Skip to main content

SU Tau

5 posts / 0 new
Last post
ocn's picture
SU Tau

Hi All, An SU Tauri Light Curve Generator check of the last 20,000 days or so (back to about mid-1961) suggests that the present long and deep min is a unique event for this star during more than half a century of observations on it. I've yet to look at the pre-1961 observations. The light curve suggests that this RCB variable has shown fades into the magnitude 16-18v/V range during numerous, previous minima but not for l-o-n-g duration being currently witnessed. It appears to have been below about V mag 160 since around November 2012. Multi-filter photometry suggests the star is quite red/reddened, as might be expected. I last observed it at 16.8V on March 31.1 2016 (UT) and sporting a V-Rc color index of about +1.4. Kind regards, Steve.

pukemaru's picture
SU Tau

I see there are a few anomalous positive observations that need to be deleted. A case of mistaken identity-maybe getting confused with the 10th magnitude star close to the west of SU TAU.

It's interesting that S APS's last decline was a lot deeper than usual.

Stephen [HSP]
Pukemaru Observatory
New Zealand

Steve Johnston
SU Tau

 I was looking at the field last night, and It was not visible to my setup,ie C11, so I reckon it must be fainter than 17.0m.

Btw, I don`t how folks get it confused with other stars in the field. When its there its pretty much on its own to find.. There plenty of others that can be misidentified, ie V452 Cas , pretty close to other stars.



Stevev J...

ocn's picture
SU Tau



Regarding the ID, it should be pretty straight forward down to about 175V. There's nothing brighter than that 'close' to SU. There are 18th-19th mag companions several arc-secs N and E of the variable however that's a fair degree beyond what most of us are doing at this time. Any brighter, apparent mis-IDs suspected in the database would, in my opinion, be likely related to inexperience and/or observer fatigue. 

Also, 'close' to the variable means different things to different folks. 'Scope size, FOV, and *experience play vital roles !  I should know ... I remember trying to go after SU Tau at maximum with a 2.4" when I was ALOT younger than I am today. 

BTW, used T11 at iTelescope on 'it' less than a day ago and it seems to have slightly brightened since my last look (see the DB).  SJ please try again when you can. SH, I will start an S Aps thread separately ... really another interesting RCB.

Kind regards to all,

Steve O.





ocn's picture
SU Tau

Hi All,

Have recovered SU Tau in morning twilight on Aug. 4.47 UT 2016 and it is still in deep min (16.6V). According to the AAVSO Database, the star has been fainter than 16.0V for four years now, having initially been recovered in the morning sky and reported deeply faded by ROE on Aug. 8, 2012 at mag 16.7V. Apparently we are witnessing the longest duration deep minimum of SU Tau ever recorded, since observations of it began in 1908.

kind regards,



Log in to post comments
AAVSO 49 Bay State Rd. Cambridge, MA 02138 617-354-0484