The document summarizes testing of the refurbished Leuschner 30-inch telescope's ability to detect exoplanet transits. Photometric calibrations were performed using Landolt standards, determining the telescope's zero point, airmass, and color corrections in B, V, and R filters. Observations of the open star cluster M34 were used to test magnitude measurement accuracy. Aperture sizes of 9, 11, 13, and 15 pixels were tested on stars similar to exoplanet target stars WASP-43b and WASP-56b, determining that a 13 pixel aperture yielded the smallest magnitude fluctuations. Observations were taken of WASP-43b and WASP-56b over three nights, detecting the known

1. Testing the refurbished Leuschner 30-inch telescope and its ability to detect planets around other Stars
Eileen Gonzales, Adam Fries, Adrienne Cool
San Francisco State University
Abstract
Site Characterization
Conclusions and Summary
The 30-inch Ritchey-Chretien telescope at Leuschner Observatory has recently been
refurbished through a collaboration between San Francisco State University (SFSU) and UC
Berkeley. The telescope is equipped with an SBIG STL-11000M CCD and is now being
operated remotely from both campuses. We have carried out observations from SFSU to test
the telescope's performance and to characterize the site in Lafayette, CA. We present the
results of photometric calibrations in B, V and R filters carried out using Landolt standards,
and of the seeing at the site and measured sky brightness in B, V and R filters. Finally, using
observations of the open star cluster M34, we test the accuracy with which we can measure
relative magnitudes, with the goal of using this telescope to detect exoplanet transits.
Seeing
Accuracy of magnitude measurements using M34
Figure 1: Histogram of the V-Filter seeing at
Leuschner. Typical range for seeing between
2.5-3 arcseconds.
Sky Brightness
Figure 5: Sub figures a-d
show the variation in
magnitude for a star of
similar brightness to
WASP-43 for aperture
sizes of 9,11,13,and 15
pixels. The mean
magnitude depends on
aperture size because a
fraction of the star’s flux
lies outside the aperture.
The best aperture size for
the WASP targets was
determined to be 13
pixels.
Figure 2: Sky Brightness in the B, V , and R filters
in magnitudes per square arcseconds.
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The goal of accuracy testing was to determine how small of a variation we can detect with the Leuschner telescope, since the transit of an exoplanet reduce the brightness of the host star
between 0.01-1% (http://www.iac.es/proyecto/tep/transitmet.html). If we can detect variations in magnitude at this order, we will be able to detect transiting exoplanets. The immediate goal was
to see of the transits of our targets WASP-43b and WASP-56b were detectable.
Aperture Size
Various size apertures were tested on stars in the open cluster M34 to see which one yielded the smallest fluctuations in measured magnitudes for a star similar in brightness to our
exoplanet targets. Apertures of 9, 11, 13, and 15 pixels were tested.
Photometric Calibrations
Figure 4 : A 5-second exposure of M34
taken with the Leuschner Telescope.
____________________________________________________________________________________________________________Detecting Exoplanet Transits
(a) (b) (c) (d)
Using the results from testing on M34, it was determined that the best apertures size was 13 pixels and that best results were obtained by using a single reference star brighter than the target by
0.2-1.5 magnitudes.
WASP-43b
Figure 6: Relative photometry on 3/22/2014, outside
of transit. Standard deviation of residuals is 0.006
magnitudes.
Figure 10: Relative photometry out of transit,
3/23/2014. Standard deviation of residuals is 0.006
magnitudes.
Figure 8: Relative photometry on 3/24/2014,
during a transit. Standard deviation of residuals
is 0.11 magnitudes, larger than previous nights
due to intermittent cloud coverage.
Date ∆V σ σ of mean
3/22 1.417 0.006 0.001
3/23 1.428 0.007 0.001
3/24 1.450 0.011 0.001
On the first two nights, relative photometry yielded
measurement accuracies of 0.006-0.007 magnitudes for both
targets. On the third night, during the transit windows,
intermittent clouds reduced the accuracy to 0.009-0.011
magnitudes. Nevertheless, we were able to detect a significant
dimming of both targets during transit
In the case of WASP-43, the target was 0.028 magnitudes
fainter during transit than it was on average the two previous
nights. This is consistent with the known transit depth of 0.026
magnitudes (Hellier et al. 2011, A&A, 535, L7), considering the
uncertainty on the difference (σ = 0.014; σ 𝑚𝑒𝑎𝑛 = 0.001). For
WASP-56, the target was 0.018 magnitudes fainter during
transit than the previous two nights. Considering the
uncertainties (σ = 0.013; σ 𝑚𝑒𝑎𝑛= 0.001), this is also consistent
with the known transit depth of 0.010 magnitudes (Faedi et al.
2013, A&A, 551, A73). Given that the standard deviations of
the mean in both cases are approximately 0.001 magnitudes,
both transits are detected with a high degree of significance.
WASP-56b
Table 1: Comparison of WASP-43
values over 3 nights of observations.
Figure 7: Relative photometry on 3/23/2014,
outside of transit. Standard deviation of residuals
is 0.007 magnitudes.
Figure 9: Relative photometry out of transit,
3/22/2014. Standard deviation of residuals is 0.007
magnitudes.
Figure 11: Relative photometry on 3/24/2014,
during transit. Again intermittent clouds yield larger
standard deviation of residuals than other nights at
0.009 magnitudes
Date ∆V σ σ of mean
3/22 0.167 0.007 0.001
3/23 0.158 0.006 0.001
3/24 0.181 0.009 0.001
Table 2: Comparison of WASP-56
values over 3 nights of observations.
In summary, current techniques allow us to achieve measurement accuracies on the order of 0.006 to 0.007 magnitudes for individual measurements with the Leuschner Telescope. With repeated measurements, this mean that it is indeed possible to detect exoplanet transit with the Leuschner
telescope. To improve the accuracy measurements, we need to determine other methods to use to further lower the detection limit. To increase our confidence in detections, data should be taken before and after the transit.
Photometric calibrations for the B, V, and R filters were determined using Landolt Chart 132.
The Landolt stars were used to determine Leuschner’s zero point, airmass correction, and
color correction.
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Filter Z a c Color index
B 21.89 -0.308 0.010 𝑚 𝐵 − 𝑚 𝑉
V 21.65 -0.232 -0.092 𝑚 𝐵 − 𝑚 𝑉
R 21.18 -0.111 -0.17 𝑚 𝑉 − 𝑚 𝑅
Table 1: Photometric calibrations for the Leuschner telescope, as
determined on November 4, 2013
Figure 3 : Landolt Chart 132. The stars used for
calibrations are labeled.
Why Using M34____________________________
M34 was used to determine how best to analyze the
transit data for targets WASP-43b and WASP-56b.
It was chosen since it is an uncrowded field with
many stars of constant magnitudes.
We observed WASP-43 and WASP-56 on three nights, with the
last night including a known transit for both targets. To
determine if we detected the transits, we measured magnitudes
for each target relative to a brighter reference star.