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Plans for a
1.8 m Adaptive
Optics Telescope
and a
1.1 m Wide Field
Telescope at PARI
J. D. Cline, M. W. Castelaz
(Pisgah Astronomical Research Institute)
AAS 200th meeting, Albuquerque, NM, June 2002
Wednesday, June 5, 2002, 10:00am-7:00pm.
Session 64.08
Radio and Optical Observatories
at the Pisgah Astronomical
Research Institute (PARI)
 PARI is
 a not-for-profit public foundation
 dedicated to providing research
and educational access to radio
and optical astronomy for a
broad
cross-section of users
 PARI is located on 200 acres in the
Pisgah Forest west of Asheville,
NC
 The site is relatively free of light
and radio interference
N
26-m East
Optical
Ridge
26-m West
12-m
 For use by Visiting and Resident
scientists:
 Two 26-m radio telescopes, one
12.2 m radio telescope, one
4.6 m radio telescope, several
dedicated optical telescopes
 Locations for future telescope
development
 Lab and Office Space
The Radio Telescopes
Two 26-m radio telescopes with 1.42, 4.8, 6.7,
and 12.2 GHz receivers are shown here. The
telescopes slew, set, guide, and track. They can
be operated together (300 m near E-W baseline)
or separately.
26 m West
26 m East
The 4.6-m radio telescope feeds include 1.42,
4.8, 6.7, and 12.2 GHz. This telescope is used
for education/public outreach through the
School of Galactic Radio Astronomy (SGRA;
this meeting Session 47.03).
4.6-m
The 12.2-m antenna is
available for consortium
sponsorship and use at
frequencies up to 60 GHz.
12.2-m prime focus feed
The PARI Optical Ridge
Aerial Image of the Optical Ridge. At an altitude of 910 m,
the ridge runs East-West with steep sloping sides to the North
and South. The highest point on the horizon is 5 degrees, with
an average of 2 degrees. The 1.8 m and 1.1 m locations are
shown (red), along with existing telescopes (blue).
Lat: 35d 11.828m N,
Long: 82d 52.346m W
Altitude: 934
Telescopes Other Than the 1.8 m and
1.1 m on the PARI Optical Ridge
• Questar (18 cm, f/14.3, 81.2
arcsec/mm), 2k x 2k 13 um/pix CCD
36 arcmin FOV), UBVRI filters
• Solar/Lunar 12.7 cm telescope with
SBIG STV, live video feed to Internet
• All-sky fisheye 24 hour telescope
• Polaris continuous photometry
telescope
• Atmospheric Seeing/Transparency 24hour monitoring 12.7 cm telescope
and SBIG STV
• 0.2 m telescope for Galactic Plane
Survey, operating since October 2000
• 0.28 m telescope for gamma ray burst
afterglow
Plans for a
1.8 m Adaptive Optics Telescope
•
4 cm Thick Fused Silica Adaptive
Optics Mirror
•
F-Ratio = 1.5
•
Spherical Surface Figure
•
Wavefront Errors = l/50 (l/30 allotted to
steady state operational dynamics)
Characteristics of the 1.8 m Adaptive
Optics Primary Mirror Cell
•
Three Flexural Supports
•
40 Actuators to a Back Structure
•
Cell Weight = 1400 lbs
•
Mirror Weight = 550 lbs
Mirror
Glass
Block
Actuator
One of the
actuators is
shown. The
back of the
mirror is
coupled to
the actuator
through a
glass block
for thermal
insulation.
Telescope Definition
Telescope definition is an open issue and
depends on input from the astronomical
community. Suggestions for use and design
beyond those listed below are welcome.
Please feel free to contact us (e-mail
[email protected]) or leave a note here for us to
contact you..
Telescope Uses and Designs
under consideration:
 Large Field Prime Focus Camera for
 Gamma Ray Burst Afterglow
Photometry
 Supernova Search
 Near Earth Object Search
 LIght Detection And Ranging (LIDAR) for
atmospheric research
 High Resolution (0.01 A/pix) Spectrometer
Plans for a
1.1 m Wide Field Telescope
The telescope will be field corrected
prime focus camera with a 1.73 degree
diameter field of view.
