To be completely honest, there were moments when I felt genuinely frustrated trying to bring all components of the changed observatory setup under reliable control. So many devices have to be aligned with one another and countless failure possibilities have to be taken into account, and just when you think everything is under control, new challenges keep emerging.

Shutter Drive Failure

Right after the observatory was built, my experience with the shutter drive system was already less than ideal. I finally sent the motor unit back to England and received new motors housed in better insulation. It has since become clear, however, that there are still other small details capable of effectively preventing an entire imaging night...

One notable example was the upper bearing shaft which bent without warning, causing the drive chain to jam and nearly drain the motor battery completely. The design flaw responsible for this issue can be seen in the lower image, where the manufacturer originally provided only a thin sheet of metal, secured to the observatory dome with just two screws… My solution finally was a reinforcement using an aluminum profile to stiffen the far too thin sheet metal around the pulley, as shown in the photo. The „elegance of this solution“ could very well serve as a reference design for the manufacturer 🙂

In the end, some of the difficulties were also caused by missing prerequisites and preparatory work on my side…

Tilt of the Image Train

In my recent IC 410 data, the focus was not uniform across the field, which strongly suggested that something in the alignment of the optical axis within the camera–filter wheel–rotator–coma corrector assembly (the image train) was not quite right.

In astrophotography, a tilted image train means that the camera sensor is not perfectly aligned with the optical axis of the telescope, causing parts of the image to be out of focus or distorted while other areas appear sharp.

It was therefore essential to ensure that the image train was free of tilt, which is why I had previously mounted a dial gauge directly to the lower part of the focuser housing. By rotating the filter wheel housing, this setup provides a clear indication of any tilt along the optical axis.
With this measurement profile (rotation of 140 degrees, probe radius 90 mm from the optical axis), it looks more likely that I am measuring the curvature of the filter wheel’s cover rather than a true tilt of the image train. If I take the two end values, I get an absolute difference of 0.02 mm (ignoring measurement uncertainty, see the Video below). Scaled to the edge of the ASI 2600’s APS-C sensor, this would correspond to roughly 0.0031 mm, i.e. about 3.1 microns—so in practice this would probably be negligible…This measurement was, of course, carried out only after the system had been carefully reassembled and precisely set up.

OCAL-Collimation

One thing upfront, once again: if you are looking for an exercise that truly puts your patience to the test, collimation is a perfect choice. To this day, I have never completed it in less than two hours, and each time I came very close to giving up altogether.

During collimation, the primary and secondary mirrors of a reflector telescope are carefully adjusted so that they are precisely aligned with each other and with the optical axis of the telescope, and this can be done using different methods such as a laser, directly on a star, or more elaborately—but more precisely—with a camera-based collimator like the OCAL. The collimation process will receive its own dedicated article in the near future, not least because the OCAL user manual is arguably one of the poorest pieces of documentation ever written on this subject.

The Guiding Drama …

One topic that has consistently troubled me since moving away from ASIAIR is guiding. While ASIAIR does rely on PHD2 under the hood, it keeps the software completely in the background, sparing the user from direct interaction with the rather archaic interface of PHD2.

I do not want to go into the full, rather discouraging story of trying to get used to PHD2 and eventually abandoning it again. In any case, it became clear that N.I.N.A. simply did not work reliably with the ASI120MM Mini, the standard guiding camera. Whether this was due to cabling issues, the simultaneous use of multiple ASI cameras—including my main camera—or other factors remains unclear. Ultimately, this cost me many unproductive nights and a significant amount of valuable exposure time.

In the end, I decided to switch to the standalone autoguider MGEN-3 by Lacerta, which is generally well regarded within the community. The first tests worked quite well, but even here a new issue has recently emerged. I do now hope, that this will be – at least on of the last remaining issues – that prevents a fully remote operation: In principle, it is an excellent device designed for maximum simplicity through its “one-push guiding” concept, yet in my setup a small detail currently stands in the way of true remote use: After stopping the autoguider, the focal length of the guide scope has to be re-entered each time, even though the MGEN-3 can be integrated into N.I.N.A. When power is lost, this parameter is not retained. I am actually in contact with the MGEN developers and am confident that a pragmatic solution can be found.

Hope on the Horizon: N.I.N.A.

After all these „problem descriptions“, there is, however, one genuinely positive and noteworthy aspect upcoming. According to many colleagues, the sequencer software of my choice (N.I.N.A.) should be an extremely powerful piece of software that allows almost every aspect of an observatory setup to be controlled. Ultimately, this—together with its independence from specific manufacturers, unlike ASIAIR—was the decisive reason why I chose to switch to N.I.N.A.

Until now, I had only known this functionality from hearsay and a handful of tutorials. Now. for the first time, I have worked through one of N.I.N.A.’s core components myself: the so-called Advanced Sequencer. With this tool, it is possible to run an entire imaging session fully automated. In the next article, I will describe the settings required to achieve this. One thing can already be revealed: with this N.I.N.A. – tool and some additional plugins, you can control almost everything. The first sequence is ready for the test, just the weather is telling a different story …