Meade Model 4500 Reflecting Telescope (User Manual)
The Model 4500 provides stunning optical performance on the Moon, planets, and in deep-space, where its larger aperture is most advantageous. The telescope includes a high-precision equatorial mount with manual slow-motion controls on both axes. The all-aluminum tripod allows for a solid, but lightweight, observing platform.
#531 Electric Motor Drive: For fully automatic tracking of astronomical objects, the Meade #531 Motor Drive is available for attachment to equatorial telescope Models 285, 395, and 4500.
A Word about “Power:” When buying a telescope one of the least important factors to consider is the power, or magnification, of the instrument. The key to observing fine detail, whether on the surface of the Moon or on a license plate one mile in the distance, is not power, but aperture- i.e.., the diameter of the telescope’s main (objective) lens or primary mirror. The power at which a telescope is operating is determined by the eyepiece employed; all Meade telescopes include one or more eyepieces as standard equipment, and optional eyepieces are available for higher or lower powers. Within reason power is useful, but the most common mistake of the beginning observer is to “overpower” the telescope and to use magnifications which the telescope’s aperture and typical atmospheric conditions can not reasonably support. The result is an image which is fuzzy, ill-defined, and poorly resolved, through no fault of the telescope. Keep in mind that a smaller, lower-power, but brighter and well-resolved, image is far superior to a large, high-power, but dim and poorly-resolved, one.
How to Calculate Power: The magnification, or power, at which a telescope is operating is a function of the focal length of the telescope’s main (objective) lens (or primary mirror) and the focal length of the eyepiece employed. The focal length of the objective lens is the distance between the lens and the point at which it brings light rays to a focus; this focal length (in mm) is printed on a label affixed to the optical tube of every Meade telescope. The focal length of each eyepiece (which typically ranges from 4mm to about 40mm) is printed on the upper surface of the eyepiece. To calculate power, divide the focal length of the eyepiece into the focal length of the objective lens. Example: The Meade Model 390 telescope has an objective lens focal length of 1000mm; when this telescope is used with a 25mm eyepiece, a power of 1000 ÷ 25 = 40 power (written as “40X”) results.
Choosing Your Eyepieces: Depending on how much you plan to use your telescope, and for what applications, you may wish to add 2 or 3 eyepieces and/or a multiplying “Barlow” lens, to the eyepieces included as standard equipment. On any of Meade Models 230, 285, 390, 395, or 4500, eyepieces of 25mm or 40mm focal length are best suited for extended star fields or nebulosity’s (such as the Orion Nebula), or for terrestrial applications: these eyepieces result in low-powers, wide fields, and bright images. On the Moon and planets eyepieces between 4mm (high power) and 18mm (moderate power) are advised, although the highest powers should be employed only under favorable atmospheric conditions. The Meade #126 2x Short-Focus Barlow Lens can be used in conjunction with an eyepiece, and results in a doubling of the power obtained when the eyepiece is used alone.
Using an Electric Motor Drive: Meade equatorially mounted telescope Models 285, 395, and 4500 include manual slow-motion controls for tracking astronomical objects as they move across the sky. While the stars, Moon, planets, and other celestial objects do not appear to be in motion when viewed without a telescope, in fact all such objects are in constant apparent motion due to the earth’s rotation on its axis once every 24 hours. The effect of the telescope’s magnification is to greatly speed up this apparent motion, to the point where, without operation of the telescope’s tracking controls, objects quickly (within 10 to 30 seconds) move out of the telescopic field of view. Alternately, the Meade #531 Electric Motor Drive may be added optionally to any Meade equatorial model, and results in completely automatic tracking of astronomical objects. The #531 Motor Drive has no external wires or cords; the drive’s DC servo motor is powered by 3 internal AA-size (user-supplied) batteries.
|Meade Model 4500 Reflecting Telescope Instruction ManualSource: Meade Instruments Corporation web site.|
A. Introducing the Meade Model 4500
The Model 4500 is an easy-to-operate, high performance 4.5″ (114mm) reflecting telescope, intended for astronomical observing. Equipped with a deluxe equatorial mount and aluminum tripod, the telescope’s motion is continuously adjustable for tracking celestial objects. Your telescope comes to you ready for adventure; it will be your companion in a universe of planets, galaxies, and stars. Please note that the Model 4500 is a Newtonian reflecting telescope optimized for astronomical observing performance and is not intended for terrestrial observing.
