HONIR: an optical and near-infrared simultaneous imager,
spectrograph, and polarimeter for the 1.5-m Kanata
telescope
Hiroshi Akitayaa , Yuki Moritania , Takahiro Uia , Takeshi Uranob , Yuma Ohashib , Koji S.
Kawabataa , Asami Nakashimac , Mahito Sasadad , Kiyoshi Sakimotob , Tatsuya Haraob ,Hisashi Miyamotoe , Risako Matsuib , Ryosuke Itohb , Katsutoshi Takakib , Issei Uenob ,Takashi Ohsugia,b , Hidehiko Nakayaf , Takuya Yamashitaf , and Michitoshi Yoshidaaa Hiroshima Astrophysical Science Center, Hiroshima University, Kagamiyama 1-3-1,

Higashi-Hiroshima 739-8526, JAPAN;b Department of Physical Science, School of Science, Hiroshima University, Kagamiyama

1-3-1, Higashi-Hiroshima 739-8526, JAPAN;
c Nagoya City Science Museum, 17-1, Sakae 2-chome, Naka-ku, Nagoya 460-0008, JAPAN;
d Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto

606-8502, JAPAN;
e Molex Japan Co., Ltd., Fukami-Higashi 1-5-4, Yamato, Kanagawa 242-8585, JAPAN;
f National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588,

JAPAN
ABSTRACT
We have developed an optical and near-infrared instrument HONIR (Hiroshima Optical and Near-InfraRedcamera) with imaging, spectroscopy, and polarimetry capabilities in two (one optical and one near-infrared)
bands simultaneously. Imaging capability with a ﬁeld of view of 10 arcmin by 10 arcmin has been available
since 2011, as reported in the previous SPIE conference. In addition, spectroscopic and polarimetric opticalcomponents (grisms, an Wollaston prism, a half-wave plate, and focal masks) were installed in the instrument,
which enabled us to perform spectroscopy and linear polarization measurement by imaging polarimetry andspectro-polarimetry. Spectral resolution of R = λ/∆λ ∼ 440 − 800 is achieved in spectroscopy using a slit
mask with an 1′′ .3 width. In polarimetry, instrumental polarization is less than ∼ 0.05 % with stability ofbetter than ∼ 0.05 %, which is suﬃciently small to achieve an aimed accuracy of polarization measurementof ∼ 0.1 % at primal observing wavelengths.

1. INTRODUCTIONHONIR (Hiroshima Optical and Near-InfraRed camera) is an optical and near-infrared simultaneous imager,
spectrometer, and polarimeter attached at the Cassegrain focus of the 1.5-m Kanata telescope at Higashihiroshima Observatory (Hiroshima, Japan) operated by Hiroshima Astrophysical Science Center, Hiroshima
University (Fig. 1).
We had accomplished many observational results on variable or transient objects, such as blazers,1–3
supernovae,4 young stellar objects, and so on, by use of the optical and near-infrared simultaneous instrument
TRISPEC,5 which is capable of imaging, spectroscopy, and polarimetry, since 2006. To improve the research
activity, we planned developing a new instrument HONIR with much higher sensitivity and spacial resolution
than TRISPEC.
We began developing HONIR in 2007. The optical and near-infrared simultaneous imaging capability(Fig. 2) was introduced in 2011 as reported in the previous SPIE conference.6 In addition, we installed a
Further author information: (Send correspondence to H. Akitaya)
H. Akitaya : E-mail: akitaya@hiroshima-u.ac.jp, Telephone: +81 82 424 5765, Fax: +81 82 424 5765

function of spectroscopy in 2013. A polarimetric function, which enables us to perform imaging polarimetry
and spectro-polarimetry for linear polarization, in combination with an imaging function or a spectroscopyfunction in existence, was installed in early 2014.
We describe basic design and speciﬁcations of HONIR in Section 2. Details of the imaging capability,
spectroscopic capability, and polarimetric capability are described in Section 3, 4, and 5, respectively. We
summarize current status of HONIR and mention future prospects in Section 6.

2. BASIC DESIGN AND SPECIFICATIONS OF HONIR
Optical design of HONIR is shown in Fig. 3. Principal optical components of HONIR, except for a mechanicalshutter and a half-wave plate for polarimetry, are placed on an optical bench cooled down to ∼ 65 K ina vacuum chamber. An incident ray from the telescope is once focused at the telescope focal plane in thechamber, followed by a collimator lens and a cold stop at the exit pupil plane of the telescope. A following
dichroic mirror splits the ray into a folded optical ray (“Optical Arm”; 0.5–1.0 µm) and a forthright nearinfrared ray (“IR Arm #1”; 1.15–2.4 µm). Focal images are ﬁnally focused on an optical CCD detector andFigure 1. HONIR attached on the Kanata Telescope.

