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In the beginning...

TDS Observatory started with the purchase of San Diego State University’s surplus 24” telescope mount in the late ‘70s at the school’s surplus auction by astronomy majors, Sina Sadjadi and Jesse Goldbaum. Sina had convinced Jesse, whose interests were more in theory than observation, to split the cost of the mount by telling him that the resale value of the parts would be worth more than the sum - but Sina really had another plan.

Sina and Jesse were introduced to Mike Hoffert and Larry Dingle, who happened to possess a NASA surplus 25” mirror blank. When it was discovered that the SDAA was leasing observatory plots at $500 for a member’s lifetime, there was no choice but to build. Optics, tube assembly, a 400 sq. ft. building with roll off roof and a lot of manual labor with assistance from Mike Anderson and several other volunteers finally came to fruition a few years later. TDS Observatory would become the cornerstone for TAI.

Sina Sadjadi next to the TDS 24”

TDS 24” AIS - instrumentation on the 24”

TDS 24” AISCL - software available to operate the 24”

TDS 24” USB Topology - layout of all the USB devices on the 24”

TDS Photo Gallery - photos and images taken at TDS Observatory

TDS 24” History - background about the 24”

TDS Observatory is located at SDAA’s TDS site about sixty miles east of San Diego. Please check their website for directions other related information. The site includes power and water (restrooms). The observatory is a roll-off roof structure with a temperature controlled back room that doubles as a small dormitory and workshop. Internet and cell phone access are available.

The primary telescope in use at TDS Observatory is the 24” F8 Ritchey-Chretien, situated on a German equatorial mount. The 24” maintains accurate computer controlled pointing and tracking using a SiTech controller with brushless DC servo motors and Renishaw optical encoders on each axis. Scientific quality CCD cameras, filter wheels, focusers and guiding are also under computer control, which is ASCOM based and typically accomplished via programs such as MaxIm DL. The telescope provides two optical paths, accessed near the focal plane via a manually controlled flip mirror.

The primary imaging camera on the ‘open’ optical path is a liquid cooled, wide field 4K x 4K 9 PL16803 CCD camera that can reach about -35 C. The ‘flipped’ optical path typically hosts high speed narrow field imaging applications. Both paths include filter wheels with Sloan photometric filters. The open path filter wheel also includes several narrow band filters and a 100 lpm transmission grating. Please use the links below to obtain more information.

Click on the image to open a dynamic PDF of the TDS 24” Ritchey-Chretien OTA. (3D Adobe viewer required.)