its main mirror is also bigger.

The main disadvantage of the mount are its, “virtual” axis. Due to the special construction of the bearings with ball joints, you do not have to use right angled axes (in relation to the fork and tube), but instead you can use angled (thus “virtual”) axes. Unfortunately this makes an update we have planned for the KRO more complex and more expansive: adding absolute encoders.

We can’t use encoders you simply connect to the rotating axes, thus we do not have such. We have to use quite big ring encoders mounted directly on the RA friction wheel and the tube (DEC). We will discuss the usage of encoders on the future in a separate post.

So one can ask now, why the heck to use such unusual axes? For the DEC axis it is mainly to provide an easy adjusting mechanism to adjust the orthogonality error.

And for RA axis (which is also hold by a ball joint bearing) it was mainly done to overcome the big and expansive rolling contact bearings. Due to the special bearing construction, the friction wheel itself becomes part of the bearing, and minimizes, for fork mounts typical cantilever load, to nearly zero.

Another advantage of the ball joints (for RA and DEC axes) developed by Pressberger, are the materials they are built from. The balls are hard chrome plated steel balls, sitting in a Teflon bearing cup. This type of bearing looks like an artificial hip joint. The pair of materials (hard chrome plated steel balls, Teflon) make up a really tight fit, since the Teflon, at high bearing pressure, bends around the ball (due to the flexibility of Teflon) and reduces the friction to a minimum. The ball more or less, swims on the Teflon. And there is another advantage: the initial breakaway torque, which is quite a problem for friction wheel drives (slip), will be reduced to zero.

The pole block shows, that the mount is clearly designed for stationary usage. Not only due to the weight of the whole thing, but also due to the static angle of the pole block. The angle of the pole block should be 90° – geographic latitude and is welded in this way. But there is the possibility to adjust the mount with four push/pull screws in the pole block. So the mount/telescope can be oriented exactly to north and geographic latitude.

Current Problem with the mount:

During inspection and testing at Davidschlag, we noticed that the friction wheels are corroded on their bearing surface. The surface there is quite the same as the ball joints: hard chromed plated.

Removing the chrome from the steel wheel is quite difficult (turning it down) and will result in a smaller friction wheel which will not fit anymore.

So we decided to rebuild the two friction wheels (RA and DEC axes) completely and scrap the old ones. The positive side effect: we can also turn the required encoder mountings directly on the new friction wheels.

But all in all, the mount and the telescope are in quite a good shape.

After finalizing the last tests in Davidschlag, we will dismantle the whole thing. We will report in a future post about this major project milestone.

Tech – The Camera

The Telescope we got for this project, also came with a high sensitive CCD camera. Namely a SBIG STL-1001E.

This camera makes use of the Kodak enhanced KAF-1001E CCD chip with 1024×1024 pixel. The pixel size itself is huge: 24µm x 24µm, and therefore the camera is extremely light sensitive. The chip size is 24.5mm x 24.5mm, the detector type is full-frame.

There is also a separate guide image sensor inside the camera, although it will not be used within the KRO project (we plan to use a separate guide scope + high sensitive guide cam connected to PHD2 guiding software).

Our camera mounted to the Keller corrector of our scope in the prime focus. (Photo by Günther Truhlar)

The camera is also equipped with an active two staged Peltier cooling system, which also supports liquid cooling to reach even lower temperatures. With the air cooling alone, we can reach -40°C easily. The usage of the liquid cooling system is not planned for KRO so far, but we can switch easily to it in the future if needed.

The image download is done via an USB 1.1 connection. This is fast enough since the images are rather small (1024x1024x16bit) and the chip read out works also quite slow to prevent heating up the read out amplifier and introducing read out noise.

Internally in the camera we have a 5-slot filter wheel, where we are currently have RGB-filters, one clear-filter and one 12nm h-Alpha filter. The filter wheel is controlled via the same USB interface and also works with our imaging software Astroart.

In our current telescope configuration (1980mm focal length, 600mm aperture, prime focus) we can cover an area of about 0.71° x 0.71° with 2.49″ per pixel resolution.

The best observed seeing on our future observatory site was <0.5″. So the camera do not make use of the best observation conditions, but for now it serves our needs.

Quantum efficiency of the KAF 1001E image sensor. (Image by SBIG)
Technical specifications of the camera. (Image by SBIG)
Technical specifications of the camera. (Image by SBIG)

You can find further details regarding the camera here:

Under Construction – The Dome

In the previous post we talked about the search for the dome and its technical spec.

Now we got the dome delivered and started with the construction of. We ordered the dome without professional construction and setup, since we’d like to do this on our own.

The first major problem we encountered, was the delivery to the observatory site. As mentioned in “A project begins – And who drives it” the site is quite remote in the alps, and therefore we do not have a highway up to the front door of the observatory 😉 … it is more like a very steep and winding farm track, only used by the local farmers with their tractors.

So the delivery vehicle made it to the first hairpin bend and got stuck! Fortunately, the local farmer helped us out and towed the delivery truck and its trailer with his tractor up to the observatory.

The tractor pulling the delivery up the hill. On the trailer you can see the tightly packed parts of our dome. (Photo by Johannes Stübler, 09.08.2018 )

The farmer also helped us with his tractor to unload the delivery, since the parts were quite huge (4m x 2.5m, barley road legal).

Unloading the delivery truck. (Photo by Johannes Stübler, 09.08.2018 )

On the next day, with quite bad weather, we started to mount the dome drive ring to the concrete dome base. This was quite a tricky installation, since the parts have to fit together perfectly, and they also have to be adjusted perfectly to guarantee a smooth dome turn afterwards. So we need to adjust some parts. The base ring construction did take some days – it was the most complicated part in dome construction.

