Telescopes

The Clay Center Observatory is equipped with seven research-grade telescopes clustered coaxially on one computerized equatorial fork mount.

Telescope Mount and GAM
Manufactured for the Clay Center Observatory by DFM Engineering in 2002, the mount sits atop a five-story-high pier that is independent of the building. The steel cell for the 25-inch primary mirror has multiple 12-bolt patterns (per KPNO standard). Equipped with a 30-inch-diameter friction drive in right ascension and a 28-inch-diameter friction drive in declination, the mount will support a 65-kg instrument load with a center of gravity 36 cm behind the mounting plate.

• Tracking accuracy: ±0.5 arcsecond in 5 minutes, ± 5.0 arcseconds in 1 hour
• Pointing accuracy (with refraction and alignment correction): < 30 arcseconds RMS
• Set, guide and tracking rates: variable from 0° to 4.0° per second

The attached Guide-Acquire Module (GAM) allows up to 5 instruments to be mounted at the focal plane (N, S, E, W, and axially), fed by a rotating translating diagonal mirror. This arrangement provides unified acquisition and guiding for multiple instruments. The GAM has standard bolt patterns and integral support for visiting instruments, and it offers full computerized remote control via the Internet.

• Computerized X-Y translating stage with guide probe for off-axis camera or eyepiece
• Internal six-position filter wheel for 2-inch square photometric filters (currently installed: U, B, V, R, I, and Clear)
• Internal eight-position filter wheel for 1.0-inch-diameter circular filters

0.64-m (25-inch) f/9.6 Ritchey-Chrétien OTA
Our unique, high-resolution primary and secondary mirrors are made from zero-expansion-coefficient substrate. They were custom-figured in 2002 for the Clay Center Observatory by world-class opticians at Brashear LP in Pittsburgh, Pennsylvania. Taking more than one year to figure and polish, they provide diffraction-limited performance and a wide, flat field. The full-thickness Zerodur primary is an f/2.8 hyperboloid figured to 1/90 wave RMS at 632.8 nm. The Astrositall hyperboloid secondary has a surface figure of 1/100 wave RMS at 632.8 nm. The optical tube features computer-controlled aperture doors, as well as two sets of primary and secondary baffles. Users can select either a 2-inch-diameter unvignetted field with minimal central obstruction or a 4-inch-diameter unvignetted field with a slightly larger central obstruction. The combination of superb optics and good local seeing enables the 25-inch telescope to produce sharper images than telescopes several times its size.

10-inch Meade Instruments Schmidt-Cassegrain
• Effective aperture: 203.2 mm
• Focal length: 2540 mm
• Focal ratio: f/10
• Ultra-High Transmission Coatings (UHTC)
• Primary Mirror Locking Mechanism
• Computerized temperature-compensated focuser

7-inch Meade Instruments Apochromatic Refractor
• Effective aperture: 178 mm
• Focal length: 1600 mm
• Focal ratio: f/9
• Ultra-High Transmission Coatings (UHTC)
• Computerized temperature-compensated focuser

4-inch Takahashi FSQ 106 Fluorite Astrograph, Modified Petzval Design
• Effective aperture: 106 mm
• Focal length: 530 mm
• Focal ratio: f/5.0
• Image Circle: 88 mm
• Imaging field: 8.5°
• Built-in adjustment mechanism permits 360° camera rotation

70-mm Televue Ranger Apochromatic Refractor
• Effective aperture: 70 mm, air-spaced doublet
• Focal length: 480 mm
• Focal ratio: f/6.8
• Imaging field (35-mm film): 4.3° × 2.9° (5.2° diagonal)
• Computerized temperature-compensated focuser

70-mm Coronado Instruments Nearstar hydrogen-alpha telescope
• Effective aperture: 70 mm
• Focal length: 400 mm
• Focal ratio: f/5.7
• Bandwidth and bandpass: <0.8Å centered at 656 nm
• Thermal stability: 0.005 Å per °C
• Blocking: >105 from EUV to far IR