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	Secondary mirror -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-10-18)
		A secondary mirror (or secondary) is a second light gathering and focusing surface in a (additional info and facts about reflector telescope) reflector telescope.
		Light gathered by the (additional info and facts about primary mirror) primary mirror is directed towards a (A central point or locus of an infection in an organism) focal point typically past the location of the secondary.
		That said, secondaries and their supports can cause minor distortion to the (additional info and facts about point spread function) point spread function, resulting in the cross-shaped "diffraction spikes" radiation from bright sources in many popular images.
	www.absoluteastronomy.com /encyclopedia/s/se/secondary_mirror.htm (170 words)

	Gemini South’s Secondary Mirror Sports Shiny Silver Coat
		The Gemini South secondary mirror passing under a magnetron, which is applying the reflective silver layer, in the vacuum coating chamber during the silver coating process on 9 October 2003.
		Until recently, all of Gemini's mirrors were coated with aluminum, which is the material used by most telescopes (Subaru is the only other telescope in the 4-meter to 10-meter class with a silver coating on a secondary mirror, and it's bare rather than protected.) No large telescopes at present have silver-coated primary mirrors.
		The three-step process applied recently to Gemini South's secondary mirror was a success: the mirror's emissivity was measured in laboratory tests to be 0.9% at 3.8 microns wavelength and is expected to be even lower near 10 microns.
	www.gemini.edu /science/gs-secondarymirror.html (1133 words)

	Reflectors
		The light bouncing off the primary mirror has to be aimed directly at the secondary mirror, and the secondary mirror must direct the light to the center of the eyepiece.
		A smaller, secondary mirror sends the light out the side of the tube, so the image can be viewed without blocking the incoming light.
		Telescopes with mirrors can be built much larger than refractors, and it is not uncommon to see amateur built instruments with mirrors of 16, 24, and even 40 inches in diameter.
	www.starstuff.com /reflectors.htm (513 words)

	The Secondary Mirror, M2 Unit (Site not responding. Last check: 2007-10-18)
		The M2 mirror is a convex hyperbolic mirror with an external diameter slightly in excess of 1 meter.
		The central obstruction area of the mirror (central part which is not optically used) is equipped with an interface used for the mounting of optomechanical auxiliary equipment used for particular observations and for optical alignment.
		This stage tilts the mirror along an axis contained in the plane perpendicular to the M2 mirror optical axis and ideally positioned at the mirror vertex.
	www.ulo.ucl.ac.uk /~diploma/year_one/www.eso.org/projects/vlt/unit-tel/m2unit.html (762 words)

	Telescope Mirror Images (Site not responding. Last check: 2007-10-18)
		The main mirror is called a primary, and the secondary is the smaller mirror that redirects light to an eyepiece.
		Light from the primary is reflected a second time by this mirror, and due to the convex surface of the mirror (it's curved outward) it redirects all light toward the central hole in the primary.
		Once installed, the secondary will be in a special mounting, which will move the secondary mirror toward, or away from the surface of the primary.
	www.mdia.org /Mirrors.htm (442 words)

	[No title] (Site not responding. Last check: 2007-10-18)
		The secondary mirror is suspended between the window and the primary mirror by means of a plurality of support struts.
		Many applications require the secondary mirror to be located near the window where external temperatures are extreme (high altitude in aircraft, for example) and the cavity temperature must be controlled, resulting in a large thermal gradient near the window.
		A fold mirror may be used to reflect light from the secondary mirror onto the tertiary mirror which couples the light to the focussing optics or imager.
	www.wipo.int /cgi-pct/guest/getbykey5?KEY=01/65297.010907&ELEMENT_SET=DECL (3597 words)

	Rob's Astronomy Guide - Amateur Telescope Making
		The mirrors need to be ground to a precision of 1/8 wave or less to produce a high quality image, avoid mirrors that have an accuracy of 1/6 wave.
		Position the secondary mirror in the center of the focuser and adjust the mirror so the hole at the end of the tube is centered in the secondary mirror and focuser.
		Subtract this distance from your primary mirrors focal length to determine the distance from the primary mirror to the secondary.
	geologynet.com /astronomy/atm.htm (1276 words)