Figure 2. Optical and near-infrared imaging observation of M42 (RGB pseudo color).

a near-infrared HgCdTe VIRGO-2K detector separately by a camera lens in each arm after passing through aband-pass ﬁlter and/or a grism.
HONIR is equipped with six rotating turrets to insert arbitrary optical components into the optical train.
A focal mask turret (Turret #1) provides the telescope focal plane with one of aperture masks or slit masks
for imaging, spectroscopy, polarimetry, or experimental measurements (e.g. a pinhole mask). A pupil maskturret (Turret #2) at the pupil plane contains a cold stop with a diameter of 26 mm for imaging observation,an Wollaston prism for polarimetry, and some masks for experiments. Each arm after split by the dichroic
mirror has two turrets (Turret #3 and #4 for the IR Arm #1, and #5 and #6 for the Optical Arm). They
contain band-pass ﬁlters (in the turret #4 and #6) and grisms (#3 and #5). Each turret is rotated by astepping motor controlled by the integrated control system Motionnet (Nippon Pulse Motor Co., Ltd.).
The detector in the Optical Arm is a fully-depleted back-illuminated CCD array with 2048 × 4096 pixels
with a pixel size of 15 µm (Hamamatsu Photonics K. K.,), which is controlled by the Messia 5 7 and MFront
2 8, 9 systems. An image is read at a frame rate of 17.4 sec/frame with a readout noise of ∼ 4 e− /pixel at again of 2.7 e− /ADU.
For the IR Arm #1, a HgCdTe VIRGO-2K array with 2048 × 2048 pixels (20 µm pixel size) controlled by
the Messia 5 and MACS2 10 systems is used. A full image area of the detector is read at a frame rate of 4.5
sec/frame via four readout ports in parallel at a readout noise of ∼ 24 e− /pixel at a gain of 11.6 e− /ADU. We
are currently developing a new readout system for the VIRGO-2K array, based on design of the Kiso Control
Array,11 aiming to read a whole image at ∼ 1.2 sec/frame via 16 readout ports in parallel with a smaller
readout noise.12
Our design leaves room for appending an extra infra-red arm (IR Arm #2; see the upper part of Fig.
3(a)), which consists of an additional dichroic mirror that folds the incident near-infrared ray in the existing
IR Arm #1 with wavelengths of 1.15-1.35 µm (J band), a pair of a ﬁlter and grism turrets, a camera lens,and an extra infra-red detector. A function of simultaneous observation in three bands (optical, J, and H–K
bands) will be achieved in consequence.
Basic speciﬁcations of HONIR is summarized in Table 1. Details of the basic optics, cryostat, mechatronics,
and readout systems for the detectors are also described in the previous conference paper on this instrument.6
(a)

(b)

Figure 3. (a) Optical layout of HONIR and (b) components in the vacuum chamber.

Table 1. Basic specifications of HONIR.

PropertyArm

Wavelength coverage (µm)
Field of view (FoV) (arcmin)
Plate scale (arcsec/mm)c
Size of the whole FoV (mm)c
Sampling rate (arcsec/pix)
Size of the whole imaging area (mm)dFilters
Spectroscopy

Slits
GrismsPolarimetry

Masks
Analyzer
Modulator
Type
VendorFormat (pixels)
Pitch (µm)
Size (mm)Detector

IR Arm #1a
1.15–2.40
10 × 10

Optical0.5b–1.0
10 × 10
11.14853.8 × 53.8

0.294
0.295
30.7 × 30.7
40.9 × 40.9
Bb, V, RC , IC , Y
Y, J, H, Ks< 0.58 µm cut ﬁlter< 1.33 µm cut ﬁlter
1′′ .3 (0.12 mm), 2′′ .2 (0.2 mm), 6′′ (0.54 mm)
BK7; 300 gr/mm (Optical)
BK7; 180 gr/mm (IR-short),
S-FTM16; 120 gr/mm (IR-long)
9′ .7 × 0′ .75 × 5 slots, 2′′ .2 × 45′′ × 5 slits
YLF Wollaston prism
Pancharatnam type super-achromatic half-wave plate
CCD
HgCdTe VIRGO-2K
Hamamatsu Photonics
Raytheon
2048 × 4096
2048 × 2048152030.72 × 61.44
40.96 × 40.96

a

To be divided into the IR Arm #2 for 1.15–1.35 µm and the IR Arm #1 for 1.45–2.40 µm whenanother arm will be installed in future.
b
Partially transparent at 0.4–0.5 µm (B band).
c
At the telescope focal plane.
dOn the detector.

3. IMAGING OBSERVATION
Imaging observation is performed by inserting a focal mask with a square aperture with 10 arcmin by 10
arcmin and band-pass ﬁlters in the optical trains. Images with a ﬁeld of view of 10 arcmin by 10 arcmin at an
optical and near-infrared bands are simultaneously focused on the CCD detector and the HgCdTe detector,
respectively. A pixel scale is 0.294 arcsec/pix on the optical CCD detector, and 0.295 arcsec/pix on thenear-infrared HgCdTe detector.

