Difference between revisions of "Lesedi"

Revision as of 23:56, 6 June 2020

Lesedi is a 1-metre, Alt-Az, f/8, Ritchey-Chretien telescope built by APM Telescopes, and installed in the dome that previously housed SAAO's 30-inch Grubb Parsons equatorial. There are two Nasmyth foci, each with an instrument rotator and identical corrector optics. This page describes the facility and its operation.

Contact numbers

To receive calls, the phones in the warm room and on the observing floor can be reached by the following numbers:

Extension number: 9109 (to phone from within the observatory)

To make calls if you have a problem that isn't addressed in this wiki or the fault forum (remember to dial the ** where given):

1.9m/74-inch observer: 9107

1.0m/40-inch observer: 9108

Cape Town remote observing station: 7027

Standby electronics technician: **103

Standby mechanical technician: **104

Standby IT technician: **113

A guided tour of the dome

The purpose of this section is to introduce you to the facilities and equipment you will need during your run. The tour begins at the front door of Lesedi's dome. To aid orientation, the domes of MeerLICHT, Lesedi, and the 40 inch are aligned East-West, perpendicular to the main road that passes SALT at the Northern end of the plateau and leads to the "Robotic Row" of telescopes in the South. A code (which you can obtain from the standby technicians/your support astronomer/other observers) is required to open the door.

Main lighting circuit switch

Just inside the entrance on the left-hand wall is a master switch to control all the lighting circuits in the building. Switch it on if you are working in the building, and always ensure that it is switched off when you leave, especially if people are observing remotely.

Light switches

Foyer and stairwell light switches can be found on the right-hand wall as you enter the dome, just around the corner to the right, at the foot of the stairs (foyer light switch on the right, stair lights on the left). There is a second switch for the stairwell lights at the top of the stairs.
Light switches on the left at the top of the stairs. The left-hand switch is for the stairwell lights; the other for the observing floor incandescents.
The switch for observing floor fluorescent lights is located up the ladder on the observing floor, on the dome control console mounted on wall above the North end of the pier. These are also under software control.
The slew lights on the ring beam are under software control only.

Ground floor facilities

As you enter the dome on the ground floor, you will find the following facilities:

Fire extinguisher: mounted on the left-hand wall as you enter.
First aid kit: on a shelf to the right as you enter the dome.
Toilet: through the first door on the left as you enter the dome. The light switch is outside the door on the right. The right-hand switch operates an extractor fan(!).
Kitchen:, second door on the left. It has a microwave, coffee maker, kettle, toaster, snackwich and an array of cutlery and crockery in the cupboard under the sink. There are jars of teas, coffees, hot chocolate and sugar. If these jars become empty, return them to the hostel kitchen in your night lunch bag for refilling. The kitchenware is cleaned daily by the hostel staff, except at weekends.

The control room

The control room, or "warm room", is the door on the right-hand side, opposite the kitchen. It contains an air-conditioned server room and has the following resources at your disposal:

A PC ("lesedi-nuc") for running the telescope and instrument control systems.
Several network cables and power sockets for use with laptops.
Lights on a dimmer switch (push and hold to adjust the brightness) and a desk lamp.
An air conditioner to heat or cool the room.
A stereo compatible with iPods and iPhones, and plays CDs, MP3s from DVDs and USB devices, and has a radio.
A phone (you'll need a PIN from IT to dial out).

The Observing Floor

At the top of the stairs, be careful not to trip over the raised hatch in the floor (this is for lowering the primary mirror for aluminising). You will find Lesedi on a raised pier, surrounded by a metal grid floor, accessed by a ladder. The North end of the pier is nearest the stairs. Familiarise yourself with the following:

Dome control console at the North end of the pier.
Dome lockout switch beside the dome control console at the North end of the pier. Note that this does not lock out the telescope, only the dome. Lockout should be switched on (a red light on the box will flash) if people are working on the dome, otherwise left off.

The Telescope

The Nasmyth ports are identified as left and right, defined from the point of view of someone standing behind the parked telescope, i.e. looking at the back of the primary mirror cell. SHOC is mounted on the right-hand port, and Sibonise will be commissioned on the left. Future instruments (Mookodi (a low-resolution spectrograph incorporating a high-speed imager to replace SHOC) and a fibre-fed echelle) will be co-mounted on an instrument selector on the right-hand port. A motorised tertiary mirror allows an instrument on either port to be selected in seconds.

The telescope is parked facing East, the dome to the West. There shouldn't be any need for manual interaction with the telescope during the night, but you should ensure that the observing floor is clear of ladders and other obstacles before moving the telescope, and that the mirror covers are closed before opening the dome.

