This is a summary of normal IGRINS use for observers at the McDonald 2.7m telescope
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To startup the telescope follow the dome opening procedure. Be sure to monitor the weather conditions and abide by the dome closing conditions while observing!
If all prior steps were completed, then the remaining steps are:
Turn off the dome lights and passage lights.
Prop open the doors on both sides of the dome.
Open the Louvers using the Air Controller panel by the east door.
Open the slit by holding down the "Dome Open" button on the console. This will take a few minutes. You will hear a clank when the dome is fully open. Once the slit is open, you can let go of the button.
Press and hold the "Cover Open" button on the console to open the mirror cover. You will hear a sound when it fully opens (note the light indicator no longer works, so listen for the sound). Once it is open, you can let go of the button.
On the TCS computer or atlas, select Tools → Enable Dome Automation
Start of Night
Check and zero the telescope pointing
If TCS has not been reset since the prior night of observing, your pointing will be easier to find than if TCS was reset during the day.
Follow either of the directions outlined here:
Note: Since IGRINS has returned to McDonald Observatory in late 2024 the pointing has been difficult to obtain because the zeroes are often far off when TCS is reset. Be prepared to spend up to several hours in the beginning of the night pointing (particularly spiraling around using the paddle in the SCV), especially if you are not an experienced user of McDonald HJST. Our advice to make pointing easier is to pick a star near zenith that has several surrounding bright stars (see example 29 Peg) because if the telescope is very far off in pointing nearby bright stars clustered by dim stars are easier to identify in the slit view camera images than clusters of all dim stars. Remember to take into account the slit rotation when looking at finder charts!
Focus the telescope
Use the yellow hand paddle in the observing room to adjust the telescope focus [add image of location in observing room]
Make sure there is a star near the center of the SVC field of view that is bright enough to measure the FWHM of its PSF but not so bright it saturates the detector [take image of plots we look at in the SCV]
It might be useful to set up a spreadsheet to record your focus values VS. star PSF FWHM
Select minimum and maximum range of focus values to check [Note: need to add a reasonable range of values], start at the lowest range
Start at the minimum and loop through the following procedure (there is hysteresis in the system so we always step through the same way)
Step up in values of 100-200
Take a slit view camera image
Click the star to measure its FWHM [put in image of the plots we use to measure this from the SCV]
Keep an eye on the shape of the star’s PSF and make sure it looks reasonable [show an example of the tail that can appear when things are out of focus]
Write down a table with the focus value the FWHM of the star
Repeat the above steps, filling up your table, until you reach the maximum focus value to check or you are confident you are out of focus
Find the focus value that gives the best FWHM (it might be useful to plot your table in a spreadsheet)
Go back to the minimum focus value
Slowly in small steps raise your focus value until your reach the value that gave you the best FWHM
Take another exposure of your star and double check you get the expected FWHM
If you are confident the PSF FWHM is good, you are now in focus!
Note: If there are large changes in temperature over the night and/or you notice stellar PSFs in your SVC images look bad, you might want to refocus
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Move the telescope to Zenith
Using the TCS select Next → Zenith and click yes on all of the pop-up windows.
Click “Go Next” at the top of the TCS window.
Slew the telescope to Zenith by holding down the Autoslew botton on the dome floor console.
Ensure the rolling ladder is not on the raising platform.
Use the yellow hand paddle to raise platform east until you can comfortably reach the mount that connects IGRINS to the telescope.
Not so high that IGRINS or the electronics rack will hit the platform floor!
Get the wheel attachment from the red tool box on the opposite side of platform east (near the ladder that brings you to the second floor in the dome).
There are four screws on the IGRINS rotator plate that need to be loosened.
3 should have star-like handles you can manually loosen (unless a Darrin has been applied recently… then good luck)
The last screw requires a specialized wrench kept..[I don't know where this is kept; a picture of the wrench and the special bolt would be good]
Once all of the screws on the rotator plate are loosened, attach the wheel attachment to the rotator peg on the rotator plate.
This can be a little fussy to attach because the wheel and peg have interlocking parts, so a headlamp or flashlight can be helpful for getting the right orientation of the wheel.
You’ll know the wheel is in position when it is near flush against the rotator plate.
Turn the wheel to rotate IGRINS in the appropriate direction.
This requires some elbow grease!
If you have difficulty moving IGRINS with the wheel alone, attempt applying some pressure on the edges of the electronics rack to loosen the rotator plate.
DO NOT PUSH ON THE CRYOSTAT
Encoder settings for different position angles can be found here.
Once you think you are close to your desired rotation position check the value on the encoder and adjust as needed.
Once you reach the desired position
Remove the wheel and return it to the tool box.
Screw in the 3 star-handled screws on the rotator plate. They should be tight!
Use the wrench to tighten the last special screw and return the wrench to it’s found location.
Verify that the cooling cables are NOT UNDER THE PLATFORM before using the hand paddle on the dome floor console to lower platform east.
This may require that you lower the platform a little, jump off, adjust the cables, and continue lowering the platform (repeat as needed).
In the control room:
In the ICC on the SCV GUI change the the rotator value (box 10) and on the TCSProxy change the rotator value.
Resume observing!
Note: the on sky drift for guiding while observing is always higher when IGRINS is not in PA = 90 deg, so you may have to adjust the frequency that the guiding offsets are sent to the TCS (box 15 in the SCV GUI).
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Move the telescope to Zenith
Using the TCS select Next → Zenith and click yes on all of the pop-up windows
Close the IGRINS window cover
Rotate IGRINS back to a PA of 90 degrees, if needed
Raise the east platform using the yellow hand paddle
Close the IGRINS window cover using the handle
Be sure to secure the handle using the velcro strip
Stow the telescope
Using the TCS select Next → Stow and click yes on all of the pop-up windows
Press and hold the button on the dome floor console to move the telescope to the stow position
Close the Mirror Window Cover
Using the button on the Colossus Console (the console in the dome with all the red buttons). You should hear the motor stop when it is fully closed.
Close the dome
Using the button on the Colossus Console. There will be a loud sound when it finishes closing.
Put any wind screens that are over the dome slit back to their stow positions using the hand paddle
Park the dome
Using the TCS select Tools → Park Dome and click yes on all of the pop-up windows
Close the dome doors
Close the dome vents
Using the control panel on the East side of the dome near the door
E-stop the telescope
Using the button on the Colossus Console
Turn on the passage lights (only once dome is closed fully)
Using the button on the Colossus Console
From the control room
Log-out of ATLAS
Click the power button on top right hand side of the lower monitor
Turn off the heater in the observing room
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