4. SPECTROSCOPY
Spectroscopy of HONIR is performed by inserting a focal slit mask at the telescope focal plane and a grism
into each optical train after split by the dichroic mirror.
Three types of focal slit masks made from aluminum alloy are used for spectroscopy: a 2′′ .2 (0.20 mm)
width slit for R ∼ 350 (when used with the nominal grisms), an 1′′ .3 (0.12 mm) width slit for R ∼ 600, and a6′′ (0.54 mm) width slit for spectro-photometry (Fig. 4(a)). Every slit has a length of 9′ .7 (52 mm).
Three grisms have been installed in the grism turrets (Table 2, Fig. 4(b)-(d)).
A BK7 “Optical” grism is used at the Optical Arm, which covers the entire optical wavelengths between
0.45 and 1.1 µm. A BK7 “IR-short” grism and a S-FTM16 “IR-long” grism are alternatively used at the IR#1 Arm, covering 0.95–1.53 µm (Y, J, and partial H bands) and 1.15–2.38 µm (partial J, H, and K bands),
respectively (Fig. 5). To suppresses contamination of secondary diﬀracted rays, combine use of an ordersorting ﬁlter, a 0.58 µm cut ﬁlter for the Optical grism and an 1.33 µm cut ﬁlter for the IR-long grism, is also
possible.

Table 2. Specifications of the grisms.

Name
Arm
Wavelength coverage on the detector
Wavelength of the maximum eﬃciency (µm)
Material
Wedge angle (degrees)
Grooves (gr/mm)
Blaze angle (degrees)
Groove pattern typeb
Size (mm)Eﬀective diameter (mm)ab

Optical
Optical0.58(0.45a)–1.1
0.683
BK7
21.5
300
23.0
54-039R
51 × 51× 21
47

IR-short

IR-long
IR #1
0.95–1.43
1.33(1.15a)–2.38
1.232
1.933
BK7
S-FTM16
23.5
22.5
180
120
23.9
26.7
54-870R
54-831R
59 × 59 × 27
59 × 59 × 26
55
55

Without an order sorting ﬁlter.
Model number of Richardson Gratings, Newport Corporation.

Throughput of spectroscopy, including reﬂectance of the telescope mirrors, is about ∼ 15 − 20 % at the
major wavelength ranges.
Actual wavelength resolution (R = λ/∆λ) was evaluated by measuring line widths of emission lines of arc
lamps (Fig. 6). When using the 1′′ .3 slit, R ∼ 440 (V band)–800 (z’ band) with the Optical grism, ∼ 630 (Jband) with the IR-short grism, and ∼ 570 (H band)–440 (Ks band) with the IR-long grism are achieved.
An example of spectroscopic observation of a celestial object is shown in Fig. 7.
(a)

(b)

(c)

(d)

Figure 4. Pictures of (a) the slit masks, (b) the Optical grism, (c) the IR-short grism, and (d) the IR-long grism.

(a)

(b)

(c)

Figure 5. Image samples of spectroscopy of sky emission lines by (a) the Optical grism, (b) the IR-short grism, and (c)the IR-long grism.

(a)

(b)

(c)

1000

1000

800

800

800

600

600

600

R

R

0.12mm slit
0.20mm slit
0.54mm slit

R

1000

400

400

200

200

0
0.5

0.6

0.7

0.8
0.9
Wavelength (um)

1

0
1.0

1.1

400

200
0.12mm slit
0.2mm slit
1.1

1.2
1.3
wavelength (um)

1.4

0.12mm slit
0.2mm slit

0
1.5

1.2

1.4

1.6
1.8
2.0
wavelength (um)

2.2

2.4

Figure 6. Spectral resolution measured from emission lines of arc lamps with (a) the Optical grism, (b) the IR-shortgrism, and (c) the IR-long grism.

Intensity (arbitrary unit)

Opt
IR short (+2)
IR long

5

0
0.5

1.0

1.5

2.0

2.5

Wavelength (um)Figure 7. Spectroscopy of an Wolf-Rayet star WR006 with the 1′′ .3 mm slit normalized at the continuum level.

5. POLARIMETRYHONIR is equipped with an Wollaston prism, a rotatable super-achromatic half-wave plate, and focal masks,
to perform linear polarization measurement.