As the dome base ring, with its lower stationary part, and the upper rotating part was completed (see image below), we started with the actual dome construction.


The finished dome base ring, the upper part rotates. (Photo by Johannes Stübler, 12.08.2018)

Since the individual parts are 8mm fiberglass, they were quite heavy, and we needed a lot of man power to move them around. To make us the life easier, we decided to build the dome on the concrete place in front of the observatory, and then lift it up and bolt it to the base ring.

The dome will become really stable only after it is finished, and so it was a challenge to hold the parts in place until they are bolted together. Luckily we had a lot helpers and so we managed to build the dome in one single day!

This was also necessary, because we had ordered the crane for the next day to lift the dome to its end position on the observatory.

The observatory got its dome on 18.08.2018 and was now so far built to start with the interior fittings.

The final result and a little topping-out ceremony. (Photo by Günther Truhlar, 18.08.2018)

On the same day, we also did our first dry run, and hooked up the dome to a powerline, installed its electronics and fired it up: it moves quite well and smooth! So the dome is ready for operation.

Our tech guys setting up the dome electronics. (Photo Johannes Stübler, 18.08.2018)

There is still a lot of work to do, so stay tuned for more!

Tech – The Dome

After starting the KRO project, we had to decide how we would like to build our observatory, or to be precise the “telescope room”. Since our partner in this project, the “Sternfreunde Steyr”, already had a dome there, we also decide to go with a dome (to not break the overall look of the observatory site).

So the big task of searching for a dome manufacturer began. Since the KRO will be a fully remote controlled site, the dome had to fulfill some needs:

  • Size – since our telescope is quite large, we needed at least a 4m dome
  • fully remote controllable (via PC)
  • ASCOM compatible

After some search we found a manufacturer in Poland, which builds such domes for a quit reasonable price. And better, they already built and installed 4m domes for professional observatories in Chile, Namibia and several other quite remote locations. The company is named “ScopeDome“.

It was immediately clear that we would go with a 4m dome. So we get in touch with the company and ordered a rough technical drawing, so that we can test (at least on paper) if our telescope will fit (They also send us some pictures of their projects).


The images on the left side are showcasing some of ScopeDomes 4m domes in Chile (Photos by ScopeDome). On the right side we have a technical drawing of the 4m dome with our telescope fitted into it (Drawing by Johann Bachlmayr)

The most important feature, is of course, the ability to remote control the dome. This is possible through the quite comprehensive software package. With this software, running on the telescope server, we are able to fully control the dome over a remote connection.

Screenshots of the main screens of the ScopeDome controll software. (Screenshots by Johannes Stübler)

After checking all parameters, we ordered a 4m dome for the KRO project in the first half of this year. Some weeks later, we got a huge delivery – all the components of our new dome. It was like Christmas 🙂 …

In the next period of fine weather, we started with the assembly of the dome, which we will discuss in Under Construction – The Dome.

Under Construction – Observatory Construction

It is now quite some time ago, since we posted our last update on the Kepler Remote project. But we weren’t deedless in the meantime. We manged to build an almost finished observatory which will become the home of KRO telescope.

As mentioned in the previous post A project begins – And who drives it we found a really good spot, and started to build an infrastructure there in cooperation with the “Sternfreunde Steyr”. The Sternfreunde Steyr, already built a hut and a dome last year.

The hut and the dome of the observatory site, built by the Sternfreunde Steyr. On the right, there is already the base for their second dome. The free spot on the left (covered in snow) will be the place where the  KRO is built. (Photo by the Sternfreunde Steyer)
The read area will be the future construction site for the KRO. (Photo by Johannes Stübler, 06.06.2018)

As the spot for the KRO was now defined, we started with the excavation. Digging into the soil was easier than first thought, and therefore the actual construction of the observatory building could begin.

The KRO building mainly consists of two parts (two floors):

  • The maintenance room/Sever room which houses the telescope electronics and provides some storage space too (ground floor).
  • The dome with the instrument itself (first floor).

The building is built entirely of concrete, since it also functions as the base for the telescope itself. The KRO is a remote observatory and therefore we do not need separated bases (during operation nobody should be in the building) for the building and the telescope, but the building had to be quite strong.

The building is now more or less finished, and just waits for the arrival of the dome. The dome construction, placement on the observatory building and dome description will be discussed in “Tech – The Dome”.

A project begins – What we want to do

For a long time the 0.6m f/3.3 reflector Telescope was used to hunt minor planets. And successfully so!
In cooperation with Herbert Raab (and his “Astrometrica” software) the LAG members Erich Meyer and Erwin Obermair discovered 27 minor Planets (from 1996 to 2005). But in recent years the Teleskope lay dormant, partly due to the fact that robotic telescopes where far better suited for a sky survey and partly due to other projects the operators started.

In January 2018  we, the LAG (Linzer Astronomische Gemeinschaft), bought the Telescope.

The 60cm Deltagraph, the designer of the mount Ing. Pressberger (Center) and the Telescope Owners, left Ing. Erich Meyer and right Erwin Obermair.
(Picture: Vereinschronik/LAG)

A major problem is the very aged Telescope Control that only worked with MS-DOS. Thus it is time for an Upgrade!

Our Goal and Motivation is to create a remote observatory in the darkest and thus for astrophotography best part of Upper Austria. The intermediate goal is to modernize the Telescope Control, enable remote operation and of course move the Telescope from its current location, Davidschlag, to its new Home in a 4m Dome at the observatory outpost “South”.
In the long run we plan a fully robotic operation of the telescope and make the pictures available for LAG Members, Sternfreunde Steyr Members and interested 3rd Parties.

Additionally in cooperation with the “Sternfreunde Steyr“ we want to create a night light protected area, a STAR PARK.

Stay tuned for our next update on the specs of the Telescope.