HOWPol Specification

Basic specifications

Wavelength 0.45 -- 1.0 micron

Field of view Imaging: 15' diameter
Wide-field imaging polarimetry (WFPol): 7' x 7'
Narrow-field imaging polarimetry (NFPol): 15' x 1'
Spectroscopy (LSpec): 2.3" x 15'

Filter B, V, R, I, z', polarizing

Grism (plan) Low-res 420/mm, R=400, (TBD: High-res R>1000)

Wollaston prism (WFPol) Wedged double Wollaston made of six rutile blocks
(NFPol) Wedged double Wollaston made of six magnesium fluoride blocks and two fused silica wedges
CCD (CCD_0, CCD_1) Two fully depleted 2k-4k CCDs (HPK/NAOJ), 200 micron-thick depletion layer

Limiting mag Photometry(*6): R = 19.2
Imaging polarimetry(*7): R = 16.0

(*6)10-min exposure, delta_R = 0.02 mag, (*7)10-min exposure, delta_P = 0.5%

Basic specifications
Wavelength	0.45 -- 1.0 micron
Field of view	Imaging: 15' diameter Wide-field imaging polarimetry (WFPol): 7' x 7' Narrow-field imaging polarimetry (NFPol): 15' x 1' Spectroscopy (LSpec): 2.3" x 15'
Filter	B, V, R, I, z', polarizing
Grism (plan)	Low-res 420/mm, R=400, (TBD: High-res R>1000)
Wollaston prism	(WFPol) Wedged double Wollaston made of six rutile blocks (NFPol) Wedged double Wollaston made of six magnesium fluoride blocks and two fused silica wedges
CCD (CCD_0, CCD_1)	Two fully depleted 2k-4k CCDs (HPK/NAOJ), 200 micron-thick depletion layer
Limiting mag	Photometry(6): R = 19.2 Imaging polarimetry(7): R = 16.0

Main optical train (design value)

Total F (including telescope) F / 6.9

Diameter of pupil image 23.9 mm diameter

Distortion of pupil image
(80% encircled energy) less than 52 micron at 450 < lambda < 1100 nm,
less than 32 micron at 600 < lambda < 1100 nm

Transmission larger than 38% at 450 < lambda < 1100 nm

Focal length of Camera lens 148 mm

Distortion of focused image
(80% encircled energy) less than 30 micron (0.6 arcsec) at 450 < lambda < 1100 nm

Main optical train (design value)
Total F (including telescope)	F / 6.9
Diameter of pupil image	23.9 mm diameter
Distortion of pupil image (80% encircled energy)	less than 52 micron at 450 < lambda < 1100 nm, less than 32 micron at 600 < lambda < 1100 nm
Transmission	larger than 38% at 450 < lambda < 1100 nm
Focal length of Camera lens	148 mm
Distortion of focused image (80% encircled energy)	less than 30 micron (0.6 arcsec) at 450 < lambda < 1100 nm

Some specifications (observationally/experimantally confirmed)
Pixel scale 0.29428 arcsec/pixel at distortion center

Magnification (scale at focal mask):(scale at CCD) = 1 : 0.5654 at distortion center

Linearity Deviation is less than 1 % from ~50 ADU (TBD) to 55000 ADU

Conversion factor (~ gain) of CCD 2.19 +/- 0.15 photoelectrons/ADU

Total efficiency B: 7.5%, V: 20.4%, R: 30.0%, I: 27.7% (2008.07) (including typical airmass + telescope)

Offset of shutter open time +0.014 sec

Offset angle of Ns rotator for north-top -63.4 deg (2012/06/30)

Position of Ns rotator axis (Uncorrected image) X=395, Y=1082 on CCD_1 (in raw image, 2x2 bin; 2012-06-30)
(Uncorrected image) X=7, Y=2192 on CCD_1 (in raw image, 1x1 bin; 2011-07-15)
(Distortion corrected image) X=TBD, Y=TBD

Position of WFPol mask center (Uncorrected image) X=-54, Y=2083.3 on CCD_1
(Distortion corrected image) X=TBD, Y=TBD

Position of distortion center (Uncorrected image) X=18.23, Y=2164.40 on CCD_1
(Distortion corrected image) X_dcen=1730.64, Y_dcen=1764.47

Distortion function r = 1.334127E-5 * r'^2 + 1.0 * r', where
r = sqrt[ (x-X_dcen)^2 + (y-Y_dcen)^2 ], and (x,y) is position on uncorrected image
r' = sqrt[ (x'-X_dcen)^2 + (y'-Y_dcen)^2 ], and (x',y') on corrected image

Some specifications (observationally/experimantally confirmed)
Pixel scale	0.29428 arcsec/pixel at distortion center
Magnification	(scale at focal mask):(scale at CCD) = 1 : 0.5654 at distortion center
Linearity	Deviation is less than 1 % from ~50 ADU (TBD) to 55000 ADU
Conversion factor (~ gain) of CCD	2.19 +/- 0.15 photoelectrons/ADU
Total efficiency	B: 7.5%, V: 20.4%, R: 30.0%, I: 27.7% (2008.07) (including typical airmass + telescope)
Offset of shutter open time	+0.014 sec
Offset angle of Ns rotator for north-top	-63.4 deg (2012/06/30)
Position of Ns rotator axis	(Uncorrected image) X=395, Y=1082 on CCD_1 (in raw image, 2x2 bin; 2012-06-30) (Uncorrected image) X=7, Y=2192 on CCD_1 (in raw image, 1x1 bin; 2011-07-15) (Distortion corrected image) X=TBD, Y=TBD
Position of WFPol mask center	(Uncorrected image) X=-54, Y=2083.3 on CCD_1 (Distortion corrected image) X=TBD, Y=TBD
Position of distortion center	(Uncorrected image) X=18.23, Y=2164.40 on CCD_1 (Distortion corrected image) X_dcen=1730.64, Y_dcen=1764.47
Distortion function	r = 1.334127E-5 * r'^2 + 1.0 * r', where r = sqrt[ (x-X_dcen)^2 + (y-Y_dcen)^2 ], and (x,y) is position on uncorrected image r' = sqrt[ (x'-X_dcen)^2 + (y'-Y_dcen)^2 ], and (x',y') on corrected image

Some specifications (plots)

Filter transmission curves (Ascii data files > [B] [V] [Rc] [Ic] [z'])