Meade AT90EDT instruction sheet Lens Shade Outer Diameter, Resolving Power Dawes’ Limit

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AT90EDTfrom Astronomy Technologies

Thank you for choosing this Astro-Tech AT90EDT high-performance apochromatic ED triplet refractor.

The images from its fully-collimatable 600mm f/6.7 ED (Extra-low Dispersion) air-spaced triplet optics are virtually color-free, even at high magnifications, thanks to its use of advanced Ohara FPL-53 ED glass. At its price, we believe you’ll find that the optical performance

of your AT90EDT is little short of astonishing.

This instruction sheet will provide you with information on how to get the most out of your new refractor, and how to properly maintain your telescope so it can give you a lifetime of observing enjoyment.

Please familiarize yourself with your telescope’s parts and functions before operating it for the first time.

PARTS OF THE AT90EDT	Mounting shoe for		Focusing
Lock knob for 360°	optional finder
rotatable focuser			scale on
	2”		focuser
Lock knob for			drawtube
	eyepiece
focuser drawtube		1.25”
	holder
Retractable dew shield		eyepiece
		holder

						Fine
						focus
	Mounting shoe for					knob
	optional finder	Left coarse
	Brass compression ring
Dust cover		focus knob	2”			Right
			eyepiece
						coarse
			holder
				1.25”		focus
		2” eyepiece				knob
				eyepiece
		lock knob		holder
	1.25” eyepiece	1.25”
	lock knob				1.25” eyepiece
		eyepiece
		holder				lock knob

Astro-Tech AT90EDT Apochromatic ED Triplet Refractor Specifications

Aperture		90mm (3.54”)	Finder	mounting shoe provided for optional
Focal Length		600mm	Astro-Tech multiple reticle finder or similar finder
Focal Ratio		f/6.7	Lens Shade			retractable
Objective Type	collimatable air-spaced triplet		Lens Shade Outer Diameter		.......................	130mm
	using Ohara FPL-53 ED glass		Objective Lens Cover			slip-on metal
Optical Coatings		fully multicoated	Tube Diameter			114mm o. d.
Resolving Power (Dawes’ Limit)		1.29 arc seconds	Tube Length (lens shade retracted)			18.9” (480mm)
Visual Limiting Magnitude		12.3 maximum	Tube Length (lens shade extended) ....			21.75” (552mm)
Light Grasp (versus the eye)		165x	Optical Tube Weight			11.45 lbs. (5.2 kg)
Field Stops	three knife-edge baffles		Case	aluminum-frame foam-fitted
Focuser	dual-speed rack and pinion			lockable hard case, with carrying handle
	with 11:1 reduction ratio fine focus;		Case Dimensions			28” x 9” x 9”
2” and 1.25” compression ring eyepiece holders;			Lowest Usable Power		15x (40mm eyepiece)
360° rotating camera angle/observing angle adjuster			Highest Terrestrial Power		85x (7mm eyepiece)
Focuser Travel		4.7” (120mm)	Highest Practical Power		150x (4mm eyepiece)
with millimeter scale on drawtube for repeatable focus			Theoretical Maximum		200x (3mm eyepiece)