INSTRUCTION MANUAL - Optical Vision Ltd
Contents
1. 45 toward the focuser outside the tube wall Fig o The secondary mirror is aligned by adjusting the three smaller screws surrounding the central bolt The primary mirror is adjusted by the three adjusting screws at the back of your scope The three locking screws beside them serve to hold the mirror in place after collimation Fig p Aligning the Secondary Mirror Point the telescope at a lit wall and insert the collimating cap into the focuser in place of a regular eyepiece Look into the focuser through your collimating cap You may have to twist the focus knob a few turns until the reflected image of the focuser is out of your view Note keep your eye against the back of the focus tube if collimating without a collimating cap Ignore the reflected image of the collimating cap or your eye for now instead look for the three clips holding the primary mirror in place If you can t see them Fig q it means that you will have to adjust the three bolts on the top of the secondary mirror holder with possibly an Allen wrench or Phillip s screwdriver You will have to alternately or loosen one and then compensate for the slack by tightening the other two Stop when you see all three mirror clips Fig r Make sure that all three small alignment screws are tightened to secure the secondary mirror in place 14 Correctly aligned Needs collimation m Focuser Support for secondary mirror Primary mirror Secondary2. example a 200mm f 5 telescope with a 40mm eyepiece produces a magnification of 25x and an exit pupil of 8mm This combination can probably be used by a young person but would not be of much value to a senior citizen The same telescope used with a 32mm eyepiece gives a magnification of about 31x and an exit pupil of 6 4mm which should be fine for most dark adapted eyes In contrast a 200mm f 10 telescope with the 40mm eyepiece gives a magnification of 50x and an exit pupil of 4mm which is fine for everyone 12 OBSERVING THE SKY Sky conditions Sky conditions are usually defined by two atmospheric characteristics seeing or the steadiness of the air and transparency light scattering due to the amount of water vapour and particulate material in the air When you observe the Moon and the planets and they appear as though water is running over them you probably have bad seeing because you are observing through turbulent air In conditions of good seeing the stars appear steady without twinkling when you look at them with unassisted eyes without a telescope Ideal transparency is when the sky is inky black and the air is unpolluted Selecting an observing site Travel to the best site that is reasonably accessible It should be away from city lights and upwind from any source of air pollution Always choose as high an elevation as possible this will get you above some of the lights and pollution and will ensure that you aren t in an
3. mirror Primary mirror Mirror cell Locking screw Adjusting screw mm Primary mirror clip Ignore the reflected image for now GD Primary mirror clip Primary mirror clip u P Primary mirror clip Aligning the Primary Mirror Find the three locking screws at the back of your telescope and loosen them by a few turns Adjusting screw Locking screw Locking screw Adjusting screw If you see 3 large nuts protruding If you see 6 Phillip s head from the back of your telescope 2 SD screws but 3 protruding from and 3 small Phillip s head screws 99 the back of your telescope the besides them the Phillip s head 3 protruding screws screws are the locking screws locking screws and the ones and the large nuts are the 99 next to them are adjusting adjusting screws Screws hex bolt Locking screw Adjusting screw If you see 3 hex bolts and 3 Phillip s head screws the hex bolts are the locking screws and the Phillip s head screws are the adjusting screws You will need an Allen wrench to adjust the locking screws Now run your hand around the front of your GDP telescope keeping your eye to the focuser you will see the reflected image of your hand The idea here being to see which way the primary Secondary mirror is defected you do this by stopping at the mirror point where the reflected image of the secondary mirror is closest to the primary mirrors edge Fig s When you get to that point
4. ELESCOPE TO LOOK DIRECTLY THE SUN PERMANENT EYE DAMAGE WILL RESULT USE A PROPER SOLAR FILTER FIRMLY MOUNTED ON THE FRONT OF THE TELESCOPE FOR VIEWING THE SUN WHEN OBSERVING THE SUN PLACE A DUST CAP OVER YOUR FINDERSCOPE OR REMOVE IT TO PROTECT YOU FROM ACCIDENTAL EXPOSURE NEVER USE AN EYEPIECE TYPE SOLAR FILTER AND NEVER USE YOUR TELESCOPE TO PROJECT SUNLIGHT ONTO ANOTHER SURFACE THE INTERNAL HEAT BUILD UP WILL DAMAGE THE TELESCOPE OPTICAL ELEMENTS
