... Contamination on optical surfaces degrades the throughput of an optical system. ... Contamination is particularly pernicious on the unprotected aluminum that is commonly used on the large first-surface mirrors of reflecting telescopes. ... During that period, the covers of their protective cases is opened whenever the 3.5-m telescope primary mirror cover is opened for nighttime observing. ... CO2 clean exposed mirrors in SS case. ... Light scattering measurements performed on cleaned mirrors. ...
... Operating at a wavelength of 10 ?m, it produces a 135њx135њ image with a resolution of 0.9њ. ... The clouds move from the west-southwest. ... At the same time as the IR images, visible light images were taken with an Apple Computer QuickTake electronic camera. ... At 1540 MDT, the large central cloud is visible in both images. At 1544 MDT, a distinctive cloud is apparent near the center in the visible image and right of center in the IR. The performance of the SDSS cloud scanner is excellent. ...
... The very demanding goal of 50 milliarcseconds root-mean-square (mas RMS) for the astrometric precision of the Sloan Digital Sky Survey implies that focus and collimation motions of the secondary must be very smooth. The Apache Point Observatory 3.5-m telescope secondary is a hot-gas-fusion borosilicate lightweight (25% of solid) mirror. ... Differential rotation provides tilt motions. ... Also, we made measurements with the indicators sensing the motion of the whiffletrees near actuators 1 and 2. ...
... The plug-plates of SDSS project are responsible for locating the optical-fiber plugs spatially and for defining the plug tilt with respect to the surface of best focus. ... Approximately 700 holes will be drilled in each plate. ... Histogram of the hole diameter for dv100. ... The hole tilt as a function of radius is compared to the ideal tilt from the optical design (kent005) and to the finite element model of the plug-plate in its drilling fixture (drl42) is shown in Figure 5 and Figure 6 . ...
... Drilling comments . Plate measurements . ... The plug-plates of SDSS project are responsible for locating the optical-fiber plugs spatially and for defining the plug tilts normal to the fiber axis. ... Approximately 700 holes will be drilled in each plate. ... Histogram of the x location error for ke100. ... In the absence of deformation of the plate during drilling or measurement, it would appear that either measurement or drilling machine error is the source of the scale difference. ...
... Cell depth measurements . Back-plate hole measurements . ... On May 3, 1994 at the Optical Sciences Center at the University of Arizona, measurements of cell depths and locations of the back-plate holes were made. ... Figure 1: Cell labels and coordinate system for the 2.5-m primary mirror. ... This is within 3% of the design value. ... These are plotted against x. Figure 4: Residual cell depths after removing the design radius of curvature of the back-plate and the mean cell depth. ...
... Plates and Drilling . ... We drilled 22 plates. The plates were 3.5" diameter 1/8" thick disks of aluminum. 50 holes were drilled in each test plate, 10 each in five concentric circles. ... Five plates (#12-16) were drilled using a carbide spade drill. ... The spade drills were shorter for the current tests, which we thought might improve position accuracy and reduce diameter variation; but the twist drills had the same geometry as in the 3/93 tests, so should have yielded similar results. ...
... Each ferrule will be used to plug approximately 300 holes. We must be sure the ferrules will not wear excessively during use; 1 mil reduction in diameter of a ferrule is enough to reduce light throughput by approximately 1%. ... Stainless steel ferrules offer lower precision (which will lose us approximately 1/2 to 1% light compared to ceramic), but they are relatively inexpensive, readily available with the hole diameter we require, and immune to cracking. ... Hence the wear was not very deep. ...
... Plates and Drilling . ... Results . ... In January of 1992 we drilled and measured a set of test plates testing several techniques including drilling with a carbide twist drill and drilling followed by reaming [R. Owen, et al., unpublished]. ... The test plates were 3.5" diameter 1/8" thick disks of aluminum. 50 holes were drilled in each test plate, 10 each in five concentric circles. ... This diameter was the optimal value for our plug plates determined from the 1/92 drilling tests. ...
... Holes in the plug plates for the Sloan Digital Sky Survey must be positioned and sized accurately. We tested several techniques by drilling holes in a number of test plates and measuring the characteristics of each hole. ... Four different kinds of drill bit were used, two plates per type of bit, for a total of eight test plates. ... Plate 1: Speed Test . ... Based on the drilling tests, we can hold hole diameter error to 15 ?m RMS (likely better if we can get bit-to-bit variation down). ...
... However, focal plane curvature is such that an attempt must be made to approximately place the ends of the optical fibers feeding the spectrographs on the best focal surface rather than simply a plane. ... We deform the plate during drilling so that all the holes can be drilled with their axes parallel. ... The mandrel is the shape that the plate should have for drilling if all holes are drilled with their axes parallel and if the plate is deformed to match the best focal surface in the telescope. ...
... This report examines the mechanical properties of a cylindrical plug held into a cylindrical hole by a ribbed plastic sleeve of uniform cross-section (figure 1). ... Figure 1: ribbed platic sleeve The plug is entirely retained by friction between the ribs and the plug and hole. ... is the coefficient of static friction and is the normal force of the plug (or hole) on each rib. Using to denote the stress on a compressed rib, the retention force due to one rib is: . ...
Sloan Digital Sky Survey Telescope Technical Note 19910801 . ... It has long been apparent that an all-sky picture of clouds over an observatory site and available in near real-time would be a great benefit to personnel using a telescope. ... We have anecdotal evidence from J.T. Williams of MMTO and David Westfall, formerly of CFHT and now of New Mexico Institute of Mining, that video-rate 10 micron cameras are very effective at imaging clouds. ... The focal length of the mirror is 25 mm. ...
... CREO plans to produce an optical tape storage system with a capacity of 1000 GBytes per tape. ... The drive fits in one rack and average power consumption is 1000 W single phase. ... Hence the drive will just do the job if we store raw data, and with a moderate amount of data compression before storage, we will get a comfortable margin. ... We were concerned about drive reliability. ... The Exabyte 8 mm drives currently available write 2 GByte at a maximum data rate of 0.25 MByte/second. ...
... The following thoughts have occurred to us recently regarding the 6x5 ccd camera array for the Cosmological Survey Telescope. ... Heat is conducted away from the ccd via a copper cold finger to a cold plate which is shared by all 30 ccd modules. ... Located at the ccd locations on the cold plate are spring loaded platforms which are thermally coupled to the cold plate with copper braid (not shown). ... The ccd can, the window, the filter assembly, and the ccd assembly is called the ccd module. ...
The mosaic camera was mounted today in preparation for first light. The Gunn/Carr/Rockosi/Lupton team from PU were supported by French Leger/UW, Angie Prosapio and Steve Bastian from FNL, Mark Klaene and Jon Davis from APO, Alan Uomoto/JHU, and Larry Fiscelli/UC. ... Everyone monitors the progress of the mosaic camera as it is lifted in the saddle to the underside of the mirror cell. ... The camera is up in place. ... The camera mounted on the telescope and in position for first light. ...