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11_10_87/AST\INF

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Tape/disk: Home » CEEFAX disks » telesoftware2.adl
Filename: 11_10_87/AST\INF
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File size: 070A bytes
Load address: 0000
Exec address: 0000
Duplicates

There is 1 duplicate copy of this file in the archive:

File contents
ASTRO is a general utility for converting between two sets of spherical
polar coordinates (the kind used in normal lattitude and longitude). It is
however presented by being put to a use that will be appreciated by all
amateur astronomers - namely converting between three of the more commonly
used methods of mapping the heavens. 

The answers given by this version for conversion between equatorial and
galactic coordinates are correct to within a degree or so of the chart
given in 'Nortons Star Atlas' but this program converts for the entire sky
whereas Nortons only converts between galactic lattitudes +50 to -50.
Inaccuracies are due to rounding and the accuracy of the conversion
parameters (see below) rather than any inadequacy of the method.

ASTRO works by taking one of the intersections between the equators of the
two systems as a common point and calculating within the hemisphere with
this point at its centre. Points in the other hemisphere are reflected
onto the calculated hemisphere before conversion and then back again
after.

Multiple conversions may easily be strung together as is demonstrated by
options 5 and 6 in this program.

ASTRO requires three parameters for each conversion which are coded into
the program: these are the longitudes of the common intersection referred
to both equators (in degrees) and the dihedral angle between the planes of
the two equators which must have the correct associated sign. This angle
must be less than 90 degrees and both longitude measurements must increase
from it which may mean that one or other system could need the sign of
longitude measurements changed at input and output. This is demonstrated
in altazimuth coordinates in this program.

