SBIG CCD CAMERA SYSTEM

The Meade LX200R 14'' is fitted with Meade f/6.3 Focal Reducer which has a measured focal length of +140.3mm.

Depending of the separation of the lens and the CCD, various reductions are possible and the current system produces a focal ration of f/6.35.

Faster focal ratios produce a larger field but at a cost of so much vignetting, that the autoguider chip is hardly illuminated at all.

The detector is an SBIG STL-1001E which has a CCD of 1024 x 1024 x 24 microns. Thus the field of view is 37.41 arcmin square with one pixel corresponding to 2.19 arcseconds. The autoguider chip is 7.38 arcmin x 5.57 arcmin with pixels which are 0.675 arcseconds square. The CCD is cooled by a 2 stage Peltier device using air and water cooling and operates at -5C. Control of the CCD is by CCDSoft.

The system is focused using FocusMax, with a Finger Lakes Instruments Precision Digital Focuser (PDF).

The internal filter wheel in the CCD is computer controlled and currently has the following photometric filters: U B V R and a Schott BG20 filter which attenuates the NaD yellow street light pollution.

Zoom Lens Spectrograph:
See this page on the spectrograph.

Cassegrain Focus

Optics and Aberrations:
At f/19 all of the aberrations are less than the seeing disk the small field of view. The plate scale of 26.6 arcseconds/mm means that the AP 7 CCD camera has a field of view of only 5.4 arcminutes. Each pixel corresponds to 0.638 arcseconds, so it well suited to imaging of planetary surfaces or other sources where high angular resolution is required.

Focus Drive and Encoder:
The secondary mirror is mounted on a lead screw which has a linear encoder. There is no temperature compensation, so that focus changes can occur as the telescope structure expands or contracts. A movement of 1 mm of the secondary produces a focus shift at the Cassegrain focus of 15.6 mm. The secondary can move through a range of 30 mm, which moves the Cassegrain focus from -240 mm to +240 mm relative to the Cassegrain mounting plate. The nominal focus is at +70.0 outside the mounting plate surface. This is where the slit of the spectrograph and the aperture stops of the UBV photometer are placed.

TV Slit Viewing and Calibration Optics:
A mirror at 45 degrees to the optical axis folds the Cassegrain focus on to the Acquisition TV camera. The camera consists of a Collins Electro Optics I3 CCD Video camera which is equipped with a recursive video frame averager. Since the intensifier can be damaged by over illumination it is protected by a bright object sensor. The output from the camera is displayed in the Control Room on a monochrome video monitor. With the acquisition mirror in the DIRECT / CALIBRATION position, the camera can view the Cassegrain field for source acquisition. In this mode light from a calibration lamp can be fed to the spectrograph slit. There are neutral density filters in the calibration beam which can be selected to attenuate the calibration lamps. When the mirror is in the SLIT VIEWING position, the slit can be viewed for spectroscopy.

UBV Photometer

Speckle Interferometer