715 
—09 +10 +01 —17 +07 —05 —05 +17 —02 —04 +06 +18 —03 +07 +08 +02 +14 +37 
—14 ~28 +20 —36 --23+4 14—40 +32—51-+04 00443439 00 +26 439 +14+423 26 
05 —0T —12—05-=15 —16 — 17 —09 05 99-100 — 14 = 34 05 4-05 — 16-217 
If on each plate a systematic difference exists between the E. and 
W. side, this reduction will produce a systematic error, increasing 
with the R. A. because the ring is not closed; the accidental errors, 
also because we have but three zones, will be eliminated to only a 
very slight degree. All the same the very considerable jumps in the 
limiting magnitude will thus be practically neutralized. This is evident 
also from the regular course of the reduced numbers of stars, which 
now run nearly parallel with the course of density according to the 
FRANKLIN-ADAMs plates, which is not the case with the non-reduced 
numbers. These numbers for the separate quadrants are given in the 
following list; (for the middle rows it gives two values, the upper 
one of which is always taken from the N-plate): 
h h 
5 4 
5 N40 36 32 28 24 20 16 12 8 4 0 56 52 48 44 40 36°32 28 
5o 
147 7124 110.39 30 25 36 53 16 75 63 53 53 30 12- 13, 13° 25 
240 
134 120 138 73 29 28 40 2753 69 172 73 45 39 39 41 24 19 
151 130 124 142 71 30 27 39 2852 70171 75 49 36 40 41 27 17 
23° 
154 159 174 163 146 90 38 21 4652 83 79 74 46 52 58 54 51 31 
: 143 176 170 143 93 36 20 4852 85 78 75 51 48 60 49 55 28 
2° 
Le 184 151 159170116 49 34 41 48 58 58 57 70 55 61 35 47 49 
1 
4 aL 
ee 24 20 16 12 8 4 O 56 52 48 44 40 36 32 28 24 20 16 12 
oe 19 14 38 42 42 3831 68 75 123 107 154 80 60 72 76 63 80 
15 37 69 78 70 88 70 101 89 81 “11155 Ii 46 69. 50 71 ’60 
gi; 15 36 64 83 75 81 83 85 85 86 69174 79 41 68 51 70 58 71 
16 46 65 62 65 7456 68 68 67 78 83 56 44 51 49 66 71 47 
a 11 45 61 67 71 6866 57 65 71 69 93 63 40 51 51 67 73 
ne 54 30 39 33 41 43 48 66 76 83 74 83 43 36 42 54 61 40 
1 
These numbers must be multiplied by 12? : 13? to obtain the 
numbers per square degree. If we may assume, that the average 
limiting magnitude of these 55 plates corresponds to the average 
value for the entire sky, the limiting magnitude deduced from the 
entire zones 23°—24° by means of the tables of “Groningen 27”, 
viz. 12.20 must be used here. 
