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about 30.000 stars with b , a and early f type classification were extracted from the michigan catalogue of two dimensional spectral types for the hd stars ( nancy houk et al . , 1975 - 1988 ; hereafter mc ) . in the southern sky region from @xmath3 to @xmath1 , 1500 objects are classified as cp2 stars . the limiting magnitude of this survey is 11 , the maximum of the distribution of magnitudes is between 8.5 and 10 for both subgroups .
74% of all extracted cp2 stars are members of the si - subgroup .
they are more concentrated towards the galactical plane than the cooler stars . in the galactic area from @xmath4 to @xmath5 , there are 84% of all hotter silicon stars and 58% of all srcreu stars . as expected , this result is in accordance with the galactic distribution of main sequence stars . a tendency to clustering for the investigated stars was not found .
bidelman & macconnell ( 1973 ; hereafter bc ) list 781 cp2 objects .
their classification is based on the same objective - prism plates as the sample of the michigan catalogue .
most of the compared stars have the same or a similar spectral classification in mc and bc .
photometric values are given for 981 stars in the geneva system ( rufener 1988 ) as well as in the 3-filter @xmath2 system ( maitzen & vogt 1983 ) .
430 out of 645 bc stars with known geneva photometric indices , have a significant peculiarity .
75% of 339 bc - stars are peculiar in @xmath2 .
three quarters of this sample are members of the si subgroup .
hd 134185 was classified as f0/2 v in mc ( f2 v in the geneva catalogue ) , but as si in bc .
si may be a typographical error meaning sr , but the photometric @xmath2 value confirms non - peculiarity .    the spectral class of hd 91756 is given as fm @xmath6 del in mc , ( a0 ) in the geneva catalogue and ap(srcr ) in bc .
the geneva peculiarity index @xmath7 shows no significant value for this star .
hd 110072 is identified as ap(srcr ) in mc and bc but as k0 in the geneva catalogue and the simbad database .
the photometric values in the geneva catalogue point to a late a - type star .
a total of 78 stars are identified as non - cp2 stars in mc but as si , sr or srcreu in bc .
the spectral classification and photometric values in the geneva catalogue are also different for these objects .
therefore , we started an observing run with @xmath2 photometry for a sample of them .
only 29 of the discrepant stars are peculiar in the geneva photometric system .
21 objects with known geneva indices were measured with a ccd in the @xmath2 system by h.m .
maitzen and e.  paunzen ( maitzen et al . 1997 ) .
observations were performed with the 61-cm bochum telescope at eso - la silla on three nights from 29 to 31 may 1995 .
the three filters g@xmath8 , g@xmath9 and y were used ; their characteristics are listed in the following table .
we regard a star as photometrically peculiar if @xmath12 or @xmath13mag . to check
the peculiarity found this way , the geneva criterion @xmath14mag ( north & cramer 1981 ) may be applied .
we were unable to find here a significant influence of interstellar reddening on the @xmath15-values , which might be expected from the relatively blue wavelength of @xmath16 compared to those of @xmath17 and @xmath18 .
obviously the rather low amount of reddening did not succeed in producing sensible differential effects on the a - values .      comparing the classification performances of both sources ( mc and bc ) with the help of the new available photometric evidence ,
one notes that for eleven b - type stars with a giant luminosity class according to mc , the bc - peculiarity assignments are in better agreement with our results then the mc types . only in three cases
are the geneva - based @xmath19 values ( north & kroll 1989 ) typical of giants while the @xmath2 index shows no peculiarity .
houk n. , cowley a.p . , 1975 ,
university of michigan catalogue of two - dimensional spectral types for the hd stars , volume i , astronomy dept .
ann arbor , michigan houk n. , 1978 , university of michigan catalogue of two - dimensional spectral types for the hd stars , volume ii , astronomy dept .
mich . , ann arbor , michigan houk n. , 1982 , university of michigan catalogue of two - dimensional spectral types for the hd stars , volume iii , astronomy dept .
mich . , ann arbor , michigan houk n. , smith - moore m. , 1988 , university of michigan catalogue of two - dimensional spectral types for the hd stars , volume iv , astronomy dept .
, ann arbor , michigan    north , p. , cramer , n. , 1981 , in : upper main sequence cp stars , 23rd liege astrophys .
universit de lige , p. 55 rufener f. , 1988 , catalogue of stars measured in the geneva observatory photometric system ( fourth edition ) , observatoire de genve
a number of about 1500 spectroscopically classified cp2 stars in the southern sky ( @xmath0 to @xmath1 ) was extracted from the michigan catalogue ( vols . 
 i - iv ) .    
 this sample was compared with the classification from bidelman & mc connell ( 1973 ) . 
 we confirmed the spectral classification with the known photometric peculiarity indices in the geneva system and in the 3-filter @xmath2 system ( maitzen 1976 ) . 
 10% of these stars show discordance between their respective types from the michigan and bidelman catalogues . 
 several objects were measured with a ccd in the @xmath2 system in spring 1995 . 
 eight stars are peculiar in @xmath2 . 
 furthermore , we have investigated the galactic distribution of all programme stars . 
 we conclude that the distribution resembles the one of early - type stars , where the hotter ( = silicon ) stars are more concentrated towards the galactic plane than the cooler ( = strontium ) objects .