www.baader-observatories.com
Update August 2025:
In early August 2025, we modernized the observatory of Mr. Dipl.-Ing. Günter Knerr: the previous 10Micron GM4000 QCI was replaced with a 10Micron GM4000 HPS II. The reason for the upgrade is HPS technology with absolute encoders on both axes, enabling more precise (also unguided) tracking. This eliminates the need for a parallel autoguider: fewer cables, fewer PC programs, fewer settings, fewer potential points of failure.
Due to the installation conditions, disassembly and installation were carried out with a 60-tonne mobile crane with a long boom. After the mechanical work, the mount and peripherals were commissioned. The mount carries the substantial load of approx. 140 kg with ease.
Already on the first night shortly after installation, the polar axis was mechanically aligned to within a few arcminutes using the firmware functions “3-Star Align” and “Polar Align.” On the second night, following a manual alignment with 15 stars, a 5-minute unguided exposure with the PlaneWave CDK 24 was achieved. An automated alignment with 100 positions in N.I.N.A. is planned for the coming nights, which should enable unguided exposures of over 10 minutes.
Over the years, many pieces of equipment change—observing instruments and their mounts included. Forty-seven years ago, a photo tripod was sufficient, then came the Orion 1 from Wachter and, finally, a heavy home-built mount. A robust but ultimately underpowered ALT-7 had to be replaced to accommodate the new instrumentation. Having started in 1973 with a 60 mm refractor from Hertel & Reuss, I have now arrived at a PlaneWave CDK24 (I have serial number 00002). The mount was expected to carry the following instrument combination without difficulty: a CDK24, a 6" f/9 Astrophysics, and a PENTAX 75.
A rough calculation of the weight showed that the recommended maximum instrument weight of 150 kg was almost reached. A large mounting plate held the CDK slightly off-center so that the refractor still had space beside it. As a result, with all conceivable add-ons, the weight quickly reached a level that could no longer be balanced with the standard number of counterweights and the standard counterweight shaft. Seven counterweights of 20 kg each were therefore required. This is where it became clear how important it is to have a competent partner. For Baader it was no problem to supply a longer declination shaft outside of series production, allowing all weights to be mounted with some margin. Only in the new observatory with its roll-off roof (previously a much too small 3.2 m dome) was I able to use the mount’s balance mode. Everything was quickly balanced (<0.2% imbalance) so that both motors only needed to do minimal work. Because of the very short lever arm on the instrument side, even larger variable accessories such as the CCD camera are no problem.
Next came the adjustment. Using initial models of 3–5 stars each, the mount was mechanically corrected on the very practical and refined pier adapter via threaded spindles. Only after the N/S direction and the polar altitude were sufficiently accurate (0.03 RT = 0°00'48″ in azimuth, 0.04 Dn = 00°01'31″ in polar altitude, and 0°10'03″ orthogonality error) could the correction software take over the task in declination and right ascension—that is, in dual-axis.
From experience with the old observatory and the identical equipment, it also became apparent that even a steel pier with a wall thickness of 12.5 mm was no longer sufficiently rigid and vibration-free. Even with a filling of special sand, the limits became evident. Here as well, Baader was able to offer me a double-walled trapezoid pier, 1 m high and 155 kg (unfilled). With the internal cable routing, one also avoids tripping over or tangling cables when slewing the mount at night.
The modern 10 Micron software also communicates smoothly with the most common software applications, such as MaximDL or the older planetarium program “The Sky6.” It is important that the mount software is under continuous development. Control of the tracking can be performed directly at the instrument via hand controller, on the PC itself, or via the Internet. What more could one want? Well, you could call it “complaining at a high level,” but some things could still be improved. For example, it would be desirable if the external program required to synchronize the time between the mount and the Internet—and the associated switch from CET to CEST—were part of the base software. Especially at focal lengths of more than 4 m, exact timekeeping is essential for the GoTo function. Perhaps there will be such a solution in a future software generation 3.0?
What I would urgently recommend to any buyer, however, is the retrofit for deeper sub-zero temperatures below −15 °C. I had no problems using the mount, but the slew speed had to be reduced by one third to prevent the motor from stalling. As mentioned, this is not an issue for normal observing, but those interested in satellites or the ISS could encounter difficulties with automatic tracking.
The mount has now been running fault-free for eight years, which—at this level of utilization—is a genuine mark of quality. Even today I would choose the GM 4000 again; however, instead of the QCI I would likely opt for the new HPS version, even though I can find any object in the CDK either with a 20 mm eyepiece in the field of view or on the 24 × 36 mm CCD chip.
The amateur astronomer Günter Knerr uses—based on a custom build—a garden house as a professional observatory. Read the article to see how this spectacular project with a roll-off roof came together step by step: Spectacular: a garden house as an observatory