Figure 1: Meade Model 4500: 4.5″ Equatorial Reflecting Telescope
1. Tripod legs
2. Equatorial mount
3. R.A. flexible cable control
4. Dec. flexible cable control
6. Counterweight shaft
7. Counterweight lock
8. Safety washer/thumbscrew
9. Latitude lock
10. Polar axis
11. Latitude adjustment knob
12. Optical tube assembly
13. Optical tube saddle plate
14. Cradle rings
15. Cradle ring lock knobs
16. Viewfinder bracket mounting bolts
18. Focuser thumbscrew
20. Viewfinder bracket
21. Declination axis
22. R.A. lock
23. Dec. lock
24. 6 x 30 viewfinder
25. Telescope front dust cover
26. Viewfinder bracket thumbscrews
27. R.A. setting circle
28. Dec. setting circle
29. Latitude dial
30. Azimuth lock
31. Focus knobs
32. Polar shaft acorn cap nut
33. Azimuth base
34. Azimuth shaft bolt
35. R.A. worm block assembly
36. Dec. worm block assembly
37. Cradle ring attachment knobs
38. Tripod leg Phillips-head fastener screws
39. Tripod-to-mount attachment points
40. Accessory shelf
41. Accessory shelf central mounting knob
42. Tripod leg brace supports
43. Tripod leg lock knobs
1. This Manual
These instructions detail the set-up, operation, specifications, and optional accessories of your Meade Model 4500. In order that you may achieve maximum enjoyment of the instrument, we urge that you take a few minutes to read all of this manual before making first observations through the telescope. As you read this manual, the technical terms associated with telescopes will be made clear.
2. Standard Equipment
- Complete optical tube assembly with a 4.5″ (114mm) diameter primary mirror, viewfinder mounting bolts with mounting nuts and 1.25″ rack-and-pinion focuser. Mirror focal length = 910mm; f/8.
- Equatorial mount with pre-attached heavy duty, continuously adjustable, aluminum tripod and leg braces.
- MA25mm (36X) eyepiece (1.25″O.D.)
- Cradle rings with lock knobs
- 6 x 30 viewfinder and bracket
- Counterweight with counterweight shaft
- Flexible cable controls for both telescope axes
- Accessory shelf with mounting knob
B. Unpacking and Assembly
Your Meade Model 4500 comes to you packaged almost entirely pre-assembled. You will find upon opening the gift box that there are two compartments within that contain the optical tube assembly and the tripod with equatorial mount. The accessories described above will be located within compartments custom-cut into the Styrofoam block inserts. (References herein [e.g., (6)] are to Fig.1 unless otherwise specified.)
- Remove and identify the telescope’s Standard Equipment listed in Section A.2., above.
- The three tripod lock knobs (43) have been removed from the bottom section of each tripod leg to insure safe arrival of the tripod assembly. To install, thread in each tripod lock knob into the threaded hole located at the right side of each of the three gray colored castings (see Fig.1 inset) at the bottom of each tripod leg. Tighten the tripod lock knob only to a “firm feel” to avoid damage to the tripod caused by over tightening.
- Spread the tripod legs (1) to full extension so that the leg braces (42) are taut (should one of the tripod leg braces slip out of the center triangle fastener, merely reposition the brace and slide it back into position). Adjust the tripod with the attached equatorial mount (2) to the desired height by loosening the tripod lock knobs and extend the sliding inner section of each tripod leg; then tighten each knob.
- Remove the mounting knob (41) from the round accessory shelf (40). Place the accessory shelf on top of the center triangle leg brace fastener of the tripod (1) so that the threaded stud protruding from the bottom of the shelf (40) passes through the hole in the center. Then replace and tighten the accessory shelf mounting knob (41).
- Attach the flexible cable controls (3) and (4). These cable controls are secured in place with a firm tightening of the thumbscrew located at the end of each cable.