In the program the respective longitudes are RACORR and GACORR and the
angle is RAGA.
00000000  41 53 54 52 4f 20 69 73  20 61 20 67 65 6e 65 72  |ASTRO is a gener|
00000010  61 6c 20 75 74 69 6c 69  74 79 20 66 6f 72 20 63  |al utility for c|
00000020  6f 6e 76 65 72 74 69 6e  67 20 62 65 74 77 65 65  |onverting betwee|
00000030  6e 20 74 77 6f 20 73 65  74 73 20 6f 66 20 73 70  |n two sets of sp|
00000040  68 65 72 69 63 61 6c 0d  70 6f 6c 61 72 20 63 6f  |herical.polar co|
00000050  6f 72 64 69 6e 61 74 65  73 20 28 74 68 65 20 6b  |ordinates (the k|
00000060  69 6e 64 20 75 73 65 64  20 69 6e 20 6e 6f 72 6d  |ind used in norm|
00000070  61 6c 20 6c 61 74 74 69  74 75 64 65 20 61 6e 64  |al lattitude and|
00000080  20 6c 6f 6e 67 69 74 75  64 65 29 2e 20 49 74 20  | longitude). It |
00000090  69 73 0d 68 6f 77 65 76  65 72 20 70 72 65 73 65  |is.however prese|
000000a0  6e 74 65 64 20 62 79 20  62 65 69 6e 67 20 70 75  |nted by being pu|
000000b0  74 20 74 6f 20 61 20 75  73 65 20 74 68 61 74 20  |t to a use that |
000000c0  77 69 6c 6c 20 62 65 20  61 70 70 72 65 63 69 61  |will be apprecia|
000000d0  74 65 64 20 62 79 20 61  6c 6c 0d 61 6d 61 74 65  |ted by all.amate|
000000e0  75 72 20 61 73 74 72 6f  6e 6f 6d 65 72 73 20 2d  |ur astronomers -|
000000f0  20 6e 61 6d 65 6c 79 20  63 6f 6e 76 65 72 74 69  | namely converti|
00000100  6e 67 20 62 65 74 77 65  65 6e 20 74 68 72 65 65  |ng between three|
00000110  20 6f 66 20 74 68 65 20  6d 6f 72 65 20 63 6f 6d  | of the more com|
00000120  6d 6f 6e 6c 79 0d 75 73  65 64 20 6d 65 74 68 6f  |monly.used metho|
00000130  64 73 20 6f 66 20 6d 61  70 70 69 6e 67 20 74 68  |ds of mapping th|
00000140  65 20 68 65 61 76 65 6e  73 2e 20 0d 0d 54 68 65  |e heavens. ..The|
00000150  20 61 6e 73 77 65 72 73  20 67 69 76 65 6e 20 62  | answers given b|
00000160  79 20 74 68 69 73 20 76  65 72 73 69 6f 6e 20 66  |y this version f|
00000170  6f 72 20 63 6f 6e 76 65  72 73 69 6f 6e 20 62 65  |or conversion be|
00000180  74 77 65 65 6e 20 65 71  75 61 74 6f 72 69 61 6c  |tween equatorial|
00000190  20 61 6e 64 0d 67 61 6c  61 63 74 69 63 20 63 6f  | and.galactic co|
000001a0  6f 72 64 69 6e 61 74 65  73 20 61 72 65 20 63 6f  |ordinates are co|
000001b0  72 72 65 63 74 20 74 6f  20 77 69 74 68 69 6e 20  |rrect to within |
000001c0  61 20 64 65 67 72 65 65  20 6f 72 20 73 6f 20 6f  |a degree or so o|
000001d0  66 20 74 68 65 20 63 68  61 72 74 0d 67 69 76 65  |f the chart.give|
000001e0  6e 20 69 6e 20 27 4e 6f  72 74 6f 6e 73 20 53 74  |n in 'Nortons St|
000001f0  61 72 20 41 74 6c 61 73  27 20 62 75 74 20 74 68  |ar Atlas' but th|
00000200  69 73 20 70 72 6f 67 72  61 6d 20 63 6f 6e 76 65  |is program conve|
00000210  72 74 73 20 66 6f 72 20  74 68 65 20 65 6e 74 69  |rts for the enti|
00000220  72 65 20 73 6b 79 0d 77  68 65 72 65 61 73 20 4e  |re sky.whereas N|
00000230  6f 72 74 6f 6e 73 20 6f  6e 6c 79 20 63 6f 6e 76  |ortons only conv|
00000240  65 72 74 73 20 62 65 74  77 65 65 6e 20 67 61 6c  |erts between gal|
