Tech – Server

Finally our command and control servers for the telescope arrived. Now we can port the already set up and tested environment from a desktop PC to a “real” Server. This added a lot of headroom for the virtualization of our productive environment.

The next task is the conversion from our virtualized Windows only command solution using ASCOM to a virtualized Linux only solution using INDI. The past showed that ASCOM is not up for the task handling such a project.

The first task of these new servers would be running the surveillance cameras and providing us some real time insights into the dome and the observatory surroundings during the next winter – this will help us to harden the dome against moisture and snow intrusion.

Some pictures from us setting up the servers.

(Photo by Günther Truhlar, 02.07.2019)



Tech – Reassembling the Telescope (Part 1)

After we got the telescope body back from sandblasting and painting (read here what happend) we were ready for the first test fit. We need to find out the margins we have to add the absolute encoders and their mounting mechanic.

We also measured out the dimensions of the ball bearings we need to mount the encoders.

(Photo by Günther Truhlar, May 2019)

After the measuring was done we disassambled the telescop again to prepare it for mounting the encoders. Therefore we have to wait for the delivery of the ball bearings and some metal parts.

Once we received all parts we assamble the whole telescope and bring it back to its original loaction in Davidschalg for testing. When all works fine, the installation of the telescope at the Kepler Remote Observatory site in the Star Park Hohe Dirn is planned for next year.

Tech – Sandblasting and painting the body

Since we dismantled the telescope for technical enhancement, we also took the opportunity to repaint it. However, this brought up some minor problems.

The first one was, that the steel body of the OTA was not manufactured really precise. So after removing all the filler, we saw a very wavy main mirror box and spider ring.

Another Problem was, that with the sandblasting, not all of the filler has been removed, which lead to some sections (especially on the spider ring) with a lot of tiny ripples.

Waviness and filler residues on the spider ring. (Photo by Günther Truhlar, 27.01.2019)
The sandblasting also reveals some inaccuracy in the welding seam. Fortunately this is just an optical “problem”, the welding seam itself is ok. (Photo by Günther Truhlar, 27.01.2019)
Filler residues on the underside of the spider ring. These need to be removed entirely before repainting the telescope. (Photo by Günther Truhlar, 27.01.2019)

For now we roughly painted it again to prevent it from corrosion, but we also came to the conclusion, after full update, we have to redo the paintjob properly, removing all the rest of the original filler, applying new filler again to remove the waves and ripples in the metal frame and paint it again.

To be honest, doing the paintjob prior the mechanical enhancements was not very smart, so we were not really concerned due to the poor first “paintjob”. Now we do not need to care that much about the paint since we have to repaint it anyway in the end.

Tech – Motorized main mirror cover

Over the winter it was not possible to work at the KRO site to finish electrics and other building related stuff due to heavy snowfall (Read in an upcoming post more about the weather conditions at the KRO site).

However, due to this circumstances we had time to dismantle the telescope in Davidschlag (Want to know more?) and start with the technical updates we have planned for it.

One of these updates is building a main mirror cover to prevent the mirror from gathering dust when not used.

For this we had to develop a light weight motorized construction, which we can add to the mirror box.

We came up with a light aluminum frame (split into two flaps) which is powered by a 12V Motor.

The frame now looks like this (without flap cover):

The finished main mirror cover frame with the small 12V motor on the right, powering both cover flaps. (Photo by Günther Truhlar, 07.02.2019)

The following video shows the frame in action:


Tech – Dismantling the telescope

Since the winter was/is very hard in the alps, at least on the top of the mountains, and we couldn’t work at the observatory site, we had some time to work on the telescope. To be able to do so, the first thing was, dismantling the telescope at its current location, Davidschlag.

A last picture of the old telescope on its original location. Next time when it is back there, it will be highly updated and initial testing can begin. (Photo Erich Meyer, Erwin Obermair, 1999)

We found a day where we didn’t had any snow and the weather was fine enough to.

So we organized some transport capabilities and some aid to handle the fairly heavy telescope parts and start dismantling it. Luckily we didn’t had big problems, it all went quit well and so the telescope was in pieces and packed after a few hours. The following pictures show the process.



We have also made a timelapse video of the whole day:


We temporarily stored the telescope in a garage of an observatory colleague and we started working on improving the tech, namely the encoders and the motorized main mirror cover.

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.