The telescope D50 came into existence in period 2000-2008. The original intention was to create
cheap mid–aperture telescope for optical observation of high–energy sources, using (revitalizing) some older unused equipment. During the quite long and problematic (re)construction phase the decision was taken to use the beside–arising BART’s new system RTS2 and apply the full automatization. The telescope’s observational phase started in 2008, in spite of many problems and limitations. After 4 years of successful but problematic operation, we decided to conduct minor reconstruction, which resulted in much better, more reliable and more capable telescope. The telescope has returned to operational state in summer 2013, but we are still improving and fine–tuning some properties and parameters.
The telescope is located in the same observational site as telescope BART, just a few meters far, in the historical part of observatory of Astronomical Institute of Academy of sciences of the Czech Republic in Ondřejov.
The D50 telescope consists of 0.5m Newton–type telescope with coma–corrector, carried by massive fork–mount. Most of it’s parts are custom–made, some parts are old and revitalized (mount, dome, etc). The telescope is equipped with digital focuser and filter wheel with standard photometric filters (BVRI Johnson–Bessel and also clear position for unfiltered observation), as a detector we use CCD camera FLI IMG 4710 remade for use with more reliable external shutter.
The telescope is placed in the small dome with sliding–roof and the configuration is very tight – the telescope and the roof can easily collide in case of bad synchronization. The roof can be closed only when the telescope is properly parked, which puts high stress on maximum reliability of the whole system. Also, the movement area of the telescope is significantly limited because of roof’s proximity even in opened state.
The telescope is driven by RTS2 system and is now working in semi–automatic mode, which is caused by still non–solved issues after last reconstruction. The roof manipulation is not yet controlled by RTS2, so the begin and the end of observation must be made manually (from distance) by supervising/observing astronomer. The observation itself can be performed automatically, however we usually use the queues mechanism to have better control on observed targets. Still, the alert–targets (e.g. GRBs) have higher priority and are executed automatically.
The standard (non–GLORIA) observational program of D50 is based on observing of GRBs and various astrophysical objects (cataclysmic variables, symbiotic stars, AGNs etc) in long–term and also intensive observation mode. The integration of D50 into GLORIA was intended to be just via batch–mode, however we have decided to temporarily implement the available interactive–mode. But we still plan to change it in the future.
The very specific local hard–horizon (defined by roof–proximity) is a noticeable limitation, the mount will refuse to move to the forbidden area. The periodic error is much less significant after the reconstruction, but is still quite apparent. As we have not yet implemented any correction mechanism, we recommend to use exposures ≤ 20s.
The telescope D50 has relatively great mirror and sensitive detector, so we have decided to forbidden the observation of Moon. The RTI should not allow to move the telescope closer than 5deg from Moon’s center. The observation of bright planets is possible but not recommended (because of telescope’s parameters). To save the detector, only short (<0.1s) exposures should be used.