Accessing data as a guest observer
MagAO-X (but not all visiting instruments) record data in a compressed format. Standard FITS-formatted data with full headers is produced during observations, becoming available within a few minutes of the start of the observation. This document explains how to access it.
Extremely short version, for those who just need a refresher: rsync -kaz --progress guestobs@exao1.lco.cl:/data/obs/vizzy@xwcl.science/ ./my_obs/
Observation data are exported to the Adaptive optics Operator Computer, aka AOC or exao1. Note that exao1 is part of the instrument, and ships back and forth to Chile for observing runs. That means two things:
It will not be available for several weeks while it is in transit, and
It has a different IP and host-name when it’s at University of Arizona than when it’s at Las Campanas Observatory.
Guest observers will access exao1 with SSH and (preferably) rsync. (Users on Windows may be able to use WinSCP or rclone.)
Preliminaries
First, you will need an SSH key pair. Generating one is outside the scope of this document, but GitHub has a good guide. (You can choose Mac, Windows, or Linux, and you need only follow the steps under the first heading: “Generating a new SSH key”.)
The key consists of a private half, probably named something like id_ed25519, and a public half, named something like id_ed25519.pub. (Note: id_rsa and id_dsa keys are not usable with MagAO-X. You may use ECDSA or ED25519 keys.)
Send the “.pub” file to the MagAO-X team, keeping the private part private.
Connecting
This is different depending on whether MagAO-X is in Tucson or at LCO.
When MagAO-X is in the lab
Log in using the guestobs account to verify everything works and that you have access (accepting the key fingerprint if needed):
% ssh guestobs@exao1.as.arizona.edu
The authenticity of host 'exao1.as.arizona.edu (128.196.208.35)' can't be established.
ED25519 key fingerprint is SHA256:Azbcyun8qHxuhl0GE9AyG1cPajNPnfKlTQCwTfCMFT0.
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added 'exao1.as.arizona.edu' (ED25519) to the list of known h
Last login: Thu Apr 7 15:28:49 2022 from 10.8.22.67
[guestobs@exao1] $
When MagAO-X is at Las Campanas, and so are you
When located at Las Campanas, the operator computer can be reached from the LCO-STAFF network at the address exao1.lco.cl.
Log in using the guestobs account to verify everything works and that you have access (accepting the key fingerprint if needed):
% ssh guestobs@exao1.lco.cl
The authenticity of host 'exao1.lco.cl (200.28.147.221)' can't be established.
ED25519 key fingerprint is SHA256:Azbcyun8qHxuhl0GE9AyG1cPajNPnfKlTQCwTfCMFT0.
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added 'exao1.lco.cl' (ED25519) to the list of known h
Last login: Thu Apr 7 15:28:49 2022 from 10.8.22.67
[guestobs@exao1] $
When MagAO-X is at Las Campanas, and you are off-site
Access to exao1 from off-site is via exao0 in our lab at University of Arizona, which has special access to exao1 from off-site. SSH supports an option called ProxyJump, used with -J, to pass connections via another machine. To connect via exao0 over SSH:
% ssh -J guestobs@exao0.as.arizona.edu guestobs@exao1.lco.cl
[guestobs@exao1] $
Edit your SSH config file to save this option with a shorthand name. (On macOS and Linux, mkdir -p .ssh and then create or edit ~/.ssh/config.) Here is an example:
Host exao0
HostName exao0.as.arizona.edu
User guestobs
Host exao1-lco
HostName exao1.lco.cl
ProxyJump exao0
User guestobs
Now you can do ssh exao1-lco and that extra step will be taken care of. Importantly, you can use this for rsync as well! The user@host part of the rsync command (guestobs@exao1.lco.cl in the example below) can be replaced with exao1-lco.
Browsing the data
Your data are rooted in /data/obs/$SEMESTER/$EMAIL/. So, for example, /data/obs/2024A/jrmales@arizona.edu/ will contain:
[guestobs@exao1] $ ls /data/obs/2024A/jrmales@arizona.edu/
2024-02-07_004357_vib_all_loops_off
2024-02-07_004444_vib_all_loops_off
[... and so on ...]
One folder is created for every observation interval (i.e. toggle of the “recording” switch). Within those folders, there is a folder for each science camera that was actively recording (usually just camsci1 and camsci2):
[guestobs@exao1] $ ls /data/obs/2024A/jrmales@arizona.edu/2024-02-07_004444_vib_all_loops_off/
camsci1
camsci2
[... and so on ...]
Note that the UT start timestamp is appended to the folder name to prevent collisions. So, toggling the observation off and back on will create a new folder for the new “start” time.
You can use your favorite tool to browse, but we recommend rsync to handle the large numbers of images. (See the following section.)
Downloading science data
You can use rsync to get your images out. Here’s an example to download/update all images (from all semesters) for the observer vizzy@xwcl.science, skipping those you already have:
$ rsync -rz --progress \
guestobs@exao1.lco.cl:/data/obs/2024A/vizzy@xwcl.science/ \
./my_magao-x_obs/
receiving file list ... done
created directory ./my_magao-x_obs
camsci1/camsci1_20220417230302255087061.fits
8640 100% 31.25kB/s 0:00:00 (xfer#3429, to-check=1436/4867)
camsci1/camsci1_20220417230302258540922.fits
8640 100% 31.13kB/s 0:00:00 (xfer#3430, to-check=1435/4867)
[... many lines omitted ...]
sent 5016 bytes received 221150763 bytes 23279555.68 bytes/sec
total size is 221081847 speedup is 1.00
The -z option compresses the files in transit. If you’re on-site where MagAO-X lives (when it’s at UA or LCO), you can omit -z, as the compression overhead will waste more time than it saves.
Re-running this command will only sync changed files. During an observation, new frames will be processed in chunks as they are written, so you may want to re-run this command periodically.
The paths are constructed as follows: /data/obs/<observer email>/<semester>/<datestamp>/<catalog name of object>/<purpose>_<start UT>/<device>/.
So, for example, here’s mock output of tree /data/obs/ -L 3:
/data/obs/
├── 2024A
│ ├── aweinberger@carnegiescience.edu
│ │ ├── 2024-03-20_002551_HD12345_smlyot_zi
│ │ ├── 2024-03-20_012527_HD12345_smlyot_zi
[...]