Meade ETX-125EC, ETX-105EC Using The Viewfinder, Focusing the Viewfinder, Aligning the Viewfinder

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Using The Viewfinder

As with most astronomical telescopes, the ETX model telescopes present a fairly narrow field of view to the observer. As a result it is sometimes difficult to locate and center objects in the telescope’s field of view. The viewfinder, by contrast, is a low-power, wide-field sighting scope with crosshairs that let you easily center objects in the eyepiece of the main telescope’s field of view. The telescope viewfinder is a great help in locating faint astronomical objects before you begin observing through the telescope eyepiece.

1

ETX-90EC Viewfinder

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ETX-105EC/-125EC Right-Angle Viewfinder

Fig. 5: Viewfinder Installation.

ETX-90EC 8 x 21mm Erect-Image Viewfinder:

Standard equipment with the ETX-90EC, the 8 x 21mm Erect-Image Viewfinder has 8-power magnification

and an aperture of 21mm. This viewfinder presents a correctly oriented image both up-and-down and left-to-right.

ETX-105EC or ETX-125EC 8 x 25mm Right-Angle Viewfinder:

Standard equipment with the ETX-105EC and ETX-125EC, the 8 x 25mm Right-Angle Viewfinder has 8-

power magnification and an aperture of 25mm. This viewfinder presents a correctly oriented image up- and-down, but is reversed left-for-right.

Focusing the Viewfinder

The ETX model viewfinders are pre-focused at the factory. Individual eye variations may require that the viewfinder be re-focused. To check the focus, point the viewfinder at a distant terrestrial (land) object such as a telephone pole or light pole and look through the viewfinder. If the viewfinder image is not in sharp focus, follow the procedure below that applies to your telescope model.

ETX-90EC

1.Remove the viewfinder by slightly unthreading the six alignment screws (4 and 6, Fig. 6) and slipping it out of the bracket.

2.Loosen the knurled lock-ring (2, Fig. 6) located near the viewfinder’s front lens cell (1, Fig. 6). Unthread this ring (counterclockwise, as seen from the eyepiece-end of the viewfinder) by several turns.

3.Look through the viewfinder and focus on a distant object. Slowly rotate the front lens cell in one direction or the other, until the object appears sharp. One or two rotations of the lens may have a significant effect on image focus.

4.Lock the focus in place by threading the knurled lock-ring clockwise up against the viewfinder’s lens cell.

5.Replace the viewfinder into the viewfinder bracket. Gently tighten the six alignment screws. Proceed with Aligning the Viewfinder.

ETX-105EC or ETX-125EC

Turn the focus ring (2, Fig. 6) at the base of the viewfinder eyepiece (3, Fig. 6) in either direction until a sharp focus is reached.

Aligning the Viewfinder

In order for the viewfinder to be useful, it must first be aligned with the main telescope, so that both the viewfinder and the main telescope are pointing at precisely the same location. To align the viewfinder:

1.Turn the three rear alignment screws of the viewfinder bracket (6, Fig. 6) so that the viewfinder tube is roughly centered within the viewfinder bracket.

Tip: Do not overtighten the align- ment screws. When tightening one screw it may be necessary to loosen one or both of the two other alignment screws.

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2

 

 

 

 

 

4

 

ETX-125EC

 

 

 

 

1

5

3

ETX-90EC

2

 

6

Fig. 6: The Viewfinder. (1) Front lens cell; (2) Knurled lock- ring (ETX-90EC) or focus ring (ETX-105EC and ETX- 125EC); (3) Viewfinder eyepiece; (4) Front alignment screws (one not visible in photo); (5) Viewfinder bracket; (6) Rear alignment screws (one not visible).

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Contents Meade Instruments Corporation Page Contents QUICK-START Guide Slew SpeedTelescope and Electronic Controller Functions ETX-90EC Astro TelescopeTelescope Controls ETX Your Personal Window to the UniverseViewfinder Flip mirror control in the up position Computer Control PanelElectronic Controller Functions Indicator Light KeyLight Blinking Off Getting Started Aligning the Viewfinder Using The ViewfinderFocusing the Viewfinder ETX-90EC 8 x 21mm Erect-Image ViewfinderChoosing an Eyepiece Observation TechniquesAlignment Understanding Magnification Telescope Focal Length Power = Eyepiece Focal Length1900mm Power = = 26mm Terrestrial ObservingElectronic Controller Astronomical ObservingSidereal Rate Slew SpeedsModes of Operation Alt/Az ModeTelescope Mountings To move the telescope using the Electronic Controller Polar ModeYou use Polar or Equatorial mounting. By Celestial Coordinates Polar Alignment ProcedureLocating the Celestial Pole Standard Tripod Leg ETX-105EC, ETX-125EC Standard Tripod Leg ETX-90ECHigh-Latitude Tripod Leg ETX-90EC High-Latitude Tripod Leg ETX-105EC, ETX-125ECPhotography ETX-90ECExample of a format 1 photo Few Tips on PhotographyPower 2x Barlow Optional AccessoriesPower ETX-105EC ETX-125EC Eyepiece#825 Right- Angle Viewfinder General Maintenance Storage and TransportTroubleshooting Inspecting the OpticsMeade Customer Service Telescope moves off a terrestrial object while observingSpecifications ETX-105EC Astro Telescope Specifications ETX-90EC Astro TelescopeSpecifications ETX-125EC Astro Telescope Tracking Motor Speeds Changing Modes Using the Electronic ControllerAppendix a Advanced Electronic Controller Functions Northern Hemisphere PolarAppendix B Helpful Charts Appendix C Precise Polar Alignment Setting Circles Setting CirclesMoon Appendix D YOU and the UniverseAutostar Glossary PlanetsDeep-Sky Objects Pleiades is one of the most beautiful open clustersMeade Limited Warranty Meade Instruments Corporation
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