R Aqr - Cederblad 211 home


R Aquarii (Cederblad 211)

Visual observation of a symbiotic star


December 2009

R Aquarii is a symbiotic double star consisting of a Mira-type red giant transferring gas to presumably a White Dwarf (more here). From time to time, the system ejects some of this material. This material forms spiraling filaments that are known as Ced 211.

I had observed R Aqr already some weeks before with a 16 inch Dob under less than optimal seeing conditions, where I could spot the elongated form of the nebula but no further detail. This night, the seeing was better than average. With my 22" Dob at 500x without filter only the conspicuously red giant star was visibly, no nebulosity. With the OIII filter, the brightness was reduced only slightly and a bright small condensation became visible around the now very much suppressed star. On one side of the Nebula, approximately NE, an extension curving toward N could be easily seen, which had another brighter condensation at its tip. At the other side, the nebula was broader and did not extend that far. With UHC filter (Astronomik, with transmission window in the red spectral range), the star became more prominent and with H beta (Lumicon) only the star could be seen. To the left is a rough sketch of what could be seen at the eyepiece using OIII filtering.

Sometimes I suspected more material further out toward South, but I was not completely sure about this.

Another observing report by Yann Pothier is here, another observing report by Uwe Glahn with his 27" Dob is here. Here is a finder chart by Paul Alsing.  

To the left is an image taken by the Hubble Space Telescope (before it had its appointment with the ophthalmologist) with more information here.



Adam Block/Mount Lemmon SkyCenter/University of Arizona

These images were taken by David Malin (upper, Anglo-Australian Observatory) and Adam Block (lower) and show beautifully the outer filaments of Ced 211 (more details here). The part of Ced 211 that was observed by myself are the inner whitish filaments.

Due to the variability of the Mira star (presently between 6th and 11th magnitude with a period of 387 days), it is interesting to compare observations made during different phases. The observing report above dates from a time close to a maximum. Subsequent observations close to a minimum revealed the northern extension well without filter, as the main star was no longer disturbing. Pre-requirements for such a low-declination object are, of course, good seeing and culmination.

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