We use the results of our recent NLTE model atmosphere analysis of central stars of old planetary nebulae (PN) to calculate distances. We perform a comparison with three other methods (trigonometric parallaxes, interstellar NaD lines, and Shklovsky distances) and discuss the problem of the PNe distance scale. The result of the comparison of our spectroscopic distances with the trigonometric dis...

We use the results of our recent NLTE model atmosphere analysis of central stars of old planetary nebulae (PN) to calculate distances. We perform a comparison with three other methods (trigonometric parallaxes, interstellar NaD lines, and Shklovsky distances) and discuss the problem of the PNe distance scale. The result of the comparison of our spectroscopic distances with the trigonometric dis...

We report astrometric parallaxes for three well known dwarf novae obtained using the Fine Guidance Sensors on the Hubble Space Telescope. We found a parallax for SS Aurigae of π = 5.00 ± 0.64 mas, for SS Cygni we found π = 6.02 ± 0.46 mas, and for U Geminorum we obtained π = 10.37 ± 0.50 mas. These represent the first true trigonometric parallaxes of any dwarf novae. We briefly compare these re...

I used the 2.4 m Hiltner telescope at MDM Observatory in an attempt to measure trigonometric parallaxes for 14 cataclysmic variable stars. Techniques are described in detail. In the best cases the parallax uncertainties are below 1 mas, and significant parallaxes are found for most of the program stars. A Bayesian method which combines the parallaxes together with proper motions and absolute ma...

The Space Infrared Telescope Facility (SIRTF) will drift away from the Earth at ∼ 0.1 AU yr. Microlensing events will therefore have different characteristics as seen from the satellite and the Earth. From the difference, it is possible in principle to measure ṽ, the transverse velocity of the lens projected onto the observer plane. Since ṽ has very different values for different populations (d...

The distances to individual wind-driven bubbles such as Planetary Nebulae (PNe) can be determined using expansion parallaxes: the angular expansion velocity in the sky is compared to the radial velocity of gas measured spectroscopically. Since the one is a pattern velocity, and the other a matter velocity, these are not necessarily the same. Using the jump conditions for both shocks and ionizat...

Mean proper motions and parallaxes of 205 open clusters were determined from their member stars found in the Hipparcos Catalogue. 360 clusters were searched for possible members, excluding nearby clusters with distances D < 200 pc. Members were selected using ground based information (photometry, radial velocity, proper motion, distance from the cluster centre) and information provided by Hippa...

A globular cluster distance scale based on Hipparcos parallaxes of subdwarfs has been used to derive estimates of MK for cluster Miras, including one in the SMC globular cluster NGC121. These lead to a zero-point of the Mira infrared period-luminosity relation, PL(K), in good agreement with that derived from Hipparcos parallaxes of nearby field Miras. The mean of these two estimates together wi...