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Notes on archives:
Each plate in the Lowell Observatory scientific plate archives has been assigned a unique number within a group, or collection of plates. The numbers are usually in chronological order, but may appear out of order in a very few cases where the out of sequence plate may have been missing. As of the end of 1997, three collections have been identified and processed. All involve the photographic search by Lowell staff for the suspected trans-neptune object later called "planet-x". The plates within these three collections are the oldest in the Lowell archives.
The collections are:
01: The "second search for `planet-x'", consisting of 1,522 data entries and covering the period between 1911-1915,
02: The first part of the "invariable plane survey", consisting of 352 data entries and covering the period between 1905-1907,
03: The end of the "invariable plane survey", consisting of 1053 data entries and covering the period between 1914 and 1915.
Because of the large amount of information contained in the original spreadsheet version of these tables, the tabulated data that appear here is a truncated version of the originals and contain only the basic descriptive parameters of the plates. Thus, for example, information concerning the sky and seeing conditions, plate condition and dimensions, emulsion condition, image quality, observer, and other secondary information about each plate are available in the larger spreadsheet version but do not appear here.
Column descriptions: (many cells are empty or contain "NA" if the information was not readily obtainable. The "object" or field name in the majority of the plates in all three of these collections were calculated locations where "planet -x" was suspected to be located).
1. Lowell Archive Number: The first two digits indicate the collection number; the following four digits indicate the approximate chronological sequence within each collection.
2. Identification: Some plates had already been given an identification number, if so, this number appears here.
3. Local civil date of the evening on which the observing for this "night" began. This is an awkward device but required due to inconsistencies in the record keeping of nine different observers.
4. Object, or field name.
5. Right Ascension coordinate of plate center (only very approximate; the number as given by the observer and may differ from the actual plate center).
5. Declination coordinate of plate center (only very approximate; the number as given by the observer and may differ from the actual plate center).
6. Ecliptic longitude ("lambda") of plate center (only very approximate; the number as given by the observer and may differ from the actual plate center).
7. Ecliptic latitude ("beta") of plate center (only very approximate; the number as given by the observer and may differ from the actual plate center).
8. Epoch of coordinates.
9. Local time at beginning of exposure. Original log entries are very inconsistent so these have been converted to hour numbers through 12 for times up to 1 o'clock in the morning, and 1, etc. for times after 1 a.m. Thus an exposure begun at 15 minutes past midnight local time is listed as beginning on the night before (local time) at 1215.
10. Duration of exposure. Again, not a very precise number. Exposures were often halted and restarted due to mechanical drive or plateholder problems, appearance of clouds, etc.
11. Camera used. For collection 01, all plates were taken with the 40" Clark reflector. These plates have a scale of 37 arcsec/mm and a field of about 1 degree. For collection 02, the following (refracting) instruments were used: The 5" f/6.3 Voightlander (V) camera (plate scale 250 arcsec/mm, field 7 degrees). The 6 3/8" f/4.5 Roettger (R) camera (plate scale 260 arcsec/mm, field 8 degrees. The 5" f/7 Brashaer (B5) camera (plate scale 240 arcsec/mm, field about 6 degrees. The "Slipher" (S) camera plates have yet to be measured for scale and field, and the 2.3" diameter Gaertner (G) camera plates are all still missing and have not been measured. For collection 03, all plates were taken either with the 5" Brashear (B5) camera or the 9" Brashear (B9) camera (plate scale 176 arcsec/mm, field about 6 1/2 degrees.
12. Miscellaneous:
2: Original envelope found but plate missing;
3: Plate found but original envelope is missing;
4: Plate is listed in logbook or observers notes
but neither plate nor envelope can be located;
7: Plate and original envelope exist but not
described in notes or logbook;
8: Two identically labeled plates, but taken of
two different regions of sky;
10:Plate number is out of chronological order.
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