Changes
/* Dome Flats */
Dome flats give a measure of the pixel-to-pixel sensitivity variations over the CCD. The dome's white flat-field screen is not perfectly evenly illuminated by the lamps on the top end of the telescope, but the light goes through the slit, gets collimated, diffracted and re-focussed, so that is not a problem. We do not use the sky for this as you would get spectra of the Sun!
- On the TCS, click the grey "FLOOR" button near the top to change the telescope control to "TCS". - Click the red "Telescope Power is OFF" button on the top left. Telescope power will switch on, the button will turn green, and the various subsystem statuses will be populated. - Click the red "Man" button on the top right to switch the dome to auto. - Click "CLEAR", then "DOME" and select "Mirror open" from the drop down menu. - Click "CLEAR" then "TARGET" and a range of buttons will appear. Click on the "Dome Flat" button toward the right. This will slew the telescope to point to a panel on the ceiling, painted white. Once the telescope has stopped moving, the dome will switch to manual. - Above the date and time info, click the yellow "Flat Lamp OFF" button. It will turn red and the lamps on the top end of the telescope should now be on. - On the SpUpNIC Control GUI, make sure there are no mirrors in the light path (no blue border around the spectrograph schematic) and take some trial FLAT exposures to determine the exposure time required to reach ~40k counts. The lamps are quite red, so blue settings (e.g. G4) will need long exposures. It's fine to crank the slit wide open to let more light in (you do not care about resolution here). - Take e.g. 15 flats by populating the "# Exposures" box accordingly. - Once you're done, go back to the TCS and: * turn off the flatfield lights ("Flat Lamp ON" button - turns yellow/OFF) * switch the dome to auto (press "Man") * park the telescope (TARGET menu - click "Park") * close the mirror covers (CLEAR --> DOME --> Mirror CLOSE) * If you're finishing here, switch the dome back to manual and turn off telescope power (click Telescope Power is ON --> red/OFF), or if you're opening to observe leave dome in auto and power on. <!-- - Behind the control room desk, dial the rheostat fully anti-clockwise to zero [[File:rheostat.jpg|80px]]
- Flip the switch in front of it to ''On''
- Dial the rheostat up to '''140 V - do not exceed that value as you will blow the lamps''' - this value has decreased from 220 V since new lamps were installed in July 2019 - The lamps on the top end of the telescope should now be on - Open the mirror cover> <!-- - With the telescope vertical, rotate the dome to 127 degrees, so that the white flat-field screen is just to the east of the south pier
- Set the telescope RA to HA = 0
- Slew the telescope in Dec to the south pole (-90 degrees), while keeping an eye on the spectrograph cables
- If you run into the limit, an alarm will sound and the telescope will stop moving
- To recover: turn the over-ride key next to the console while backing the telescope out towards the north in Dec
- With the telescope at HA ~ 0/12 & Dec ~ -86:30, the telescope should be quite well centred on the flat-field screen - In the control room, take some trial exposures to check the count level, aim for ~40k counts - The lamps are quite red, so blue settings (e.g. G4) struggle for counts - In that case, it is fine to crank the slit wide open to let more light in (you do not care about resolution here) - Take as many flats as you like (say, 11?) once you have established an appropriate exposure time
- When you have the flats, slew the telescope back to the zenith (again keeping an eye on the cables)
- Dial the rheostat down to zero
- Flip the switch to ''Off''
- Close the mirror cover
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====Focusing The Spectrograph - running a Hartmann sequence====
