LDT Facility Instrument =E2=80=93 Available Full-Time, Remo=
te Available
Mounting Port: Instrument Cube =E2=80=93 Port C (=
large)
Manual: DeVeny User Manual v1.8 (16 Nove=
mber 2023)
Additional Information: DeVeny Gratings / Filters / Lamps,&nbs=
p;DeVen=
y_Ops_Appendix.tar
Instrument=
Scientist: Tom Bida (tbida at lowell dot edu)
The DeVeny Spectrograph is a moderate resolution optical spectrograph wo=
rking between 3200 =C3=85 and 1 =C2=B5m. R ranges between 500 and 400=
0 depending upon the grating used. The DeVeny spectrograph was built =
and known at Kitt Peak National Observatory (KPNO) as the KPNO White Spectr=
ograph, and had a long career at the 36" and 84" telescopes there before be=
ing retired. Lowell Observatory acquired the spectrograph from KPNO o=
n indefinite loan in 1998. A new CCD camera was built for it, and the=
instrument was further modified for installation on the 72=E2=80=9D Perkin=
s telescope in 2005. Following 8 years of service there, it was remov=
ed in 2013 for upgrades for installation on the LDT. The DeVeny spect=
rograph has been in use on the instrument cube since February 2015.
There are currently 10 gratings available for use. Five have recently been made available =
thanks to a long term loan from KPNO and have not yet been well characteriz=
ed at the LDT. Note that swapping the grating remains a daytime opera=
tion to minimize risk.
What's New
16-November-2023,&nb=
sp; DeVeny User Manual v1.8 Released
10-May-2022, D=
eVeny User Manual v1.7.1 Released
14-Nov-2021, D=
eVeny Image Quality Issue: Stellar PSF=E2=80=99s show an ell=
iptical/oblique component that hasn=E2=80=99t been resolved yet.
- The ellipticity source is likely =
from something errant in the optical path from the DeVeny fold mirror to th=
e slit, as it appears in both slitviewer and spectrograph images.
- Pointing and the imaged slit loca=
tions have not changed, meaning the slitviewer assembly has not moved.
- The orientation of the ellipse lo=
ng axis is generally fixed, not changing wrt rotation angle, and thence tel=
escope pupil.
- There may be rotational dependenc=
e, with images improving at rotation angles around 90 and 270 deg. Th=
is is mostly based on data taken in poor seeing, at about 60 deg El. =
See the attached file. For the curious this has the DeVeny at 6 O=E2=
=80=99clock and 12 O=E2=80=99clock when viewed from behind Cass, with the D=
VY fold mirror stage motion more parallel to the gravity vector.
- The image shape is not astigmatic=
in the sense that the orientation does not rotate pi/2 when going through =
focus. When in focus the images are flat-topped, which looks like mis=
-tracking (unlikely given the exposure times) or high-amplitude and frequen=
cy vibration or motion.
- So the most likely culprit would =
seem to be the fold mirror mount. It is vaguely possible that the har=
d-stop incident caused this though not clear how. In any case an insp=
ection of the assembly is the next thing to do. The earliest opportun=
ity for this is the week of Nov 29, and POETS will need to come off tempora=
rily.
- In the meantime, if practical, ob=
servers could consider setting the sky PA such that the rotator position is=
in the vicinity of 90 or 270 deg. This obviously won=E2=80=99t help =
the normal fixed tracking at 180 deg. If focused, objects should have=
minimal losses for slit widths > 1.5 arcsec, depending on seeing.
29-Apr-2021, Or=
der-Blocking Filters: The GG495 filter has been removed from=
the instrument; replacement plan TBD.
- Order-blocking filters GG420 and OG5=
70 are still in service.
Instrument Quick Facts:
- Spectral Channel CCD=20
- Detector: e2v CCD42-10 deep depletion device: 2048=C3=97512 13.5 =C2=B5=
m pixels (27.65 mm =C3=97 6.91 mm)
- Slit Length: 2.5=E2=80=B2 =E2=80=93 Pixel Scale: 0.34=E2=80=B2=E2=80=B2=
/pixel (spatial direction, unbinned)
- Gain: 1.52 e =E2=88=92/ADU =E2=80=93 16-bit ADC; Full-Well: =E2=88=BC 1=
00k e =E2=88=92
- Read Noise: 3.2 ADUs, about 4.9 e =E2=88=92
- Typical bias level: =E2=88=BC 2370 ADU (ambient temperature dependent)<=
/li>
- CCD Normal Operating Temperature: =E2=88=92110=E2=97=A6C
- Linearity: Linear to 97% of saturation (=E2=88=BC 63, 500 ADU)
- Readout Time: 8 s (unbinned)
- Dark Current: 4.5 e =E2=88=92/h =3D 0.0013 e =E2=88=92/s
- Fringing: 1-3% fringe amplitudes, redward of 8000 =C3=85
- Slit Viewing Camera=20
- Model: Lodestar X2 by Starlight Xpress
- Pixel Scale: 0.253"/pixel (binned 2 =C3=97 2)
- Image Size: 376 =C3=97 290 pixels
- Field of View: 95" =C3=97 73"
- Grating Complement=20
- Collection of 10 gratings that were used with the KPNO White and Gold s=
pectrographs
- 128 =C3=97 154 mm plane reflection gratings
- Range of spectral resolution from R =E2=88=BC 500 =E2=88=92 4000
- 1st order blazed gratings
- Motorized grating tilt angle stage to select central wavelength on the =
CCD
- See DeVeny Gr=
atings / Filters / Lamps for specifications
- Calibration Lamps=20
- For wavelength calibration, there are four remotely-controlled AC-power=
ed pencil-style gas discharge arc lamps:=20
- Neon (=E2=88=BC 5800 =E2=88=92 8600 =C3=85)
- Argon (=E2=88=BC 6900 =E2=88=92 9700 =C3=85)
- Mercury (=E2=88=BC 3300 =E2=88=92 5800 =C3=85)
- Cadmium (=E2=88=BC 3200 =E2=88=92 5500 =C3=85)
- The primary dome flat field calibration lamps are on the top ring of th=
e secondary mirror support structure.
- Data Reduction Software=20