Transcript Camera Comparison - Asteroid Occultation Updates

Steve Conard
Willow Oak Observatory, Gamber, MD
International Occultation Timing Association (IOTA)
Oct 20, 2012
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Bruce, Russ, and I had originally hoped to do a
thorough comparison of several video and
digital interface cameras that could used for
IOTA’s observations
Due to personal time limitations and weather,
we didn’t accomplish what we had intended
 It became a much a less controlled test, with fewer
cameras, than we had originally intended

View it as a quick comparison of several
common cameras as typically used in real-world
conditions

Data collection was not as well controlled as I
had hoped
 Intended to have a parallel telescope recording
the same field at the same time
 Did not take the time to fully learn to use the Flea
camera—resulting in only 8-bit data collected

The data have not rigorously been analyzed,
and may contain errors
 More data is available to be analyzed when time
permits
C-14 on CGE mount
Focal reducer used to
set f/number at about
4.0
 In roll-off observatory
 Video data through
IOTA-VTI to Canon ZR65 recorder
 Flea data through
Firewire to desktop PC
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“Control” was a Stellacam EX (my SN 01)
Other video cameras
 Stellacam EX (SN 02)
 Watec 902 Ultimate (SN 01 and 02)
 PC164C-EX2
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Firewire camera
 Flea 3 FL3-FW-03S3M-C

All arrays are ½” format except the PC164CEX2 which is 1/3”

Used same field for each camera
 Eplison Lyra (“Double Double”) selected to have easy
reference, and was fairly high in the sky
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Reference camera used before and after to look
for changes
Tried to pick nights with good transparency and
no visible clouds
Tangra used for data analysis
 Used auto aperture selection

Picked up to 6 stars for comparison
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Weather clear, reasonable transparancy
Tangra apertures left to automatic selection
Collected data with Stellacam EX 1 at 1 and 2
fields integration
Collected data all other cameras
 Varied gain on one Watec
 Used 1 and 2 fields on the second Stellacam EX
Collected data with Stellacam EX 1 at 1 and 2
fields integration
 Only minor difference in signal before/after with
Stellacam EX 1
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Measured Signal
PC164 Showed Saturation for
the Brightest Star
10000
Mesured Signal (DN)
Watec 2 Showed Saturation
for the Brighter Stars
1000
Stellacam EX SN 1 Before 1 Field
Stellacam EX SN 1 After 1 Field
Stellacam EX SN 2 1 Field
Watec 902 SN 2 Low
Watec 902 SN 2 High
100
Watec 902 SN 1 Medium
Supercircuits PC164C-EX2
10
9
10
11
Magnitude
12
SNR
35
30
25
Stellacam EX SN 1 Before 1 Field
Stellacam EX SN 1 After 1 Field
SNR
20
Stellacam EX SN 2 1 Field
Watec 902 SN 2 Low
15
Watec 902 SN 2 High
Watec 902 SN 1 Medium
10
Supercircuits PC164C-EX2
5
0
9
10
11
Magnitude
12
Stellacam EX SN 1 Before
Stellacam EX SN 2
Watec 902 Ultimate SN 1
Watec 902 Ultimate SN 2
PC164C-EX2
Stellacam EX SN 1 After
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PC164C-EX2 may give the best combination of
SNR and signal level
 Significantly better at all but the brightest targets,
where SNR may fold over (may not be the best choice
for a bright asteroid over a fainter star)
 It also may have other issues that weren’t
investigated here

Watec 902 Ultimate and Stellacam EX’s are very
similar
 Watec can produce almost as much signal as the
PC164C-EX2 when the gain is very high
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Weather clear, reasonable transparancy
Tangra apertures left to automatic selection
Collected data with Stellacam EX 1 at 1 and 2
fields integration
Collected data with Flea 3
 Max’ed out the gain at 24 dB
 Maximized exposure time at a 30 Hz readout rate
 Important: Flea was used in 8 bit mode
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Collected data with Stellacam EX 1 at 1 and 2
fields integration
Only minor difference in signal before/after with
Stellacam EX 1
Measured Signal
Mesured Signal (DN)
10000
1000
Stellacam EX SN 1 Before 1 Field
Stellacam EX 1 Before 2 Field
Flea 3 30Hz
Flea 3 30 Hz
Stellacam EX SN 1 After 1 Field
100
Stellacam EX 1 After 2 Field
10
9
10
11
Magnitude
12
SNR
30.0
25.0
20.0
SNR
Stellacam EX SN 1 Before 1 Field
Stellacam EX 1 Before 2 Field
15.0
Flea 3 30 Hz
Flea 3 30 Hz
Stellacam EX SN 1 After 1 Field
10.0
Stellacam EX 1 After 2 Field
5.0
0.0
9
10
11
Magnitude
12
Stellacam EX 2 Fields
Flea 3

Stellacam has much larger signal level
 This may not be true with Flea at 12-bits

Roughly the same SNR for fainter targets,
possible advantage to Flea for brighter ones
Weather clear, reasonable transparancy (same time as
video comparison above)
 Collected data with Stellacam EX 1 at 32 fields
integration
 Collected data Flea at 1.875 Hz, max exposure

 Gain at 24 dB
 Flea at 8 bits
Collected data with Stellacam EX 1 at 32 fields
integration
 Only minor difference in signal before/after with
Stellacam for the fainter targets—the bright ones
showed more change for some reason
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Signal Level
10000
Stellacam Showed Saturation
for the Brighter Stars
Signal Level
1000
Stellacam EX 1 32 Fields Before
Flea 3 1.875 Hz Run 3
Flea 3 1.875 Hz Run 4
Stellacam EX 1 32 Fields After
100
10
11.6
11.8
12
12.2
12.4
12.6
Estimated Magnitude
12.8
13
13.2
13.4
SNR
30.0
25.0
SNR
20.0
Stellacam EX 1 32 Fields Before
15.0
Flea 3 1.875 Hz Run 3
Flea 3 1.875 Hz Run 4
Stellacam EX 1 32 Fields After
10.0
5.0
0.0
11.6
11.8
12
12.2
12.4
12.6
Estimated Magnitude
12.8
13
13.2
13.4
Stellacam EX 2 Fields
Flea 3
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Stellacam has much larger signal level
 This may not be true with Flea at 12-bits
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Roughly the same SNR for fainter targets,
Stellacam showing saturation on brighter
ones