Coronagraphs

Classical Lyot

Pupil Masks

Two pupil masks are currently available, in addition to “open” (no mask).

Coronagraph Pupil Masks
fwpupil Position	Description	abs. throughput	design file	scale in telescope pupil [m/pix]	scale at coronagraph pupil [mm/pix]
open	No mask, just the telescope pupil. Note: design file includes mask over bump.	100%	magMask.fits.gz	0.0067528	0.0093501
bump-mask	Undersized pupil, oversized central obscuration, oversized spiders, and mask over bump	86.75%	bumpMask.fits.gz	0.0067528	0.0093501
fat-spider	Same as bump-mask, but one extra-oversized spider. Intended for kernel-phase type WFS.

Focal Plane Masks

There are two chrome dots on glass plates. Note: optical densities are estimated from standard chrome.

Small spot: 272 um diameter. fwfpm position: lyotsm

lyotsm characteristics
lambda [um]	spot radius [lam/D]	opt. dens.
0.600	3.285	5.0
0.656	3.00	4.75
0.700	2.82	4.56
0.800	2.46	4.11
0.900	2.19	3.67
1.000	1.97	3.22

Large spot: 453 um diameter. fwfpm position: lyotlg

lyotlg characteristics
lambda [um]	spot radius [lam/D]	opt. dens.
0.600	5.47	5.0
0.656	5.00	4.75
0.700	4.69	4.56
0.800	4.10	4.11
0.900	3.65	3.67
1.000	3.28	3.22

Lyot Stops

We have experimented with three Lyot stops with different characteristics. The labels “Large” and “Small” here refer to the clear aperture, i.e. large means a large clear aperture and therefore higher throughput. In practice we have used only LyotLg1 for observations. LyotSm is presently removed from the instrument.

LyotLg1
parameter	value	notes
fwlyot Position	LyotLg1
Throughput	63.8%	not incl. FPM
Image
Outer Diam.	7.020 mm	at 9 mm pupil plane
Inner Diam.	4.620 mm
Spider Width	0.383 mm
Bump Diam	1.149 mm
FITS file	lyotMaskLarge1.fits.gz
FITS scale at M1	0.0067528	m/pixel
FITS scale at fwlyot	0.0093501	0.0093501
DXF File	LyotStop_large1.DXF

LyotLg2
parameter	value	notes
fwlyot Position	LyotLg2
Throughput	57.3%	not incl. FPM
Image
Outer Diam.	8.041 mm	at 9 mm pupil plane
Inner Diam.	3.600 mm
Spider Width	0.383 mm
Bump Diam	1.149 mm
FITS file	lyotMaskLarge2.fits.gz
FITS scale at M1	0.0067528	m/pixel
FITS scale at fwlyot	0.0093501	0.0093501
DXF File	LyotStop_large2.DXF

LyotSm
parameter	value	notes
fwlyot Position	LyotSm	removed from instrument
Throughput	33.35%	not incl. FPM
Image
Outer Diam.	7.800 mm	at 9 mm pupil plane
Inner Diam.	3.800 mm
Spider Width	0.383 mm
Bump Diam	1.149 mm
FITS file	lyotMaskSmall.fits.gz
FITS scale at M1	0.0067528	m/pixel
FITS scale at fwlyot	0.0093501	0.0093501
DXF File	LyotStop_small.DXF

PIAA Classical Lyot Coronagraph (PIAACLC)

Phase-induced amplitude apodization (PIAA) optics reshape the beam in the pupil and focal planes, enabling more starlight suppression at low angular separations and higher throughput at large angular separations.

Inverse apodization optics after the focal plane mask correct for off-axis field effects to remove comatic distortions on companions. Inverse PIAA optics are identical to forward PIAA optics. Optical path according to naming convention is PIAA0->PIAA1->fpm->iPIAA1->iPIAA0.

The process of pupil remapping before and after the focal plane is illustrated in Guyon et al 2010: