Quote:
Originally Posted by Paul Haese
Gary does Tpoint put you at the refracted pole via the corrections it gives you?
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Hi Paul,
The actual numerical value for the ME term that TPOINT provides is for the true pole.
However, adjusting ME for the refracted pole is made trivial by use of a lookup table.
The following box is a table straight out of the TPOINT manual.
HTML Code:
lat 0m 250m 500m 1000m 1500m 2000m 2500m 3000m
85 5 5 5 4 4 4 4 4
80 10 10 9 9 8 8 8 7
75 15 15 14 14 13 12 12 11
70 20 20 19 18 17 17 16 15
65 26 25 25 24 22 21 20 19
60 32 31 31 29 28 26 25 24
55 39 38 37 35 34 32 30 29
50 47 46 45 42 40 38 36 35
45 56 54 53 50 48 46 43 41
40 66 65 63 60 57 54 52 49
35 80 78 76 72 68 65 62 59
30 96 94 92 87 83 79 75 71
25 119 116 113 108 102 98 93 88
20 152 148 145 138 131 125 118 113
15 205 200 195 185 176 168 160 152
10 305 298 290 276 263 250 238 227
deg 0ft 820ft 1640ft 3280ft 4920ft 6560ft 8200ft 9840ft
Look up your nearest latitude in the left-hand column. For example, Melbourne
is approximately -37 S so the row for 35 will be the closest. One can always
interpolate a little. Then go across the columns to one that best matches the
elevation above sea level of your observatory. For example, for an observer
at -35 S and 250m above sea level, the table gives a value of 78.
That value is in arc seconds.
For observers in the southern hemisphere, if you want to set the polar axis of
the mount to the refracted pole, then aim for ME (in arc seconds) plus the
appropriate value from the table.
(Observers in the northern hemisphere will subtract the value in the table from ME).
The actual optimal point to which one aligns the polar axis depends on what
declination and hour angle you plan on observing.
Best Regards
Gary