So, T has this 6" Reflector on a equatorial mount that needed some TLC and practice setting up - therefore this Sunday just gone we got together and had a 'learn everything you can about Eq scopes' session.
First up I had to correct my mis-remembering of the types of mounts - I had them backwards for some reason. So to clarify, Alt-Az mounts are Altitude/Azimuth mounts giving your basic Up/Down and Left/Right motion like Dobby. Equatorial mounts (or 'German Equatorial Mounts' as we learnt from YouTube) are the same but mounted on a third axis that is tilted to be perpendicular to the axis of the Earth. The Altitude and Azimuth are then named the Declination and Right Ascension respectively.
After watching a few YouTube clips,we had all this down and were ready to look at setting up the mount. We worked out setting up the axis that pointed due South, and raised to about 37.4 degrees (for Melbourne), and found which knobs controlled the RA and Declination. T had the great idea to label everything (as in the photos below). We also worked out the balacing of the tube and the counter-weight and after all that it looked like it was ready for use. Not as impossible as it first seemed.
We also decided that it was worth risking taking the primary mirror out for a cleaning, as it was pretty dirty. I had already watched a couple of clips about this, so we (well, T had the screwdriver) undid the screws holding it in and carefully removed the mirror cap and then released the primary mirror from the cap. We first tried using my air-brush to blow the dust and fibres off the mirror, but they had been there for a while and were not going to shift. I then provided a large container of luke-warm water with a drop of washing liquid in it and some cotton make-up swabs. T carefully and *very* lightly swabbed the surface of the mirror with the cotton. A change of water was soon required, as it was full of floaties, and after a second swabbing the mirror was looking like new. We dried it off with my airbrush, using the air-stream to blow the water off the edge and evaporate any drops. The result was spot and streak free.
We then started discussing the inevitable collimation of the scope, and I observed that the primary didn't have a centring dot on it, so we made one using a rig of two rulers taped together at right angles that allowed us to determine the centre and gently press a dot of black electrician's tape on to the mirror.
Reassembly was simple, as was re-reassembly after we noticed a bit still needed to go in behind the mirror and had been left out. Fortunately the secondary was still clean, so we didn't have to try removing that.
That left us with re-collimation of the mirrors. Again, I had watched several YouTube clips about this and I had made a basic collimation tool with an old 35mm canister with the end cut of and a small hole in the cap. Looking through it I could see the mirrors were out of alignment, but I couldn't see the collimation tool cap, which made it harder to align everything. I blu-tac'd some aluminium foil onto the cap and that helped a lot. Working together we adjusted the primary mirror until we could see the concentric circles we were told to expect in the YouTube videos and the paper instructions that came with the scope. We also tried without the film tube and worked on the alignment by eye - literally, as we then were seeing our own eye in the reflection. Hopefully this adjustment is as accurate as it seemed, as it looked pretty good. When T gets it out on a night and checks a point source, we'll know for sure.
And that was it. Mounted, cleaned and collimated. A good afternoon's work!