	Secondary Mirror Motions
		The forth encoder was positioned to measure the transverse motions of the secondary mirror.
		In the middle of the secondary mirror, near its center of mass is a linear bearing which rides on a gimbol.
		It is clear that the broken C axis is causing a tilt in the secondary mirror which is orthogonal to that which one would normally expect to see owing to sag in the secondary truss.
	www.astro.washington.edu /morgan/APO/Mirror.Motions/M2.Install.Heidenhains/report.html (2170 words)

	NSRT Mirror Move Day (Site not responding. Last check: 2007-10-18)
		When the mirrors get to the company that is going to give them their new coat of aluminum, first they strip the old aluminum off the glass and clean the surface very well.
		On the end of the chamber opposite the mirrors there are aluminum coated electrodes that are superheated to vaporize the aluminum, which then recondenses on the mirror surfaces in a thin layer.
		Once the mirror is raised the mirror cell (that holds the mirror in place on the back of the telescope) is rolled into place underneath.
	astrwww.cwru.edu /gallery/mirrormove.html (910 words)

	JCMT - Secondary Mirror Unit, SMU (Site not responding. Last check: 2007-10-18)
		The secondary mirror allows the JCMT to focus submillimeter radiation onto detectors built into receivers mounted at the primary focus in the receiver cabin (located below the main mirror) and at the two Nasmyth foci (located on the elevation axis).
		This is accomplished by vibrating ("chopping" or "nutating") the mirror such that the difference signal between two nearby points on the sky is obtained; since nearby points contain the same contribution from the atmosphere, to a large degree the difference represents the signal from a celestial target in one of the two beam positions.
		The secondary has a shallow cone in the centre - covering the area that corresponds to the shadow of the secondary on the main dish - that prevents radiation being reflected back into the cabin and causing standing waves.
	www.jach.hawaii.edu /JCMT/telescope/SMU?printable=1 (285 words)

	4m f/8 Secondary Mirror Control System
		The mirror can be both focused and tilted by the operation of three computer-controlled jack screws which are spaced 120 degrees apart on the back of the mirror cell.
		Units are microns of motion at the secondary mirror.
		A is on the South side of the secondary mirror when it is in its observing position; B1 is on the NW side and B2 is on the NE side.
	www.noao.edu /ctio/telescopes/4m/f8sec.html (616 words)

	Orion Telescopes and Binoculars (Site not responding. Last check: 2007-10-18)
		A catadioptric configuration consisting of a spherical primary mirror and a convex secondary mirror affixed to an aperture-wide correcting plate.
		The secondary mirror directs the focused light back down the tube through a hole in the center of the primary mirror and into an eyepiece or camera.
		In Newtonian reflectors, the secondary mirror is often referred to as the diagonal.
	www.telescope.com /sdx/176454.jsp (629 words)

	Orion Telescopes and Binoculars How do I align the secondary mirror with the collimation cap? (Site not responding. Last check: 2007-10-18)
		The secondary mirror itself should be centered in the focuser drawtube, in the direction parallel to the length of the telescope.
		When the secondary mirror is centered in the focuser draw-tube, rotate the secondary mirror holder until the reflection of the primary mirror is as centered in the secondary mirror as possible.
		Don’t worry that the reflection of the secondary mirror (the smallest circle, with the collimation cap “dot” in the center) is off-center.
	www.telescope.com /sdx/176603.jsp (467 words)

	Interfacing Visitor Instruments to the Keck Telescopes
		The f/40 secondary mirror is undersized and has a central hole so that it reflects no radiation to the detector from beyond the periphery of the primary mirror or from the primary mirror’s central obstruction, for chop angles up to +/- 150 arcsec on the sky.
		The secondary mirror chopping mechanism is contained within an annulus behind the secondary mirror so that the detector sees direct skylight through the mirror’s central hole and outside its external profile, apart from spider vanes supporting the chopping secondary assembly within the main secondary module.
		The primary mirror segments, the f/15 secondary mirror and the tertiary flat are optically polished Zerodur with aluminum coatings.
	www2.keck.hawaii.edu /observing/interfacvinst/ifvifrm-1.html (2308 words)

