Table for Grism Selection　　　   　Update: Oct 26, 2003

It is necessary to select the most suitable grism according to the wavelength resolution and sensitivity required.

General Notes:

1.       The grisms shown in the blue panels below are ready for open-use. Others are being tested or under fabrication.

2.       Spectral resolution (R = l/dl) is almost proportional to the slit width, w, if w is greater than 0.2". In the following table, w = 0.4" is adopted. Generally, wider slit degrades the spectral resolution, but raises the sensitivity when CCD binning is properly done along the wavelength direction.

Grism name

Links to

figures of

efficiency,

etc.

Lines or

Grooves

(mm-1)

Order

Dispersion
(@5500A)

(A/pix)

Center
WL

(A)

Spectral
Resolution

@0.4" slit

Order Cut
Filter

Wavelength
Coverage

(A)

0 th
order?

2 nd order?

Targets/Comments

Very low

Efficiency

Design

Drawing

Holder

75

1

5.46

6500

250

SO58

5800-10000

YES

NO

Red MOS survey even @ >9400A

SY47

4700-9400

YES

YES

Red MOS survey @ 4700-9400

L600

3650-6000

YES

YES

Blue MOS survey

LC50

3650-6000

YES

YES

Blue MOS survey even @<3500A

Low

Efficiency

Design

Drawing

Holder [a][b]

 [1][2][3][4]

150

1

2.72

6500

500

SY47

4700-9400

NO

YES

Red Low disp.

SO58

5800-10000

NO

NO

No 2nd order contami. even @ >9500A

L600

3650-6000

NO

YES

Blue Low disp

LC50

3300-6000

NO

YES(weak)

Sensitive even @ <3500A

Middle Blue

Efficiency

Throughput1

Throughput2

Design

Drawing

Holder

300

1

1.34

5500

1000

SY47

4700-8400

NO

YES

·   Red Mid disp

·   Higher sens. than 300R @ <7800A

·   >8400A out of CCD

SY47

offset slit

4700-9400

NO

YES

Larger spectral coverage

O58

5800-10000

NO

NO

·   Red Mid disp

·   No 2nd order contami. even @ >9500A

L600

3650-6000

NO

YES

Blue Mid disp

LC50

3300-6000

NO

YES(weak)

Sensitive even @ <3500A

none

3300-8300

NO

YES

Heavy contami. By 2nd order at >~7000A

Middle Red

Efficiency

Throughput1

Throughput2

Throughput3

Design

Drawing

Holder

300

1

1.34

7500

1000

SY47

4900-9500

NO

YES

·   Red Mid disp.

·  Higher sens. than 300B @ >7800A

·   4700-4900A out of CCD

O58

5800-10000

NO

NO

No 2nd order contami. even @ >9500A

2

0.67

3900

2000

L600

3650-5250

NO

---

·         Higher sens. than 300B 2nd

·         Highest spec. res.

L600

offset slit

3650-5950

NO

---

LC50

3300-5250

NO

---

Sensitive even @ <3500A

Grism name

Links to

figures of

efficiency,

etc.

Lines or

Grooves

(mm-1)

Order

Dispersion
(@5500A)

(A/pix)

Center
WL

(A)

Spectral
Resolution

@0.4" slit

Order Cut
Filter

Wavelength
Coverage

(A)

0 th
order?

2 nd order?

Targets/Comments

High 650

 

(Note 1)

Throughput

Design

Prism Drawing

Holder [1][2]

 [3][4][5][6]

665

(VPH)

1

0.61

@average

6500

2500

SY47

5300-7700

NO

NO

 

SY47

offset slit

5950-8350

NO

NO

 

2

0.28

@4000A

 

3500

L600

offset slit

3650-4350

NO

---

 

LC50

3300-4350

NO

---

 

High Echelle

 

(Note 2)

Efficiency

Throughput

Design

Drawing

Holder [1] [2]

175

(Echelle)

2

-0.98

@9300A

9720

2500

Cross Disp.

7900-10000

NO

---

 

SDSS-z’

8300-10000

NO

---

 

I

offset slit

7300-8700

NO

---

 

3

-0.63

@6600A

6550

2500

Cross Disp.

5400-7900

NO

YES

 

I

7300-7900

NO

YES

 

R

5900-7100

NO

YES

 

4

 

4980

 

Cross Disp.

4200-5900

NO

YES

 

5

 

4040

 

Cross Disp.

3600-4600

NO

YES

 

High 435

(Note 1)

Throughput

Holder [1][2]

 [3][4][5][6]

 

(VPH)

1

0.376

4000

4000

-

3800-5250

NO

NO

Being tested

Offset

4200-5650

NO

NO

Being tested

High 520

Efficiency

Holder [1][2]

 [3][4][5][6]

 

(VPH)

1

 

5200

~2500

-

 

 

 

Under fabrication

Offset

 

 

 

Under fabrication

Very High

800

Efficiency

Drawing

Prism drawing

Holder [1][2]

 [3][4][5][6]

1324

(VPH)

1

 

8000

~5000

 

7300-8700

 

 

Being tested

Very High

950

(Note1)

Efficiency

Throughput

Drawing

Prism drawing

Holder [1][2]

 [3][4][5][6]

1095

(VPH)

1

0.352

9500

6000

-

8860-10200

 

 

Being tested

Grism name

Links to

figures of

efficiency,

etc.

Lines or

Grooves

(mm-1)

Order

Dispersion
(@5500A)

(A/pix)

Center
WL

(A)

Spectral
Resolution

@0.4" slit

Order Cut
Filter

Wavelength
Coverage

(A)

0 th
order?

2 nd order?

Targets/Comments

 

Note

1.                  The image position shifts along slit-length direction (= orthogonal to dispersion direction) by +16, +222, -190 pixels for High 435, High 650 and Very high 950 grisms, respectively. (Shift direction is positive when it is from CCD chip1 to chip 2.)

2.                  The dispersion direction of the High Echelle grism is opposite. Therefore, the value of the dispersion is negative.