High-speed multicolour photometry with CMOS cameras

We present the results of testing the commercial digital camera Nikon D90 with a CMOS sensor for high-speed photometry with a small telescope Celestron 11ʺ at the Peak Terskol Observatory. CMOS sensor allows to perform photometry in 3 filters simultaneously that gives a great advantage compared with monochrome CCD detectors. The Bayer BGR colour system of CMOS sensors is close to the Johnson BVR system. The results of testing show that one can carry out photometric measurements with CMOS cameras for stars with the V-magnitude up to ≃14ᵐ with the precision of 0.01ᵐ. Stars with the V-magnitude up to ∼10 can be shot at 24 frames per second in the video mode

Tests of commercial colour CMOS cameras for astronomical applications

We present some results of testing commercial colour CMOS cameras for astronomical applications. Colour CMOS sensors allow to perform photometry in three filters simultaneously that gives a great advantage compared with monochrome CCD detectors. The Bayer BGR colour system realized in colour CMOS sensors is close to the astronomical Johnson BVR system. The basic camera characteristics: read noise (e⁻/pix), thermal noise (e⁻/pix/sec) and electronic gain (e⁻/ADU) for the commercial digital camera Canon 5D MarkIII are presented. We give the same characteristics for the scientific high performance cooled CCD camera system ALTA E47. Comparing results for tests of Canon 5D MarkIII and CCD ALTA E47 show that present-day commercial colour CMOS cameras can seriously compete with the scientific CCD cameras in deep astronomical imaging

Low-resolution spectroscopy of the chromospherically active stars 61 Cyg AB with small telescopes

We carried out high-speed low-resolution spectroscopy of two stars, 61 Cyg A and B with small telescopes. They are known as chromospherically active stars of the K5V (A) and K7V (B) spectral types. These two stars are supposed to have high-powered chromospheres. Spectroscopic monitoring of both stars showed variations of intensity in the Balmer lines and the Mg b triplets at time intervals ranging from seconds to several minutes. From the spectrum data one can find that relative variations in the Hα, Hβ lines and the Mg b triplets are about 1% and the relative power of chromospheric activity about 2 · 10⁻⁴

What limits the precision of ground-based stellar photometry and positional measurements?

Nobody has reached the photometric precision better than 0.001 of a magnitude with ground-based telescopes. At the same time, we should spend barely some seconds of time to detect a million photons from any bright star and to attain a Poisson noise of one millimagnitude. The instrumental accuracy of coordinate determination with the ground-based telescopes equipped with CCD cameras is also no better than 0.1–0.2 arcsec. Many factors limiting the precision of stellar photometry and astrometry on the ground are superimposed and occur simultaneously. We show, however, that image motions in the focal plane of telescopes, recently discovered by the authors, may be in reality the barrier both to millimagnitude photometry and milliarcsecond astrometry with ground-based instruments. It is quite essential that stellar image motions (SIM) have a chance to be found out only by using synchronous observations with several telescopes. The measurements of SIM were carried out by taking registration of a star image near to diaphragm edge, which plays a role of an optical knife. The spectra of SIM show periodic variations on the scale from a few seconds to minutes typically having amplitudes of a few tenths of arc seconds. Clearly, image motions during the integration time can cause photometric errors and frustrate exact coordinate determinations. The nature of SIM remains obscure. An important point is that image displacements measured synchronously in different telescope reference frames show significant correlations. Emphasis is given to problems of the detecting of SIM and estimating their amplitude-frequency characteristics with the Synchronous Network of Telescopes

Low-resolution spectroscopy of the chromospherically active stars 61 Cyg AB with small telescopes

We carried out high-speed low-resolution spectroscopy of two stars, 61 Cyg A and B with small telescopes. They are known as chromospherically active stars of the K5V (A) and K7V (B) spectral types. These two stars are supposed to have high-powered chromospheres. Spectroscopic monitoring of both stars showed variations of intensity in the Balmer lines and the Mg b triplets at time intervals ranging from seconds to several minutes. From the spectrum data one can find that relative variations in the Hα, Hβ lines and the Mg b triplets are about 1% and the relative power of chromospheric activity about 2 · 10⁻⁴

Pulsations Beneath the Winds: Unique Precise Photometry from MOST

Contains fulltext : 72155.pdf (publisher's version ) (Open Access)Mass Loss from Stars and the Evolution of Stellar Clusters, 29 mei 200

Coordinated observations of the red dwarf flare star EV Lac in 1998

The results of photometric studies of the flare star EV Lac obtained in the course of cooperative observations in 1998 are presented. No significant brightness variations in IR were found from simultaneous observations of the star in UBVRI and H bands, in coincidence with the observed optical flares. Within the framework of the zonal spottedness model of stars the EV Lac surface inhomogeneity parameters are estimated