	FAQ about Collimating a Newtonian telescope (Site not responding. Last check: 2007-10-18)
		The axis of the main mirror is perpendicular to the mirror at the optical center - for practical purposes taken as the center of the circular glass mirror.
		The distance along the mirror face from the center of the ellipse to the optical center is the offset multiplied by 1.414 (the square root of 2).
		A sight tube of the right length to center the main mirror in the inner opening (see simple sight tube) and with an accurately centered double cross can be used at the critical step 5 to collimate a telescope that (for any reason) does not have a center spot on the main mirror.
	www.atmsite.org /contrib/Carlin/collimation (7809 words)

	Collimating PT Optics
		This is done by moving the secondary until its vertex mark is centered in a collimating telescope mounted near the Cassegrain focus.
		By tilting the secondary mirror, the two images can be made to coincide indicating that the secondary mirror axis coincides with that of the collimating telescope.
		Use the four nylon screws on the side of the secondary mirror cell to center it in the collimating telescope.
	www.jhu.edu /~sdss/PT/Maintenance/PTCollimation.html (1775 words)

	Berthold Hamburger's Homepage/ATM
		The 2 spider vanes of the secondary holder are fixed to the 58mm brass tube.
		The thickness depends on the minor axis of your secondary mirror.
		Drill a 1mm deep hole with the diameter of the M4 washer in the top/center of your mirror holder.
	www.geocities.com /CapeCanaveral/9601/focuser.htm (868 words)

	Kendrick Astro Instruments - Newtonion Dew Removal, Newtonion Dew Heaters, Newtonion Dew Control
		We have heaters for 8" to 18" mirrors.
		These are installed behind the mirror in between the mirror and the mirror cell and are held in place by putting a thin skim of RTV silicone onto the heater and allowing the heater to dry to the back of the mirror.
		These S2, S3 and S4 heaters are installed behind the mirror in the secondary holder and are held in place by the polyester batting that is supplied with these holders.
	www.kendrick-ai.com /astro/newtonian.html (1248 words)

	Astronomers Get Ultrasharp Images With Large Telescope in Arizona (Site not responding. Last check: 2007-10-18)
		Like other secondary mirrors, this one is made of glass over 2 feet in diameter and is a steeply curved dome shape.
		"The adaptive secondary mirror made for the UA and Smithsonian Institution's 6.5-meter telescope at the MMT Observatory is a tremendous advance over conventional adaptive optics, which are systems that involve extra relay optics and mirrors in a box separate from the telescope, Lloyd-Hart said.
		The powerful computer cluster behind the secondary mirror sends electronic current through coils so that each of 336 actuator magnets spaced across the mirror is instantly moved to the desired position.
	uanews.org /cgi-bin/WebObjects/UANews.woa/3/wa/SRStoryDetails?ArticleID=6807 (1680 words)

	Animated Focal Plane Illumination Map (Site not responding. Last check: 2007-10-18)
		The consequence of your secondary mirror size selection in a Newtonian reflector is that it affects the size of the fully illuminated region at the focal plane.
		The secondary size is incrementally increased by 0.1" until it reaches 3.1".
		The 3.1" secondary mirror fully illuminates the entire 1.5" x 1.5" field which is excessive for most applications.
	www.fpi-protostar.com /bgreer/miscpages/illum.htm (354 words)

