SSP4 INFRA-RED PHOTOMETER FROM OPTEC INCORPORATED

This has been available for some time but recently I had the opportunity to use one for JH photometry. It is offered with two alternative detector sizes, 0.3mm and 1.0mm. The first of these, used with a 250mm f10 SC telescope equates to a target diameter of 25". This is less than the scintillation disc of most bright stars and is impractical for stellar work. (Similar comments apply to the SSP3 solid state unit, but the SSP5 uses a pm tube and should be better). The 1mm detector allows 82" which is practical at that level but makes centring of the image critical and the drive must be excellent. I then changed to a 200mm f6.3 telescope which allows marginal use of the 0.3mm for stellar work at 62" but is comfortable with the 1mm at 206". The use of the 0.3mm detector is puzzling as the sky background with the J and H filters is not obtrusive. There is provision for computer control but this is fairly tedious for this type of work and it was operated in the manual mode. No particular problems, but the need to reset everything before each observing session was annoying. So too, was the rather large but partly empty housing which stopped the device from going between the forks of the smaller telescope. A good instrument for anyone interested in near-infra-red photometry, particularly of Miras and other cool red variables. These tend to be 4-8 magnitudes brighter than in V at those wavelengths. Thus the operating limits of ~3-5, dependent upon how long you care to integrate the signal, are not unduly restrictive.     Price ex Optec $####.

This is a version of the standard ST7 extended into the blue and near uv region of the spectrum. It has potential, but so far U filters are not being offered, although the U filter combination used for pep, so long as is blocked for leaks in the red, would work adequately. The extended response allows for better performance in B, although B-V adds little that is not available from V-R. A warning, however, as the printed circuits in the later models are exposed to the air and suffer badly in moist conditions--so they are unsuited to roll off roof type applications in more humid climates. It requires a reasonably good computer for correct operation and analysis of the images.

Price ex SBIG $####, but this must be a US sale.