The shape and width of observed PSFs varies slightly over time, due to the change in focus of the telescope. The focus variation consists of two terms: a secular change due to the ongoing shrinkage of the Metering Truss Assembly at an estimated rate of 0.25 ?m month -1 , and short-term variations, typically on an orbital time-scale (the so-called "breathing" of the telescope). ... See Figure 5.8 ). ... Figure 5.8: Measured OTA Focus Position (microns) as Function of Days since January 1, 1994. ...

OptInt PmWiki : Pm Wiki / Changes From Pm Wiki 1 . This page is intended to describe features of PmWiki 1.0 that have been changed or eliminated in PmWiki 2.0. ... ThisGroup:SideBar&action=edit Edit menu]] . ... action=post no longer exists -- posting a new page is now performed by using ?action=edit with the post control set to a true value. ... PmWiki's ReadPage() function no longer supplies default text for non-existent pages -- this is now decided by whatever functions need the page. ...

... Bad Astronomy . ... I think I will break from my usual format of Bad Astronomy/ Good Astronomy by saying that the way we define seasons currently is not strictly bad, but I feel (in my opinion!) that it could be better. The definition of when the seasons begin is at the moment of solstice or equinox; that is, winter (in the north) starts on December 22 nd and summer starts on June 22 nd . ... Now imagine breaking up the Sun's 46 degree up-and-down yearly swing into 1 day intervals. ...

... A uv variable can change its value in any part of the uv variable stream. So it can change its value after each call to uvread , uvnext or uvscan . The uv routines which need to know if a uv variable has changed ( uvprobvr , uvcopyvr and uvupdated ) normally (i.e. by default) work on whether the particular variable(s) of interest has changed since the last ``mark'' in the uv stream. ... The uvmark routine provides greater control at marking the position in the stream. ...

Contact Russet McMillan (primary) or your Observing Specialists (secondary) for additional information. Contact Jack Dembicky for web page errors, corrections, ommisions, or additions. This page last updated: July 6, 2004 - JMD . This page last checked: September 14, 2003 - JMD . Configuring TUI to use the Echelle . Setting up the Echelle exposure parameters . Taking your Calibration lamps . ... Setting up multiple exposures . ... Stopping an exposure (discarding data) . ...