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Correct Collimation
A properly collimated (aligned) mirror system in your Starfinder
Dobsonian telescope assures the sharpest images possible.
Your Starfinder is properly aligned when the primary mirror
(3, Fig. 4) and secondary mirror (2, Fig. 4) are tilted so that the
focused image (6, Fig. 4) falls directly through the center of the
focuser drawtube (5, Fig. 4).
To inspect the view of the mirror collimation, remove the
eyepiece and look down the focuser drawtube. The round edge
of the focuser drawtube (1, Fig. 6) will frame the reflections of
the primary mirror with the secondary mirror (2, Fig. 6) the
spider vanes (3, Fig. 6) and your eye (4, Fig. 6). Properly
aligned, all of these reflections will appear concentric (i.e.
centered) as illustrated in Fig. 6. Any deviation from the
concentric reflections will require adjustments to the secondary
mirror assembly (Fig. 5), and/or the primary mirror cell.
Spider Vane Adjustments
Looking down the open end of the telescope tube, check to see
if the secondary mirror system is centered in the optical tube. If
the assembly is off-center, loosen one of the spider vane
adjustment/lock knobs while unscrewing the opposite knob.
Only make adjustments to 2 knobs at a time until the secondary
mirror is centered in the drawtube. When the spider vane is
correctly positioned, the view through the drawtube will look like
Fig. 4: Newtonian Reflecting Telescope. (1) Spider Vanes; (2) Secondary Mirror; (3) Parabolic Primary Mirror; (4) Primary Mirror Hex Screws;
(5) Focuser Drawtube; (6) Focused Image.
1
2
3
4
5
6
Fig. 5: Secondary Mirror Assembly. (1) Spider Vanes; (2) Tilt Screws;
(3)Secondary Mirror Holder.
Face-on view Edge-on view
1
3
2
Fig. 6: Correct Collimation. (1) Round Edge of Focuser Drawtube;
2) Secondary Mirror; (3) Spider Vanes; (4) Eye.
Fig. 7: Spider Vane Misalignment. (1) Secondary Mirror; (2) Round
Edge of Focuser Drawtube.
Fig. 8: Secondary Mirror Misalignment. (1) Secondary Mirror;
(2) Round Edge of Focuser Drawtube; (3) Reflection of Primary Mirror.
Fig. 9: Primary Mirror Misalignment. (1) Secondary Mirror; (2) Round
Edge of Focuser Drawtube; (3) Eye.