5.1 Wollaston prism
An Wollaston prism is inserted at the pupil of the optical train to split the incident ray into a pair of linear
polarized rays (an ordinary ray (o-ray) and extraordinary ray (e-ray)) orthogonally polarized each other, which
are focused on the detectors separately.
We selected LiYF4 (YLF) as the material of the Wollaston prism after comparison with other materials.
Physical parameters of YLF and other materials are summarized in Table 3. The YLF satisﬁes the following
requirements: (1) enough transparency between 0.5 and 2.5 µm (λtrans ), (2) large birefringence to achieve alarge separation angle between o- and e-rays (large ∆n), (3) small color dispersion of a separation angle tosuppress chromatic aberration of a stellar image with a broad-band ﬁlter (small V ), (4) small diﬀerence between
coeﬃcients of linear thermal expansion of each birefringent axis (small ∆α) to avoid thermal destruction of
the prism and divorce of optical contact during thermal cycles, and (5) past experiences using at a cryogenic
temperature (∼ 85 K).13
The Wollaston prism consists of two wedged YLF prisms with an wedge angle of 16◦ .39 optically contacted
to one another with their fast axes orthogonally directed. It measures 34 mm by 34 mm with a height of 12mm. An eﬀective aperture diameter is 30 mm. The Wollaston prism was manufactured by Nitto Optical Co.,
Ltd. Its picture and drawing are shown in Fig. 8.
A separation angle between the split beams, slightly varying with wavelength, is 0◦ .7685 at 0.47 µm and
0 .7381 at 2.4 µm, corresponding to 47.8 arcsec and 45.9 arcsec in a celestial angular scale projected on thedetectors, respectively. For V-band imaging polarimetry, at which color dispersion becomes the largest, image
elongation by color dispersion of the Wollaston prism is ∼ 0.30 arcsec, suﬃciently smaller than the typicalseeing size of ∼1–2 arcsec.
◦

5.2 Rotatable half-wave plate (HWP)
As a modulator, a rotatable half-wave plate (HWP) is inserted in front of the optical window of the coldchamber followed by a focal mask only when polarimetry is performed. A position angle of linear polarizationof the incident ray from the telescope is rotated relative to the instrument according to the variable position
angle of the HWP.
The HWP is a Pancharatnam type super-achromatic half-wave plate consisting of three pairs of an SiO2
and MgF2 layers ﬁnally covered with anhydrous silica plates on the top and bottom. Speciﬁcations of the
HWP are summarized in Table 4.
(a)

(b)

Figure 8. (a) The YLF Wollaston prism and (b) design of the prism.

.
Table 3. Comparison of candidate materials for the Wollaston prism.

Material
Calciteα − BBO
YVO4
LiNbO3
Rutile
LiYF4 (YLF)
MgF2
SiO2

λtrans a(µm)
0.21–2.1
0.19–2.1
0.45–3.4
0.50–3.8
0.55-4.3
0.30-4.0
0.13–7.0
0.20–2.4

no b
1.66
1.67
1.99292.146
2.454
1.44845
1.37713
1.54

∆n c
-0.17
-0.12
0.22250.074
0.256
0.02218
0.011760.009

λ∆n c(µm)
0.633
0.532
1.55
1.3
1.52961.0
0.62340.633

V d(0.6 µm)
22
30
11
8
15
43
71
31

V d(2.2 µm)
36
33
547
67
-29
-264
115
45

∆αe(×10−6 )
18.7
-32
-6.9
-14.7
-2.7
3
5.2
?

a

Transparent wavelength range.
Refractive index for an ordinary ray.
c
Birefringence. ∆n = ne − no at a wavelength λ∆n .
dColor dispersion of a split ray. V (λ) = ∆n(λ)/ [∆n(λ − 0.1 µm) − ∆n(λ + 0.1µm)].
eDiﬀerence between coeﬃcients of thermal expansion of two orthogonal optical axes.
b

Table 4. Specifications of the half-wave plate.

Type
Size
Eﬀective aperture
Wavefront error (at 633 nm)
Retardance (at 450–2300 nm)
Transmittance (at 450-2300 nm)
Manufacturer

Pancharatnam type super-achromatic
ϕ 100 mm, 9.6 mm thick
ϕ 92 mmλ/10180◦ ± 9◦> 90 % (> 80 % at > 2,200 nm)
Kogakugiken Corp. (Japan)

The HWP is mounted in a circular cell supported by a crossed roller bearing (CRA13008CC0; THK Co.,
Ltd.) on a base plate. The cell is rotated with a 2-phase stepping motor (PK243DA; Oriental Motor Co.,
Ltd.) on which a backlush-free gear (NS50SU 60B + 0505; Kyoiku Gear MFG Co., Ltd.) is attached. The
rotating unit is mounted on linear slide guides and moved with a ball screw driven with a 5-phase stepping
motor with an electromagnetic brake (RKS544MA; Oriental Motor Co., Ltd.). Fiducial position angles of the
HWP cell and limit positions of the slide unit are detected by photointerrupters (EE-SX3088; Omron Corp.).
A positioning accuracy of a HWP position angle is better than 0◦ .05.

(a)

(b)

Figure 9. (a) The half-wave plate and (b) the rotation unit mounted on HONIR.