 The primary mirror is a 1.1 m f/4.4 fused
quartz (honeycomb) substrate, coated
 Scale 41.5 arcsec/mm
 Conic constant –1.900 +/- 0.005
The Primary Mirror
Characteristics of the Field
Corrector at Prime Focus
We have set the condition that image quality in the
focal plane will not be limited by telescope optics,
rather by seeing and mechanical effects. To meet
this condition, a 3-element field corrector, will
be used to focus a 15 cm diameter focal plane.
The table below summarizes the properties of the
corrector. All lenses are made of BK7 glass. Lens
1 is nearest to the primary mirror at a distance of
391.35 cm, and Lens 3 is 7.16 cm from the focal
plane.
Lens
Curvature of
Lens
Radius of Diameter
Curvature
(cm)
(cm)
Distance
from
Previous
Lens
(cm)
1
Simple positive
convex
225.49
34.113
---
2
Achromatic
convex-concave
70.58
29.614
70.411
3
Simple positive
convex-plane
80.07
7.163
17.462
Schematic Showing the 3-Element
Field Corrector
Prime Focus Optical Layout
The prime focus is formed by three lenses comprising a
corrector. Shown here is the third of the lenses, along with
the shutter, and two guide cameras. Light in the center 10
cm square field (1.15o) is the science field. Two guide
cameras are located 180o apart in the fields formed by the 15
cm diameter field and chords along the science field. A third
chord area will hold several fiber optics for a future
spectrograph.
 With the field corrector, the RMS wavefront error is
less than the diffraction limit to the edge of the 15
cm focal plane.

Figure below shows spot diagrams within 1 arcsec
boxes on the optical axis and at the edge of the 15
cm focal plane, respectively.
 The image size approaches one arcsecond at the very
edge of the field of view.
 The science field is a 10 cm square, so the optics
produce less than one arcsecond images in the entire
science focal plane.
Spot diagrams based on the prime focus corrector for the
1.1 m telescope. The boxes are 24 microns, or 1 arcsec
on a side. a) The spot diagram on the optical axis, b) the
spot diagram 7.65 cm from the optical axis.
Telescope Assembly
The open structure optical tube telescope
mount we plan to use is the DFM Engineering
equatorial mount, shown above. The DFM
1.27 m polar axle and support telescope mount
will be customized for the 1.1-m mirror.
Atmospheric Seeing and
Transparency Measurement
Instrumentation
Weather Station: probes for temperature, humidity,
pressure, wind, rain.
All-Sky Camera: Live video of the sky through a fisheye
lens.
Polaris Telescope:
• Continuous 24-hour monitoring of atmospheric
transparency and seeing conditions
• 0.25 m telescope with CCD plus UBVRI filters;
81 arcsec/mm or 0.60 arcsec/pixel
Bright Star Telescope:
• Robotic 12.7 cm f/10 telescope with CCD
• Measures flux of bright (V<2.5) stars 24 hours a day
• Software automatically points telescope, images,
does photometry and outputs stellar magnitude and
sky brightness
• outputs seeing measure based on area bright
stellar image covers on CCD chip
• outputs transparency measure based on ratio of
stellar/sky surface brightness.
The Bright Star
Telescope is
seen in its clear
dome
The information from the Bright Star Telescope and the
other seeing/transparency instruments build a database of
atmospheric conditions accessible to other telescopes of
the PARI Observatories and observers using the telescopes
remotely.
We are open to new consortia to develop
projects at PARI, or an established
consortium to enhance their research and
education opportunities with projects at
PARI including development and support of
existing or new telescopes at PARI.
Contact:
Don Cline ([email protected])
Or
Michael Castelaz ([email protected])
Pisgah Astronomical Research Institute
1 PARI Drive
Rosman, NC 28772
Internet: www.pari.edu
Office: 828-862-5554
FAX: 828-862-5877
Internet: www.pari.edu