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WHT quality-control tests pending


Below is a list of on-sky WHT quality-control tests which are currently pending. They are in broad priority order (most urgent first), but the order in which they are best carried out will depend on the observing conditions, how much time is available etc. E.g. if the seeing is 0.5 arcsec, give preference to tests needing exceptional seeing. If calibration data are not specified, assume that none are needed.

*** 9/10/17 - Until further notice, please do not obtain more data for the ACAM focus-flop or scattered-moonlight tests - give priority to the the heat-dissipation test. ***

See the WHT quality-control pages for more information on each topic.

  1. ACAM focus-flop test

    Aim: to determine whether best imaging focus for ACAM depends on elevation or mount PA. (An uncorrected change of 0.1 mm would imply a defocus of 0.85 arcsec.)

    Method:

    1. Point WHT to medium elevation ~ 35 - 55 deg. Select sky PA such that mount PA ~ 0 (+- 20 deg).
    2. Set up ACAM for imaging through a red filter e.g. Sloan r.
    3. Do a focusrun (minimum exposure 10 sec), log best focus.
    4. Repeat for mount PA ~ 90, 180, 270

    Mail results to crb.

    Time required: 1 hour.

    Conditions required: seeing <~ 1.2 arcsec (any transparency or sky brightness)

    Instrument required: ACAM

  2. Scattered moonlight in ACAM vs radius from moon - symmetric in az/el?

    Aim: to measure scattered-moonlight intensity I as a function of angular distance D from the moon, and compare a plot of I vs D(azimuth) with I vs D(elevation).

    Method:

    (1) Set up ACAM for imaging in r band, bin 4*4, readout speed = fast.

    (2) Ask the OSA to fix the mount PA, with ROT MOUNT 0, then point the telescope at the moon with the TCS command GOMOON. The azimuth of the dome should match that of the telescope at all times during these tests (within a deg or so).

    (3) Ask the OSA to point the telescope successively at dEl = 4 deg, dEL = -4, dAz = 4, dAz = -4. Take a 1-sec exposure at each of the 4 positions (check not saturated).

    (4) Point the WHT well away from the moon (e.g. 60 deg away; NB try to avoid any cloud) where the telescope structure is not directly illuminated by moonlight, and take a 1-sec exposure to measure the intensity of the illumination due to moonlight scattering off sky rather than off the telescope structure.

    (5) Repeat (2) and (3) for a sample of other radial distances (i.e. apart from D = 4 deg), e.g. D = 6, 8, 12, 14, 20, 24, 30, 40, 50 deg. If time is short, use only positive values of dAZ and dEL. Don't forget to use GOMOON at each D, otherwise the proper motion of the moon will cause it to drift relative to where you think it is. Repeat (4) every hour or so, just in case conditions (e.g. cloud cover) change a lot.

    Time required: ~ 1 - 2 hours

    Conditions required: reasonably clear, any seeing, moon > 20 deg above horizon.

    Instrument required: ACAM imaging.

  3. Effect on seeing of dissipation of 500 W at WHT PF

    Aim: investigate the likely effect on seeing of the ~ 450 W to be dissipated by the WEAVE fibre-positioner motors, using a test 500-W heat dissipator mounted behind M2. We also aim to measure the dependence of this effect on telescope elevation.

    Method: follow Cecilia's instructions on a separate page.

    Time required: many hours, but mainly in parallel with science observing.

    Conditions required: seeing < 1.0 arcsec, not during twilight

    Instrument required: ACAM (or ISIS if no ACAM), LIRIS (not H or K bands) or AF2 (AG5).

  4. LIRIS imaging of polarimetric standards

    Aim: provide standard-star observations for LIRIS imaging polarimetry

    Method: see Raine's instructions

    Time required: few hours.

    Conditions required: clear, any sky brightness, seeing <~ 2 arcsec

    Instrument required: LIRIS imaging

  5. Image quality on Cass acquisition camera

    Aim: monitor above to check whether image quality (currently poor, comatic) is degrading.

    Method: about once a month (SAs will be reminded when this is required), record a slit-view exposure of a field (ideally containing several stars), using the above camera, mail the run number to crb.

