Observed Magnitude Tests April 2007
The observed magnitude tests were carried out with a 0.9m Wynne Newtonian at Kingsland
Observatory MPC J62 in County Roscommon. The purpose of this telescope is to survey for
Edgeworth Kuiper Belt Objects EKBOs at high latitudes. EKBOs are very faint minor bodies with
a detected magnitude range of around 20 to 26 mag. Most have been found around 23 mag. The
brighter ones are around 21 mag.
The aim of these tests is to find out if the telescope will perform adaquately to reach magnitudes
before recovering faint Edgeworth Kuiper Belt Objects in a routine survey. Factors like
transparency and percentage of Lunation do have a role to play in either increase to decrease
magnitude threshold. However, results were obtained over a series of nights. The field of view is
effectively 23' x 23' with a resolution of 1.35 arc/pixel. Focal length is 367.5 cm. All images were
at binning two.
Tests were carried out on the nights of the 5,6,7,8 and 9 April 2007 for observed magnitude tests. A
range of exposures of 30 secs, 75 secs, 188 secs and 472 secs in a sequence were used.
Transparency of the sky was noted and the percentage of Lunation on all nights.
All tests were carried out on the meridian at declination +23 degrees north of the ecliptic. This
location was taken as an average elevation before the routine survey. All exposures used binning 2.
DATE
EXP. 30 secs
EXP. 75 secs.
EXP.
188 secs.
EXP. 472 secs
050407
19.92
20.76
21.23
21.63
060407
19.88
20.63
21.12
21.35
070407
20.25
20.96
21.78
22.27
080407
20.14
20.87
21.64
21.97
090407
19.61
20.33
20.87
21.14
These results were under less than optimum conditions with the exception of 070407 and 080407.
The results do not neccessarily determine the limiting magnitude, however, they do provide
essentiallly a series of tests that of different varying magnitides depending on transparency
condition, with the higher relative humidity showing slightly lower magnitudes. See scatter graphs
The determination of sky transparency conditions does determine what possible magnitude one can
obtain.