	Maksutov (Site not responding. Last check: 2007-10-18)
		These calculations included effects due to the secondary mirror obstruction but should be interpreted with caution because the finite grid size used in the computation can introduce false periodicities in the point spread function (this can be seen for example in the point spread function plots with the focal plane 0.05" inside/outside the best focus).
		The secondary mirror blank was cut out from the centre of this blank in a similar fashion (using 3" aluminum irrigation pipe for the biscuit cutter) taking care not to fracture the outer ring of glass.
		The secondary mirror was mounted using a system similar to that described by Texereau [13] with the difference that an additional set of adjustment screws were included near the mirror to allow for fine tip/tilt adjustment.
	www.pyxiscamera.com /Maksutov/Maksutov.html (5568 words)

	The 6.5m MMT laser-guided adaptive optics system: Overview and progress report II
		The laser is mounted on a platform attached to the yoke of the telescope and rotates in azimuth with it.
		It is intended that this steering mirror can be replaced with a second, very-high-order deformable mirror at some later date.
		Collimated light from the steering mirror / 2nd deformable mirror is focused with a second off-axis parabola (OAP) onto the entrance to the wavefront sensor.
	www.mtwilson.edu /~tgs/papers/3126-01/3126-01.htm (2530 words)

	[No title] (Site not responding. Last check: 2007-10-18)
		The primary mirror has an axis of symmetry, and ideally the secondary mirror lies on this primary axis and is oriented so that its own axis coincides with that of the primary.
		In a TMA, the secondary mirror is the smallest and lightest mirror.
		Furthermore the secondary is optically well situated to provide a small degree of target tracking: if it is moved slightly in pitch or tilt angle, the focal plane moves with regard to the principal axis of the telescope.
	www.cea.berkeley.edu /~mlampton/TRADE_FastSteering.doc (3008 words)

	The 2.1-m Chopping Secondary User's Manual
		The net force of the secondary and counterforce mirrors on the rest of the support structure is thus nearly zero.
		Finally, a reflective cone corresponding to the area shadowed by the central hole in the primary was mounted in the center of the secondary; this is designed to reflect skylight into this region of the secondary, as seen from the detector.
		The entire f/8 secondary ring must be removed and lowered to the ground floor with the crane, and the f/15 secondary ring must be brought up and installed on the top of the telescope.
	www.noao.edu /kpno/manuals/2mchop/2mchop.html (2329 words)

	Primary Mirrors, Secondary Mirrors, Telescope Objectives, Mirror Cells, Spider Vanes, Secondary Holder, Pyrex, Plate ... (Site not responding. Last check: 2007-10-18)
		Attaching the secondary mirror is a snap with silicone caulk.
		Just apply four small dalbs of silicone caulk to the secondary holder and press the secondary mirror into the caulk and wait for the caulk to dry.
		Removal of the secondary can be accomplished using dentil floss as a cutting blade between the secondary mirror and the secondary mirror holder.
	www.meridiantelescopes.com /detprim.htm (171 words)

	[No title]
		For this we measure the mirror with a phase-shifting interferometer, whose resolution is roughly 300 EMBED Equation.3 300 pixels.
		During fabrication, the mirror must be supported uniformly and with sufficient force to resist polishing loads of 1-2 kPa, or 25-50 times the weight of the mirror.
		We supported the mirror on a rigid substrate, bonded with a thin layer of pitch, the highly viscous, tar-like material used as a polishing medium and bonding agent in optical fabrication.
	medusa.as.arizona.edu /lbtold/tech/spie4007-06.doc (2563 words)

	Parts and Suppliers
		By the end of June, Steve was done grinding the mirror and had sent the mirror to the coaters.
		And much of the size of the secondary cage is determined by the height of the secondary holder.
		The standard setup for them with my secondary mirror size is 7.3" from the center of the mirror to the end of the nut.
	users.dls.net /~donf/scope/parts.html (2081 words)

	Telescope Kit Instructions
		Attach or glue the primary mirror to the primary cell using silicon and spacers.
		Adjust the primary mirror with the collimating screws on the primary cell until the reflection of the front tube hole in the focuser is centered.
		Use the collimating eyepiece to fine collimate the scope by adjusting the secondary spider as described in the collimation instructions.
	geologynet.com /astronomy/kitinstruc.htm (504 words)

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