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Old 03-06-2011, 05:40 PM
gary
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Join Date: Apr 2005
Location: Mt. Kuring-Gai
Posts: 5,999
Quote:
Originally Posted by Paul Haese View Post
Gary does Tpoint put you at the refracted pole via the corrections it gives you?
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

Last edited by gary; 04-06-2011 at 12:57 PM.
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