Mookodi is a low resolution spectrograph and imager, designed to be operated fully robotically. It was designed and built by Liverpool John Moores University (LJMU), and installed on the Lesedi telescope in December 2021. It will undergo a period of science commissioning observations during '''This ([[Media:Mookodi_JATIS_N-Erasmus.pdf|paper]]) describes the first trimester of 2022, instrument in detail. Please also cite this paper when publishing data collected with the ability to do spectroscopy and low-cadence imagingthis instrument.''' (for a higher resolution version go [https://doi.org/10.1117/1.JATIS.10.2.025005 here] )
== Instrument Description ==
*:'''Dispersion:''' 3.88 Å/px
*:'''Resolution:'''
*::80µm (2 arcseconds) slit
*:::R = 301.0 @4671.23 Å
*:::R = 374.4 @5823.89 Å
*:::R= 492.5 @7642.02 Å
*::160µm (4 arcseconds) slit
*:::R = 172 @4671.23 Å
*'''Plate scale:''' 0.588 arcsec/px
== Data Reduction Pipelines ==
=== Bias Correction and Flat-fielding ===
We now collect automated biases and flats at the start of the night that we collate into monthly master files for users. The files can be obtained [https://io.saao.ac.za/IO/mookodi/master_files/ here]. At that link you can also find a basic reduction python script that can be used to reduce the science files using the appropriate master bias/flat file.
* As an example the script can be used as follow (command arguments should be fairly self explanatory):
python mookodi_reduction_using_masters.py --image_dir /home/data/my_target/g --master_bias_file /home/bias/2025/01/2x2_fast.fits --master_flat_file /home/flats/2025/01/2x2_g_north_up.fits --remove_cosmic true
'''Some important notes:'''
*In the case of biases, "slow" and "fast" refers to the readout mode and for your science files that can be checked by looking at the "HSHIFT" keyword in the header: slow = 0.05 and fast = 5.0
*Mookodi's derotator cable-wrap does not have a full 360 degree range so the result is that some observations are taken with north up in the images while others flipped 180 degrees with north down in the images. It is roughly correlated to which side of the meridan your observations took place. Your science images can be a mix if a derotation occured during your observation sequence. There are also subtle changes in the telescope throughput for the two orientations so you need to use flats taken at the same orientation as your science images. The supplied reduction script will warn you if you are using flats at a different orientation than your science frames (but still reduce the files). If you are reducing the data yourself with your own software, you can check which orientation your science image was taken at by using the value of the ROTANGLE and ROTSKYPA header keywords. The sky-angle = ROTANGLE-ROTSKYPA. If the sky-angle is close to 0, 360 or -360 your images are with north '''DOWN'''. If the sky-angle is close to 180 or -180 your images are with north '''UP'''.
=== Spectroscopy ===
#*'''Binning:''' Options are 1×1, 2×2, 3×3, and 4×4.
#*'''Gain:''' High (faint objects), medium, and low (bright objects)
#*'''Rate (readout rate):''' Fast (5 MHz) - read-noise of 13.6 electrons, and slow (0.05 MHz) - read-noise of 3.3 electrons (see [[Media:Mookodi_gain_readnoise.png|here]] for a summary table of gain and read-noise)
#*'''Image Type:''' This has no physical effect on the instrument configuration and only populates a header keyword with the selection (possibly useful for automated data reduction)
#*'''Instrument Mode:''' This has no physical effect on the instrument configuration and only populates a header keyword with the selection (possibly useful for automated data reduction)
#*TIPS: TODO.
''Note: It is advisable that DARK frames should be taken with the shutter in the "ALWAYS CLOSED" mode. BIAS frames (especially if multiple frames are taken) SHOULD ALWAYS be taken with the shutter in the "ALWAYS CLOSED" mode since this will deactivate the iris-shutter in the closed state and prolong the lifetime, see also [[#Suitable_Uses|high cadence imaging]] in the Suitable uses section at the top of this page. == Data Access ==
From a terminal window:
scp observer@mookodi.suth.saao.ac.za:/data/lesedi/mkd/yyyy/mmdd/* .<local path to copy to>
Password: Same as username shown above with "Saao" prefixed.
Where <code>yyyy</code> is the year, <code>mm</code> is the month, and <code>dd</code> is the day. The convention is that the data rolls over to the current date at 1200 UTC, hence all the files from a given night are stored in the folder corresponding to the date at the start of the night. e.g. All observations started on the night of 2021/12/11 will be stored in <code>/data/lesedi/mkd/2021/1211/</code>.