The following invention relates to a detection apparatus for pointing out from the earth objects in the celestial sphere such aε the sun, moon, planets, star constellations and certain satellites.

The earth and heaven can be envisaged as two spheres, the earth being one sphere inside the celestial sphere. We can determine where an object iε on both spheres by stating its position in what we call latitude and longitude. On the terrestrial sphere (the earth's surface) latitude tells us the distance in degrees from the equator, with a plus sign for nothern latitudes and a minus sign for southern latitu- des . For example, New York is at the latitude +42°, Sydney in Australia at -32°. By an agreement, the line passing from the North Pole through Greenwich in Great Britain to the South Pole is the line from which we count longitude, iε called the prime meridian. Distances to meridians west of the Greenwich prime meridian are measured with plus signs and east thereof with minus signs. New York iε on the meri¬ dian at +70° (thus 70° west of Greenwich) and Sydney is on the meridian at -151° (thus 151° east of Greenwich) . If the latitudes and longitudes for a place unknown and we know where the place iε situated on the earth (most maps have the latitude and longitude lines drawn in) .

An object in the celestial sphere can be found in the same way by knowing its "latitude" and "longitude": "Latitude" on the celestial sphere iε called declination and iε the dis¬ tance at v/hich an object in this sphere is situated from the celestial equator, which is measured in degrees with the plus sign for north of the equator and minus sign for south of the equator. "Longitude" on the sphere is called right ascension (PA) . By agreement the line passing from the

celestial north pole through the point where the sun is between March 21/22 (the vernal equinox) to the celestial south pole is the line from which PA is measured in an eastally direction. For pointing out an object on the celestial sphere with the finder in accordance with the invention, the following information iε required:

1. The local latitude on earth.

2. The longitude difference from the local time zone. 3. North /south direction.

4. The year's date and time of day.

5. The position of the object in question, i.e. RA and declination which is abbreviated to decl . These two data can be obtained from tables specially prepared for using the invention, and v/hich give the position on the celestial sphere for objects (the sun, moon, planets and satellites) at the time 0, Greenv/ich time, at different dates for a given year. The sun and moon move quickly, and the position for each date is therefore given, while for slow planets the position is given with intervallε between the dates. The tables are made up so that the positions for the individual objects are given with time differences, which eliminates the need of interpolation, v/ith the exception of the moon.

For using the information described above, the invention has been given the characterizing features disclosed in the accompanying claims.

An embodiment of the invention will now be described with reference to the accompanying drawing figures.

Figur 1 is a perspective view of the finder apparatus.

Figur 2 illustrates concentric scales for R.A. and date/- time.

Figur 3 illustrates the apparatus as seen from below.

The finder apparatus comprises a base plate 1, with two fixed legs, 2, 3 and feet 4 swivalable on the base plate 1. The angle betv/een the feet and plate iε adjusted by a slide 5 attached to the plate, the slide being fastenable to the feet 4 after adjustment. The slide has a latitude scale 6 in degrees from 0 to 70°. Rotatable on the plate 1 there is a longitude disc 7 and a datu /RA disc 8, as well as a time _ disc 9. The discs are concentricly rotatably relative the plate 1.

A semicircular plate 10 provided with a degree scale 11 is mounted normal to the time disc 9. The scale 11 is graduated from +90° to -90°, 0° being situated on the normal through the rotational center 14 of the discs. A direction arrow 12 is rotatably mounted at the center of the disc 10 and degree scale 11 for rotation in the plane of the semicircular plate 10. When a mark 13 on the direction arrow 12 points towards 0° on the degree scale 11, the direction arrow is at right angle to the normal through the rotational center 14 for the discs and is in the plane of the semicircular plate 10.

The longitude disc 7, v/hich can be rotated relative the plate 1 is adjusted relative the latter with the aid of a

. circular scale 1 5 on the underside of the disc, this scale being called "difference to time zone" and iε graduated from minus 3 hours to plus 3 hours with 10-minute intervalls between the scale markings. A window 16 iε made in the baεe plate 1 for reading against the scale. A set relationship between the base plate and the longitude disc can be fixed v/ith the aid of a screw. The north-south direction of the plate iε determined with the aid of the arrow 18, which point to the south when the apparatus is set up at a place on the nothern hemisphere.

Setting UP the finder

The finder iε turned upside down εo that the scales and such can be seen as illuβtated in figure 3. The scale 6 for latitude and the scales 15, 16 for "difference from time zone" v/ill be seen. The following measures are then taken for the finder to function from a given position on earth.

Setting longitude

The world iε devided into time zones, and this courses problems v/hen it is attempted to find an object on the celestial sphere, e.g. the sun and stars rise in Boston one hour before they do εo in Indianapolis, even if the clocks show the same time in both places. To solve this problem, the finder affords a builtin correction fot the longitude at which the apparatus iε set up, here and after referred to as the "location". There is also a correction for summer time.

The longitude of the location iε found by studying a map or otherwise ascertaining it.