Webcam

There are currently two webcams to use to keep an eye (and an ear) on the telescope:

The Mobotix camera sees the full observing floor, but has no sound.
The UniFi camera sees the shutters, the top half of the telescope and half the observing floor, and the dome can be rotated to view the opposite half. The UniFi webcam must be viewed in Chrome/Chromium (not Firefox) for the sound to work.

Filters

At present, SHOC has one 8-position filter wheel, containing UBVRI, a clear filter to match the focus of the Bessell filters, and two empty slots. The SHOC software identifies the filter in each position. Filters must not be removed from the filter wheel.

Observing limits

Meteorological constraints

The dome must be closed when any of the following weather limits is reached:

Humidity: T_external - T_dew ≤ 1.5
Wind speed: 60 km/h
Heavy cloud

In case of strong wind and rain, please park the dome shutters facing into the wind. This can be done remotely by rotating to the required azimuth in the TCS "Advanced" tab, or on-site by putting the dome in lockout and rotating left or right using the dome control console.

Meteorological information

The following should be used for regular monitoring of external conditions while observing:

DIMM seeing data and all the weather stations on the plateau are summarised on this page
For assessing sky conditions, SALT and LCO operate all-sky cameras, also available on the website above.

Telescope pointing limits

Lesedi can safely point between 30° and 89° above the horizon, at any azimuth. There are no obstructions in the dome to be aware of (assuming the observing floor has been checked for ladders etc).

If the telescope reaches an altitude limit, it will simply stop tracking and can be pointed to a new position. The azimuth rotation is limited to a range of 400° in order to avoid twisting the cables that pass through the pier. It is therefore possible to encounter an azimuth limit while tracking. If this happens, the telescope should automatically "unwind" by 360° in azimuth and continue tracking (if it doesn't, simply repoint the telescope), but in an effort to avoid this scenario, the telescope is programmed to "unwind" on pointing if an attempt is made to point within 40° of a limit.

TCS Overview

The user interface is a web browser that communicates with Lesedi's underlying control software. The browser-based software will be referred to as the "TCS" and the back-end software as the "SiTech software". The SiTech software consists of seven GUIs that must be running in the background for the TCS to function. Ideally, these GUIs will remain running at all times and the user will only interact with the TCS.

Safety

Note that there is no hardware lockout for the telescope (except for brackets that can be fitted to hold the telescope vertical for e.g. primary mirror removal). All the subsystems' motors are brushless DC motors and remain powered up all the time; powering down the motors would leave the telescope and subsystems free to move under gravity or external forces (e.g. leaning on it). There is a dome lockout, which is a physical switch in the dome that prevents the shutters and dome from moving. As a safety feature, the TCS disables all actions when the dome lockout is on and displays the warning shown in the image below. Before the telescope can be used from the TCS, you must ensure that it is safe to turn off the lockout, then do so using the switch at the North end of the pier in the dome.

The dome is locked out and the TCS cannot be used. The dome must be checked for safety before switching off the lockout and continuing.

The Controls Tab

Below is a screenshot of the main "Controls" tab of the TCS, where everything required for routine observing is located. There is one other tab, for more rarely used "Advanced" functions. The Controls tab is split into four main panels: command of the telescope and instrument selection on the left; the status of each subsystem in the middle; time and positional information on the upper right; and important buttons that need to be easily accessible on the bottom right.

Emergency Stop

It is important to note the Emergency Stop button, on the lower right of the TCS display. It is always visible on both tabs, and will stop the motion of the dome, shutters, telescope, rotators and secondary mirror. It will not stop the autoguider XY-slides, the mirror covers or the tertiary mirror. The Emergency Stop button should be clicked if anything that is moving is going to cause a hazard. Once clicked, the Emergency Stop button will be toggled to read Reset, and you must ensure that it is safe to reset all the subsystems before pressing this button to continue.

The Startup button

The Startup button is not a "power-up" button, as everything should be powered up at all times. The Startup button should be used only when you intend to open up to observe, as it opens the dome. The button runs a script that performs the following tasks in this order:

Take remote control of the dome
Switch off fluourescent lights
Switch on slew lights
Open dome shutters
Open mirror covers
Unpark telescope so it can slew
Set dome to track telescope
Select SHOC rotator
Switch off the slew lights

You can watch the startup procedure from the webcam. The status panel on the Controls tab is updated as each subsystem is activated. The SHOC rotator is selected on startup to ensure that observations are not made with the tertiary mirror in an unknown position.

If you don't want to run the full Startup procedure (e.g. because it's daytime and the dome should not open), but do need to interact with the telescope, individual subsystems can be commanded from the Advanced tab. Buttons on the Controls tab will work without running Startup (with the exception of Shutdown), though the telescope will need to be "unparked" from the Advanced tab before it can slew.