5. INSTRUCTION MANUAL REFRACTORS REFLECTORS WITH ALT A2 MUTH MOUNT 090103V2 amp 2 MOUNTS Refractor AZ2 C Dust Cap Mask Remove before Viewing Dew Cap Sun Shade Objective Lens Telescope Main Tube Finderscope Finderscope Bracket Alignment Screws Focus Locking Screw Eyepiece Diagonal Focus Tube Focus Knob FAC rOmmoom E Altitude fine adjustment control Azimuth Lock Yoke Mount Altitude Lock Knob Yoke Locking Knob Accessory Tray Tripod Leg Height Adjustment Clamp Secondary Mirror Position Dust Cap Mask Remove before Viewing Focus Tube Finderscope Bracket Finderscope Finderscope Adjustment Screws Eyepiece Focus Knob Telescope Main Tube Primary Mirror Position Yoke Locking Knob Altitude Lock Knob Azimuth Lock Knob Yoke 5 Altitude Fine Adjustment Control a Accessory Tray b Tripod Leg c Height Adjustment Clamp AZ3 MOUNTS B A D F A Dust Cap Mask G Remove before Viewing B Dew Cap Sun Shade E H C Objective Lens D Piggyback Bracket d p E Telescope Main Body ERN JN oY F Finderscope Les b G Finderscope Bracket ES AD H Alignment Screws kL 7 A NE J Focus Tube PA S j Eyepiece 4 ANS Diagonal LT SS Q L Focus Knob Je SS QUT B Uc CERTO 1 Azimuth Flexible Control Cable s E SS L 2 Altitude Flexi
6. ble Control h 1 8 Cable 3 Azimuth Adjustment Knob 4 Tube Rings a Accessory Tray 1 b Tripod Leg C Height Adjustment Clamp S SG Optional Multi function Red Dot Finder TABLE OF CONTENTS Assembling Your Telescope For AZ1 amp AZ2 saa sees Telescope Assembly CD C ME Finderscope Assembly Eyepiece Assembly i 23 mice ere ert a Lr er Telescope Assembly oru Enim ce a foerat Finderscope Red Dot FinderAssembly Eyepiece Assembly Operating Your Telescope Aligning the Finderscope Using the Red Dot Finder e nmm nn Operating the AZ1 AZS Mount Operating the AZ3 Mount Using the Barlow Lens 999 eem u eene ee RE eie FOCUSING o momen Using the Camera Adapter Tube Pointing Your Telescope Calculating the Magnification power Sky Conditions Proper Care for Your Telescope Co
7. der then screwing the specific T adapter ring then attach to your camera as you would any Eyepiece Camera Adapter T adapter for your camera optional onto the T threads on other lens Holder Tube Camera Pointing your telescope Pointing an altitude azimuth alt az mounted telescope is relatively easy With the mount level you can swivel the telescope around on a plane parallel to your horizon and then tilt it up and down from there Fig c You can think of it as turning your telescope in azimuth until it is facing the horizon below a celestial object and then tilting it up to the object s altitude However the Earth rotates and therefore the stars are constantly moving so to track with this mount you need to constantly nudge the optical tube in both azimuth and altitude to keep the object in the field In reference material for your local position the altitude will be listed as degrees minutes seconds above or below your horizon Azimuth may be listed by the cardinal compass points such as N SW ENE etc but it is usually listed in 360 degree minutes seconds steps clockwise from North 09 with East South and West being 90 180 and 270 respectively Fig m Zenith 2 Meridian Line Tilt in Altitude 1803 S Rotate in Azimuth Caiculating the magnification Power The magnification produced by a telescope is determined by the focal length of the eyepiece that is used with it To determine a magni
8. diminish Some of the best observing time is often in the early morning hours Objects are best observed as they cross the meridian which is an imaginary line that runs through the Zenith due North South This is the point at which objects reach their highest points in the sky Observing at this time reduces bad atmospheric effects When observing near the horizon you look through lots of atmosphere complete with turbulence dust particles and increased light pollution Cooling the telescope Telescopes require at least 10 to 30 minutes to cool down to outside air temperature This may take longer if there is a big difference between the temperature of the telescope and the outside air This minimizes heat wave distortion inside telescope tube tube currents Allow a longer cooling time for larger optics If you are using an equatorial mount use this time for polar alignment Adapting your eyes Do not expose your eyes to anything except red light for 30 minutes prior to observing This allows your pupils to expand to their maximum diameter and build up the levels of optical pigments which are rapidly lost if exposed to bright light It is important to observe with both eyes open This avoids fatigue at the eyepiece If you find this too distracting cover the non used eye with your hand or an eye patch Use averted vision on faint objects The center of your eye is the least sensitive to low light levels When viewing a faint object don t look d
