8
6.●
Make azimuth adjustments:
a)●
Pick a second star that is at least 40 degrees
away from the first star, and that is away
from the pole.
●●Choose●a●star●that●is●in●the●
south,●east,●or●west,●if●you●are●in●the●northern●
hemisphere;●in●the●north,●east●or●west●if●you●are●
in●the●southern●hemisphere.●●●You●can●choose●
this●star●from●the●table●in●Appendix●I●if●you●wish.●●●●
If●you●have●not●eliminated●all●of●the●orthogonality●
error,●make●sure●that●your●second●star●is●on●the●
same●side●of●the●meridian●as●the●first●star●from●
the●altitude●adjustment●portion●of●the●proce-
dure.●●●●●You●do●not●want●the●telescope●to●swap●
sides●and●introduce●any●remaining●orthogonality●
issues●into●the●azimuth●adjustment.
b)●
Use the GOTO to slew to the second star.
c)●
Make THE ENTIRE centering correction with
the azimuth adjuster.
●●Note●that●this●movement●
could●be●along●either●crosshair,●or●from●a●point●
in●between●depending●on●where●in●the●sky●you●
chose●your●second●star.●●●As●the●Horizon●Circle●
diagram●at●left●shows,●
stars●that●are●in●the●east●
or●west●will●result●in●
azimuth●adjustments●
that●are●N-S.●●●●A●star●along●the●meridian●in●the●south●(or●in●the●north●if●you●are●in●the●
southern●hemisphere)●will●result●in●azimuth●adjustments●that●are●E-W.●●●●A●star●chosen●
between●the●cardinal●compass●points●will●not●parallel●either●crosshair●as●it●is●adjusted.●●●
Wherever●you●land●after●the●GoTo●slew,●however,●the●azimuth●adjustment●will●take●you●
toward●the●center●of●the●crosshairs.●●●●(Ignore●any●small●perpendicular●displacement●as●your●
azimuth●adjustment●brings●you●to●the●center●of●the●eyepiece●crosshairs,●especially●if●your●
second●star●is●near●the●horizon,●as●it●will●likely●be●from●atmospheric●refraction.)●●●●●●
d)●
No need to Re-calibrate since you have NOT used the direction buttons to do any final centering.
●●●If●you●do●
end●up●tweaking●with●the●direction●buttons,●then●go●ahead●
and●re-calibrate,●but●you●should●not●really●need●to●do●this.
e)●
Slew back to the first star (Altitude Adjustment Star).
●●●●
Since●it●is●almost●directly●overhead,●it●should●be●virtually●
centered●in●the●crosshair.●●●●This●is●because●the●azimuth●
adjustment●you●made●is●mostly●rotating●the●mount●around●
an●imaginary●axis●that●would●go●straight●up●through●this●
star.●●●
f)●
If needed, center with the direction buttons only, and
then re-calibrate.
●●
g)●
Repeat as needed.
●●●Slew●back●and●forth●between●the●
altitude●star●and●second●star,●making●the●adjustment●de-
scribed●in●6-c●above●on●the●second●star●each●time.●●
7.● When●these●two●adjustments●are●finished,●you●will●be●very●accurately●polar-aligned.●If●you●wish,●you●can●refine●this●
further●by●using●a●crosshair●eyepiece●in●your●main●instrument●and●repeating●the●procedure.●●●The●higher●magnification●
of●the●main●instrument●will●allow●greater●precision●than●the●finderscope.●●●However,●the●finderscope●had●its●orthogonal-
ity●error●removed●during●the●altitude●portion●of●the●alignment.●●●If●you●move●to●the●main●instrument,●you●will●see●the●
effects●of●any●orthogonality●error●in●your●main●instrument●assembly,●and●you●can’t●simply●remove●this●error●by●turning●
adjustment●screws.●●●The●accuracy●when●using●your●main●instrument●also●depends●on●how●well●your●telescope●holds●its●
orthogonality.●Any●mirror●shifting●or●diagonal●misalignment●(that●applies●to●refractor●diagonals●as●well)●will●not●only●com-
promise●the●polar●alignment,●but●also●the●ability●to●accurately●center●objects●when●slewing●from●one●to●another.●Please●
refer●to●the●Orthogonality●section●for●further●discussion.