The Shutdown button

Once the Startup procedure is complete, the button will read Shutdown, and should be used to close everything at the end of observing. The shutdown script essentially reverses the Startup procedure:

Set the dome to remote control (in most scenarios it will already be in remote, but just as a precaution)
Switch on slew lights
Close mirror covers
Close dome shutters
Stop dome from tracking telescope
Park dome at az=270°
Park telescope at az=90°, alt=50°
Park rotators
Switch off slew lights
Switch off fluorescent lights (likely to be off, but as a precaution)

Control of the dome is not given up, but it can be "taken" using the lockout in the dome. It is not necessary to lockout the dome after use; staff will use this function when working in the dome.

The Advanced Tab

The Advanced tab is made up of four panels, one for telescope-related functions including mirrors and covers; one for the rotator in current use; one for the dome, including lights; and the panel containing positional and timing information and vital buttons, replicated on the Controls tab.

Green buttons indicate a state appropriate for observing. Below is an explanation of the features of the Advanced tab:

Telescope panel:

Park (alt=50° az=90°) or unpark the telescope (also turns tracking on) to enable it to slew.
Slew the telescope to specified alt-az coordinates. The telescope will then start tracking.
Start/stop the telescope tracking. Tracking should be on while observing, otherwise off.
Open/close the mirror covers. Covers should be open when observing, otherwise closed.
Put the altaz, secondary and tertiary mirror motors in Auto mode. Motors should always be in Auto unless there is a fault.

Rotator panel:

Turn tracking on/off for the rotator on which the instrument currently in use is mounted. Tracking is automatically disabled for the other rotator. Tracking "on" does not necessarily mean that the rotator is moving, but that it will move if the telescope is tracking. Rotator status can be found on the Controls tab, where the angle will be updating if the rotator is tracking.
Put the motor in Auto for the rotator currently in use. The motor should always be in Auto unless there is a fault.

Dome panel:

Take control of the dome (needed for all dome functions except controlling the slew lights)
Rotate the dome to a specified azimuth
Set the dome to start or stop tracking the telescope. Tracking should be on while observing, otherwise off.
Switch the "Lights" on/off. This refers to the fluorescent lights mounted high in the dome.
Switch on/off the slew lights. This refers to the dimmer lights mounted on the ring beam, that can be used to check on the telescope using the webcam.
Park the dome (az=270°).
Open/close the dome shutters.
Stop the dome rotation or shutter movement.

Position/timing/vital functions panel:

The schematic shows the shutter status (red=closed or moving, green=open) and position, and the telescope status (slewing=red, tracking=yellow) and altaz position. No indication of telescope presence implies that it has not tracked or slewed for the past 30 minutes.
The time is displayed in SAST, UT, LST and Julian Date.
Emergency Stop.
Startup or Shutdown, whichever is the opposite of the current status.

The typical focus value for SHOC with no filter is ~2000.

Start-up recipes

Start-up in Sutherland

Follow this procedure to prepare the telescope and dome for observing in Sutherland:

Check the weather conditions here. If windspeed <60km/h and T-T_dew > 1.5 (see observing limits), continue with step 2.
Check the observing floor and clear any obstacles (e.g. ladders) that may obstruct the telescope.
Switch off the lights everywhere except in the warm room.
Log into lesedi-nuc in the warm room, open a browser and navigate to the webcam and click "Live Feed".
Open a second browser window and navigate to the TCS (URL coming soon).
Click the STARTUP button on the TCS. This will switch on the slew lights so you can watch it open the dome, baffle and mirror covers, and set the dome to follow the telescope, then switch off the slew lights.
Select the Instrument you require by clicking either SHOC or SIBONISE to the mid-left of the display. The selected instrument name will turn green.

Start-up remotely from Cape Town

On-site technical staff should have checked the facility in the afternoon, clearing any obstacles, unlocking the dome and turning off the lights.

Check the weather conditions here. If windspeed <60km/h and T-T_dew > 1.5 (see observing limits), continue with step 2.
Open a browser, navigate to the webcam and click "Live Feed". Check that the observing floor is clear.
Open a second browser window and navigate to the TCS (URL coming soon).
Click the STARTUP button on the bottom right of the screen. This will switch on the slew lights so you can watch it open the dome, baffle and mirror covers, and set the dome to follow the telescope, then switch off the slew lights.
Select the Instrument you require by clicking either SHOC or SIBONISE to the mid-left of the display.

Instrument start-up

Follow the instructions on the SHOC wiki.

Sky flat recipe

If sky conditions are photometric during morning/evening twilight, you will be able to take sky flats:

Follow the start-up procedure.
Follow the appropriate instrument setup procedure.
On the TCS Advanced tab, left-hand side under Telescope, enter 80 in the Altitude box and enter an Azimuth to face the telescope in the opposite direction to the rising (270) or setting (90) Sun. Click Slew. Then immediately below the Slew button, click Tracking OFF.
On the instrument PC, select the required filter. If you need flats in a variety of filters, be sure to cycle through them in the correct order (e.g. UBVRI during evening twilight; IRVBU in the morning). This also applies if you need a range of prebin settings (i.e. start with low binning in the evening; high to low binning in the morning).
You can easily take a minimum of 15 flats in each filter/prebin setting with SHOC; Sibonise has longer readout times.

