Transcript Applications - Occultation

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Applications of EMCCDs to Faint
Occultations
Bruce Holenstein, Russ Genet, and Steve Conard
31st Annual Meeting of the International Occultation
Timing Association
04-06 October 2013 Toronto, Canada
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Agenda
 What is considered faint?
 What are emCCDs?
 Some SNR theory and tests
 Some projects
What is considered “faint”?
A desirable occultation out of the
reach of typical IOTA equipment
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 Targets are faint
 TNO occultations – 14th+ magnitude
 Fast cadence & HTRA
 Diffraction patterns – 200+ fps
 Small scopes are in use for portability
 Well under 1-m typical
 Lowland observing & program objects at low altitudes
 Lots of atmospheric extinction
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What are emCCDs?
CCD cameras with an extra set of registers
to multiply electrons before readout.
Top row from left: Photometrics Cascade 512B emCCD,
512B emCCD w/UV enhanced, 1k emCCD, CoolSNAP K4
Bottom row: Supercircuits 164CEX-2, Andor Luca-S
emCCD, Watec 902H2-Ultimate, two 902H2’s (PAL), Two
JAI 6740GE GigEthernet
Above: Andor iXon EM+ 887 and 897
emCCDs
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How emCCDs work
Source: Photometrics Cascade user manual
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emCCD Noise Reduction
CCD read noise reduced from 10’s of electrons per pixel to
under 0.1 per pixel. Back illumination increases QE.
CCD Read noise drops off as em
gain increases
QE curves: Andor iXon EM+ and
Photometrics Cascade 512B’s use
CCD-97 (top curve)
Sources: Andor iXon EM+ 897 & Photometrics Cascade brochures
Camera specs
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emCCDs Mounted on small scopes
Top two photos:
Photometrics Cascade 512B
mounted on a 10” SCT,
Right: Luca-S on 8” SCT, Far
right: 512B on a 10”
Newtonian
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10” SCT with Andor Luca-S, Orion filter wheel, Barlow, iXon EM+ and Van Slyke
Instruments Slider II (setup for speckle interferometry)
SNR Theory for 14” f/4 SCT
 SNR for four cameras
vs object mag.
30-fps, 100-m
elevation, 1.2 airmass,
Sky: 20th mag./sq.as.
Each magnitude fainter worked is about 300%
more targets (2.5 mag. is ~30x more!)
Camera comparison on 14” f/10 SCT
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NGC 7031- above the top of the Cygnus cross (stars ID'ed down to mag ~17)
LINEARITY CHECK – Video Rate (33ms)
Stellacam EX
Photometrics 512B emCCD
Camera comparison on 14” f/10 SCT
SNR COMPARISON – Video rate (33ms)
Stellacam EX
Photometrics 512B emCCD
(Note scales are not the same)
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mu Gem Lunar Occ. 1314Mar11
16.5 mas fit (red)
0.1 mas fit (red)
Media, PA C8, Luca-S at
333fps, unfiltered, LiMovie
Scintillation limited SNR!
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FPS (speed) - Pi Sgr at Villanova, August 10, 2011
 Villanova C8, 164CEX-2 CCD, no
filter, 30fps
 9.4mas per datum
 Gravic C8, Andor Luca-S emCCD,
Sloan r filter, 120fps
 2.4 mas per datum
 Again Scintillation limited SNR
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Some Projects
Programmable timing
trigger device (Arduino,
GPS shield)
Alt-Az Telescope Initiative
Projects
 Larger scopes are needed to
further improve SNR
Hubble Optics UL20
1-M Meniscus Mirror Telescope Prototype
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Weight under 400 lbs
Fits in back of Dodge minivan
& Jeep Cherokee
On-axis f/4 light bucket
w/possible active optics
“Big Blue” – from Russ Genet
Orion Observatory
1.5-m
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 60” scope designed and built by Russ Genet;
CalPoly students Mounir El-Koussa, Laura
Rice, and Mike Vickery; mirror cell by Donny
Mott; SiTech donated controller/drive; DOTI
donated mirror; scope finalized by Reed and
Chris Estrada
Scaled up
design to 2.4-m
Designed by Mounir El-Koussa, R.
Genet, B. Holenstein, D. Mott; funding by
Gravic and Collins Foundation
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Conclusions
emCCDs cameras can help IOTA
in certain situations
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 emCCDs have a 2 to 3 magnitude advantage at video
rates over typical IOTA cameras
 On “photon challenged” (sm. aperture) scopes
 Low altitude or contrast events where a better SNR is
needed
Challenged in certain situations
 Cameras are expensive, heavier, less portable, and
need more power
 Scintillation noise hampers fast cadence & HTRA
measures so one needs larger scopes 0.5-m & up
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Contacts
 Emails: [email protected], [email protected],
[email protected]
 Alt-Az Telescope Initiative Website - www.AltAzInitiative.org
 Yahoo Discussion Group http://groups.yahoo.com/group/AltAzInitiative