- Holding the counterweight (5) firmly in one hand, slip the counterweight onto the counterweight shaft (6). Attach the counterweight (5) and counterweight shaft (6), by supporting the unlocked (7) counterweight firmly in one hand, while threading the counterweight shaft into the base of the Declination axis of the telescope’s equatorial mount with the other (see Fig. 1). Once firmly attached, slide the counterweight to the midpoint on the counterweight shaft and secure it in place with the lock knob (7) of the counterweight. Note: If the counterweight ever slips, the secured threaded safety washer/knob (8) will not let the weight slide entirely off the counterweight shaft. Be certain that this safety washer/knob is always in place.
- Release the latitude lock (9) of the equatorial mount, and tilt the polar axis (10) of the telescope to roughly a 45° angle by turning the latitude adjustment knob (11). With the polar axis thus tilted, firmly re-tighten the latitude lock.
- Loosen the lock knobs (15) of the cradle rings (14) and open the cradle rings to position them over the optical tube assembly (12). Turn the lock knobs a few turns to keep the cradle rings closed, but to still allow the cradle rings to slide freely up-and-down the main tube.
- Remove the viewfinder bracket mounting nuts from the viewfinder bracket mounting bolts (16) that protrude from the optical tube (12), near the focuser. Place the viewfinder bracket’s mounting holes (located at the base of the bracket) over the mounting bolts, so that the bracket is oriented as shown in Fig. 1. Replace the viewfinder bracket mounting nuts, and tighten to a firm feel. Then center the viewfinder in both bracket rings by backing off the three thumbscrews (26) on each bracket ring. Orient the viewfinder so its front objective lens is pointing in the same direction as the open end (front) of the optical tube (25).
- While firmly holding the optical tube (12), position it onto the optical tube saddle plate (13), with the mid-point of the optical tube’s length lying roughly in the center of the saddle plate. Then slide the cradle rings (14) over the saddle plate of the mount. Tighten the cradle ring attachment knobs (37) to a firm feel when the cradle rings are positioned over the telescope’s saddle (13). Then tighten the cradle ring lock knobs (15) to a firm feel; do not over tighten these knobs. Please note that you may want to change the rotational position of the optical tube to gain a more comfortable observing position of the focuser (17). This adjustment may be performed several times in one observing session, as desired.
- Insert the MA25mm eyepiece (19) into the focuser, and tighten the focuser thumbscrew (18) to secure the eyepiece.
The telescope is now fully assembled. Before it can be properly used, however, the telescope must be balanced and the viewfinder aligned.
1. Balancing the Telescope
In order for the telescope to move smoothly on its mechanical axes, it must first be balanced about the 2 telescope axes: the polar axis (10) and the Declination axis (21). All motions of the polar aligned telescope (more on this later) take place by moving about these two axes, separately or simultaneously. To obtain a fine balance of the telescope, follow the method below:
- Loosen the R.A. lock (22) and rotate the telescope so that the counterweight shaft (6) is parallel to the ground (horizontal).
- Slide the counterweight along the counterweight shaft until the telescope remains in one position without tending to drift down in either direction. Then tighten the counterweight lock knob (7), locking the counterweight in position.
- Lock the R.A. lock (22), and unlock the Declination lock (23). The telescope will now turn freely about the Declination axis. Loosen the cradle ring lock knobs (15) so that the main tube in the cradle rings slides easily up-or-down in the cradle rings. Move the main tube in the cradle rings until it is balanced rotationally about the Declination axis. Re-lock the knobs (15).The telescope is now properly balanced on both axes.
2. Alignment of the Viewfinder
The wide field of view provided by the 6 x 30mm viewfinder permits easy object sighting prior to observation in the higher-power main telescope. The 6 x 30 Viewfinder (24) and viewfinder bracket (20) should be attached to the telescope tube assembly as described above (see Figure 1). In order for the viewfinder to be functional, however, it must be aligned to the main telescope, so that both the viewfinder and main telescope point at the same position in the sky. With this simple alignment performed, finding objects is greatly facilitated, since you will first locate an object in the wide-field viewfinder, then you will look in the eyepiece of the main telescope for a detailed view. To align the viewfinder follow these steps:
- Remove the telescope front dust cover (25), and the dust covers of the viewfinder.
- Place the low- power (MA25mm) eyepiece into the focuser of the main telescope.
- Unlock the R.A. lock (22) and the Dec. lock (23) so that the telescope turns freely on both axes. Then point the main telescope at some well-defined land object (e.g., the top of a telephone pole) at least 200 yards distant, and re-lock the R.A and Dec. axes. Turn the flexible cable controls, (3) and (4), to center the object in the telescopic field.