9. efractor INSERTING EYEPIECE Fig 9 1 Unscrew the thumbscrews on the end of the focus tube to remove the plastic endcap 2 Insert diagonal and re tighten thumbscrews to hold diagonal in place 3 Loosen the thumbscrews on the diagonal 4 Insert the desired eyepiece into diagonal and secure by re tightening thumbscrews FOR AZ ADJUSTING TRIPOD LEGS Fig 1 1 Slowly loosen the height adjustment clamp and gently pull out the lower section of each tripod leg Tighten the clamps to hold the legs in place 2 Spread the tripod legs apart to stand the tripod upright 3 Adjust the height of each tripod leg until the tripod head is properly leveled Note that the tripod legs may not be at same length when the equatorial mount is level ATTACHING THE ACCESSORY TRAY Fig 2 1 Place the accessory tray on top of the bracket and secure with the locking knob from underneath TELESCOPE ASSEMBLY Without multi function plate With multi function plate ATTACHING THE TUBE ATTACHING THE TUBE RINGS TO MOUNT Fig 3 RINGS TO MOUNT Fig 3 1 Remove the tube rings multifunction 1 Remove the tube rings from plate assembly from telescope telescope by releasing their by releasing their thumbnuts thumb nuts and opening and opening their hinges their hinges 2 Using one of the three threaded 2 Fasten the tube rings to the holes in the multi function plate mount using the wench ring plate assembly to the provided mounting plateform Tu
10. fication for your telescope divide its focal length by the focal length of the eyepieces you are going to use For example a 10mm focal length eyepiece will give 80X magnification with an 800mm focal length telescope Focal length of the telescope 800mm ification oom 80X Focal length of the eyepiece 10mm When you are looking at astronomical objects you are looking through a column of air that reaches to the edge of space and that column seldom stays still Similarly when viewing over land you are often looking through heat waves radiating from the ground house buildings etc Your telescope may be able to give very high magnification but what you end up magnifying is all the turbulence between the telescope and the subject A good rule of thumb is that the usable magnification of a telescope is about 2X per mm of aperture under good conditions Caiculating the field of view The size of the view that you see through your telescope is called the true or actual field of view and it is determined by the design of the eyepiece Every eyepiece has a value called the apparent field of view which is supplied by the manufacturer Field of view is usually measured in degrees and or arc minutes there are 60 arc minutes in a degree The true field of view produced by your telescope is calculated by dividing the eyepiece s apparent field of view by the magnification that you previously calculated for the combination Using the figure
11. ht of each tripod leg until the tripod head is properly leveled Note that the tripod legs may not be at same length when the equatorial mount is level ATTACHING THE ACCESSORY TRAY Fig 2 1 Place the accessory tray on top of the bracket and secure with the locking knob from underneath AZ2 refractor ery m ATTACHING TELESCOPE MAIN TUBE TO MOUNT Fig 3 4 5 6 1 Unscrew the machine screw on the altitude control locking knob 2 Insert the micro adjustable altitude control into the hole on the side of the altitude control locking knob 3 Slide telescope tube into slots on end of yoke mount Secure telescope tube onto yoke mount using the yoke locking knobs without overtightening 4 Remove machine screw from telescope tube and use this to fasten the micro adjustable altitude control FINDERSCOPE ASSEMBLY reflector AZ refractor ATTACHING THE FINDERSCOPE Fig 7 8 1 Locate finderscope optical assembly 2 Remove the two knurled thumbscrews near the end of the telescope main tube 3 Position the finderscope bracket over the screws in the telescope main body 4 Secure the finderscope bracket with the two knurled thumbscrews EYEPIECE ASSEMBLY AZ reflector INSERTING EYEPIECE Fig 9 1 Unscrew the thumbscrews on the end of the focus tube to remove the black plastic end cap 2 Insert the desired eyepiece and re tighten thumb screws to hold eyepieces in place AZ r
12. irectly at it Instead look slightly to the side and the object will appear brighter 13 PROPER CARE FOR YOUR TELESCOPE Collimating a Newtonian Collimation is the process of aligning the mirrors of your telescope so that they work in concert with each other to deliver properly focused light to your eyepiece By observing out of focus star images you can test whether your telescope s optics are aligned Place a star in the centre of the field of view and move the focuser so that the image is slightly out of focus If the seeing conditions are good you will see a central circle of light the Airy disc surrounded by a number of diffraction rings If the rings are symmetrical about the Airy disc the telescope s optics are correctly collimated Fig n If you do not have a collimating tool we suggest that you make a collimating cap out of a plastic 35mm film canister black with gray lid Drill or punch a small pinhole in the exact center of the lid and cut off the bottom of the canister This device will keep your eye centered of the focuser tube Insert the collimating cap into the focuser in place of a regular eyepiece Collimation is a painless process and works like this Pull off the lens cap which covers the front of the telescope and look down the optical tube At the bottom you will see the primary mirror held in place by three clips 120 apart and at the top the small oval secondary mirror held in a support and tilted
