wpo - the T Cep series

T Cep is a circumpolar Mira type LPV with a period of ~ 13 months. The spectroscope (Rainbow grating 20mm before CCD) was relocated onto the telescope many times during these observations but shows consistency of results. When possible T Cep will be followed through a complete cycle for expected spectral changes. main spectroscopy page...
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The complete 13 month T Cep cycle showing its variable spectrum animated - as the star fades in brightness its spectrum becomes redder eg moving right into the infra-red region. 

2000 May 31: A long break due to very poor weather and low northern altitude [since Mar 11] but the series effectively complete with this observation this morning over 14 months - shown below.

2000 Mar 11:  the 11th observation of  T Cep [bottom of page] within the last 12 months and tonight on the northern meridian below Polaris in the London murk !  Exposure has halved [16s] since the last observation 6 weeks ago as it brightens and the spectrum swings again towards the left and the visible spectrum.

2000 Jan 27: T Cep [from the reducing exposure] seems a little brighter.

1999 Dec 7 & 27: more spectra added to the spectrogram series below - T Cep seems to have 'bottomed-out' with the longest exposure [45s] on Dec 27 and perhaps on the rise again into the new millennium.
 
 

1999 Nov 16 : 7th monthly spectrum of T Cep continues this WPO series now near minimum light - hence the longer 30s exposure. This is the most marked change in the spectrum profile so far - compare the two images below taken 10 weeks apart. T Cep is currently emitting mostly in IR i.e. the peaks right of the 'A' line in above image taken via the MX9 hi-res mode. The new software allows full CCD resolution to yield a dispersion of 2nm/pixel or 4nm/pixel in binned mode. Both samples shown here.

1999 Mar 26: the first and experimental shot of T Cep (below Polaris) proved successful in good transparency but under a gibbous moon although nothing could be seen in the finder due to London's light pollution to the north.

The spectra alone [below] are barely sufficient to note the subtle changes in the star - except the brevity of May exposure and a subtle shift of flux into visible and reduction in near-IR at peak brightness at this time. The changes are more obvious in the spectrum profiles above [3 months sampled to avoid confusion] - note the overlay in Mar/Apr [as a yellow line] in visible light whilst near-IR continues to reduce evenly.