00000250  61 63 74 69 63 20 6c 61  74 74 69 74 75 64 65 73  |actic lattitudes|
00000260  20 2b 35 30 20 74 6f 20  2d 35 30 2e 0d 49 6e 61  | +50 to -50..Ina|
00000270  63 63 75 72 61 63 69 65  73 20 61 72 65 20 64 75  |ccuracies are du|
00000280  65 20 74 6f 20 72 6f 75  6e 64 69 6e 67 20 61 6e  |e to rounding an|
00000290  64 20 74 68 65 20 61 63  63 75 72 61 63 79 20 6f  |d the accuracy o|
000002a0  66 20 74 68 65 20 63 6f  6e 76 65 72 73 69 6f 6e  |f the conversion|
000002b0  0d 70 61 72 61 6d 65 74  65 72 73 20 28 73 65 65  |.parameters (see|
000002c0  20 62 65 6c 6f 77 29 20  72 61 74 68 65 72 20 74  | below) rather t|
000002d0  68 61 6e 20 61 6e 79 20  69 6e 61 64 65 71 75 61  |han any inadequa|
000002e0  63 79 20 6f 66 20 74 68  65 20 6d 65 74 68 6f 64  |cy of the method|
000002f0  2e 0d 0d 41 53 54 52 4f  20 77 6f 72 6b 73 20 62  |...ASTRO works b|
00000300  79 20 74 61 6b 69 6e 67  20 6f 6e 65 20 6f 66 20  |y taking one of |
00000310  74 68 65 20 69 6e 74 65  72 73 65 63 74 69 6f 6e  |the intersection|
00000320  73 20 62 65 74 77 65 65  6e 20 74 68 65 20 65 71  |s between the eq|
00000330  75 61 74 6f 72 73 20 6f  66 20 74 68 65 0d 74 77  |uators of the.tw|
00000340  6f 20 73 79 73 74 65 6d  73 20 61 73 20 61 20 63  |o systems as a c|
00000350  6f 6d 6d 6f 6e 20 70 6f  69 6e 74 20 61 6e 64 20  |ommon point and |
00000360  63 61 6c 63 75 6c 61 74  69 6e 67 20 77 69 74 68  |calculating with|
00000370  69 6e 20 74 68 65 20 68  65 6d 69 73 70 68 65 72  |in the hemispher|
00000380  65 20 77 69 74 68 0d 74  68 69 73 20 70 6f 69 6e  |e with.this poin|
00000390  74 20 61 74 20 69 74 73  20 63 65 6e 74 72 65 2e  |t at its centre.|
000003a0  20 50 6f 69 6e 74 73 20  69 6e 20 74 68 65 20 6f  | Points in the o|
000003b0  74 68 65 72 20 68 65 6d  69 73 70 68 65 72 65 20  |ther hemisphere |
000003c0  61 72 65 20 72 65 66 6c  65 63 74 65 64 0d 6f 6e  |are reflected.on|
000003d0  74 6f 20 74 68 65 20 63  61 6c 63 75 6c 61 74 65  |to the calculate|
000003e0  64 20 68 65 6d 69 73 70  68 65 72 65 20 62 65 66  |d hemisphere bef|
000003f0  6f 72 65 20 63 6f 6e 76  65 72 73 69 6f 6e 20 61  |ore conversion a|
00000400  6e 64 20 74 68 65 6e 20  62 61 63 6b 20 61 67 61  |nd then back aga|
00000410  69 6e 0d 61 66 74 65 72  2e 0d 0d 4d 75 6c 74 69  |in.after...Multi|
00000420  70 6c 65 20 63 6f 6e 76  65 72 73 69 6f 6e 73 20  |ple conversions |
00000430  6d 61 79 20 65 61 73 69  6c 79 20 62 65 20 73 74  |may easily be st|
00000440  72 75 6e 67 20 74 6f 67  65 74 68 65 72 20 61 73  |rung together as|
00000450  20 69 73 20 64 65 6d 6f  6e 73 74 72 61 74 65 64  | is demonstrated|
00000460  20 62 79 0d 6f 70 74 69  6f 6e 73 20 35 20 61 6e  | by.options 5 an|
00000470  64 20 36 20 69 6e 20 74  68 69 73 20 70 72 6f 67  |d 6 in this prog|
00000480  72 61 6d 2e 0d 0d 41 53  54 52 4f 20 72 65 71 75  |ram...ASTRO requ|
00000490  69 72 65 73 20 74 68 72  65 65 20 70 61 72 61 6d  |ires three param|
000004a0  65 74 65 72 73 20 66 6f  72 20 65 61 63 68 20 63  |eters for each c|
000004b0  6f 6e 76 65 72 73 69 6f  6e 20 77 68 69 63 68 20  |onversion which |
000004c0  61 72 65 20 63 6f 64 65  64 20 69 6e 74 6f 0d 74  |are coded into.t|
000004d0  68 65 20 70 72 6f 67 72  61 6d 3a 20 74 68 65 73  |he program: thes|
000004e0  65 20 61 72 65 20 74 68  65 20 6c 6f 6e 67 69 74  |e are the longit|
000004f0  75 64 65 73 20 6f 66 20  74 68 65 20 63 6f 6d 6d  |udes of the comm|
00000500  6f 6e 20 69 6e 74 65 72  73 65 63 74 69 6f 6e 20  |on intersection |
00000510  72 65 66 65 72 72 65 64  0d 74 6f 20 62 6f 74 68  |referred.to both|
00000520  20 65 71 75 61 74 6f 72  73 20 28 69 6e 20 64 65  | equators (in de|
00000530  67 72 65 65 73 29 20 61  6e 64 20 74 68 65 20 64  |grees) and the d|
00000540  69 68 65 64 72 61 6c 20  61 6e 67 6c 65 20 62 65  |ihedral angle be|
00000550  74 77 65 65 6e 20 74 68  65 20 70 6c 61 6e 65 73  |tween the planes|
00000560  20 6f 66 0d 74 68 65 20  74 77 6f 20 65 71 75 61  | of.the two equa|
00000570  74 6f 72 73 20 77 68 69  63 68 20 6d 75 73 74 20  |tors which must |
00000580  68 61 76 65 20 74 68 65  20 63 6f 72 72 65 63 74  |have the correct|
00000590  20 61 73 73 6f 63 69 61  74 65 64 20 73 69 67 6e  | associated sign|
000005a0  2e 20 54 68 69 73 20 61  6e 67 6c 65 0d 6d 75 73  |. This angle.mus|
000005b0  74 20 62 65 20 6c 65 73  73 20 74 68 61 6e 20 39  |t be less than 9|
000005c0  30 20 64 65 67 72 65 65  73 20 61 6e 64 20 62 6f  |0 degrees and bo|
000005d0  74 68 20 6c 6f 6e 67 69  74 75 64 65 20 6d 65 61  |th longitude mea|
000005e0  73 75 72 65 6d 65 6e 74  73 20 6d 75 73 74 20 69  |surements must i|
000005f0  6e 63 72 65 61 73 65 0d  66 72 6f 6d 20 69 74 20  |ncrease.from it |
00000600  77 68 69 63 68 20 6d 61  79 20 6d 65 61 6e 20 74  |which may mean t|
00000610  68 61 74 20 6f 6e 65 20  6f 72 20 6f 74 68 65 72  |hat one or other|
00000620  20 73 79 73 74 65 6d 20  63 6f 75 6c 64 20 6e 65  | system could ne|
00000630  65 64 20 74 68 65 20 73  69 67 6e 20 6f 66 0d 6c  |ed the sign of.l|
00000640  6f 6e 67 69 74 75 64 65  20 6d 65 61 73 75 72 65  |ongitude measure|
00000650  6d 65 6e 74 73 20 63 68  61 6e 67 65 64 20 61 74  |ments changed at|
00000660  20 69 6e 70 75 74 20 61  6e 64 20 6f 75 74 70 75  | input and outpu|
00000670  74 2e 20 54 68 69 73 20  69 73 20 64 65 6d 6f 6e  |t. This is demon|
00000680  73 74 72 61 74 65 64 0d  69 6e 20 61 6c 74 61 7a  |strated.in altaz|
00000690  69 6d 75 74 68 20 63 6f  6f 72 64 69 6e 61 74 65  |imuth coordinate|
000006a0  73 20 69 6e 20 74 68 69  73 20 70 72 6f 67 72 61  |s in this progra|
000006b0  6d 2e 0d 0d 49 6e 20 74  68 65 20 70 72 6f 67 72  |m...In the progr|
000006c0  61 6d 20 74 68 65 20 72  65 73 70 65 63 74 69 76  |am the respectiv|
000006d0  65 20 6c 6f 6e 67 69 74  75 64 65 73 20 61 72 65  |e longitudes are|
000006e0  20 52 41 43 4f 52 52 20  61 6e 64 20 47 41 43 4f  | RACORR and GACO|
000006f0  52 52 20 61 6e 64 20 74  68 65 0d 61 6e 67 6c 65  |RR and the.angle|
00000700  20 69 73 20 52 41 47 41  2e 0d                    | is RAGA..|
0000070a
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