How to take images

Bright objects (K < 9) are easily imaged in single exposures of 1 second or less.  Fainter objects require longer exposures and are best observed in a nodding mode in order to subtract the sky background.  On a night with good seeing, the focus should be checked if the image for a point source starts to exceed 1".

1. Check mechanism positions.

A. Put Direct Imaging Mirror (DIM) IN.

B. Make sure all lamps are off, the filter in NOT blanked, and the shutter is OPEN.

C. Unless imaging the slit, make sure the slit wheel is OPEN.

2. Check exposure-related settings.

A. Unless taking test image, turn Autosave ON and make sure desired values are entered for path, filename, object, etc.

B. Enter desired values for Itime, Coadds, and Cycles.

C. Select desired Obs Mode. If nodding, give values to TO.

D. Enter desired wavelength (μm) or wavenumber (1/cm) and click related button.

3. Adjust position of object on the chip as desired.

A. Take test exposure (with AUTOSAVE OFF and one cycle, press GO).

B. Enter current and desired object positions in one of three ways:

1. Draw a line from the current position to the desired position with shift middle-mouse button,

2. Enter the desired pixel coordinates in the From and To boxes, OR

3. Enter the desired pixel coordinates with the f and t keys by:

a. In DV image, click on objects current position.

b. Press f key.

c. Move cursor to desired position (but do NOT push mouse button).

d. Press t key.

C. Select TCS Offset tab in lower part of DV.

D. Check that angle and plate scale are correct (270 and 0.2 respectively for CSHELL in standard position).

E. Click Offset Telescope.

4. When object is in position Press GO (after AUTOSAVE ON and number of cycles entered).

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LAST UPDATE: February 1, 2010