US2006075A - Star and time finder - Google Patents

Description

June 25, 1935. B. F. LOFGREN STAR AND TIME FINDER Filed June 26, 1933 lNV NTOR Patented June 25, 1935 UNITED STATES PATENT OFFICE STAR AND TIME FINDER Benjamin F. Lofgren, Salt Lake City, Utah Application June 26, 1933, Serial No. 677,590

4 Claims.

This invention is a star and time finder. It is particularly adapted to the use of Boy Scouts.

There are many uses for this device among which are the following:

5 1. To determine the time at night by observing the stars.

2. To determine the time by the sun.

3. To locate the position of certain constellations and stars at any time.

4. To determine the latitude of the place of observation. a

5. To determine north when the north star is obscured but a known star is visible.

6. To find which constellation the sun is in at any time.

7. To measure angles.

8.To find tangents of angles for calculating distances and heights.

Fig. 1 shows the back plate, Fig. 2 the face plate and Fig. 3 shows the face of the device when complete.

The device as constructed, consists of four principal parts, some of which have several members.

The first part, illustrated in Fig. 1, is a circular plate called the back plate. On one side of this plate is a circle A with center 0, marked into 24 hours and subdivisions of hours, a circle B on and within which is the representation of various stars and constellations in their proper relative angular positions around the axis 0, corresponding to their angular positions around thecelestial axis, that is, representing their right ascensions, with markings which show the declination of the 5 sun at various dates, and a concentric circle C on which is represented the succession of days of the year circularly about the circumference. The

axisthrough thecenter ii of circles A, B, C perpendicular to the plate represents the celestial axis 40 about which all heavenly bodies appear to revolve when 0 is held between the observers eye and a celestial pole. A part of the area within these circles is cut away at V, V, V, V, P for visibility, particularly making Polaris visible through P when the axis is between the eye and the north celestial pole. There are two particular spokes S and T left in the relative positions to represent the directions from Polaris of the stars Caph and Dubhe respectively. This makes the radii through theright ascensions of these stars recognizable at the same time that the stars are visible, so as to facilitate the orientation of the device. Since the star Polaris is not atbut is near the pole on the same side as Caph the plate is cut away near the center 0 adjacent the spoke representing Caph. This makes the square shaped opening P near the center.

The second part, illustrated in Fig. 2, is a plate called the face, on which is a circle H marked into 24 hours with subdivisions and numbered 12 hours for A. M. and 12 hours for P. M., a concentric circle F marked into degrees, and an arc K giving tangents of the angles in circle F. The night hours are marked so that they can be read in the dark. This is done with raised markings which can be felt although engraved markings may be used. It might be done in other ways such as with luminous paint.

This second plate has a considerable area about the center cut away to increase the visibility when the plate is heldbefore the eye.

The plate containing circles H and F is placed with the unmarked side against the back of the plate containing circles A, B, C and by means of brackets M, L, L, J is held against the latter plate yet is rotatable in relation thereto about a common axis through the center 0. The brackets M, L, L, J are fixed to the face plate and extend over the edge of the back plate to hold them together.

The surface containing A, B, C is called the back of the combination and the face has two parts, one that contains H, F, K which can be rotated relatively to the back and the part which is the reverse side of the back. Thisinner part of the face contains the name or title of the device and cross-section lines which are not claimed in the invention.

On the outer edge or" the face, adjacent the 12 midnight is the bracket M which is used to determine the relative angular position of the markings on the back and face sides of the device. The back can be rotated under this bracket so that any chosen date on circle C can be brought under the bracket M and opposite 12 midnight on circle H. i r

The third part of the device is a plumb-line shown in Fig. 3. It is suspended on the face of the combination on the axis of circles A, B, C, H, F. As the plumb-line hangs it passes over the markings in circles H, F and K. r

The fourth part is a marker N, shown in Fig. 3. It is made to be attached to the combined plates in various radial positions so that one part extends radially outward beyond the edge of the plates. This not only makes aparticular radius recognizable in a dim light but lengthens the radius to increase accuracy. A bobby pin can be used for this marker.

The book of instruction gives various diagrams.

tables and instruction for several uses of the device.

It has been known for centuries that the apparent rotation of the stars around the earth is regular and that time can be reckoned by observing the stars. One instrument in particular, the astrolabe, was used by seamen to find latitude, longitude and time. It was made in many forms, combining various calculations.

The present device, however, is so constructed that the zero hour of the solar day can be set at the proper angular position relatively to the sidereal zero hour for each day of the year and the sidereal hour lines on the device can be correct ly oriented with respect to the position of the stars by holding the axis of the device parallel to the celestial axis and sighting the proper radius parallel to the line joining Polaris and a particular star. The correct orientation of the device is produced by having Polaris visible through the proper place near the axis and having easily distinquishable radii for sighting toward chosen stars. After the zero sidereal hour and the zero solar hour are correctly oriented the device not only gives local time but shows the direction of each right ascension plane since each radius intersecting the axis determines a plane.

A circle marked into degrees with a plumb-line suspended at the center is not new. But the combination with the other members as described makes an instrument with new uses, for example, with this instrument it is possible to determine the north direction and tell the time with a single view of a star whose declination is known or given on the device.

The brackets L, L are fixed to the face plate at equal distances from zero angle in circle F so that when the plumb-line hangs freely over the zero angle the line across the brackets L, L is horizontal. Then if the line across the brackets is sighted at a point above or below horizontal the plumb-line will measure the vertical angle on circle F.

