| Wolfgang
Vollmann |
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| Star: Struve 2093 Date: 2006 July 26 Time: 21:00-24:00 UT Seeing: 5 <1-10 Seeing Scale (10 best)> Transparency: clear Location of site: Vienna, Austria Site classification: Suburban Conditions: Moon: Sky darkness: 4.5 <Limiting magnitude> Telescope: 130/1040mm refractor Camera: SBIG ST237A CCD Exposures: 6 or 12 x 10 seconds for astrometry. Distance/PA measurement was done with these images also except where noted (bright stars need shorter exposure times of 1 sec or less) Image measurement: astrometry with Astrometrica software and UCAC2 or USNO B1.0 catalog (see http://www.astrometrica.at); with exact focal length and image orientation I measured distance and PA with AIP4WIN software. I took means of measuring all my images for a star. There is a scatter of 0.2 arcsec in separation and 0.2 deg in PA. Scatter in PA is much larger if the stars are very close. Note: All images have north up Eyepieces: n/a Magnification: n/a |
Eta Her has a very faint
wide companion. It was
difficult to measure until I tried stacking my 12 exposures -- same
technique
as with minor planets for my short 10 second exposures. My mount
unfortunately
doesn't track longer than this unguided. While measuring the stacked
images of
faint companion B I noted a still fainter and closer companion, marked
X on the
image. This star is real, since it is there even when stacking images
1-4, 5-8
and so on. So I measured it too!  |
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