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TT Ari observing campaign

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weo's picture
TT Ari observing campaign

A new AAVSO observing campaign has been initiated on the novalike (VY Scl subclass) CV TT Ari. Please see AAVSO Alert Notice 469 for details (link via the homepage or directly at or the campaigns page ( The email version of the Alert Notice will be distributed when the utility is fixed (technical difficulties again with it).  Good observing, Elizabeth


Hi all,

I have some questions about the determination of the error (webobs page) of the CCD measurements of TT Ari.

Normally I express the error as the SDev of three measurements, with V and B or V and Rc, transformed; each single shot exposure equals, for my instrumental setup, 50 seconds.

The request of the alert is a time definition of one minute so is it possible to express the error as the instrumental magnitude difference of the check star with respect to the previous observation, for example, or what do you suggest for doing all the same procedure?

I think it would be interesting to do at least groups of twenty minutes observations or more, what do you think about?

Thanks for your attention

Tiziano Colombo


MZK's picture
TT Ari Campaign

Based on my reading of the alert, the desired criteria are:

1) fast imaging (a time resolution of at least 1 minute to detect rapid flickering, etc) - (50 seconds would work fine) (but SNR > 50)

2) time series of at least 3.3 hours to cover complete cycles (not 20 minutes)

3) tranformation to standard magnitudes not critical (temporaral variation not accuracy is of most importance) (work with one filter, your choice UBV clear, for each time series) (try another filter on another night) (if you had a big scope and really fast camera you could switch filters during a time series with same time resolution??)

4) not appropriate/desired to bin/average three images since you lose time resolution

Anyone else have different thoughts?

KTC's picture
Use the error from a time-series

If you take a time-series of this target, look at the standard deviation of check minus comp in your data...and choose a comp that is somewhat brighter (approx 1.5 magnitudes) than TT Air, and a check that is similar in brightness to TT Ari. 

The above value you determine for standard deviation should be suitable for long as weather/sky conditions remain similar.

I hope this helps.

roe's picture
TT Ari Color

I've had some good weather and have been able to get a couple of runs on TT Ari.  I've added I interspersed with V and have found the average V-I index to be about 0.05 mag.  This is the "whitest" star I have ever observed.  Fun!

Jim Roe [ROE]

weo's picture
TT Ari observations needed now through October 20

Dr. Nikolaus Vogt informs us that the MOST satellite is now devoting all of its observing time to TT Ari and will continue through 2012 October 20. Serial UBV or unfiltered CCD observations over 3.3 hours at least some of the time are urgently requested. For more information and instructions, please see AAVSO Alert Notice 469. Thank you, and good observing,  Elizabeth Waagen

P.S. I neglected to mention when I initially posted this message that, according to Dr. Vogt, the CCD observations are extremely important "in order to define the magnitude zero point, as well as to compare the accuracies of both observing methods, ground-based and satellite." If you are not able to observe in all three bands, go ahead and observe in whichever of UBV you have available to you. Many thanks!

padovan's picture
TT Ari

Hi all,

I posted yesterday on another forum anyway this are the data of my preferred starTT

Taken from New Mexico iTelescope with my T5.

best regards

 Stefano Padovan,AAVSOpsd                          


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