    Time required: 0 on-sky time, can be done during science exposures

    Conditions required: seeing <~ 2 arcsec

    Instrument required: Cass acquisition TV

  6. On-sky PSF when using Halpha filters in ACAM

    Aim: to measure the on-sky PSF delivered when observing through the 50-mm Halpha filters installed in the ACAM filters wheels. These particular filters are known to have high transmitted-wavefront errors, and the worst few may degrade the seeing by ~ 1 arcsec.

    Method: install in the ACAM filter wheels a few of the narrow-band Halpha filters, listed on the above link. #58, 61, 62, 63, 66, 67, 73 and 77 have already been done by Cecilia and Ovidiu. The highest priority now are 74 (may be bad), then 64, 65, 71, 75 and 76 (might be bad). In seeing <~ 1 arcsec, do a focusrun through each filter (exposure time at least 7 sec) and through a broad-band red filter (ideally Sloan r) and determine best FWHM. Mail to crb@ing.iac.es: the number of the exposure with minimum FWHM, for each filter.

    Time required: few hours, spread over several nights

    Conditions required: seeing < 1 arcsec

    Instrument required: ACAM

  7. Calibration exposures for sky-brightness meter

    Aim: check of photometric calibration of the new top-end sky-brightness meter:
    http://icsdev.ing.iac.es:8081/SQM/
    to keep an eye on any photometric drift. Last measurement was November 2012.

    Method: take ~ 100-sec exposures of the twilight-free sky (if saturating, reduce exposure time), <~ 45 deg from the zenith, >~ 30 deg from the galactic plane, and >~ 20 deg away from the ecliptic (see chart on control-room wall for plot of these in RA, Dec), through each of Sloan r, g and, if possible (only if already mounted in the wheels) through non-Sloan broad-band filters at similar wavelengths, e.g. Bessell or Harris (doesn't matter which) V and R. Take also an unsaturated image of a Landolt standard through each of the filters used. Mail the file numbers to crb. No calibration exposures needed.

    Time required: 0.5 hour.

    Conditions required: no twilight, no cloud, any seeing, any sky brightness, any dust.

    Instrument required: ACAM imaging

  8. Check PSF delivered by ACAM, as a function of radius

    Aim: measure any degradation of PSF with radius in the field.

    Method: focus ACAM through a red filter (preferably Sloan R, but any red filter is OK), point to globular cluster (e.g. M13, RA ~ 17) (NB may be too crowded for focusing) or Milky Way, take short exposure. Repeat in U and Z bands. No calibration exposures needed.

    Time required: 20 mins

    Conditions required: seeing < 0.5 arcsec

    Instrument required: ACAM

  9. Spectrophotometric standards

    Aim: to update the information about spectrophotometric standards on the ING web pages.

    Method: see Javier's web page for details.

    Time required: several hours (but can be done bit by bit).

    Conditions required: seeing <~ 2 arcsec, any sky brightness, non-photometric for the imaging, and no more than thin cloud for the spectroscopy.

    Instrument required: ACAM imaging and spectroscopy

  10. Measure zeropoint for any instrument for which you are specialist

    Aim: measure the instrument zeropoints (mags in each band for 1 detected photon/sec for imaging, 1 detected photon/sec/A for spectroscopy) at regular intervals.

    Method: obtain unsaturated images of imaging or spectrophotometric standards (ideally more than one, e.g. three) through the relevant filters. Avoid exposures shorter than ~ 2 sec (could be affected by shutter timing). Avoid very low elevations (i.e. high airmass). The counts/sec can be measured from the raw images - no flat-fielding or other calibrations needed.

    Time required: typically ~ 30 mins

    Conditions required: photometric, any seeing, any sky brightness.

    Instrument required: any



Done, no longer required (but might be needed again one day):

  1. Throughput of Cass TV and autoguider

    Aim: to check the throughput of the Cass TV (AG4) and autoguider (AG6) cameras (follow up to fault 22146)

    Method: obtain an unsaturated image of a star of approx known mag on each of AG4 (e.g. from pointing grid star catalogue) and AG6 (e.g. from guide-star catalogue). Record the filter used (if any). Mail results to crb.

    Time required: 0.3 hours.

