Collecting  Photons

More changes.

Early in 2009 I replaced the trusted 350 with a SBIG STL 11000 equipped with Baader HαLRGB filters.  This has been a major change that required a complete re-learning of the processing skills and a complete change of the software, both for the acquisition process and for the raw data calibration.

The second change was the mounting: the old G11 has been replaced with the G42 mount from the friendly firm Gemini. If and the weather will clear I should be able to characterize the mount properly and I will post the resulting analysis here. The mount is really gorgeous and so far it is doing really well. See here for a first light

A further assessment of the ASA astrograph.

After three months of happy ownership the scope revealed itself as a true wonder with only two problems. The first one, showed itself on the very first day: the EOS adapter was designed in a way that the flash nose of the 350D prevented the camera from inserting at the imaging end. This was bed news, but was easily fixed by cutting a grove in the plastic body of the camera. This was done with a small metal file, and I needed to remove about 2 mm of plastic; see here for a detailed picture. This small modification of the camera seems to be necessary for every Canon camera, except, perhaps, the venerable 300. The second problem was the presence of severe flexures somewhere in the train. Click on the photo to get the story.

The main astrograph: ASA 10", f 3.6 with Wynne corrector.

In 2008, after 8 month of excruciating wait, finally arrived my new astrograph. This is a very fast Newtonian scope with a 3" field corrector made by the Austrian company ASA. It is an instrument of enormous beauty, this I can tell for sure.  The first light image can be seen here. It is a modest shot taken during full moon AND thin clouds. Subframes were limited to 2' only due to the immense sky gradient (30x2' subs). Nevertheless, the result hints at the tremendous light gathering of the instrument. The G11 seems to be perfectly happy under the combined weight of astrograph, apo triplet and finder.

The Losmandy G11 mount

In 2006 I bought a second hand Losmandy G11 to replace the original Celestron fork. Unfortunately, the preliminary tests of the G11 performances were very disappointing: the mount was tracking much worse than the fork. The periodic error was much larger (about 45" compared to 20") with large high speed errors that made autoguiding impossible. After much studying of many available sources on the web I decided to replace the original worm and bearings. Now performances are comparable to what I was used with the fork mount. However the new mount is much more stable to external perturbations, and carry the weight much, much better. So it is an improvement, really, but it took quite an effort.

A final, amazing, improvement came in 2008 with the installation of a new monolithic worm block made by the French company Ovision. Click on the picture to get the full story.

Celestron 8

The C8 is a venerable instrument I bought in 1985 when I was living in California. The fork mount has a Byers worm gear with an excellent smoothness.  This is something it really paid when I started autoguiding. The AR motor is controlled by a home made variable frequency power supply which control also the DC declination motor. The power supply accepts TTL signals coming from the computer parallel port for autoguiding. The guide scope is a cheap 70 mm refractor is riding piggyback with an Atik camera. Nowadays the optic tube is unused but the fork mount has been modified in my light weight travelling imaging platform.

The old set-up (2005-2006)

Before the construction of the observatory the telescope was sitting on the pier, covered by a triple layer of insulation during bad weather. On especially severe storms everything was disassembled and brought inside. The equipment, computer included, survived for over a year in these abysmal conditions!