5.3 Focal masks for polarimetry
A focal mask with discrete rectangular slots or slits are used for polarimetry. For imaging polarimetry, a maskwith ﬁve discrete rectangular slots with a size of 9′ .7 by 0′ .75 (52 mm by 4 mm in actual scale on the focal
plane) at every 15′ (8.4 mm) is used. For spectro-polarimetry, ﬁve discrete slits with a 2′′ .2 (0.2 mm) widthand 45′′ (4.0 mm) length at every 15′ (8.4 mm) is used (Fig. 10(a)(b)). Thus, o-ray and e-ray images orspectra are focused on a detector without their overlapping.
Considering the worries about unexpected polarization generation at aperture edges, machinable ceramic(MACELITE HSP black by Ariake Materials Co., Ltd.), not metal material, is used as a base of the masks.
Every edge of the apertures was carved very sharply (Fig. 10(c)).
Five pairs of an o-ray and e-ray images or spectra are focused on the optical and infrared detectors (Fig.
11). Spectral resolution of spectro-polarimetry is R ∼ 200 − 600, the same as that of spectrometry with a 2′′ .2
slit (Section 4).

5.4 Measurement of linear polarization
Normalized stokes parameters q = Q/I and u = U/I, or a polarization degree p and a position angle θ, arederived from four pairs of observed intensity signals of an o-ray and e-ray of images or spectra obtained atfour half-wave plate position angles of ψ = 0◦ .0, 45◦ .0, 22◦ .5, and 67◦ .5 using the formulae14
1 − aQ (λ)q(λ) =,
1 + aQ (λ)√κ(λ, 0◦ .0)
aQ (λ) =,κ(λ, 45◦ .0)κ(λ, ψ) =1 − aU (λ),
1 + aU (λ)√κ(λ, 22◦ .5)
aU (λ) =,κ(λ, 67◦ .5)u(λ) =

p(λ) =(2)

Ie(obs) (λ, ψ),Io(obs) (λ, ψ)

(3)

and
√

(1)

q(λ)2 + u(λ)2 ,1
θ(λ) = atan
2

(

u(λ)
q(λ)

)
,

(4)

where Io(obs) (λ, ψ) and Ie(obs) (λ, ψ) are observed signals of an o-ray and e-ray, at a wavelength λ and a position
angle of the HWP ψ, respectively. Using these formulae, diﬀerence of transmittance eﬃciencies between an
(a)

(b)

(c)

Figure 10. Focal masks for (a) imaging polarimetry and (b) spectro-polarimetry. (c) Magnification of a slit edge of thespectro-polarimetry mask.

o-ray and e-ray in the instrument, and variation of terrestrial atmospheric transmittance between a pairof distinct exposures (ψ = 0◦ .0 and 45◦ .0 for q measurement, or 22◦ .5 and 45◦ .0 for u measurement) arecompletely cancelled out.

5.5 Polarimetric performance
We aim at achieving an accuracy of linear polarization measurement less than 0.1 % to detect typically smallcelestial polarization signals of the order of a few percent or less. Small instrumental polarization with small
ﬂuctuation, which is expected by operating an instrument at a Cassegrain focus of a telescope, is required forthe aimed polarization accuracy.
5.5.1 Instrumental polarization
Instrumental polarization of imaging polarimetry and spectro-polarimetry was evaluated by observing unpolarized standard stars.15, 16
An average of the measured instrumental polarization (qinst , uinst ) and its standard deviation (σqinst , σuinst )at various telescope positions and observational epochs for imaging polarimetry are shown in Fig. 12 andTable 5. Between V and H bands, instrumental polarization is at 0.04–0.09 % and stable within 0.04–0.12%. At B and Ks bands, slightly larger instrumental polarization of ∼ 0.2 % with a stability of 0.2–0.3 % ismeasured.
Fluctuation of instrumental polarization among the ﬁeld of view is evaluated at RC and J bands bymeasuring linear polarization of an unpolarized standard star at diﬀerent positions on the focal plane. Figure
14 shows the measured instrumental polarization over the ﬁeld positions. In Table 6, an average of the
instrumental polarization over the ﬁeld of view and its standard deviation among the various positions areshown. At RC band, instrumental polarization is ∼ 0.03 % on average and ﬂuctuates by ∼ 0.1 %. At J-band,
instrumental polarization is ∼ 0.1 % that ﬂuctuates by ∼ 0.2 %.
Figure 13 shows instrumental polarization of spectro-polarimetry at three independent observational epochs.
Instrumental polarization is small and stable at a level better than 0.05 % in optical wavelengths. At nearinfrared wavelengths, the ﬂuctuation among the epochs is a few × 0.1 %, slightly larger than that at optical
wavelengths.

Figure 11. Image samples of imaging polarimetry (left) and spectro-polarimetry (right) on the optical CCD detector.

Table 5. Instrumental polarization of imaging polarimetry.

λcenter a(µm)
0.44350.54910.65340.7694
1.2485
1.63802.1455

Band
B
V
RC
IC
J
H
Ks
a
b
c

qinst [%]
-0.23
-0.01
0.02
-0.03
-0.09
0.03
0.10

uinst [%]
0.06
-0.06
-0.06
-0.04
-0.01
-0.02
-0.16

σqinst [%]
0.21
0.02
0.06
0.03
0.09
0.10
0.22

pinst b[%]
0.24
0.06
0.06
0.05
0.09
0.04
0.19

σuinst [%]
0.05
0.03
0.06
0.05
0.08
0.03
0.19

σpinst c[%]
0.22
0.04
0.08
0.06
0.12
0.10
0.29

Central wavelength of the band.
√
2
Amplitude of the instrumental polarization; pinst = √qinst+ u2inst .

