Site Tests of Astronomical Seeing
Cabrillo College Observatory is located at the end of
"Well Road", along Porter Gulch at the extreme northwest corner of
campus. Well Rd is the inconspicuous one-lane dirt road leading into the eucalyptus
grove, off Soquel Drive immediately east of Porter Gulch Road and next to the
western entrance to the upper campus, shown on the photograph at right. Here's
a
link to the Topozone.com topographic map of the
college area, showing a red "cross" at the observatory. At right is
the Google-Earth view of the Cabrillo Campus with the obseravatory and entrance
road intersection with Soquel Drive labelled.
While this site is astronomically not as good as our previous location on the hilltop above campus, it has the advantage of no line-of-sight to any lights whatsoever, and is isolated from the rest of the campus. It has good western and northern horizons, 15-20 degree southern horizons, and 20-23 degree eastern horizons. Our enclosures were moved in the summer of 2003. The observatory is surrounded by oak and chapparral hillsides on two sides, and Porter Gulch Creek on the other. The observatory consists of two buildings - a 640 sqft storage building, and the dome building.
The
Dome Building
The 340 sqft dome building houses our 12" Meade LX200 telescope on a Losmandy G11 mount with Gemini navigation system. It has a 6' fiberglass HomeDome from Technical Innovations installed on the roof, and a concrete pier with a 4'x4'x4' foundation for 8' concrete pier supporting the LX200. The scope is housed in a 16'x8' room which is thermall isolated from the "warm room". The warm room has a desk facing the telescope through a window with 2 computer stations - "Spock" controls the SBIG ST4000xcm CCD camera while "Sulu" navigates and focuses the telescope. Each are WinXP machines. The computers are networked together and connected to the internet via a 80211b wireless connection. The dome is controlled by motors interfaced with infrared sensors which automatically keep the telescope and dome in synch.We have an ST4000XCM 4.2 megapixel color CCD camera with 2-stage thermoelectric cooling for dedicated imaging at this telescope.
Outside the 12" building is our photometry station. On observing nights, we carry out a 3'x5' table stop and mount it on permanent cinder block supports. Then bring out a weather-guard box which contains a computer system. And finally, our 10" Meade LX200 Schmidt-Cass is carried out and placed on a steel adapter bolted to a concrete pier. The telescope wedge and steel adapter have been marked so that with a simple twist the telescope is polar aligned to fairly good accuracy. An underground conduit carries datalines from the telescope + Optec SSP3A photometer to the computer. 3-person student teams man this station on observing nights and typically take data on eclipsing binary stars. Single channel photometry is done with the Optec SSP3A photometer connected to a computer. Data acquistion and data reduction is accomplished with the RPHOT photometry software package, which I wrote back in the early '90's and license to Optec for distribution to many individuals, colleges and research institutions around the world. Here is a .pdf version of a paper on the RPHOT package. (you must have the free Adobe Acrobat reader installed when you click).
Our Meade 10" LX200, donated by a Boulder Creek resident, has a dedicated pier and table support. It too has a wood weather-guard box'ed computer system which is carried out and placed on a table supported by cinderblocks, with underground conduits for data/control. Students can sit at the computer and remote control the telescope to objects which would be very difficult to find by star-hopping.
We have access to the well-equipped Cabrillo College photolab and dark rooms.
Our Astro 9A/B/C astrophotography students can choose from a growing array of
equipment. Our new SBIG ST4000XCM color CCD camera is mounted on the 12"
LX200 dome scope for color imaging. We recently acquired our second SBIG
ST2000xcm CCD camera with a single-shot color 1600x1200
detector. We also have an SBIG STV camera used for CCD photometry mainly. In
2005, we acquired a Meade
DSI and also a Meade
DSI Pro and LPI imagers. Also a Minolta Dimage 5 which can be coupled
to the eyepiece for color digital stills of the moon, and a Canon ZR45mc camcorder
for taking planet and lunar photos suitable for stacking and processing. In
the geology/astronomy lab room we have 6 computers for photo processing, and
a Dimage Elite II film and negative scanner. Best of all, we have a Losmandy
GM8 mount for autoguided astrophotography, shown at right with Aura, an Astro
9 student. It's beautifully machined and works like a champ. Astrophotography
classes are generally taught in the Fall only. Telescopes suitable
for guided astrophotography include the 12" LX200 under the dome, the 10"
LX200, 8" LX200GPS, 8" f/4 Meade LXD75 Schmidt-Newtonian and 80mm
Megrez APO flourite refractor.
Two other concrete piers are available for mounting our other telescopes. During observing nights, most students are engaged in projects with portable instruments. These include...
-17" f/5 home-made Dobsonian
-13" f/5 Odyssey Dobsonian
-12.5" f/5 "Star Splitter" Dobsonian
- Three 8" Meade SCT's
- 8" Odyssey Dobsonian
- two 6" Newtonians
- 6 pair of 7x50 binoculars
- 2pair 10x70 binoculars usually mounted on tripod
- Megrez II 80mm Flourite APO refractor
- Meade 8" f/4 Schmidt Newtonian on LXD75 mount
- Kiwi video time inserter for occultation work
- Meade 8" f/10 LX200gps, DSI Pro, and MaxIm DL/CCD software
In
Winter '03/04 we built a redwood deck and grassy knoll northwest of the main
pad. This gives us a lower horizon towards the east and northeast - our darkest
direction. Astronomy clubber Jeff Jolin donated a nice campground-sized picnic
table on the knoll above the deck. The deck is fitted with surrounding seating
suitable for a whole Astro 8 or Astro 9 class by thrifty use of available materials.
It also serves as a BBQ spot for star parties.
Our old steel shipping containers were rusting away, leaking, and too small. Chuck Mornard and the CEM Department's construction engineering class of Spring '05 did a fantastic job of hammering together a fine building. Thank you, Chuck! (The building is in the background of the GM8 picture above right.). In Spring '07 I proposed a replacement for the main observatory dome shed with a similar building to be constructed by CEM once again. It got high ranking in the division spending proposals and was constructed during December '07 January '08. Having the computers and people in a separate room will eliminate the problem of warm air rising right through the open dome slit and across the optical path. This will improve the notoriously poor seeing we have experienced. It'll also be more comfortable and spacious for the astronomers. Here's a photo page on the the whole process...