Zeropoints

Configuration	Date	Zeropoints* for J / H / Ks	used pupil stop
INGRID at Cassegrain		see INGRID page
NAOMI+OSCA+INGRID	Sept. 02	21.42 / 21.67 / 20.99	OSCAobs
NAOMI+OSCA+INGRID	Apr. 03	21.5 / 21.4 / -	OSCAobs
NAOMI+OSCA+INGRID	Aug. 03	21.61 / 21.91 / -	NAOMIobs

Astrometry

Using OSCA the field of view on INGRID is inverted as compared to NAOMI+INGRID alone. This means in case of NAOMI+OSCA+INGRID within GHRIL: North is UP and East to the left (until end 2002). After the change to GRACE there is a flip in FOV orientation: North is DOWN and East to the right (since 2003).
It was verified that the platescale on INGRID stays the same with and without OSCA.

Instrumental features to be aware of

As coronography increases the dynamic range compared to non-coronographic observations the obtained data are also more sensitive to instrumental features/artefacts. These can lead to false detections and/or a significant decrease in sensitivity. The main features seen in OSCA data obtained during commissioning are blobs along the x and y axes (see Fig. below). These blobs are caused by diffraction on the edges of the segments of the deformable mirror (DM) of NAOMI. They are thus not a feature of OSCA but using OSCA these effects are clearer visible. It is advised to either ignore the regions along the x and y axes during analysis or to verify any possible detection by obtaining additional images taken with a different position angle of the derotator. The rotation of the field will not change the orientation of the DM pattern.

Figure information: A bright (H ~ 4 mag) behind the 0"65 OSCA mask. The occulting mask appears to be saturated with the chosen cut levels. The blobby structure (DM pattern) in x and y direction is indicated. The faint lines seen in 45 degrees direction are caused by the secondary support spider. For the shown image the OSCA Lyotstop was not installed. The Lyotstop veines shall remove the remaining diffraction by the secondary spider seen here. Also the quadrant boundary of the INGRID detector is visible.