13. llimating a Newtonian Cleaning Your Telescope Betore you begin This instruction manual is applicable to all the models listed on the cover Take a moment to find the model closest to your telescope on p 2 and p 3 Follow the instructions for your specific model in the manual Read the entire instructions carefully before beginning Your telescope should be assembled during daylight hours Choose large open area to work to allow room for all parts to be unpacked Calculating the Field of View Calculating the Exit Pupil Observingthe Sky Selecting an Observing Site Choosing the Best Time to Observe Chooling the Telescope Adapting Your Eyes Caution NEVER USE YOUR TELESCOPE TO LOOK DIRECTLY AT THE SUN PERMANENT EYE DAMAGE WILL RESULT USE A PROPER SOLAR FILTER FOR VIEWING THE SUN WHEN OBSERVING THE SUN PLACE A DUST CAP OVER YOUR FINDERSCOPE TO PROTECT IT FROM EXPOSURE NEVER USE AN EYEPIECE TYPE SOLAR FILTER AND NEVER USE YOUR TELESCOPE TO PROJECT SUNLIGHT ONTO ANOTHER SURFACE THE INTERNAL HEAT BUILD UP WILL DAMAGE THE TELESCOPE OPTICAL ELEMENTS FOR amp 2 ADJUSTING TRIPOD LEGS Fig 1 1 Slowly loosen the height adjustment clamp and gently pull out the lower section of each tripod leg Tighten the clamps to hold the legs in place 2 Spread the tripod legs apart to stand the tripod upright 3 Adjust the heig
14. nderscope rectangular slot and tighten the thumbscrew to bracket over the screws in hold the bracket in place the telescope main body 4 Secure the finderscope qu bracket with the two knurled thumbscrews INSERTING DIAGONAL AND EYEPIECE Fig 7 1 Loosen the thumbscrew on the end of the focus tube 2 Insert a diagonal into the focus tube and re tighten the thumbscrew to hold the diagonal in place 3 Loosen the thumbscrews on the diagonal 4 Insert the desired eyepiece into the diagonal and secure by re tightening the thumbscrews OPERATING YOUR TELESCOPE Aligning the finderscope Using the Red Dot Finder ON OFF trol The Red Dot Finder is a zero magnification pointing tool that Brightness uses a coated glass window to superimpose the image of a Control small red dot onto the night sky The Red Dot Finder is equipped with a variable brightness control azimuth Altitude adjustment control and altitude adjustment control Fig e The Adjustment Red Dot Finder is powered by a 3 volt lithium battery located Control underneath at the front To use the Finder simply look through the sight tube and move your telescope until the red dot merges with the object Make sure to keep both eyes open when sighting Aligning the Red Dot Finder These fixed magnification scopes mounted on the optical tube are very useful accessories When they are correctly aligned with the telescope objects can be quickly located and bro
15. ng the variable brightness control clockwise until you hear a click Continue rotating the control knob to increase the brightness level Insert a low power eyepiece into the telescope s focuser Locate a bright object and position the telescope so that the object is in the centre of the field of view With both eyes open look through the sight tube at the object If the red dot overlaps the object your Red Dot Finder is perfectly aligned If not turn its azimuth and altitude adjustment controls until the red dot is merged with the object Plastic shipping cover Oberating the AZ1 AZ2 mount This telescope has an altitude up down azimuth left right mount to control telescope movements Loosen the azimuth lock knob to make left right direction movements then tighten to lock Loosen the altitude lock knob to make course up down changes Altitude fine adjustments can be made by rotating the knurled wheel on the altitude fine adjustment rod after tightening the altitude lock knob AZ1 Fig g AZ2 Fig h Operating the AZ3 mount This mount has controls for movement in altitude up down and azimuth left right Coarse azimuth movement is controlled by a locking knob located near the tripod head for left right rotation Loosen the knob to make large direction changes then lock it for fine adjustments Coarse Altitude movement is controlled by a friction bolt Use the micro adjustment control cables to make small altitude and azim