    Conditions required: clear, any seeing

    Instrument required: Cass

  2. Measurement of telescope slew speeds

    Aim: check that slew speeds in azimuth, elevation and rotator position (at each focal station) are as expected (~ 1 deg/sec)

    Measure approx slew speeds in deg/sec for any of the above. About 3 measurements of each movement will be enough. Mail results to crb.

    Time required: none (measurements are taken during slews for science or other observations)

    Conditions required: any

    Instrument required: any

  3. Ghosting in ACAM

    Aim: to quantify ghosting (to intensity ~ 0.1% of main image) in ACAM as a function of position in the field of view.

    Method:

    1. Setup ACAM CCD with usual window, no binning, readout speed = fast. Use nominal focus of ACAM in Sloan r, check FWHM looks OK.
    2. Point to a mag ~ 13 star, acquire within ~ 50 pixels of centre of ACAM field of view.
    3. Take 1 sec unguided exposure through Sloan r filter. *Check that image is not saturated* and use fainter star if necessary.
    4. Take 10 sec unguided exposure - this probably will be saturated, but fainter ghosts will be detectable.
    5. Repeat steps 3 and 4 with the star centred at each of these positions: ~ 1 arcmin from the centre at position angle (on the CCD) 0, 45 90, 135 ... 315 deg. E.g. position angle 0 corresponds to x ~ 0, y ~ 240 relative to centre of field of view, and position angle 45 corresponds to x ~ 170, y ~ 170. This yields 16 images.
    6. Repeat steps 3 and 4 for radius 3 arcmin, same 8 position angles, yielding another 16 images.
    7. Repeat steps 3 - 6 through Sloan g filter, yielding another 32 images. Mail results to crb@ing.iac.es.
    8. Time required: 2 hours.

      Conditions required: any

      Instrument required: ACAM imaging, Sloan g and r filters

  4. FWHM of top-end sky-brightness monitor

    Aim: to check the pointing and response FWHM of the sky-brightness monitor (it reads out every few sec).

    Method: point at moon, then at elevations 5, 10, 15, 20, 25, 30 deg higher than moon. Point back to moon and repeat for -5 ... -30 deg (or as low as possible). Repeat, for positive and negative steps in azimuth. At each pointing, note the sky brightness recorded by the WHT top-end sky-brightness monitor (second column, labelled 'Teles mags', not the column labelled 'Zenith Mags') and mail the results to crb.

    Time required: 0.5 hour.

    Conditions required: moon at elevation >~ 20 deg, no cloud.

    Instrument required: none.

  5. Scattered moonlight in ACAM vs radius from moon, with 380-mm baffle

    Aim: to check the effectiveness of a 380-mm diameter baffling ring installed in the below-Nasmyth turret 15/2/12 or 25/2/12, and to check for any vignetting of guide stars (i.e. at large radius in the focal plane).

    Method (start with the baffle in):

    (1) Set up ACAM for imaging in r band, bin 4*4, readout speed = fast.

    (2) Ask the OSA to point the telescope at the moon.

    (3) Ask the OSA to point the telescope successively dEl = 4, 6, 8, 12, 14, 20, 24, 30, 40, 50... deg from the moon in elevation (ideally higher than the moon, until the zenith is reached, but lower elevation than the moon is also useful), at the same azimuth as the moon, and take a 1-sec exposure at each position. Record the value of dEL for each run.

    (4) Point the telescope well away from the moon, so that no moonlight falls on any part of the telescope structure, and take another 1-sec exposure. If there is any cloud around, try to pick an area of sky with no cloud.

    (5) Image a series of guide stars on the Cass autoguider (the aim is to monitor any large-radius vignetting by the baffle), recording for each one the RA, Dec, mag, r, theta, seeing (on autoguider), exposure time (on autoguider, probably ~ 1 sec), S:N (on autoguider) and the run number. Do 4 guide stars at one sky PA (any PA), then rotate by 180 deg and do 4 more. With these 8 stars, sample a range of r (goes from 0 to 40000) and theta. Sampling r is particularly important, to help see at what radius any vignetting sets in.

    Ask the OSA to remove the 380-mm baffle, and repeat (1) - (5) above.

    Mail the dEl and run numbers for steps (3) - (5) to crb.

    Time required: ~ 3 hours (including 0.5 hour to remove baffle).

    Conditions required: reasonably clear, any seeing, moon > 20 deg above horizon.

