OMI AS A SURVEY TELESCOPE
The ability to view large areas of the sky is important in many
areas of research. The capability of a telescope to detect objects
scales as the etendue, which is defined as the product of collecting
area (A) times its field of view (Ω).To calculate the etendue
OMI uses 7.1 square degrees which is the widest extent of the
image square.
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OMI SURVEY CAPABILITIES COMPARISON
|
|
Telescope
|
Diam (m)
|
Ω(deg²)
|
AΩ
|
|
LINEAR
|
1.0
|
2
|
1.5
|
|
OMI
|
1.0
|
7
|
6.0
|
|
SDSS
|
3.6
|
3.9
|
6
|
|
CFHT
|
3.6
|
1
|
8.0
|
|
Pan-STARSS
|
3.6
|
7
|
60
|
|
LSST
|
8.4
|
9.6
|
300
|
|
Mag r'
|
Exp. (s) s/n=3
|
Exp. (s) s/n=10
|
Exp. (s) s/n=50
|
|
19
|
0.27
|
1.46
|
29
|
|
20
|
0.73
|
4.5
|
97
|
|
21
|
2.221
|
17.4
|
405
|
|
22
|
8.5
|
81
|
2013
|
|
23
|
43
|
456
|
11,275
|
|
24
|
247
|
2710
|
68,351
|
|
25
|
1526
|
16,755
|
422,641
|
|
26
|
9,435
|
105,672
|
-
|
|
27
|
59,505
|
666,463
|
-
|
|
Anticipated limiting magnitude vs. exposure
|
The OMI field showing the Pleiades on the image circle used to
calculate the etendue and the actual image on the sky of the CCD
chip.
The camera has a field of 2.22º x 2.22º with an image
scale of 0.76 arcsec/pixel.
The OMI has the ability the image thousands square of degrees
per night depending on how deep the exposure.
|
deg² (s/n=3)
|
deg² (s/n=5)
|
Mag. (r')
|
|
7,654
|
4,173
|
21
|
|
5,689
|
1,437
|
22
|
|
2,362
|
295
|
23
|
|
530
|
51
|
24
|
|
90
|
8.3
|
25
|
|
14.7
|
-
|
26
|
|
OMI survey capabilities based on an 8
hour night (16s download time).
|
LIMITING MAGNITUDE
The OMI should reach visual magnitude 24 in 315s. By adding several
observations it be able to reach magnitude 28.0.
s/n =3, FWHM=1.25", visual (r'), 16s download, Zϑ =
0°
 Calculated
with the OMI Photometric Tool.
PHOTOMETRY
Accurate photometry is crucial for detecting Earth sized planets
around red dwarf stars. We should be able to do differential photometry
to 0.0016 with 600 seconds exposure with a σ = 1 on a 17th
magnitude star
Calculated with the OMI Photometric tool.
ASTROMETRY
Based on a FWHM of 1.25 arcseconds and a signal to noise ratio
of 5 we expect to determine positions to within 0.1 arcseconds
and better with brighter stars.
From: "Detecting and Measuring faint point sources with a
CCD by Herbert Raab, Astronomical Society of Linz. Austria"
PointSources.pdf (click here)
Next: Optical Tube
Assembly
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