My Observatories and Telescopes
I built this fold-off roof observatory back in 2002. It has garage door spring counterpoises which negate much of the weight of the roof panels and make it easy to open and close manually. A 4:1 mechanical advantage block and tackle system make closing it even easier since it can be done from inside the structure. The observatory was first used to house my 10" Newtonian (shown below) and later my 12.5" Newtonian (also shown below). My earliest planetary imaging experiments with a webcam were done in this observatory using the 10" Newtonian during the favorable Mars opposition of 2003. A computer cubby in back of the observatory houses a PC used for gathering and processing image and video data from cameras used on the telescope.
At the far left is my 10" Newtonian reflector with an f/6 primary but which actually ends up with f/18.5 at the focus. This trick is achieved by mounting an apochromatic Barlow lens on the spider in the upper part of the tube facing the primary mirror with a small, 1" minor axis diagonal mirror behind it. The slightly longer second conjugate focus required to get the image outside the tube results in a magnification factor of about 3.1x instead of the 2.5x for which the Barlow was designed, giving the long focal ratio very useful for planetary imaging, but in the short tube of an f/6 Newtonian. The central obstruction was quite small also, only 13%. I call this my "Barlow Newtonian", sort of a catadioptic variety of Cassegrain where the Barlow lens take the place of the hyperboloidal secondary. To the above left, you see this telescope mounted on a Losmandy G-11 mount and tripod before the mount was installed on the pier in the observatory.Note how tiny the central obstruction is. That is the little white dot you see suspended in the aperture. The Barlow lens and diagonal are actually a bit smaller than this obstruction which is the cell to hold them.
The other telescope, which replaced the 10" on the G-11 mount in mid 2004 is a 12.5" Newtonian, also f/6. It has a conventional diagonal mirror bringing the f/6 focus out to the side of the tube where it can be used as is, or further amplified using Barlow lenses or microscope objectives. I used this telescope extensively with an SBIG ST-8 CCD camera in my double star program. The camera was coupled to the telescope by way of a 2" eyepiece compatible 2x Barlow lens giving me a focal length of 178 inches, f/15. This provided sufficient plate scale for accurate double star measurement of separation and position angle (see the spring 2007 issue of JDSO, p 82). I have also used the telescope at much longer focal ratios for lunar and planetary imaging with webcams, some of which are in the Photos section of this web site.
This is my roll-of roof observatory that I built in 2007 to house a 7.25" Schupmann Medial refractor (see below). The floor plan was 12'x12' giving ample room for the long tube instrument. A central pier supports a Meade Starmaster German equatorial mount upon which the telescope is mounted. A computer cubby on the south side (left in picture) houses a computer used for recording and processing video data from cameras coupled to the instrument.
At the left you see my 7.25" aperture Schupmann medial refractor that I built using an optics set ground, polished and figured by Jim Daley and used as his main telescope for several years until he replaced it with a 9" (Jim is now working on a 14"). The telescope has a focal length of 100" and a focal ratio of f/14. The final image is absolutely free from chromatic aberration, both primary and secondary. In this respect it is superior to an apochromat. In addition, it has the advantage that a slight adjustment of the tiny field mirror can introduce prismatic color which will cancel atmospheric dispersion. I use this telescope for visual observations as well as webcam imaging of the moon and planets where its unobstructed aperture, complete freedom from chromatic aberration, and long focal length make it the ideal instrument for this kind of work. The 7.25" aperture is also a better match to the typical seeing we have in NJ than my larger Newtonians that I frequently had to stop down to get usable planetary videos because of the poor local seeing. In the picture above you can just see the tiny CCD based DBK21 color video camera perched above the instrument at the back (small blue rectangle). To obtain the even longer focal ratios needed for proper digital sampling with the CCD, I use 2x or 3x Barlow lenses to give me focal ratios of f/27.5 or f/45.5. I also use a home made amplifying lens based on the Schupmann principle which gives me exactly f/50, but the seeing is rarely good enough to use it.
Here is a Google Earth view of my observatory complex as seen by either a NASA satellite or high altitude aerial photography. You can even see the asphalt/aluminum foil tape with which I sealed the joins of the aluminum roof panels, as well as the track for the roll-off roof of observatory #3. I wish I had known when the picture was being taken, I would have gone out and waved.
By the way, the whole structure (including the tape) survived hurricane Sandy, but the nearby huge apple tree did not survive the snowfall that followed it. It was obstructing the view to the east anyway and I had been threatening it with a chainsaw...