Harvard Plate Collection Metcalf Telescope

DASCH
Digital Access to a Sky Century @ Harvard
A New Look at the Temporal Universe

Plate Classes

Every plate is assign a class designation to indicate the type of exposure that was taken. The following table comes primarily from the Harvard Annals, Vol 26, page 9. This list is divided into three groups, indicated by the Notes column below:

The list from the above references is incomplete and does not account for all of the classes that appear in the database. These additional classes are marked with the derived note and given a description that follows the examples given in the above reference. Nevertheless, there are still several classes that must be marked unknown class until additional information is available

Curator Alison Doane notes that chart plate is an ordinary plate that documents the sky, like a patrol plate.

There are currently 72 plate classes in the database.

Plate Class Table
ClassClass DescriptionNotes
Atrails on North and South PolesB plates only
Btrails of stars between +65 and +85B plates only
C multiple exposure calibration plate, 2 or more fields, blue (class C plates calibrate with Pole or Harvard Standard Regions)Nov 1933 Cambridge, Jan 1934 Bloemfontein
Ctrails of stars between +55 and +65 at upper and lower culmination, to determine atmospheric absorptionB plates only
C1calibration plate, yellow plate with filterNov 1933 Cambridge, Jan 1934 Bloemfontein
C2calibration plate, red plate with filterNov 1933 Cambridge, Jan 1934 Bloemfontein
CSmultiple exposure calibration out of focus (soft focus) blue platederived
Dtrails of stars between -30 and +55B plates only
Dspectrum plate, high dispersion prism, blue plateNov 1933 Cambridge, Jan 1934 Bloemfontein
D1high dispersion spectrum widened, blue plateCombo example
D1spectrum plate, high dispersion prism, yellow plate w/filterNov 1933 Cambridge, Jan 1934 Bloemfontein
D2spectrum plate, high dispersion prism, red plate w/filterNov 1933 Cambridge, Jan 1934 Bloemfontein
Espectra of stars near the polesB plates only
Ecunknown classderived
Erunknown classderived
Ffocus plate, blueNov 1933 Cambridge, Jan 1934 Bloemfontein
Fspectra of stars near the zenithB plates only
F1focus plate, yellow with filterNov 1933 Cambridge, Jan 1934 Bloemfontein
F2focus plate, red with filterNov 1933 Cambridge, Jan 1934 Bloemfontein
FD1focus plate with prism, yellow filterCombo example
Ggrating used on chart plateNov 1933 Cambridge, Jan 1934 Bloemfontein
Gspectra of stars near the equatorB plates only
Hchart plate long exposure (previous designation was L)Nov 1933 Cambridge, Jan 1934 Bloemfontein
Hcharts of stars, generally with exposures of 1 hourB plates only
Ispectrum plate, long dispersionCombo example
Ispectra of stars with exposures of about 1 hourB plates only
Jtrails of stars near the equatorB plates only
Ktest plates on the poles, trails of 10 min., first with, and then without, prism.B plates only
Lchart, single exposure, in focus blue-sensitive plate (MAJORITY)Nov 1933 Cambridge, Jan 1934 Bloemfontein
Lcharts of stars between +47 and +57, - 5 and -7, and -17 with exposures of about 15 minutesB plates only
L1chart, single exposure, in focus yellow-sensitive with filterNov 1933 Cambridge, Jan 1934 Bloemfontein
L2chart, single exposure, in focus red-sensitive with filterNov 1933 Cambridge, Jan 1934 Bloemfontein
L2Schart, single exposure, in focus red-sensitive with filter out of focus (soft focus)derived
L3chart, single exp. with other than the 3 standard colorsNov 1933 Cambridge, Jan 1934 Bloemfontein
L4chart, single exp. but UV or any special filterNov 1933 Cambridge, Jan 1934 Bloemfontein
LSchart, single exposure, in focus blue-sensitive out of focus (soft focus) plate derived
Lgiguided single exposure on blue plate, moving objectCombo example
Lichart, single exposure, in focus blue-sensitive trailed platederived
Mmiscellaneous photographs not included in the above classesB plates only
Mmultiple exposure on one field, blueNov 1933 Cambridge, Jan 1934 Bloemfontein
M1multiple exposure on one field, yellow with filterNov 1933 Cambridge, Jan 1934 Bloemfontein
M2multiple exposure on one field, red with filterNov 1933 Cambridge, Jan 1934 Bloemfontein
M2Smultiple image with red screen, red plate with filter, out of focus (!!)Combo example
MGmultiple exposure on one field, blue, grating used on chart platederived
MSmultiple exposure on one field, out of focus (soft focus) blue platederived
MS2multiple image with red screen, red plate with filter, out of focusderived
Msunknown classderived
Nunknown classderived
Ospectrum plate, short dispersionNov 1933 Cambridge, Jan 1934 Bloemfontein
OSspectrum plate, soft dispersion out of focus (soft focus)derived
Ppolar adjustment (chart) C, D trails, 2 exposuresNov 1933 Cambridge, Jan 1934 Bloemfontein
PGpolar adjustment (chart) C, D trails, 2 exposures grating used on chart platederived
PanPannekoek: blue plates, multiple exposure taken on AC patrol camera ca. 1924-25Combo example
Poleunknown classderived
Runknown classderived
Sout of focus (soft focus) blue plateNov 1933 Cambridge, Jan 1934 Bloemfontein
S1out of focus (soft focus) yellow plate with filterNov 1933 Cambridge, Jan 1934 Bloemfontein
S2out of focus (soft focus) red plate with filterNov 1933 Cambridge, Jan 1934 Bloemfontein
SMmultiple exposure on one field, out of focus (soft focus) blue platederived
Tout of focus plate Nov 1933 Cambridge, Jan 1934 Bloemfontein
T1two exposures, different fieldsNov 1933 Cambridge, Jan 1934 Bloemfontein
TMmultiple exposure on one field, blue, out of focusderived
Ularge prismsNov 1933 Cambridge, Jan 1934 Bloemfontein
VRunknown classderived
WMilky WayCombo example
Xunknown classderived
dspectrum plate, low dispersion prism, blueNov 1933 Cambridge, Jan 1934 Bloemfontein
d1spectrum plate, low dispersion prism, yellowNov 1933 Cambridge, Jan 1934 Bloemfontein
d2spectrum plate, low dispersion prism, redNov 1933 Cambridge, Jan 1934 Bloemfontein
gguided plateNov 1933 Cambridge, Jan 1934 Bloemfontein
itrailed plateNov 1933 Cambridge, Jan 1934 Bloemfontein
lunknown classderived