σq2inst + σu2 inst .

Fluctuation of the instrumental polarization: σpinst =Table 6. Variation of instrumental polarization in the field of view.

Band
RC
J

Averagequ-0.01 -0.03
0.08 -0.06

Standard deviation
σq
σu
-0.06
0.08
0.09
0.14

5.5.2 Polarization eﬃciency
We measured polarization eﬃciency of the optical train by observing a star through a broadband wire-gridlinear polarizer (Edumund Optics, Inc.; #68-751; > 1000 contrast at 0.5–3 µm), namely an artiﬁcially 100 %polarized star, by imaging polarimetry. Five stars with a color ranging from B − V ∼ 0.0 to 1.3 were observed.
Apparent polarization degrees for the 100 % polarized stars deduced with the formulae in Section 5.4 have atendency to decrease at shorter wavelengths, reaching about ∼ 38 % at B-band. This strong depolarization,
especially at the shorter wavelength, is probably due to birefringence of an YLF crystal of the Wollaston prism,
by which cross talk between linear polarization and circular polarization occurs.
Observed polarization parameters q, u, and p of a celestial object should be ﬁnally divided by the measured
polarization eﬃciency to deduce a real polarization degree of the object. Measured polarization eﬃciency ineach band presents ﬂuctuation due to the color diﬀerence of the observed stars (σpWG in Table 7), whichcauses an error ϵpe = 100(σpWG /pWG ) [%] as a ratio to the observed polarization degree after correcting the
(a)
0.4

(b)

(c)

0.2

B
V
R
I

0.0

0.5

0.2

0.4
0.3

0.0

p_inst [%]

u [%]

u [%]

-0.2

-0.4
-0.2
-0.6
-0.4
-0.8

-0.6

-0.4

-0.2
q [%]

0.0

0.2

-0.8
-0.4

0.2
0.1
0.0

J
H
Ks

-0.1
-0.2

0.0

0.2
q [%]

0.4

0.6

-0.2
0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2
um

Figure 12. Instrumental polarization and its fluctuation among various telescope positions. (a) Optical bands, and (b)near-infrared bands. (c) Averaged amplitude of the instrumental polarization and its fluctuation (error bars).

polarization eﬃciency. The error ϵpe is 0.2–1.0 % at between RC and H band, 1.0–1.5 % at V and Ks bands,
and ∼ 2 % at B band. Actual error by polarization eﬃciency correction is ϵpe /100 × pobs [%], where pobs [%]is an observed polarization degree of the target object. In almost cases for objects with a polarization degreeof a few percent, an error caused by the ﬂuctuation of the polarization eﬃciency is < 0.1 %.
Polarization eﬃciency measured by spectro-polarimetry is consistent with that of imaging polarimetry(Fig. 15(a)).
5.5.3 Position angle calibration
A position angle of the optical axis of a super-achromatic half-wave plate varies with wavelength. Figure 15(b)shows observed position angles of a star through a chromatic wire-gird polarizer with a constant position
angle of the 100 % linear polarization over the whole of observable wavelengths, by imaging polarimetry andMar. 27
Apr. 6
Apr. 140.4

q_inst [%]

0.2
0.0
-0.2
-0.4

u_inst [%]

0.4
0.2
0.0
-0.2
-0.4
0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

um

Figure 13. Instrumental polarization of spectro-polarimetry (q(λ), u(λ)) at three epochs.
6

0.6

R
J

5
0.4
4
0.2%
3

0.2

0.0

1

u[%]

ddec [arcmin]

2

0

-0.2

-1
-0.4

-2
-3

-0.6
-4

R
J

-5
5

4

3

2

1

0

-1

dRA [arcmin]

(a)

-2

-3

-4

-0.8
-5

-6

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

q[%]

(b)

Figure 14. Fluctuation of instrumental polarization in the field of view. (a) Polarization vectors in the field of view.
(b) Distribution of normalized stokes parameters.

.
Table 7. Measured polarization of a star through a wire-grid polarizer.

Band
B
V
RC
IC
J
H
Ks

λcenter [µm ]0.44350.54910.65340.7694
1.2485
1.63802.1455pWG a[%]
38.4
50.9
62.6
73.8
88.7
93.4
96.9

σpWG a[%]
0.8
0.8
0.6
0.5
0.2
0.1
1.1

θWG b[degree]
11.1
2.3
0.0
2.0
1.8
-1.5
-3.4

σθWG b[degree]
1.9
0.4
0.0
0.3
0.5
0.5
0.5

ϵpe c[%]
2.1
1.5
0.9
0.7
0.3
0.2
1.2

a

An average and standard deviation of measured polarization degrees of various stars
through a wire-grid polarizer.
b
An average and standard deviation of measured position angles of wire-grid stars.
c
An expected error ratio to an observed polarization degree of a target object after
correction of polarization eﬃciency. ϵpe = 100(σpWG /pWG ).

spectro-polarimetry. Variation of the position angle, caused by the wavelength dependency of the optical axisof the HWP plate, is within 15 degrees and consistent between imaging polarimetry and spectro-polarimetry.
The instrumental position angle against celestial coordinate, which should be corrected for the observed
position angle, is determined by measuring polarization position angles of strongly polarized standard stars
whose position angle has been known.15, 16 A typical accuracy of determination of the instrumental position
angle is within 0◦ .1.