- With the front of the viewfinder already centered in the front bracket ring, look through the viewfinder and loosen or tighten, as appropriate, one or more of the rear viewfinder bracket ring thumbscrews (26) until the viewfinder’s crosshairs are likewise centered on the object previously centered in the main telescope.
- Check this alignment on a celestial object, such as a bright star or the Moon, and make any refinements necessary, using the method outlined above.With this alignment performed, objects first located in the wide-field viewfinder will also be centered in the main telescope’s field of view. (Note: The viewfinder and telescope present an image which is upside-down.)
C. Understanding Celestial Movements and Coordinates
To line up the Model 4500 with the pole, follow this procedure:
- Release the Azimuth lock (30) of the Azimuth base (33), so that the entire telescope-with-mounting may be rotated in a horizontal direction. Rotate the telescope until the polar axis (10) points due North. Use a compass or locate Polaris, the North Star (see diagram), as an accurate reference for due North.
- Level the mount, if necessary, by adjusting the heights of the three tripod legs.
- Determine the latitude of your observing location by checking a road map or atlas. Release the latitude lock (9) and tilt the telescope mount with the latitude adjustment knob (11) so that the pointer indicates the correct latitude of your viewing location on the latitude scale (29). Re-tighten the latitude lock (9).
- If steps (1) – (3) above were performed with reasonable accuracy, your telescope is now sufficiently well-aligned to the North Celestial Pole for visual observations.
Once the mount has been polar-aligned as described above, the latitude angle need not be adjusted again unless you move to a different geographical location (i.e. a different latitude). The only polar alignment procedure that need be done each time you use the telescope is to point the polar axis due North, as described in step (1) above.
D. Using the Telescope
With the telescope assembled, balanced and polar aligned as described above, you are ready to begin observations. Decide on an easy-to-find object such as the Moon, if it is visible, or a bright star, to become accustomed to the functions and operations of the telescope. For the best results during observations, follow the suggestions below:
- To center an object in the main telescope, loosen the telescope’s R.A. lock (22) and Dec. lock (23). The telescope can now turn freely on its axes. Use the aligned viewfinder to first sight-in on the object you wish to observe; with the object centered on the viewfinder’s crosshairs, re-tighten the R.A. and Dec. locks.
- If you have purchased an assortment of eyepieces always start an observation with a low power eyepiece (e.g., the MA25mm eyepiece); get the object well-centered in the field of view and sharply focused. Then try the next step up in magnification. If the image starts to become fuzzy as you work into higher magnifications, then back down to a lower power; the atmospheric steadiness is not sufficient to support high powers at the time you are observing. Keep in mind that a bright, clearly resolved but smaller image will show far more detail than a dimmer, poorly resolved larger image. The MA25mm eyepiece included with the Model 4500 presents a wide field of view, ideal for general astronomical observing of star fields, clusters of stars, nebulae, and galaxies; it is also probably the best eyepiece to use in the initial finding and centering of any object.
- Once centered, the object can be focused by turning one of the knobs of the focusing mechanism (31). You will notice that the astronomical object in the field of view will begin to slowly move across the eyepiece field. This motion is caused by the rotation of the Earth on its axis, as described in Section C, although the planets and stars, are, for practical purposes, fixed in their positions in the sky. The platform on which the telescope is sitting (the Earth) rotates once every 24 hours under these objects. To keep astronomical objects centered in the field of the polar aligned telescope, simply turn the R.A. flexible cable control (3). These objects will appear to move through the field more rapidly at higher powers. Note that the Declination flexible cable control is used only for centering purposes, and not for tracking.
- Avoid touching the eyepiece while observing through the telescope. Vibrations resulting from such contact will cause the image to move. Likewise, avoid observing sites where ground-based vibrations may resonate the tripod. Viewing from the upper floors of a building may also introduce image movement.
- You should allow a few minutes to allow your eyes to become “dark adapted” before attempting any serious astronomical observations. Use a red filtered flashlight to protect your night vision when reading star maps or inspecting the components of the telescope.
- Avoid setting up the telescope inside a room and observing through an open window (or worse yet, a closed window). Images viewed in such a manner may appear blurred or distorted due to temperature differences between inside and outside air. Also, it is a good idea to allow your telescope a chance to reach the ambient (surrounding) outside temperature before starting an observing session.
