Wed, 04/10/2019 - 09:49
I am a high school physics teacher (it will be my first remote observation experience) and would like to introduce variable star observation to students by remote telescopes. I have an access to a remote telescope at 05.15-05.45 am at Hawaii time for 30 minutes (for telescope's spec: https://lco.global/observatory/2m/). I am wondering time duration and time ( close to Hawaii's sunrise time.) Is it problematic for variable star observation and do some light curve analysis.
although you have a large telescope available for 30 min you would need more time for light curve analysis.
Most variables do have periods which are (much) longer than 30 min.
You did not specify what target you are going to observe. The timing (close to sunrise) is normally not critical (I observe until sun being -9 degree below the horizon), it only depends how deep you want to go, hence how dim is your object of interest.
Is there any variable star its transient below 30 mins for educational purposes?
Hi, Ozhan: This may not be exactly what you're looking for, but it might get the kids interested/excited. The (very faint) recurrent nova "U Sco" needs to be monitored to detect its next outburst (see AAVSO alert at https://www.aavso.org/aavso-alert-notice-664) You could use your 30 minutes to take a 1-minute exposure plus a few 5-minute exposures (say, 2 unfiltered for maximum sensitivity, and 2 in V-band for best photometry). The goals are :
(1) see if U Sco is visible/detectable at all. If it's too faint to see, then it's not yet in outburst. If it IS visible (but not in outburst) then you can check the feasibility (signal level, SNR) of measuring its lightcurve, and also report a quiescent magnitude value.
(2) If lightcurve project is feasible, then you can use this demonstratoin to figure out how much telecope time you'll need, and request that for follow-up observation. Good scientific value as well as educational excitement.
(3) Regardless of the result of (1), consider asking for more half-hour slots for periodic monitoring of this star in anticipation of something happening.
Bob gave a good proposal as U Sco is very dim and a BIG telescope will help getting some decent data.
Of course it would need more than just 30 min of observing time in the end as Bob mentions.
Another object ight be ASASSN-18ey a possible black hole X-ray bunary
IT has just shown another outburst and is presently in V filter still mag 14.5 or so. It has shrort term variations probably non-periodic. SO short exposures with a 2 m class telescope could give some more clues, although I have seen from the description of the scope and its CCD that it takes 12 s to read the CCD which is rather long. So in the end you will not be able to get shorter than 15 sec or so expsoures (I assume that a 3 sec expsoures with a 2m scope is sufficicent to get decent SNR for a 14.5 mag target.
As Josch mentions, 30 minutes on a telescope that you've never used before, with new software, may make it difficult to plan much of anything. Will you be able to preprogram the object, so that you have given the operator or software the RA,DEC, filter, exposure time, number of exposures, etc. prior to the observing window, or do you just gain access and have to take control yourself, and have to confirm the location with the finding chart? That latter process eats into your observing time. I'm willing to bet that they are assuming you will just image one object, perhaps with multiple exposures or multiple filters, and not try to do a time series.
That said, if you are trying to see variation in an object in 30 minutes, you are basically confined to a compact object like a CV. A rule of thumb is a signal/noise of 100 for a 15th magnitude object in a V filter with a 40cm telescope takes about one minute. Scaling to the 2m aperture, that means you can do 3.5 magnitudes fainter, or about V=18.5, in the same length of time.
One event that takes place in less than 30 minutes is an eclipsing cataclysmic variable. Their eclipses usually last 5-10 minutes, and have considerable structure, depending on the orientation of the two stars and the accretion disk with its hot spot. You'd have to search VSX for eclipsing CVs, find some that will be visible during your observing window, and then look at the ephemeris to see if any eclipse is taking place during that 30-minute interval.
There are some high-amplitude delta Scuti stars (often classified as SX PHE types) with periods of 30-90 minutes, and so one of those might give a reasonable piece of the full light curve in the observing window.
Or, you can do something perhaps more standard, like taking BVRI of a globular cluster and doing a color-magnitude diagram.