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ENGLISH | 

11

CALCULATING MAGNIFICATION

You can change the power of your  telescope just by changing the eyepiece (ocular)   To determine the magnification of 
your telescope, simply divide the focal length of the telescope by the focal length of the eyepiece used   In equation format, 
the formula looks like this:

                              Focal Length of Telescope (mm)
Magnification =   ______________________________
                              Focal Length of Eyepiece (mm)

Let’s say, for example,  you are using the 20 mm  eyepiece that came with your telescope   To determine the magnification 
you simply divide the focal length of your  telescope (the AstroMaster 130AZ for this example has a focal length of 660 
mm) by the focal length of the eyepiece, 20 mm   Dividing 660 by 20 yields a magnification of 33 power   
Although the power is variable, each instrument under average skies has a limit to the highest useful magnification   The 
general rule is that 60 power can be used for every inch of aperture   For example, the AstroMaster 130AZ is 5 inches in 
diameter   Multiplying 5 by 60 gives a maximum useful magnification of 300 power  Although this is the maximum useful 
magnification, most observing is done in the range of 20 to 35 power for every inch of aperture which is 100 to 175 times 
for the AstroMaster 130AZ telescope   You can determine the magnification for your telescope the same way   

DETERMINING FIELD OF VIEW

Determining the field of view is important if you want to get an idea of the angular size of the object you are observing    
To calculate the actual field of view, divide the apparent field of the eyepiece (supplied by the eyepiece manufacturer)  
by the magnification   In equation format, the formula looks like this:

                        Apparent Field of Eyepiece
True

 

Field

 =     _________________________

                                        

Magnification

As you can see, before determining the field of view, you must calculate the magnification   Using the example in the 
previous section, we can determine the field of view using the same 20 mm eyepiece that is supplied standard with 
the AstroMaster 130AZ telescope   The 20 mm eyepiece has an apparent field of view of 50°   Divide the 50° by the 
magnification, which is 33 power   This yields an actual field of 1 5°  

To convert degrees to feet at 1,000 yards, which is more useful for terrestrial observing, simply multiply by 52 5   
Continuing with our example, multiply the angular field of 1 5° by 52 5   This produces a linear field width of 78 75 feet at a 
distance of one thousand yards  

Summary of Contents for 31055 AstroMaster 130AZ

Page 1: ...INSTRUCTION MANUAL 31055 AstroMaster 130AZ ENGLISH T E L E S C O P E 130AZ 1 3 0 M M R E L E C T O R ...

Page 2: ......

Page 3: ...ting Magnification 11 Determining Field of View 11 General Observing Hints 12 ASTRONOMY BASICS 12 CELESTIAL OBSERVING 13 Observing the Moon 13 Observing the Planets 13 Observing the Sun 13 Observing Deep Sky Objects 14 Star Hopping 14 Seeing Conditions 16 ASTROPHOTOGRAPHY 17 Planetary Lunar Photography with Special Imagers 17 Terrestrial Photography 17 TELESCOPE MAINTENANCE 18 Care and Cleaning of...

Page 4: ...omical observing capability Read this manual carefully before embarking on your journey through the Universe It may take a few observing sessions to become familiar with your telescope so keep this manual handy until you have fully mastered your telescope s operation The manual provides detailed instructions reference material and helpful hints guaranteed to make your observing experience as simpl...

Page 5: ...ENGLISH 5 1 Telescope Optical Tube 6 Accessory Tray 2 Red Dot Finder 7 Tripod 3 Eyepiece 8 Azimuth Lock 4 Focus Knob 9 Alt Az Mount 5 Pan Handle 10 Dovetail Mounting Bracket Fig 1 7 8 10 9 6 1 5 2 3 4 ...

Page 6: ...ripod leg brace center of Figure 2 2 Hold the tray flat side facing down Align the center of the tray to match the center of the tripod brace and push down slightly Figure 2 4 Fig 2 1 Fig 2 2 Fig 2 3 Fig 2 4 4 Rotate the tray until the ears are under the leg brace support of each leg and push slightly They will lock in place Figure 2 5 The tripod is now completely assembled Figure 2 6 5 You can ex...

Page 7: ... Before you attach the optical tube make sure that the pan handle and azimuth lock are fully locked Then put the dovetail bracket in the horizontal position as shown in Figure 2 12 This will ensure that the mount does not move suddenly while attaching the telescope optical tube Also remove the objective lens To mount the telescope tube 1 Remove the protective paper covering the optical tube 2 Loos...