- Avoid viewing objects low on the horizon. Objects will appear better resolved with far greater contrast when viewed higher in the sky. Also, if images appear to “shimmer” in the eyepiece, reduce power until the image steadies. This condition is caused by air turbulence in the upper atmosphere.The Meade Model 4500 may be used for a lifetime of rewarding astronomical observing, but basic to your enjoyment of the telescope is a good understanding of the instrument. Read the above instructions carefully until you understand all of the telescope’s parts and functions. One or two observing sessions will serve to clarify these points forever in your mind.The number of fascinating objects visible through your Meade reflector is limited only by your own motivation. Astronomical software, such as Meade’s AstroSearch, or a good star atlas, such as Meade Star Charts will assist you in locating many interesting celestial objects. These objects include:
- Cloud belts across the surface of the planet Jupiter.
- The 4 major satellites of Jupiter, visible in rotation about the planet, with the satellite positions changing each night.
- Saturn and its famous ring system, as well as several satellites of Saturn, much fainter than the major satellites of Jupiter.
- The Moon: A veritable treasury of craters, mountain ranges and fault lines. The best contrast for viewing the Moon is during its crescent phase. The contrast during the full Moon phase is low due to the angle of illumination.
- Deep-Space: Nebulae, galaxies, multiple star systems, star clusters hundreds of such objects are visible through the Model 4500.
E. Using Setting Circles
Setting circles of the polar aligned equatorial mount can facilitate the location of faint celestial objects not easily found by direct visual observation. To use the setting circles, follow this procedure:
- Use a star chart or star atlas, and look up the celestial coordinates, Right Ascension and Declination (R.A. and Dec.), of an easy-to-find bright star that is within the general vicinity of the faint object you wish to locate.
- Center the determined bright star in the telescope’s field of view.
- Manually turn the R.A. setting circle (27) to read the R.A. of the object now in the telescope’s eyepiece.
- The setting circles are now calibrated (the Dec. setting circle (28) is factory calibrated). To locate a nearby faint object using the setting circles determine the faint object’s celestial coordinates from a star chart, and move the telescope in R.A. and Declination until the setting circles read the R.A. and Dec. of the object you are attempting to locate. If the above procedure has been carefully performed, the faint object will now be in the field of a low power eyepiece.The R.A. Setting Circle must be manually re-calibrated on the current Right Ascension of a star every time the telescope is set up, and reset to the centered object’s R.A. coordinate before moving to a new R.A. coordinate setting. The R.A. Setting Circle has two sets of numbers, the inner set is for Southern hemisphere use while the outer set of numbers (the set closest to the R.A. gear), is for use by observers located North of the Earth’s equator (e.g., in North America).
F. Calculating Power
The power, or magnification of the telescope depends on two optical characteristics: the focal length of the main telescope and the focal length of the eyepiece used during a particular observation. For example, the focal length of the Model 4500 telescope is fixed at 910mm. To calculate the power in use with a particular eyepiece, divide the focal length of the eyepiece into the focal length of the main telescope. For example, using the MA25mm eyepiece supplied with the Model 4500, the power is calculated as follows:
Power = 910mm ÷ 25mm= 36X
Meade Instruments manufactures several types of eyepiece designs that are available for your telescope. The type of eyepiece (“MA” Modified Achromatic, “SP” Super Plössl, etc.) has no bearing on magnifying power but does affect such optical characteristics as field of view, flatness of field, eye-relief, and color correction.
The maximum practical magnification is determined by the nature of the object being observed and, most importantly, by the prevailing atmospheric conditions. Under very steady atmospheric “seeing,” the Model 4500 may be used at powers up to about 228X on astronomical objects. Generally, however, lower powers of perhaps 75X to 175X will be the maximum permissible, consistent with high image resolution. When unsteady air conditions prevail (as witnessed by rapid “twinkling” of the stars), extremely high-power eyepieces result in “empty magnification,” where the object detail observed is actually diminished by the excessive power.