One size in which this device is made gives a circumference 01" one foot length. The hour marks then are one half inch apart. By rolling the device edgewise along a surface it becomes a measure in feet, inches and fractions of an inch.

It is very difficult to see a star through a small hole in an opaque disk, and when the star is once located through the hole just the least inattention or movement breaks the line of sight. In order to hold a disk between the eye and a star and be able to see the star through a particular point in the disk there should be a rather large opening adjacent the particular point so that small movements will not cut oil the line of sight to the star. And yet the particular point in the disk must be easily recognizable in star light. The star Polaris is one of the stars used to orient the device, but Polaris is about 1% degrees away from the true pole. In order to make it easy to bring the axis of the device between the eye and the true pole the line of sight to Polarisis made to pass through the corner of a rectangular opening somewhat ofi the center of the disk. The openings V, V, V, V, and especially P facilitate the finding of Polaris through the disk and yet the line of sight can be brought into the proper place near the center, which action is very difiicult if only a small opening is made for the sight of Polaris.

In order to orient the device angularly with respect to the celestial axis and zero right ascension it is necessary to have a particular radius of the device pointing in a particular direction in the heavens. The spokes S and T are made recognizable in star light and are in the proper posi tions to point to the well known stars Caph and Dubhe respectively when the device is oriented. The marker N can then be placed on the radius of any right ascension and thus locate the position of any of the stars or constellations given on. the device.

If the device is oriented by using the sun as a star (having the right ascension shown for the date on circle C) then the position of the stars and constellations can be located in the day time even though they can not be seen.

To tell time by the sun: use the face of the device as a sun dial.

To tell time by the stars: set the proper date of circle C under the marker M. Face Polaris keeping the face or" the device toward you. Bring the line of sight o1": Polaris into the corner of P nearest the center. Point the spoke 5 toward Caph or the spoke T toward Dubhe (one of the pointers in the big dipper). The plumbdine now hangs on the correct local time on circle 1-1.

To measure the vertical angle to a distant point: sight across rackets L, L with the zero of circle F toward the bottom. The plumb-line shows the vertical angle on F.

To measure the height of a tree: measure out a convenient distance from the base of the tree, say 90 feet, measure the vertical angle on circle F to the top of the tree from the end of the base line, say 35 degrees. On arc K adjacent circle F it shows that the tangent (tan) of 35 degrees is .7, which means that the height of the tree is .7 times the length of the base line or .7 times 90 feet equals 63 feet.

One who has an elementary knowledge of astronomy and of angles or one who receives some simple instructions can use the device for all the uses named on page 1 and for many others.

I claim:

1. In a device as described-a, circular plate containing a concentric circle marked to represent the hours in a day, a large part of said plate being cut away about the center, in combination with a second plate containing markings about a central point which represent various heavenly bodies about the celestial axis in their relative angular positions known as right ascension and containing a circle marked to represent the days in a year, a part of said second plate being cut away near the central point in the position which represents Polaris and parts cut away so as to leave visually distinguishable in star light a spoke along the radius which represents the right ascension of a particular bright star, a plumb-line suspended from the central point of said second plate, means to attach said plates so they are relatively rotatable, and a marker which shows the angular position of the first said plate in relation to said second plate.

2. In a device as described, a circular plate containing a circle marked to represent the hours in a day, a second circle marked into degrees and markings adjacent said second circle which show the tangents of the degrees marked in said second circle, a large part of said plate being cut away about the center, in combination with a second plate containing a circle marked to represent the days in a year and markings about a central point which represent various heavenly bodies about the celestial axis in their angular positions known as right ascension, a plumb-line suspended from the central point of said second plate, means to attach said plates so they are relatively rotatable about a common center, and a marker which shows the angular position of the first said plate in relation to said second plate, a part of said second plate being cut away a little off center in the position which represents Polaris and parts cut away so as to leave visually distinguishable in star light spokes along certain radii which represent the right ascensions of certain bright stars.

3. In combination, a first circular plate, a second circular plate, means to attach said plates so as to leave them relatively rotatable about a common axis, a plumb-line suspended at the center of said second plate, said first plate contains a circle marked to represent the hours in a day, a circle marked into degrees and markings showing the tangents of the degrees, a large part about the center of said first plate being cut away; said second plate containing a circle marked to represent the days in the year and markings about the center which represent the various heavenly bodies about the celestial axis in their relative angular positions known as the right ascension, a part of said second plate being cut away a little off center in the position that represents Polaris and parts being cut away for greater visibility but so as to leave visually recognizable in starlight a spoke along a radius which represents the right ascension of a bright star,

4. In a device as described a plate having a relatively large central part cut away and containing a circle marked to represent the hours in a day, a second circle marked into angular degrees and markings adjacent said second circle which show the tangents of the angles given, in combination with the second plate containing a circle marked to represent the days in a year and markings about a central point which represent various heavenly bodies about the celestial axis in their relative angular positions known as right ascension, means to attach first said plate and said second plate together so they are relatively rotatable about an axis through the center of said circles, such means consisting of brackets attached to first said plate and extending over the edge of said second plate, a plumb-line suspended at the central point of said second plate, and means to easily orient said plates with respect to the heavenly bodies, such orienting means consisting of a relatively large opening in said second plate a little off center in the position representing Polaris, with other openings in said second plate which permit a considerable part of the sky to be visible through the plate and a particular spoke left in said second plate which is visually recognizable in starlight, said spoke being used for sighting between particular stars.

BENJ. F. LOFGREN.

Images