    Instrument required: ACAM imaging.

  6. ISIS zeropoint

    Aim: measure ISIS throughput.

    Method: see Marie's document ('Discretionary tasks') linked from the main ISIS page.

    Time required: 1 hour.

    Conditions required: photometric, any seeing, any sky brightness.

    Instrument required: ISIS

  7. Cassegrain wobble

    Aim: investigate Cassegrain oscillations (period few 10s sec)

    Method: see the recipe provided by Cecilia

    Time required: 2 hours.

    Conditions required: seeing <~ 2 arcsec, any transparency or sky brightness

    Instrument required: ACAM, ISIS, ISIS slit-viewing camera

  8. Cass pointing test (carried out by telescope operator), using ~ 70 - 100 stars.

    Aim: improve Cass pointing rms (should be <~ 1.5 arcsec).

    Method: see pointing-test instructions on a separate page.

    Time required: 2 - 3 hours.

    Conditions required: any, as long as seeing is <~2.5 arcsec

    Instrument required: any imager (including acquisition camera) allowing stars to be acquired rapidly at rotator centre.

  9. Check pointing rms

    Aim: compare actual Cass pointing rms (which has been unusually good over the last 3 months) with CALIBRATE rms.

    Method: determine rotator centre on detector of your choice, carry out the usual 7-star CALIBRATE, then point at ~ 20 stars scattered over the sky in azimuth and elevation, and measure for each the AZ, EL offset required to bring it to the rotator centre. Mail results to crb.

    Time required: 0.5 hours.

    Conditions required: seeing <~ 2.5 arcsec, any transparency, any sky brightness.

    Instrument required: any

  10. Check field distortion for ACAM

    Aim: check the field distortion (i.e. the scale in arcsec/pixel as a function of position in the field), only measured once since commissioning.

    Method: find a pair of stars separated by between 20 and 50 arcsec (i.e. point pretty much anywhere on the sky), take R-band exposure ~ 10 sec (to average out seeing), check neither star saturated. Offset telescope to each of a grid of positions +- 1, 2, 3, 3.5 arcmin along each axis, take 10-sec exposure at each point (include offset in title of run. Mail file numbers to crb.

    Time required: ~ 0.5 hour.

    Conditions required: seeing <~ 1.5 arcsec, any moon

    Instrument required: ACAM, imaging mode

  11. Measure focus offsets for new Sloan filters in ACAM

    Aim: measure more accurate focus offsets between the Sloan filters.

    Method: point the telescope anywhere on the sky at high elevation (for good seeing). Use focusrun (keep all the images) to determine the best focus in Sloan r (use exposures of at least 7 sec when doing a focus run). Record the telescope focus and the filter-specific offset (shown on the ACAM gui) and the offset as recorded on the TCS info page (DF). Repeat the test for each of the new Sloan filters u g i z, and record the TCS focus, focus offset and DF, and anything unusual about the best-focus image (e.g. elongated, or not otherwise consistent with seeing). Highest priority (after r) are u and z (for which we have two measurements so far, but not in very good agreement).

    Mail results (best-focus values for each filter) to crb, ldp.

    Time required: 2 hours.

    Conditions required: seeing <~ 1 arcsec

    Instrument required: ACAM

  12. Measure stability of ACAM focus offset imaging vs spectroscopy

    Aim: check the change in telescope focus required when switching between imaging (Sloan r) and spectroscopy modes. Usually, it's 0.22 mm, but on at least two occasions, it's been measured as 0.11 mm. We need to explore whether the change depends on telescope position (flop, flexure).

    Method: point anywhere on the sky at high elevation (for good seeing). Set rotator mount PA near 0 deg. Determine the best focus in Sloan r, using focusrun (keep all the exposures), and a wavelength region corresponding roughly to Sloan r, i.e. ~ 6200 A, which lies at y(unwindowed) ~ 2120 or y(standard window) ~ 1320. Record the telescope focus and the filter-specific offset (shown on the ACAM gui) and the offset as recorded on the TCS info page (DF). Switch to spectroscopic mode, record the filter offest on the TCS info page, acquire on the 1-arcsec slit a star anywhere in the field, determine best spectroscopic focus, and record the offset between imaging and spectroscopic focus. Only rotator mount PA = 0 is required. Repeat (determine best imaging and spectroscopic focus) at elevation 40 deg, at each of rotator mount PAs near 0, 90, 180 and 270 deg, and record the telescope focus and offset between imaging and spectroscopic focus at each. Mail results to crb, ldp.