Assorted eyepieces are available both to increase and decrease the operating eyepiece power of the telescope. If the Model 4500 is used on a regular basis, a selection of four to five eyepieces is recommended. For example, an eyepiece assortment of focal lengths 40mm, 25mm, 12.5mm, 9mm, and 6mm yields a magnifying range of 22.5X, 36X, 72X, 101X, and 150X respectively. A high quality Barlow Lens, such as the Meade #126 2x Telenegative Barlow Lens, serves to double the power of each of these eyepieces. To use the Barlow Lens, insert the #126 unit into the telescope’s focuser first, followed by an eyepiece; the power thus obtained is then double the power obtained when the eyepiece is used alone. For example, the MA25mm eyepiece, when used in conjunction with the #126 2x Telenegative Barlow Lens yields 72X.
As with any quality instrument, lens or mirror surfaces should be cleaned as infrequently as possible. Front surface aluminized mirrors, in particular, should be cleaned only when absolutely necessary. In all cases avoid touching any mirror surface. A little dust on the surface of a mirror or lens causes negligible loss of performance and should not be considered reason to clean the surface. When lens or mirror cleaning does become necessary, use a camel’s hair brush or compressed air gently to remove dust. If the telescope’s dust cover is replaced after each observing session, cleaning of the optics will rarely be required.
2. Mount and Tripod Adjustments
Every Meade Model 4500 equatorial mount and tripod is factory inspected for proper fit and function prior to shipment. It is unlikely that you will need to adjust, or tighten these parts after receipt of the telescope. However, if the instrument received unusually rough handling in shipment, it is possible that some of these assemblies can be loose. To make adjustments you will need a 1/2″ or 11/16″ socket or adjustable end wrench, a 5/64″ hex wrench, and a Phillips-head screwdriver.
The equatorial mount has four main areas that can be adjusted: A loose polar shaft can be tightened by releasing a 5/64″ hex set-screw that is on the side of the 11/16″ polar shaft acorn cap nut (32), and then turning the 11/16″ acorn cap nut clockwise to a firm feel, and then tightening the 5/64″ hex set-screw. A loose Azimuth base (33), can be tightened by turning the 11/16″ Azimuth shaft bolt (34), located underneath the mount and in between the three tripod legs, clockwise to a firm feel. The R.A. (35), and Dec. (36) worm block assemblies can have backlash removed by releasing the 2 Phillips-head screws on each assembly, applying pressure to the worm block against the worm gear, and then tightening the Phillips-head screws. Note that over tightening of any of the nuts, bolts, or screws can inhibit the smooth rotating action of the axes and gears, and may result in stripping the threads.
The tripod legs have 1/2″ nuts (39), and Phillips-head screws (38) that may have backed off, may also be tightened to a firm feel for the most sturdy performance of the telescope.
3. Collimation (Alignment) of the Optics
All Meade Model 4500 telescopes are optically aligned at the factory prior to shipment. It is unlikely that you will need to align, or collimate, the optics after receipt of the instrument. However, if the telescope received unusually rough handling in shipment, it is possible that the optics must be re-aligned for best optical performance. In any case this alignment procedure is simple, and requires only a few minutes the very first time the telescope is used. Take the time to familiarize yourself with the following collimation procedure, so that you will recognize a properly collimated instrument and can adjust the collimation yourself, if necessary.
a. Correct collimation
The properly collimated (aligned) mirror system in the Model 4500 assures the sharpest images possible. This occurs when the primary mirror and diagonal mirror are tilted so that the focused image (see diagram) falls directly through the center of the focuser drawtube (17, Fig. 1). These mirror tilt adjustments are made with the diagonal assembly (Fig. 5) and the primary mirror cell (Fig. 6), and will be discussed later.
To inspect the view of the mirror collimation, look down the focuser drawtube with the eyepiece removed. The edge of the focuser drawtube (1, Fig. 7), will frame the reflections of the primary mirror with the 3 mirror clips (2, Fig. 7), the diagonal mirror (3, Fig. 7) , the spider vanes (4, Fig. 7), and your eye (5, Fig. 7). Properly aligned, all of these reflections will appear concentric (i.e. centered) as illustrated in Figure 7. Any deviation from the concentric reflections will require adjustments to the diagonal assembly (Fig. 5), and/or the primary mirror cell (Fig. 6).
b. Spider vane adjustments
If the diagonal mirror (1, Fig. 8) is left or right of center within the drawtube (2, Fig. 8), loosen the spider vane adjustment/lock knobs (1, Fig. 5) located on the outside surface of the main tube and slide the entire diagonal assembly up or down the tube along the slotted holes, until the diagonal mirror is centered in the drawtube.