5.6 Initial results
Figure 16 shows interstellar polarization spectra measured by imaging polarimetry and spectro-polarimetrycompared with the previous measurements in the literature.17

6. SUMMARY
We have developed an optical and near-infrared simultaneous instrument HONIR since 2007. In addition
to the existing imaging capability, we have now introduced spectroscopy and polarimetry capabilities. Everyfunction presents good performance in general with some issues to be improved aside. Much further evaluationof the performance of the instrument and its improvement are in progress.
(a)

(b)

1.0

14
12
theta [deg] (0 @ R-band)

0.8

p

0.6

0.4

0.2

0.0
0.4

10
8
6
4
2
0
-2

Spectro-polarimetry
Imaging Polarimetry
0.6

0.8

1.0

1.2

1.4

1.6

Wavelength [um]

1.8

2.0

-4
2.2

2.4

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

um

Figure 15. Polarization spectra of a star through a chromatic wire-grid polarizer. (a) Polarization degree and (b)Position angle (relative to RC -band).

(a)
6

(b)
5.0

HD150193
Cyg OB2 #11
Whittet+92

5HD29835
Whittet+92

4.0

4
p [%]

p [%]

3.0
3

2.0
2
1.0

1

0

0.0

180

40

HD29835
Whittet+92

160
30
PA [deg]

PA [deg]

140
120
100
80

20

10

60
40
0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

0
0.2

0.4

0.6

Wavelength [um]

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

um

Figure 16. Measured insterstellar polarization spectra by (a) imaging polarimetry and (b) spectro-polarimetry. Previous
measurements by Whittet et al.17 are also shown.

An improved readout system for the HgCdTe VIRGO-2K detector, which achieves a faster readout frame
rate, will be in operation12 in the near future. Installation of an oﬀset guider system and an additional
near-infrared arm (IR Arm #2) are also major goals of the development of the instrument.

ACKNOWLEDGMENTS
We are grateful to S. Sato, S. Sako, K. Okita, Y. Hirahara, M. Kino, N. Takahashi, M. Konishi, and K. Yanagisawa for helpful comments and kind cooperation. The development of the instrument has been supported inpart by Optical & Near-Infrared Astronomy Inter-University Cooperation Program, supported by the MEXT
of Japan. This research has been supported in part by the Grant-in-Aid for Scientiﬁc Research (23244030,
23340048, 26287031) from the JSPS and MEXT, Japan. Y.M., R.I., and K.T. are supported through the
JSPS (Japan Society for the Promotion of Science) Research Fellowship for Young Scientists. Evaluation of
performance of the optical elements was supported by Advanced Technology Center, National Astronomical
Observatory of Japan.

REFERENCES[1] Abdo, A. A., Ackermann, M., Ajello, M., Axelsson, M., Baldini, L., Ballet, J., Barbiellini, G., Bastieri,
D., Baughman, B. M., Bechtol, K., and et al., “A change in the optical polarization associated with a
γ-ray ﬂare in the blazar 3C279,” Nature 463, 919–923 (2010).
[2] Ikejiri, Y., Uemura, M., Sasada, M., Ito, R., Yamanaka, M., Sakimoto, K., Arai, A., Fukazawa, Y.,
Ohsugi, T., Kawabata, K. S., Yoshida, M., Sato, S., and Kino, M., “Photopolarimetric Monitoring of
Blazars in the Optical and Near-Infrared Bands with the Kanata Telescope. I. Correlations between Flux,
Color, and Polarization,” Publ. Astron. Soc. Jpn. 63, 639–675 (2011).
[3] Sasada, M., Uemura, M., Arai, A., Fukazawa, Y., Kawabata, K. S., Ohsugi, T., Yamashita, T., Isogai,
M., Nagae, O., Uehara, T., Mizuno, T., Katagiri, H., Takahashi, H., Sato, S., and Kino, M., “Multiband