    Time required: 1 - 2 hours.

    Conditions required: seeing <~ 1 arcsec

    Instrument required: ACAM

  13. Test image quality delivered by filter #60 in ACAM

    Aim: measure image PSF delivered by ACAM through filter #60, which has 'lots of internal speckles', but is a possible substitute for filter #58 (bad PSF) for a service programme. However, it may also degrade the transmitted wavefront, so we need to measure the PSF.

    Method: install filter #60 in the wheel, do a focus run, find best focus and take an image. Take an image through the Sloan r filter (use nominal ACAM imaging focus). Mail run numbers to crb.

    Time required: 0.3 hours.

    Conditions required: seeing <~ 1.5 arcsec.

    Instrument required: ACAM imaging.

  14. Measure telescope focus vs elevation at Nasmyth

    Aim: determine whether there is any change of telescope focus with elevation. For Casssegrain focus, the telescope-control software includes a correction. For Nasmyth, it doesn't, which doesn't sound right.

    Method:

    The NAOMI DM needs to have been flattened, and NAOMI set up for imaging on the AG7 camera in the red (NAOMI dichroic #3). Do standard focus runs at each of elevations 20 30 40 ... 90 deg.

    Mail results (best focus vs elevation) to crb.

    Time required: 1 - 2 hours.

    Conditions required: seeing <~ 1 arcsec

    Instrument required: NAOMI/AG7

  15. Measure colour terms for ACAM filters

    Aim: Determine relations between observed counts, star mag and star colour for different filters. Method: Take short exposures of two Landolt standard-star fields (with at least 3 standard stars visible on ACAM) in each of Sloan u g r i z, old Sloan filters g1 g2 r i and Bessell U B I Z.

    Time required: 1 - 2 hours

    Conditions required: photometric, seeing < 2.5 arcsec, any moon

    Instrument required: ACAM

  16. Sensitivity of Cass TV in the red

    Aim: discover why bright, but very red, objects are invisible on the Cass acquisition TV, inconsistent with the predicted throughput of the optics/CCD out to ~ 1 micron.

    Method:

    (1) Take z, i, r... images of the very red object with ACAM (coordinates available from crb), and deduce at what wavelength it vanishes.

    (2) Do the tests suggested by Neil (you'll need help from the OSA):

    "To check the optics in the focal reducer barrel, you can move the slide to the OUT position and get an image of the central 1 arcmin of the slit area. Then the light passes through the "relay lens" only, reflected from the slit. You can even eliminate the slit by looking at the field in "direct tv" view, i.e off the back of the Acqcomp mirror. Of course for this test you may have find out which point on ACAM corresponds to the slit centre and then acquire the mystery star on ACAM. This is just to ensure the mystery object is within the smaller field of view, hopefully in the middle."

    Record the image numbers from both ACAM and Cass TV.

    Mail a report to crb, nom.

    Time required: 1 hour.

    Conditions required: any

    Instrument required: ACAM, Cass TV

  17. Check ACAM narrow-band filter focus offsets

    Method: Point the telescope anywhere on the sky at high elevation (for good seeing). Use focusrun (keep all the images) to determine the best focus in Sloan r (use exposures of at least 7 sec when doing a focus run). Record the telescope focus and the filter-specific offset (shown on the ACAM gui) and the offset as recorded on the TCS info page (DF). Repeat the test without filters in the beam (i.e. clear) and then for each of the Halpha filters: #61 63 65 66 69 71 72 73 74, and record the TCS focus, focus offset and DF, and anything unusual about the best-focus image (e.g. elongated, or not otherwise consistent with seeing). Mail results to srix, crb.

    Time required: 2 hours.

    Conditions required: seeing <~ 1 arcsec

    Instrument required: ACAM

  18. Check blind-offset accuracy, over distances up to 20 arcmin, using ~ 10 - 20 stars pairs listed in Janet Sinclair's technical note (copy in the green binder of miscellaneous star lists on the control desk).