Page 8: ...nd of one of the eyepieces into the diagonal and tighten the thumb screw Again make sure the thumbscrew is not protruding into the diagonal before inserting the eyepiece Figure 2 13 2 The eyepieces can be changed to other focal lengths by reversing the procedure in step 2 above Fig 2 13 ...

Page 9: ...e of crown and flint glasses are corrected for red and green light Blue light may still be focused at a slightly different point Figure 3 1 A A cutaway view of the light path of the cutaway view of the light path of the Refractor Refractor optical optical design design IMAGE ORIENTATION The image orientation changes depending on how the eyepiece is inserted into the telescope When using a star dia...

Page 10: ...fore it can be used The alignment procedure is best done at night since the LED dot will be difficult to see during the day Figure 3 3 Figure 3 4 To align the red dot finder 1 To turn on the red dot finder turn the switch to the on position Figure 3 3 2 Locate a bright star or planet and center it in a low power eyepiece in the main telescope 3 With both eyes open look through the glass window at ...

Page 11: ...ation most observing is done in the range of 20 to 35 power for every inch of aperture which is 100 to 175 times for the AstroMaster 130AZ telescope You can determine the magnification for your telescope the same way DETERMINING FIELD OF VIEW Determining the field of view is important if you want to get an idea of the angular size of the object you are observing To calculate the actual field of vi...

Page 12: ...il seen under these conditions is greatly reduced If you wear corrective lenses specifically glasses you may want to remove them when observing with an eyepiece attached to the telescope When using a camera however you should always wear corrective lenses to ensure the sharpest possible focus If you have astigmatism corrective lenses must be worn at all times ASTRONOMY BASICS Up to this point this...

Page 13: ...ts polar caps You will be able to see the cloud belts of Jupiter and the great Red Spot if it is visible at the time you are observing In addition you will also be able to see the moons of Jupiter as they orbit the giant planet Saturn with its beautiful rings is easily visible at moderate power Planetary Observing Hints Remember that atmospheric conditions are usually the limiting factor on how mu...

Page 14: ...an object For successful star hopping it is helpful to know the field of view of your telescope If you re using the standard 20 mm eyepiece with the AstroMaster telescope your field of view is approximately 1º If you know an object is 3º away from your present location then you just need to move 3 fields of view If you re using another eyepiece consult the section on determining field of view Belo...

Page 15: ...connecting the two stars 6 Look through the telescope and the Ring Nebula should be in your field of view The Ring Nebula s angular size is quite small and difficult to see 7 Because the Ring Nebula is rather faint you may need to use averted vision to see it Averted vision is a technique of looking slightly away from the object you re observing So if you are observing the Ring Nebula center it in...

Page 16: ...d 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 ob...

Page 17: ...trial as well as prime focus astrophotography 35 mm or DSLR camera you will need to remove your lens from the camera and attach a T Ring for your specific camera brand Then you will need a T Adapter 93625 to attach on one end to the T Ring and the other end to the telescope focus tube Your telescope is now the camera lens PLANETARY LUNAR PHOTOGRAPHY WITH SPECIAL IMAGERS In recent years a new techn...

Page 18: ...olution is isopropyl alcohol mixed with distilled water The solution should be 60 isopropyl alcohol and 40 distilled water Or liquid dish soap diluted with water a couple of drops per one quart of water can be used Occasionally you may experience dew build up on the optics of your telescope during an observing session If you want to continue observing the dew must be removed either with a hair dry...

Page 19: ...3326 A Barlow lens doubles the magnification of any eyepiece with which it is paired The 2x Omni is a 1 25 barrel is under 3 inches 76mm long and weights only 4 oz 113 g Moon Filter 94119 A This is an economical 1 25 eyepiece filter for reducing the brightness of the moon and improving contrast so you can observe greater detail on the lunar surface UHC LPR Filter 1 25 94123 This filter is designed...

Page 20: ...w w standard eyepiece 1 5 Linear FOV w standard eyepiece ft 1000yds 78 5 Mount Altazimuth Pan Handle Control for Altitude yes Azimuth Lock yes Tripod Leg Diameter 1 25 yes TheSkyX First Light Edition software yes Highest Useful Magnification 300x Limiting Stellar Magnitude 12 3 Resolution Raleigh arc seconds 1 07 Resolution Dawes Limit arc seconds 0 89 Light Gathering Power 345x Optical Tube Lengt...

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