US Naval Observatory CCD Astrograph

The telescope is a twin astrograph with 2 tubes mounted in parallel on a Boller & Chivens mount. Originally it carried a blue corrected lens and a visual bandpass corrected lens. The "blue lens" was replaced by a new "red lens", which is decribed in the following table. The CCD camera for our project is mounted behind the red lens. The visual lens is used for guiding with an ST-4 autoguider on an x,y slide, capable of moving in a 2 degree field of view.

  Parameters of the telescope optics

clear aperture

206 mm

focal length

2057 mm

plate scale

100 "/mm

number of lens elements


spectral bandpass of lens

550 - 710 nm

Airy disc diameter (610nm)

15 micrometer

usable flat field of view

9 degree

CCD camera

The CCD camera we use for the project was obtained from Spectral Instruments and uses a single 4k KODAK chip.

An interference filter is used as the window for the camera. The filter is plane parallel to lambda/4 specifications.

Parameters of the 4K CCD camera

number of pixels

4094 x 4094

field of view

61 x 61 arcmin

pixel size

9.0 micrometer

pixel scale

0.905 arcsec/pixel

spectral bandpass used

579 - 642 nm


14 bit

readout noise

13 electrons

full well capacity

85,000 electrons

operating temperature

-18 C

limiting magnitude

16.0 in 100 seconds