    Method: Go to one star of pair, record x,y on detector, blind-offset to second star, record offset which TO needs to make in azimuth and elevation to restore restore to same coordinates. Dan has already taken some measurements, but more are useful.

    Time required: up to 1 hour.

    Conditions required: any, as long as seeing is <~1.5 arcsec

    Instrument required: imager (including acquisition camera)

  19. Check image FWHM at Cass does not depend on telescope elevation (following the re-insertion of a loose top-end locking pin Dec 2007).

    Method: Determine best telescope focus using aux-port, at elevations ~ 90, 60, 40, 20 deg.

    Time required: ~ 1 hour

    Conditions required: any, as long as seeing is < 1 arcsec

    Instrument required: aux port (or any Cass imager)

  20. Check zenith distance for vignetting: ZD at which (1) the upper edge of (unlowered) lower dome shutter starts to vignette the telescope, and (2) (lower priority) the telescope is completely vignetted. This information is required before we can safely operate GLAS with the proposed new ZD limit = 67 deg.

    Method: observe stars at successively greater ZD (probably easiest to pick these near the meridian, i.e. RA = ST), with the telescope out of focus, to give a view of the primary mirror.

    Time required: 0.5 hours

    Conditions required: any

    Instrument required: acqusition camera in TV mode

  21. Check scale and distortion on Cass TV camera in ISIS slit-view mode, required for the new ISIS acquisition tool being written by Craige.

    Method: (1) Acquire star roughly at centre of slit, record x and y.

    (2) Offset star to each of a series of 8 positions on a square 3 x 3 grid centred at the above, separation between positions = 10 arcsec, recording x and y at each position.

    (3) Repeat (2) for positions on a 3 x 3 grid with separations 1 arcmin. The aim is to determine the scale near the centre of the TV, and to get some idea how much the scale varies across the field.

    Time required: 1 hour.

    Conditions required: any, as long as seeing is <~2 arcsec

    Instrument required: Cass TV camera viewing ISIS slit

  22. Check atmopsheric dispersion observed by ACAM

    Method: focus ACAM through a red filter, point to a star at elevation ~ 20 deg, obtain images in U and B bands.

    Time required: 10 mins

    Conditions required: any, as long as seeing is < 1 arcsec, can be done in twilight

    Instrument required: ACAM

  23. Characterise wings of stellar PSF in normal seeing

    Method: point to bright star V ~ 5, insert R filter, take exposures of 1, 10, 100 sec.

    Time required: 20 mins

    Conditions required: any, as long as seeing is <~1.5 arcsec

    Instrument required: ACAM

  24. Characterise NAOMI NGS AO performance

    Aim: fill in gaps in our current performance matrix = PSF as a function of mag, seeing, band, radius from guide star.

    Method: obtain open-loop and closed-loop (AO-corrected) exposures of stars for each of the areas of parameter space listed below. For the near-IR data, 5-point dithers are required. The individual exposures should be at least 7 sec in duration.

    Calibrations required: flats.

    (1) Radius = 0, i.e. measuring PSF at guide star:

    The following permutations are required:
    
    Seeing ~ 1.0 arcsec, guide-star mag 8, 10, 12, 14, for each
    of H (INGRID) and R (OASIS) bands.
    
    Seeing ~ 0.5 arcsec, guide star mag 10, 12, 13, 14, for 
    R band
    
    

    (2) Radius > 0, using star pairs, from:

    http://catserver.ing.iac.es/aotools/pairfind.html

    with the guide star of specified mag on-axis, and the other star lying a specified number of arcsec away:

    The following permutations are required:
    
    Any seeing <~ 0.8 arcsec; 
    for guide star mag <= 9; for each of star separations 5, 10 and 20
    arcsec, in each of H and R bands.
    If there's time, repeat for J and I bands as well 
    

    Time required: ~ 1 night

    Conditions required: seeing <1.0 arcsec

    Instrument required: NAOMI/INGRID, OASIS (not GLAS)

  25. Measure OASIS and INGRID zeropoints

    Aim: measure OASIS and INGRID throughputs.

    Method: (1) With OASIS in imaging mode, obtain unsaturated images of 2 different Landolt standards through each of the MR454, MR591, MR661, MR735, MR875 filters, slow readout, binned 4*4.

    (2) With INGRID, obtain unsaturated images of an IR standard star in each of Z J H K bands.

