ISIS offers a wide variety of observing setups as it allows the user to choose the central wavelengths, slit width, dichroic, on-chip binning and detector readout speeds, and it offers distinct observing modes such as long-slit spectroscopy and spectro- and imaging-polarimetry, with a choice of standard and electron multiplying, frame-transfer detectors. Therefore to manage overheads of
multiple setups during service-mode observing the number of setups offered is restricted. Nevertheless, non-default settings involving dichroics, central wavelengths, slit width, read speed and binning are allowed if their need is justified scientifically in the service application. Additional overheads involved in such non-standard setups will be accounted to the programmes requesting them.
Imaging polarimetry and observations requiring the QUCAM electron multiplying, frame-transfer CCDs are
in general excluded from the ISIS service programme because of the greater overheads involved
and the limited opportunity to carry out such observations.
Spectropolarimetry observations, however, can be requested. They will be attempted whenever (1) a
spectropolarimetry-trained observer is rostered, and (2) there is
enough time to carry out the extended day-time set-up. The
latter condition may not be satisfied e.g., on winter
service nights when ISIS has just been mounted on the
telescope. The probability of completing spectropolarimetry proposals
is therefore not as high as for normal ISIS service proposals.
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2. ISIS default settings
The following settings are the default for service observations:
- Data will be obtained in slow read-out mode.
- Detector window will be [585:1550,1:4200] in the blue arm and [555:1520,1:4200] in the red arm. The slit length, defined by these default windows, is 3.2 arcmin (blue) and 3.5 arcmin (red).
- Default on-chip binning is 1x1 in both arms.
- The 5300 Barr dichroic will be in place.
- The GG495 order sorting filter will be in the red light path.
- The Red+ and EEV12 CCDs for the red and blue arm, respectively, will be in use.
- The standard central wavelengths are those listed in the available ISIS offered observing modes.
- The default position angle of the slit is parallactic unless otherwise specified in the target list.
Exceptions to these default settings will be considered if justified in the service proposal.
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3. Observing modes offered
The tables below list the gratings and central wavelengths offered in the red and blue arms on service nights, along with spectral dispersions and wavelength ranges. Notice that the response of the system+dichroic should also be taken into account (wavelength ranges in parentheses).
|
ISIS red arm observing modes (with REDPLUS)
|
|
Grating
|
Central
wavelength (Å)
|
Dispersion
(Å/mm)
|
Dispersion
(Å/pix)
|
Total Spectral
range (Å)
|
Unvignetted range
(2400 pixels)
|
50% unvignetted range
(3285 pixels)
|
|
R158R
|
7500
|
121
|
1.81
|
3735:11265 (5300:10000)
|
5294:9706 (5300:9706)
|
4481:10519 (5300:10000)
|
|
R316R
|
6450
|
62
|
0.93
|
4521:8379 (5300:8379)
|
5320:7580
|
4903:7997 (5300:7997)
|
|
R316R
|
8650
|
62
|
0.93
|
6721:10579 (6721:10000)
|
7520:9780
|
7103:10197 (7103:10000)
|
|
R600R
|
5900
|
33
|
0.49
|
4873:6927 (5300:6927)
|
5299:6501
|
5077:6723 (5300:6723)
|
|
R600R
|
7000
|
33
|
0.49
|
5973:8027
|
6399:7601
|
6177:7823
|
|
R600R
|
8200
|
33
|
0.49
|
7173:9227
|
7599:8801
|
7377:9023
|
|
R600R
|
9200
|
33
|
0.49
|
8173:10227 (8173:10000)
|
8599:9801
|
8377:10023
|
|
R1200R
|
5600
|
17
|
0.26
|
5072:6127 (5300:6127)
|
5291:5909
|
5177:6023 (5300:6023)
|
|
R1200R
|
6200
|
17
|
0.26
|
5672:6727
|
5891:6509
|
5777:6623
|
|
R1200R
|
6800
|
17
|
0.26
|
6272:7327
|
6491:7109
|
6377:7223
|
|
R1200R
|
7400
|
17
|
0.26
|
6872:7927
|
7091:7709
|
6977:7823
|
|
R1200R
|
8000
|
17
|
0.26
|
7472:8527
|
7691:8309
|
7577:8423
|
|
R1200R
|
8600
|
17
|
0.26
|
8072:9127
|
8291:8909
|
8177:9023
|
|
R1200R
|
9200
|
17
|
0.26
|
8672:9727
|
8891:9509
|
8777:9623
|
|
ISIS blue arm observing modes (with EEV12)
|
|
Grating
|
Central
wavelength (Å) |
Dispersion
(Å/mm)
|
Dispersion
(Å/pix)
|
Total Spectral
range (Å)
|
Unvignetted range
(2820 pixels)
|
50% unvignetted range
(3670 pixels)
|
|
R158B
|
4500
|
120
|
1.62
|
1182:7817 (3200:5300)
|
2216:6784 (3200:5300)
|
1528:7472 (3200:5300)
|
|
R300B
|
4500
|
64
|
0.86
|
2730:6269 (3200:5300)
|
3282:5718 (3282:5300)
|
2915:6085 (3200:5300)
|
|
R600B
|
4000
|
33
|
0.45
|
3087:4912 (3200:4912)
|
3372:4628
|
3182:4818 (3200:4818)
|
|
R600B
|
4500
|
33
|
0.45
|
3587:5412 (3587:5300)
|
3872:5128
|
3682:5318 (3682:5300)
|
|
R1200B
|
3600
|
17
|
0.23
|
3130:4070 (3200:4070)
|
3277:3923
|
3179:4021 (3200:4021)
|
|
R1200B
|
4250
|
17
|
0.23
|
3780:4720
|
3927:4573
|
3829:4671
|
|
R1200B
|
4900
|
17
|
0.23
|
4430:5370 (4430:5300)
|
4577:5223
|
4479:5321
|
The unvignetted spectral range of the H2400 grating is 304Å and its dispersion is 0.11Å/pixel.
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Basic calibrations (biases, tungsten flats
and CuAr-CuNe arcs) will be obtained by default in the afternoon/morning for each observing setup used during the service night, as well as one arc per target during the night.
Additional calibrations (e.g., flux standards, radial velocity standards solar analogue stars, more frequent arcs) should be requested explicitly in the
proposal, and they will be accounted to the total time requested.
