Celestron 4SE Observing Deep Sky Objects, Seeing Conditions, Solar Observing Hints, Transparency

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Solar Observing Hints

Solar Observing Hints

The best time to observe the Sun is in the early morning or late afternoon when the air is cooler.

To center the Sun without looking into the eyepiece, watch the shadow of the telescope tube until it forms a circular shadow.

To ensure accurate tracking, be sure to select solar tracking rate.

Observing Deep Sky Objects

Deep-sky objects are simply those objects outside the boundaries of our solar system. They include star clusters, planetary nebulae, diffuse nebulae, double stars and other galaxies outside our own Milky Way. Most deep-sky objects have a large angular size. Therefore, low-to- moderate power is all you need to see them. Visually, they are too faint to reveal any of the color seen in long exposure photographs. Instead, they appear black and white. And, because of their low surface brightness, they should be observed from a dark-sky location. Light pollution around large urban areas washes out most nebulae making them difficult, if not impossible, to observe. Light Pollution Reduction filters help reduce the background sky brightness, thus increasing contrast.

Seeing Conditions

Viewing conditions affect what you can see through your telescope during an observing session. Conditions include transparency, sky illumination, and seeing. Understanding viewing conditions and the effect they have on observing will help you get the most out of your telescope.

Transparency

Transparency is the clarity of the atmosphere which is affected by clouds, moisture, and other airborne particles. Thick cumulus clouds are completely opaque while cirrus can be thin, allowing the light from the brightest stars through. Hazy skies absorb more light than clear skies making fainter objects harder to see and reducing contrast on brighter objects. Aerosols ejected into the upper atmosphere from volcanic eruptions also affect transparency. Ideal conditions are when the night sky is inky black.

Sky Illumination

General sky brightening caused by the Moon, aurorae, natural airglow, and light pollution greatly affect transparency. While not a problem for the brighter stars and planets, bright skies reduce the contrast of extended nebulae making them difficult, if not impossible, to see. To maximize your observing, limit deep sky viewing to moonless nights far from the light polluted skies found around major urban areas. LPR filters enhance deep sky viewing from light polluted areas by blocking unwanted light while transmitting light from certain deep sky objects. You can, on the other hand, observe planets and stars from light polluted areas or when the Moon is out.

Seeing

Seeing conditions refers to the stability of the atmosphere and directly affects the amount of fine detail seen in extended objects. The air in our atmosphere acts as a lens which bends and distorts incoming light rays. The amount of bending depends on air density. Varying temperature layers have different densities and, therefore, bend light differently. Light rays from the same object arrive slightly displaced creating an imperfect or smeared image. These atmospheric disturbances vary from time-to-time and place-to-place. The size of the air parcels compared to your aperture determines the "seeing" quality. Under good seeing conditions, fine detail is visible on the brighter planets like Jupiter and Mars, and stars are pinpoint images. Under poor seeing conditions, images are blurred and stars appear as blobs.

The conditions described here apply to both visual and photographic observations.

Figure 7-1

Seeing conditions directly affect image quality. These drawings represent a point source (i.e., star) under bad seeing conditions (left) to excellent conditions (right). Most often, seeing conditions produce images that lie some where between these two extremes.

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Contents INSTRUCTION MANUAL ASSEMBLY INTRODUCTIONHAND CONTROL Hand Control Command Tree TELESCOPE MAINTENANCEAPPENDIX A - TECHNICAL SPECIFICATIONS TELESCOPE BASICSSome of the many standard features of the NexStar include Battery Compartment Accessory Tray / Leg BraceON/OFF Switch NexStar 4 SEAssembling the NexStar Powering the NexStarThe Hand Control Star Pointer Installation Figure 3-2 - The Rear Cell with Visual AccessoriesThe Eyepiece EyepieceStarPointer DiagonalStar Pointer Operation Removing the Optical TubeFigure 3-3 The Star Pointer Finderscope with Mounting Bracket Quick Release KnobAttaching the NexStar to the Tripod The NexStar Hand Control Hand Control Operation Alignment ProcedureDefinition Named StarsSky Align HintsTips for Using Sky Align Auto Two-Star AlignTwo Star Alignment Helpful HintOne-Star Align Solar System AlignEQ North / EQ South Alignment Tips for Using Solar System AlignEQ AutoAlign Improving Pointing Accuracy EQ Two-Star AlignEQ One-Star Align EQ Solar System AlignObject Catalog SyncUndo Sync Selecting an ObjectSlewing to an Object Finding PlanetsTour Mode Constellation TourSetup Procedures Direction ButtonsNine available slew speeds Rate ButtonCamera Connecting a Camera to the NexStar MountSave Database Db Controlling your Camera Camera WizardObject Type Scope Setup Features IdentifyPrecise GoTo MENU Utility Features HelpfulHint Sun MenuSet Mount Position NexStar SE ALIGNMENTLIST NexStar Menu TreeImage Orientation Fig 5-2a - Actual image orientation as seen with the unaided eyeFig 5-2b - Reversed from left to right, as viewed through the eyepieceFocusing Calculating MagnificationDetermining Field of View General Observing Hints The Celestial Coordinate System The celestial sphere seen from the outside showing R.A. and DECMotion of the Stars Polar Alignment Aligning the NexStar 4 on a WedgeWedge Align moves in right ascension and declinationAttaching a Camera to the NexStar Photography with the NexStarFinding the North Celestial Pole The position of the Big Dipper changes throughoutthe year and the night Observing the Moon Observing the PlanetsObserving the Sun Lunar Observing HintsObserving Deep Sky Objects Seeing ConditionsSolar Observing Hints TransparencyCare and Cleaning of the Optics Page Page Appendix A - Technical Specifications SpecificationElectronic Specifications Software SpecificationsAppendix B - Glossary of Terms Page Appendix C - RS-232 Connection Appendix D - Maps of Time Zones Page Page Page Page Page Page Page CELESTRON TWO YEAR WARRANTY Celestron 2835 Columbia Street Torrance, CA Tel. 310 Fax. 310 Copyright 2006 Celestron All rights reservedProducts or instructions may change without notice or obligation #11049-INST Printed in China $10.00