The difference in degrees between the longitude of the location and standard longitude for the time zone of the location is now determined. In North America the standard time zone longitudes are 76° for the east coast, 90° for the central area, 105° for the mountain area and 120° for the Pacific Ocean coast. In West Europe the standard time zone is 0° for Greenwich time and 15° for Central European time.

For each degree the location iε west (east in southern latitude) of the standard longitude the scale 15, 16 for "difference from time zone" be moved forward (+) 4 minutes. If the location is easts (west for southern latitude) the scale shall be moved backwards (-) 4 minutes. This setting

is performed by turning the disc 8 relative the base plate 1 and setting the correct part of one hour + or - in the window 16.

Consider the example: Portland Maine is situated 70° longi¬ tude which is 5° west of the standard longitude for its time zone. Accordingly, the distance from the time zone in the window shall be set at -20 minutes (-5 x 4 = -20) for Port¬ land. When summertime prevails, i.e. when the clocks are moved forward an hour, one hour shall be added to the set¬ ting for the difference from the time zone. The correction for Portland shall then be +40 minuter. When normal time iε used, the scale iε moved back one hour.

Setting latitude

The location latitude shall be first determined, and this can be found from tables or by using a map. Latitude is set by carefully moving the legs 2/3 and feet 4 apart until the right latitude is shown on the scale 6. The slide 5 then passes through a slit between the feet 4. The two legs and slide 5 then form a triangle, the latitude scale 6 functions both for nothern (+) and southern (-) latitudes.

Directions solely applying to the nothern hemisphere

Check that "nothern hemisphere" (NHem) is shown in the window 20 cut out in the disc 9 and thus above it. If not, dismount the apparatus and turn over the disc 9 and/or the disc 8.

The hemisphere window 21 on the declination (semicircular) disc 10 show "NHem". If not, the screw fixing the declina¬ tion plate is removed, the direction arrow turned 180° and the screw put back in place again, first through either of the declination plates and then through the direction arrow and finally through a second declination plate.

Check

Set the latitude scale at 40°, the difference from the time zone scale, i.e. the scale 15, 16 at 0°. RA scale 25 to the RA indicator 24 to 9 hours, and the time scale 22 to

MIDNIGHT to the datum scale 23 adjusted to february 5th. For this see later instructions for use. The direction arrow should now point to the zenith, i.e. normal to the location.

Directions solely for the southern hemisphere

Turn the apparatus upside dov/n, remove the north arrow 26, which is fastened with the aid of a piece of double-εided tape. Replace the north arrow 26 directly on the south arrow 18 situated at the free end of the slide 5.

Check that thw southern hemisphere (SHe ) can be seen in the window 20 and also just below it. If not, remove the central screw, turn the disc 9 and/or the datum/time disc 8 upside down until SHem can be seen at both places.

The window 21 on the declination plate 10 shall now show SHem, if not loosen and turn the arrow 12 180°.

Check

Set the latitude scale 6 at 40°, the scale 15, 16 at 0, RA scale to 9 hours, and february 5th to midnight on the datum and time scale. Set the declination scale at -40°. To do this see the following instructions for use. The direction arrow shall now point to the zenith, vertically upwordε .

Function of the apparatus

First check that the direction arrow, i.e. the entire appa¬ ratus with stand and arrow are set to the correct latitude and correct "difference from the time zones".

Carry out the following to set the direction arrow towards the desired object. The arrow 18 is directed in a north- south direction v/ith the soutn arrow directed south for the nothern hemisphere. The opposite applies for the southern hemisphere v/hen the north arrow shal be directed towards the north. The north-south direction can be found with the aid of a compass, for example. It iε also important that the entire stand iε mounted in a horizontal plane. Set the time to the date, and RA to the RA indicator. Do not confuse the RA scale with the time scale. They both have scales in hours and minutes .

Set the declination for the object on the declination scale 11.

The direction arrow should now point towards the object in question. For pointing tov/ardε a new object, return to the measures for setting the time/date. After some use it should not be a problem to sight along the direction arrow to find the object on the celestial sphere for which data are given.

Example 1

Where can the star constellation Orion be found in Boston on January the 25th at 9. p.m., eastern standard time?

1. It can be found from the table that Boston is on the latitude +42° and longitude +71°. The apparatus iε then set

v/ith the latitude scale of 42° and the scale for the diffe¬ rence from the time zone at -16 minutes. The latter depends on the fact that Boston iε 4° east of the eastern standard time: -4 x +4 = 16.

The apparatus iε now put in a noth/south direction with the arrow 18 directed tov/ards the south, see what has been previously described. Due to this being an example, the measure 2 is not necessary.

The position of the star constellation Orion iε set by taking data from tableε of the kind described in the intro¬ duction. It will be found thath RA iε 5 hours 35 minutes and the declination iε 0°. 5 hours 35 minutes is first set on the RA scale. Then the time 9 pm on the time scale iε set against January 25th on the date scale. The declination of 0° is then set on the declination scale, see figure 5. The direction arrow will nov/ point southwards rather high above the horizon where Orion can be found.