William Optics Megrez 88 User Manual download pdf (Page 1)

Astronomy TECHNOLOGY TODAY

By James R. Dire, Ph.D.

In 2003, I became interested in purchas-

ing a hydrogen-alpha solar telescope for view-

ing the sun. For about the same price as a

dedicated H-alpha telescope, I decided to pur-

chase a 0.7-angstrom bandwidth, 40-mm (1.6

inch) H-alpha filter set and a high-quality 80-

mm (3.1 inch) f/6 refractor to use with it. I

had never owned a good quality refractor and

this equipment would allow me to conduct

solar observations as well as use the refractor

for wide-field nighttime observing, and possi-

bly CCD imaging. Since my main goal was

narrow bandwidth H-alpha observing, it did-

n’t matter whether the telescope was an achro-

matic or apochromatic refractor. So I bought

an achromatic refractor.

I should explain the differences between

these two refractor types. Refracting lenses

suffer from what is called chromatic aberra-

tion; different wavelengths of visible light do

not focus at the same distance from the lens.

To counter this effect, refractors usually have

two or more objective lenses. In a two-lens

system, the doublet is designed so that two

different visible wavelengths focus at the same

point. This is called an achromat. Most of the

chromatic aberration is eliminated, except

near the short-wavelength end of the visible

spectrum. In a three-lens system, the triplet is

designed so that three different visible wave-

lengths focus at the same point. This is called

an apochromat, or APO for short. The result

is that all visible chromatic aberration is elim-

inated. Because there are more elements in the

objective, APOs are usually heavier and more

expensive than achromatic refractors.

My 80-mm telescope performed quite

well with the H-alpha filter. The nighttime

views where also stunning. I was hooked on

refractors! The scope did show noticeable pur-

ple fringing around bright stars and planets,

as well as the Moon, the usual sign of chro-

matic aberration in doublets. CCD imaging

did not work well with the telescope because

of this aberration.

For that reason, as well as aperture fever,

I sold the 80-mm achromat and purchased a

4-inch f/7.9 apochromatic refractor. The

The William Optics

Megrez 120-mm

Refractor

NOTE FROM EDITOR

A feature article detailing the functionality of the William Optics

Digital Display Gauge is scheduled for followup this spring in ATT.

The particular WO Megrez 120 that Dr. Dire tested was shipped by

William Optics to Suffern, New York, for display at WO’s NEAF

2010 exhibit, and the Digital Display Gauge was demonstrated re-

peatedly while there. The subject scope was then shipped by ATT from

Suffern to its offices in Louisiana, where it was tested for accuracy of

collimation and overall mechanical and digital function. From there

telescope was shipped by ATT to Dr. Dire’s home in Hawaii. By the

time he received the scope, the DDG would not power on.

The cause of failure of the DDG unit to power on is simple:

ATT ’s managing editor has since confessed to having drained the bat-

tery in the DDG unit and forgetting to replace it before repacking the

scope for shipment to Dr. Dire. The DDG feature was just too cool

for him to resist using the battery to exhaustion.

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Summary of Contents

Page 1 - Refractor

Astronomy TECHNOLOGY TODAY 35By James R. Dire, Ph.D.In 2003, I became interested in purchas-ing a hydrogen-alpha solar telescope for view-ing the sun

Page 2 - Astronomy TECHNOLOGY TODAY

APO provided higher magnification for solarviewing and worked quite well for digital im-aging (see image gallery at www.wildwood-pines.org). A higher

Page 3

onto the top of one of the tube rings. Almost all of my viewing was done witha 12-mm Tele Vue Nagler eyepiece providing75x magnification. My first ta

Page 4

William Optics adjustable focal reducer set at0.75. This resulted in an effective 675-mmfocal length at f/5.6.Again, my first target was the doubleclu

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William Optics Megrez 88 User Manual Page 1

Browse online or download User Manual for Telescopes William Optics Megrez 88. WO Megrez 120 Articles.qxd:Layout 1

Summary of Contents

Comments to this Manuals

William Optics Megrez 88 User Manual Page 1

Browse online or download User Manual for Telescopes William Optics Megrez 88. WO Megrez 120 Articles.qxd:Layout 1

Summary of Contents

Comments to this Manuals

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