Observing Plan for the August 6-7, 2014 Engineering Nights (DES Readiness Test)

(Late) Afternoon

Note that we are asking for an unusual set of calibration exposures - please start early to complete this in time.

Run the calibration script five times to get a "SuperCal" set of zeros and dome flats:

Script: prenight_calibration.json (note that this is a (standard) DES script. From the the Observer Console GUI select Exposure Control --> Load Exposure Script --> Select DECam Script then choose DES/prenight_calibration.json in the dialog window)


Operations Tests

  • obstac test run
  • End of Night run DES Night Summary

Obstac test run

Run standard DES observing for two hours, starting between 2:45 and 5:30 UTC (9:45pm-12:30am CDT, 10:45am-1:30am CLT). For the sake of developer and off-site support alertness, earlier in this window would be better.

(The DES wide-survey footprint rises at 0:30 UTC (7:30pm CDT, 8:30 CLDT). Starting obstac before this will not be constructive.
We need to observe one SN shallow field, SN-E1. This field rises 4:15 UCT (11:15pm CDT, 12:15 CLT). So, the two hour test needs to last until at least 4:30 or 4:45 UTC, so we should start no earlier than 2:45 UTC. Deep field SN-C3 rises at 7:30 UTC (3:30 CLT), which we want to avoid observing, so we need to start before 5:30UTC (1:30 CLT).)

nightsum test run

Setup and run nightsum following the documentation available here

Star Flats

We have not done a valid u-band star flat since 9/2013 so this would be good to repeat. We should also take g-band star flats, since the last batch were in very poor seeing, and also it is useful to have the u-g colors to use in deriving a color term for the star flat.

Ideally we would do this in darker conditions but unfortunately this will be tough to arrange. When the moon is down near the ends of the nights, there are no low-Galactic-latitude fields available where we have good stellar density. So some compromises will be necessary. And in the early parts of the night, the full Moon is close to our favorite star-flat fields. Unfortunately it seems like star flats at the start of a night is the best option even though the Moon will be bright.

Here are three options for fields to use this month:

RA=13:27:00  DEC=-48:45:00 (at airmass <1.5 until 01:00 UT)
RA=15:00:00  DEC=-45:00:00 (at airmass <1.5 until 02:30 UT)

There are 22 exposures in the sequence, so 2 x 22 x (30+30)s = 44 minutes to do this whole thing.

The pointing is not critical (1 arcmin accuracy is fine), but you will need to move the telescope back
to the starting position when beginning each filter.

The star flats should be done in clear weather, although seeing as poor as 1.5-2" will give data of at least some value. Better seeing is better...

The 5 scripts can be found in the Engineering/engineering_20140806 folder. They are named Starflat<filter>.json_
You must move the telescope by hand to the desired starting point before running the script. Then it does everything with relative positioning.


Dave Gerdes & co have identified 5 KBOs in the Y1 SN survey fields which will not return to those fields this year. If there is time at the end of one night when no engineering tasks are pending, we could recover these objects to improve their orbit solutions. Dave suggests the following sequence:

KBOs 1, 3, 5: 2:26:40.10, -3:36:35.8 (will put KBO 1 in S15, KBO 3 in N7, and KBO 5 in N15)
KBO 2:        2:33:46.10, -5:15:11.5 (will put it in the middle of S4)
KBO 4:        2:41:48.40, -4:22:46.4 (will put it in the middle of S4)

The observing protocol would be:

  • 1 exposure, 200 s in i band, at each of the three locations above
  • Repeat the three exposures with a time delay of 1 hour or more (they will have moved >1 arcsec)

AOS correction test

The AOS system is designed to hold focus and/or alignment at a position other than zero. For example, the user should be able to specify that a defocus of +50 um be used. In this case, the PID loop would drive the system to that setting and hold the system 50 microns out of focus.

This feature has never been tested (most users prefer in focus and aligned). However, what the system has defined as zero is not necessarily correct (it is very close) and we may wish to employ this feature in the future (to correct a decenter offset for example).

  • Select a target location (pick your favorite region away from galaxy (70 > |b| > 30) and take a few z band exposures (20 s) with AOS enabled (should be by default) to get the system in focus and aligned.
     FOCUS.AOS set set_point 500,0,0,0,0,0
    • The above command tells the system to keep decenter x (dx) at +500 microns. The terminal should return a message "PID now XXXX" with the dictionary value for set_point shown.
  • Take 3 z band images (20 seconds) and check telemetry to see if dx has moved to 500. (SISPI telemetry window, AOS tab, 3rd plot is AOS Decenter).
  • If decenter x appeared to move to 500 microns (if it moved to -500 microns continue anyway).
  • Take 3 z band images (20 seconds) and check telemetry to see if dx is stable.
  • Take 3 z band images (20 seconds) and check telemetry to see if dx is stable.
  • Screen capture the AOS Decenter plot and attach to log book.
  • Email above plot to

Thank you!

AOS dither

This data set is similar to the data set taken in Feb 2014 (AOS/Donut Data) [[]]

Here, 4 sets of 25 (r band) images will be collected.

  1. Move to a point on the sky, closest to Zenith, about 20 degrees from the galactic plane to get a reasonable dense star field.
  2. Take 5x 30 second r-band images, 30 seconds, AOS on — to focus,align
  3. Make a note of the current z trim from ICS in case recovery is needed.
  4. Load and run
  5. This script will.
    1. Change focus trim by -3000 microns from in focus value, leave other trim values at their AOS settings. Turn AOS off, Leave LUT on.
    2. Take 25 images with small dithers.
    3. Change focus trim to be -1500 from in-focus value, again leave other trim values as is. Keep AOS off, LUT on.
    4. Take 25 images with small dithers
    5. Change focus trim to be +1500 from in-focus value, again leave other trim values as is. Keep AOS off, LUT on.
    6. Take 25 images with small dithers
    7. Change focus trim to be +3000 from in-focus value, again leave other trim values as is. Keep AOS off, LUT on.
    8. Take 25 images with small dithers
  • Note that exposure 1,26,51,76 and 100 all change the focus. with exposure 100 returning the system to original focus values.
  • The script was generated using ~sispi/reil/engineering_20140806/ and could be modified as needed.