Orientation of COSMIC

• Direct Imaging Mode
• Reimaged (aka Spectrographic or Tower) Mode

Direct Imaging Mode

The rotation of COSMIC is controlled in the instrument window by the Base Position Angle. The nominal angle is 180^o, which produces the following orientation for the IRAF command ``display ccd001 1'':

N

W E

S

Reimaged Mode

The rotation of COSMIC is controlled in the instrument window by the Base Position Angle. The nominal angle is 180^o, which produces the following orientation for the IRAF command ``display ccd001 1'':

S

E W

N

For this display mode, spectra will have blue at the bottom of the image.

For the IRAF command ``display ccd001[*,-*] 1'', the orientation is:

N

E W

S

which is the usual sky parity. For this display mode, spectra will have blue at the top of the image.

If the Base PA is set to 270^o, then for the IRAF command ``display ccd001[*,-*] 1'', the orientation is:

W

N S

E

If the Base PA is set to 90^o, then for the IRAF command ``display ccd001[*,-*] 1'', the orientation is:

E

S N

W

In the default Base PA of 180^o, the longslits will run E-W (i.e. slit PA is +90^o). If you wish for the slit PA to be +45^o, for example, then you will set the Base PA to be 225^o.

The Base PA has an allowed range of between 70^o to 300^o .