    (3) With OASIS in spectroscopic mode, 22-mm enlarger, obtain spectrum of spectrophotometric standard in MR454, MR591, MR735, MR875 modes.

    (1) has higher priority than (2), which has higher priority than (3).

    No calibrations required.

    Time required: 30 mins

    Conditions required: photometric, any seeing, any sky brightness

    Instrument required: NAOMI/OASIS

  26. Measurement of spatial shift introduced by ISIS HW plate

    Aim: measure shift of image relative to ISIS slit when introducing half-wave plate into beam (expected to be small)

    Acquire star of mag ~ 7 - 10 on 1-arcsec slit in usual slit-view mode, start autoguiding. Take series of red-arm spectra (doesn't matter which ISIS configuration) with star offset perpendicular to slit by 0 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 0 arcsec. Exposure times should be at least 10 sec (but watch out for saturation). Insert half wave plate (hwin) at PA = 0 (hwp 0) and repeat. These data will tell us the error in initial acquisition, and any additional shift (perpendicular or parallel to the slit) introduced by the half-wave plate. If there's time, repeat for half-wave plate PA = 90 (hwp 90). Mail results to mh, cf, crb.

    Time required: 0.8 hour.

    Conditions required: seeing <~ 1.5 arcsec

    Instrument required: ISIS, any configuration

  27. ACAM override script / spec standards

    Aim: test scripts for ACAM overrides and get spectra of spec standards.

    Method: see Javier's instructions

    Time required: 0.5 hour

    Conditions required: any

    Instrument required: ACAM

  28. ISIS focus / astigmatism tests

    Aim: check consistency of red/blue-arm focus; checking on-sky for astigmatism

    Method: see Marie's document linked ('Discretionary tasks') from the ISIS main page. Check with Marie in advance of the S/D night that this document is still current.

    Time required: 1 hour.

    Conditions required: seeing <~ 0.6 arcsec, no cloud or thin cloud, any sky brightness.

    Instrument required: ISIS

  29. Characterisation of tracking at Cassegrain focus

    Aim: to characterise open-loop and closed-loop tracking at Cassegrain, and in particular any significant oscillations on time scales of 10s of sec.

    Method:

    1. Point anywhere on the sky, elevation between 40 and 85 deg. Configure ACAM for imaging through an r (or other broad-band) filter, readout speed = fast.
    2. Focus ACAM (doesn't have to be perfect).
    3. Take a trial 3-sec image with ACAM through r filter. Pick a star which has plenty of counts but isn't near saturation. Define an ACAM window of 100*100 pixels centred on the star.
    4. Close autoguider loop, turn on autoguider logging. Start multrun of 200 3-sec images with ACAM, stop it after ~ 15 min. Turn off autoguider logging.
    5. Open autoguider loop, start autoguider logging. Start multrun of 200 3-sec images with ACAM, stop it after ~ 15 min. Turn off autoguider logging.
    6. If there is time, repeat at several elavtions.
    7. Mail image numbers to crb, cf.

    Time required: 0.7 hours.

    Conditions required: seeing <~ 1.5 arcsec

    Instrument required: ACAM

  30. ISIS dome flats

    Aim: check for the presence of ripples which have been reported with the below set-up in night sky observations around 3300A, but were not seen in tungsten lamp flats with the same set-up. (This test is requested by Marie.)

    Method: Point the telescope to the dome-FF position, open mirror petals and switch on all FF lamps. Find an exposure time for which you get around 30000 c/pixel at peak, and take as many of flats as you can (20 should be enough).

    Time required: minimum half an hour.

    Conditions required: night time, in bad weather when the dome has to be closed.

    Instrument required: ISIS, D5300, bin blue 2 2, rspeed blue slow. One of the following gratings: - R158B centered at 3930 A - R300B centered at 3930 A - R600B centered at 3800 A The spectrograph focus is easy to check and change, so that would be useful. It is not needed to change tip-tilt or rotation of CCD.

  31. Template lines for the above sections...

    Aim:

    Method: details... Mail results to crb...

    Time required: ? hours.

    Conditions required: seeing <~ ? arcsec

    Instrument required: ?

Last Updated: 22 February 2016

Chris Benn crb@ing.iac.es



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