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Re: [vsnet-id 859] TU Aql identification > No, actually, although perhaps the original records could be > examined (not really worth it, however). The BD position is in fact > closer to TU Aql, and at epoch 1855 the companion star would have been > some 10" further north (i.e. farther from the BD position). TU Aql > does spend a fair bit of time brighter than the companion, so this is > reasonable. On the other hand, the historical astrometric catalogues > have tagged the northern component (brighter in the blue, so always > measured on the blue-sensitive plates instead of the variable), so some > decision was made way-back-when (maybe AGK1?) to assign it to that star. I remember that the observation to compile the BD catalog was done with a transit method with a low-power telescope. It is not hard to believe that these two objects were unresolved under such a circumstance (the separation of the components is only a few time larger than the original recording precision). I had experience with this field with a 10-cm telescope, and recognized a beutiful close double at a magnification power of 50. I don't think I could have resolved the pair reasonably with a magnification of 20. It might be interesting to look back the pulsation cycle of TU Aql back to the original recording time. However, as you correctly mentioned, the AGK object is (almost) certainly not TU Aql itself. By the way, this region of the BD catalog seems to be less accurate in coordinates than in the neighboring ones. There may have been a reason to degrade the accuracy when the observer came accross this field. Regards, Taichi Kato
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