Photopolarimetric Monitoring of an Outburst of the Blazar 3C 454.3 in 2007,” Publ. Astron. Soc. Jpn. 62,
645–652 (2010).
[4] Yamanaka, M., Kawabata, K. S., Kinugasa, K., Tanaka, M., Imada, A., Maeda, K., Nomoto, K., Arai,
A., Chiyonobu, S., Fukazawa, Y., Hashimoto, O., Honda, S., Ikejiri, Y., Itoh, R., Kamata, Y., Kawai,N., Komatsu, T., Konishi, K., Kuroda, D., Miyamoto, H., Miyazaki, S., Nagae, O., Nakaya, H., Ohsugi,T., Omodaka, T., Sakai, N., Sasada, M., Suzuki, M., Taguchi, H., Takahashi, H., Tanaka, H., Uemura,M., Yamashita, T., Yanagisawa, K., and Yoshida, M., “Early Phase Observations of Extremely Luminous
Type Ia Supernova 2009dc,” Astrophys. J. 707, L118–L122 (2009).
[5] Watanabe, M., Nakaya, H., Yamamuro, T., Zenno, T., Ishii, M., Okada, M., Yamazaki, A., Yamanaka,Y., Kurita, M., Kino, M., Ijiri, R., Hirao, T., Nagata, T., Sato, S., Kawai, T., Nakamura, Y., Sato, T.,
Ebizuka, N., Hough, J. H., and Chrysostomou, A., “TRISPEC: A Simultaneous Optical and Near-Infrared
Imager, Spectrograph, and Polarimeter,” Publ. Astron. Soc. Pac. 117, 870–884 (2005).
[6] Sakimoto, K., Akitaya, H., Yamashita, T., Kawabata, K. S., Nakaya, H., Miyamoto, H., Harao, T.,
Itoh, R., Matsui, R., Moritani, Y., Nakashima, A., Ohsugi, T., Sasada, M., Takaki, K., Ueno, I., Ui,
T., Urano, T., and Yoshida, M., “An optical and near-infrared multipurpose instrument HONIR,” in[Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series], Society of Photo-Optical
Instrumentation Engineers (SPIE) Conference Series 8446, 844673 (Sept. 2012).
[7] Nakaya, H., Komiyama, Y., Miyazaki, S., Yamashita, T., Yagi, M., and Sekiguchi, M., “New Focal Plane
Array Controller for the Instruments of the Subaru Telescope,” Publ. Astron. Soc. Pac. 118, 478–488(2006).
[8] Nakaya, H., Doi, Y., Kamata, Y., Komiyama, Y., and Miyazaki, S., “HyperSuprime: electronics,” Proceedings of SPIE 6269, 62693G (2006).
[9] Nakaya, H., “CCD Readout Electronics for Subaru Telescope Instruments,” Publ. Astron. Soc. Pac. 124,
485–493 (2012).
[10] Nakaya, H. and Sato, S., “Multi-array control system for a wide-wavelength observation,” Proceedings of
SPIE 3354, 368–372 (1998).
[11] Sako, S., Aoki, T., Doi, M., Ienaka, N., Kobayashi, N., Matsunaga, N., Mito, H., Miyata, T., Morokuma, T., Nakada, Y., Soyano, T., Tarusawa, K., Miyazaki, S., Nakata, F., Okada, N., Sarugaku, Y.,
and Richmond, M. W., “KWFC: four square degrees camera for the Kiso Schmidt Telescope,” in [Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series], Society of Photo-Optical
Instrumentation Engineers (SPIE) Conference Series 8446, 84466L (Sept. 2012).
[12] Ui, T., Sako, S., Yamashita, T., Akitaya, H., Kawabata, K. S., Nakaya, H., Moritani, Y., Itoh, R., Takaki,
K., Urano, T., Ueno, I., Ohsugi, T., Yoshida, M., Nakao, H., and Hashiba, Y., “Development of a newreadout system for the near-infrared detector of HONIR,” Proceedings of SPIE 9147, in this conference(2014).
[13] Perrin, M. D., Graham, J. R., and Lloyd, J. P., “The IRCAL Polarimeter: Design, Calibration, and Data
Reduction for an Adaptive Optics Imaging Polarimeter,” Publ. Astron. Soc. Pac. 120, 555–570 (2008).
[14] Kawabata, K. S., Okazaki, A., Akitaya, H., Hirakata, N., Hirata, R., Ikeda, Y., Kondoh, M., Masuda,S., and Seki, M., “A New Spectropolarimeter at the Dodaira Observatory,” Publ. Astron. Soc. Pac. 111,
898–908 (July 1999).
[15] Schmidt, G. D., Elston, R., and Lupie, O. L., “The Hubble Space Telescope Northern-Hemisphere gridof stellar polarimetric standards,” Astron. J. 104, 1563–1567 (Oct. 1992).
[16] Turnshek, D. A., Bohlin, R. C., Williamson, II, R. L., Lupie, O. L., Koornneef, J., and Morgan, D. H., “Anatlas of Hubble Space Telescope photometric, spectrophotometric, and polarimetric calibration objects,”
Astron. J. 99, 1243–1261 (Apr. 1990).
[17] Whittet, D. C. B., Martin, P. G., Hough, J. H., Rouse, M. F., Bailey, J. A., and Axon, D. J., “Systematic
variations in the wavelength dependence of interstellar linear polarization,” Astrophys. J. 386, 562–577(Feb. 1992).