Mt. Wilson Solar Photographic Archive Digitization Project

This page explains how the plates in the Mt. Wilson Solar Photographic Archive are being rehoused.

Storage at Carnegie

Previous Storage Files
The Ca K plates have been stored in paper envelopes housed in wooden cabinets. The large collection of these plates exceeded the drawer space and some groups of plates were stacked in boxes. The more vulnerable groups have been relocated. The wooden boxes emit gasses which are harmful to the photographic emmulsion and a part of the project is to move the plates to more inert archival boxes. The top image to the left shows a bank of drawers, most of which on the left are empty. Starting about where the one is pulled out, the drawers contain Ca K plates from the 1950's era. The lower image gives a closeup of the drawer with one plate envelope pulled out. The discoloration of the paper is partly from its higher than desireable acid content and from the action of the wooden box walls.

The bottom figure shows the storage of the plates obtained by Prof. Robert Leighton between 1959 and 1964. These include some of the finest examples of spectroheliograms available. Many were published in 1966 by The Carnegie Observatories in a volume authored by Dr. Alan Title and entitled "Selected Spectroheliograms".

Storage at UCLA

The top image shows the shelving setup in use at UCLA. The metal racks are coated with an inert paint and the top is protected against accidental fire sprinkler activation by a plastic cover. The humidity in the room is monitored regularly. Each of the boxes contains a set of plates each enclosed in a new 4-flap envelope of archival paper. The boxes are labeled for their range of plate numbers and organized according to year. The volume required for each plate is increased as a result of this rehousing and the resulting boxes require either greater floor space or compact shelving.

The second image shows a typical plate in its 4-flap envelope. The open box at the rear shows the included layer of cardboard material which provides cushioning of the ends and sides of the box. No glue is used in either the box or the 4-flap envelope. The plate can be removed or returned to the 4-flap envelope without any sliding motion thus avoiding scratchs on the image surface.

The Archive Lab in the Physics and Astronomy Building

At the end of the summer of 2004 the Astronomy Division moved from its old quarters in the Math Sciences Building into the new Physics and Astronomy Building. The basement and sub-basement levels of this building were designed to provide laboratory space and the Mt. Wilson Solar Photographic Archive Project was assigned one of these new laboratories. Due to problems with the air conditioning system, the move into these labs was delayed until the end of 2004. This move is now complete and this photo shows Archivist Liz Werden rehousing the CaK plates on builti-in benches. The built-in cabinets provide temporary storage for plates, empty boxes and fresh four-flap envelopes.

The upper image to the left shows the Esko-Graphics Scanmate F14 scanner and its workstation while the lower middle image shows the racks with the plates scanned and rehoused as of July 2005.
The bottom image at the left shows our rack housing the primary computers and storage systems for the project. The computer on top of the rack is a Windows Server 2003 system used for tagging the images and carrying out FORTRAN based reductions. The system in the rack is a Linux machine used for hosting the RAID storage systems and carrying out the extractions from the full deck scans. Visible on top of both these computers is an external disk for backups which is locally mounted through a usb port. In the middle and bottom of the rack are the two RAID systems providing us with about 3.3 terabytes of storage. The empty slots in the rack will be used for additional RAID systems as the need arises. Below and to the right of the rack is the UPS which is configured to automatically shut down the system in the event of a power outage in excess of 5 minutes and remain off until reset locally.