16. rn the knurled black wheel directly underneath the mounting platform on the alt az mount while holding the tube rings in place to secure the telescope in place ATTACHING THE TELESCOPE MAIN TUBE TO TUBE ATTACHING THE TELESCOPE RINGS Fig 4 RINGS Fig 4 1 Find the center of balance of the telescope tube Place this in between the two tube rings Close the hinges around the telescope and fasten securely by tightening the thumb nuts Do not over tighten the thumb nuts 1 Remove the telescope tube from the paper covering 2 Place telescope tube in between the two tube rings Close the hinges around the telescope and fasten securely by tightening the thumb nuts without over tightening TELESCOPE ASSEMBLY INSTALLING CONTROL CABLES Fig 5 1 Slide the sleeve end of the cable over the nipple on the end of the worm gear Secure the cable by tightening the set screw against the flat surface on the nipple ON JEAN Small finderscope Large finderscope Red dot finder ATTACHING THE FINDER ATTACHING THE FINDERSCOPE SCOPE Fig 6 BRACKET RED DOT FINDER Fig 6 1 Locate finderscope optical 1 For finderscope only Locate the finderscope assembly bracket and carefully remove the rubber o ring 2 Remove the two knurled from it Position the o ring into groove on the thumbscrews near the end finderscope tube of the telescope main body 2 Slide finderscope assembly red dot finder into the 3 Position the fi
17. s in the previous magnification example if your 10mm eyepiece has an apparent field of view of 52 degrees then the true field of view is 0 65 degrees or 39 arc minutes Apparent Field of View 52 True Field of View 0 65 Magnification 80X To put this in perspective the moon is about 0 5 or 30 arc minutes in diameter so this combination would be fine for viewing the whole moon with a little room to spare Remember too much magnification and too small a field of view can make it very hard to find things It is usually best to start at a lower magnification with its wider field and then increase the magnification when you have found what you are looking for First find the moon then look at the shadows in the craters Caiculating the exit pupil The Exit Pupil is the diameter in mm of the narrowest point of the cone of light leaving your telescope Knowing this value for a telescope eyepiece combination tells you whether your eye is receiving all of the light that your primary lens or mirror is providing The average person has a fully dilated pupil diameter of about 7mm This value varies a bit from person to person is less until your eyes become fully dark adapted and decreases as you get older To determine an exit pupil you divide the diameter of the primary of your telescope in mm by the magnification Diameter of Primary mirror in mm Exit Pupil TURN Magnification For
18. sed by temperature changes flexures etc This often happens with short focal ratio telescopes particularly when they haven t yet reached outside temperature Refocusing is almost always necessary when you change an eyepiece or add or remove a Barlow lens 10 Altitude fine adjustment Altitude fine adjustment Azimuth adjustment A Altitude adjustment Azimuth adjustment D ue lt Altitude adjustment Azimuth locking knob Altitude fine adjustment Azimuth fine adjustment Eyepiece Refracting Telescopes Eyepiece Barlow Reflecting Telescopes Using the Camera Adapter Tube When you connect a camera directly to your telescope for prime focus photography you sometimes require an adapter so that the camera can be focussed Some reflectors need more length than the focuser can travel in order to focus the camera and some refractors are designed to be used with diagonals so when used with only a camera their focal length has to be extended This is particularly true when photographing near objects Your camera with its telescope lens may focus on a distant object such as a star but will require the 2 5 camera adapter tube to focus on a near object such as a bird The camera adapter tube is easily installed by GD screwing it onto the T threads of the eyepiece the other end of the camera adapter tube Fig l 0 This makes the telescope into a lens which you hol
19. stop and keep your hand there while looking at the back end of your telescope is there a adjusting screw there If P there is you will want to loosen it turn the screw to the left to bring the mirror away from that point If there isn t a adjusting screw there then go across to the other side and tighten the adjusting screw on the other side This will D gradually bring the mirror into line until it looks like Fig t It helps to have a friend to help for primary mirror collimation Have your partner adjust the adjusting screws according to your directions while you look in the focuser After dark go out and point your telescope at Polaris the North Star With an eyepiece in the focuser take the image out of focus You will see the same image only now it will be illuminated by starlight If necessary repeat the collimating process only keep the star centered while tweaking the mirror Primary mirror stop and keep your hand here Both mirrors aligned Both mirrors aligned with with collimating cap in eye looking in focuser Cleaning your telescope Replace the dust cap over end of telescope whenever not in use This prevents dust from settling on mirror or lens surface Do not clean mirror or lens unless you are familiar with optical surfaces Clean finderscope and eyepieces with special lens paper only Eyepieces should be handled with care avoid touching optical surfaces 15 CAUTION NEVER USE YOUR T