If the diagonal mirror (1, Fig. 8) is above or below of center within the drawtube, thread in one of the spider vane adjustment/ lock knobs while unthreading the other. Only make adjustments to 2 knobs at a time until the diagonal mirror is in the drawtube. When the spider vane is correctly positioned, it will look like Fig. 9. (Note that the diagonal mirror is misaligned.)
c. Diagonal holder adjustments
If the diagonal mirror (1, Fig. 9) is centered in the drawtube (2, Fig. 9), but the primary mirror is only partially visible in the reflection (3, Fig. 9), the 3 Phillips-head diagonal tilt screws (2, Fig. 5) must be unthreaded slightly to the point of where you can rotate the diagonal holder (3, Fig. 5) from side-to-side by grasping the diagonal holder with your hand and rotating until you see the primary mirror become as centered in the reflection of the diagonal mirror as possible. Once you are at the best position, thread in the 3 Phillips-head diagonal tilt screws to lock the rotational position. Then, if necessary, make adjustments to these 3 Phillips-head screws to refine the tilt-angle of the diagonal mirror until the entire primary mirror can be seen centered within the diagonal mirror reflection. When the diagonal mirror is correctly aligned, it will look like Fig. 10. (Note that the primary mirror is shown out of alignment.)
d. Primary mirror adjustments
If the diagonal mirror (1, Fig. 10) and the reflection of the primary mirror (2, Fig. 10) appear centered within the drawtube (3, Fig. 10), but the reflection of your eye and the reflection of the diagonal mirror (4, Fig. 10) appear off-center, you will need to adjust the primary mirror tilt Phillips-head screws of the primary mirror cell (3, Fig. 6). These primary tilt screws are located behind the primary mirror, at the lower end of the main tube. See Fig. 4. To adjust the primary mirror tilt screws, first unscrew several turns, the 3 hex-head primary mirror cell locking screws (2, Fig. 6) that are next to each primary mirror tilt Phillips-head screw. Then by trial-and-error, turn the primary mirror tilt Phillips-head screws (3, Fig. 6) until you develop a feel for which way to turn each screw to center the reflection of your eye. Once centered, as in Fig. 7, turn the 3 hex-head primary mirror cell locking screws (2, Fig. 6) to relock the tilt-angle adjustment.
e. Star testing the collimation
With the collimation performed, you will want to test the accuracy of the alignment on a star. Use the MA25mm eyepiece and point the telescope at a moderately bright (second or third magnitude) star, then center the star image in the telescope’s field-of-view. With the star centered follow the method below:
- Bring the star image slowly out of focus until one or more rings are visible around the central disc. If the collimation was performed correctly, the central star disk and rings will be concentric circles, with a dark spot dead center within the out-of-focus star disk (this is the shadow of the secondary mirror), as shown in Fig.11C. (An improperly aligned telescope will reveal elongated circles (Fig. 11A), with an off-center dark shadow.)
- If the out-of-focus star disk appears elongated (Fig. 11A), you will need to adjust the primary mirror Phillips-head tilt screws of the primary mirror cell (3, Fig. 6).
- To adjust the primary mirror tilt screws (3, Fig. 6), first unscrew several turns the 3 hex-head primary mirror cell locking screws (2, Fig. 6), to allow free turning movement of the tilt knobs.
- Using the flexible cable controls (3) and (4), Fig. 1, move the telescope until the star image is at the edge of the field-of-view in the eyepiece, as in Fig. 11B.
- As you make adjustments to the primary mirror tilt screws (3, Fig. 6), you will notice that the out-of-focus star disk image will move across the eyepiece field. Choose one of the 3 primary mirror tilt screws that will move the star disk image to the center of the eyepiece field.
- Repeat this process as many times as necessary until the out-of-focus star disk appears as in Fig. 11C, when the star disk image is in the center of the eyepiece field.
- With the star testing of the collimation complete, tighten the 3 hex-head primary mirror locking screws (2, Fig. 6).
H. Specifications: Model 4500
Primary (main) mirror focal length: 910mm
Primary mirror diameter: 4.5″ (114mm)
Focal ratio: f/8
Mounting: German equatorial