Observing recipes

Acquiring a target

1. Follow the facility start-up procedure.

2. Check that the selected target is within the pointing limits. If you're not sure, or want to find out the exact altaz of your target, you can enter the coordinates into the input boxes on the upper left panel of the Controls tab, then click "Visibility...". This brings up a panel that shows the altitude and azimuth of the target at that moment.

Then/or, either:

3(a) In the TCS Controls tab enter the RA, Dec and Equinox into the boxes on the upper left panel and click Go.

or:

3(b) In the TCS Controls tab click Catalogue HOW DOES THIS WORK??.

The telescope will slew to the target, and its movement will be plotted in yellow dots on the schematic in the right-hand panel. The "Go" button will become a "STOP" button, which you can click to stop the telescope. Once it reaches the target coordinates, the telescope will start to track and red dots will show the track progress on the visibility plot. If nothing happens, the target is probably out of the observing window - return to step 2.

4. The telescope will track the target until you click STOP. To run SHOC, follow the instructions on the SHOC wiki.

5. Lesedi's pointing is excellent, so your target should land very close to the centre of the SHOC image. The image orientation with no "flips" applied in the SHOC software (check the Advanced tab of the SHOC control) is North Up, East to the left, when the rotator sky angle is 0, North down, East to the right with a sky angle of 180. Add more about rotation.

To adjust the pointing (e.g. to position a target and comparison star in the field),

6. Focus the telescope using the Adjust Focus... button, which brings up a box in which you can enter the focus increment. A reasonable starting point for SHOC focus with a filter in the beam is ~2000 - you can check the focus position in the status panel on the Controls tab. A reasonable increment for small adjustments is ~5. Clicking + or - then adds or subtracts 5 microns to the focus position.

Autoguiding

Ultimately the autoguider control will be integrated into the TCS, but for now it has a standalone GUI. To start the autoguider sofware:

          ssh -Y observer@1ms1.suth.saao.ac.za
          cd /home/observer/xyslide_lodestar_GUI_V5
          sudo ./main_prog -depth 24

Points to note:

The XY slides can move 20000 steps in X and 15000 in Y.
To guide while using SHOC, select Slide 0.
To start continuous exposures with the autoguider Lodestar camera, enter a number (~2 seconds) in the box on the right, and click CONTINUOUS. *********
If the status of any of the error codes (Err, XLL, XUL, YLL or YUL) is 1, click RESET, then INITIALISE.
It is not yet possible to select a guide star from a catalogue, so for now it's a bit of a fishing expedition.
Put values in both X and Y boxes and click GOTO to move the slides. As Y approaches 10000 it begins to vignette the SHOC field. *********
For a sky angle of 0, i.e. North up, both the N-S and E-W buttons should be green. For a sky angle of 180, they should both be clicked and turn red.
FAKE should always be red while guiding, as this is a test function.

Troubleshooting

Symptom	Cause	Solution	Who to call
TCS displays a warning stating that "The lockout has been engaged in the dome. No commands will be allowed until it is disabled. Try again or contact a technician for assistance...."	The dome is manually locked out.	Call a technician to check if the telescope and dome are in a safe state. If it is safe to do so, the lockout switch by the North pier needs to be turned to the OFF position.	Mechanical or electronic standby.
The autoguider Lodestar camera is not reading out, or the guider GUI keeps crashing.	The Lodestar camera needs rebooting.	Unplug the Lodestar camera cable from the Icron device mounted on the underside of the pier, then plug it in again in the same port.	Electronic standby if on site, otherwise mechanical standby can fix this.
One of the subsystems (rotator, secondary or tertiary mirror) doesn't respond.	Either (i) the motor is not in auto, or (ii) there is a comms issue with one or more subsystems, or (iii) the controller is in a fault state.	(i) On the Advanced tab of the TCS, check that there is a green "AUTO" indicator beside the relevant subsystem. If the button says "MANUAL", click it to put the motor in AUTO mode. If that doesn't help, or if it is already in AUTO, the problem is likely (ii) or (iii) and you'll need assistance.	Electronic or IT standby.
The dome didn't open on startup.	There is likely a comms problem.	Call a technician to remedy.	Electronic or IT standby.
There is an error message saying "No Instrument selected".	The tertiary mirror is facing neither SHOC nor Sibonise's Nasmyth port.	Click on either "SHOC" or "Sibonise" in the Instrument panel of the Controls tab.	You can fix this!