20. ught to the centre of the field Alignment is best done outdoors in day light when it s easier to locate objects If it is necessary to refocus your finderscope sight on an object that is at least 500 yards metres away For 5x24 and 6x24 finderscope twist the end of the finderscope until focus is reached Fig a For 6x30 finderscope loosen the locking ring by unscrewing it back towards the bracket The front lens holder can now be turned in and out to focus When focus is reached lock it in position with the locking ring Fig b 1 Choose a distant object that is at least 500 yards away and point the main telescope at the object Adjust the telescope so that the object is in the centre of the view in your eyepiece 2 Check the finderscope to see if the object centred in the main telescope view is centred on the crosshairs 3 For the 5x24 finderscope use the three alignment screws to centre the finderscope crosshairs on the object Fig c For the 6x30 finderscope with spring loading adjust only the two small screws Fig d Azimuth adjustment Sight Tube Like all finderscopes the Red Dot Finder must be properly aligned with the main telescope before use This is a simple process using the azimuth and altitude control knobs 1 Open the battery cover by pulling it down you can gently pry at the 2 small slots and remove the plastic shipping cover over the battery Fig f Turn on the Red Dot Finder by rotati
21. uth movements such as centreing objects in view The micro adjustment controls have limited travel so it is best to centre them on their threads before making a coarse adjustment Fig i Using the Barlow lens A Barlow is a negative lens which increases the magnifying power of an eyepiece while reducing the field of view It expands the cone of the focussed light before it reaches the focal point so that the telescope s focal length appears longer to the eyepiece The Barlow is inserted between the focuser and the eyepiece in a reflector and usually between the diagonal and the eyepiece in a refractor or a catadioptric Fig j With some telescopes it can also be inserted between the focuser and the diagonal and in this position it gives even greater magnification For example a 2X Barlow when inserted after the diagonal can become 3X when placed in front of the diagonal In addition to increasing magnification the benefits of using a Barlow lens include improved eye relief and reduced spherical aberration in the eyepiece For this reason a Barlow plus a lens often outperform a single lens producing the same magnification However it is greatest value may be that a Barlow can potentially double the number of eyepiece in your collection Focusing Slowly turn the focus knobs Fig k one way or the other until the image in the eyepiece is sharp The image usually has to be finely refocused over time due to small variations cau
22. y ground fog Sometimes low fog banks help to block light pollution if you get above them Try to have a dark unobstructed view of the horizon especially the southern horizon if you are in the Northern Hemisphere and vice versa However remember that the darkest sky is usually at the Zenith directly above your head It is the shortest path through the atmosphere Do not try to observe any object when the light path passes near any protrusion on the ground Even extremely light winds can cause major air turbulence as they flow over the top of a building or wall If you try to observe on any structure or even a sidewalk movements you make may cause the telescope to vibrate Pavement and concrete can also radiate stored heat which will affect observing Observing through a window is not recommended because the window glass will distort images considerably And an open window can be even worse because warmer indoor air will escape out the window causing turbulence which also affects images Astronomy is an outdoor activity Choosing the best time to observe The best conditions will have still air and obviously a clear view of the sky It is not necessary that the sky be cloud free Often broken cloud conditions provide excellent seeing Do not view immediately after sunset After the sun goes down the Earth is still cooling causing air turoulence As the night goes on not only will seeing improve but air pollution and ground lights will often
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