Twilight Monitor

Goal: inform acquisition of twilight sky flats and transition to observing with short exposure times
Objective: monitor sky brightness in ugrizy bands as a function of alt,az, and sun angle below the horizon.

Initial Design

This device has no lens. It is basically composed of a photodiode attached to an electrometer. The optics are baffles and iris to collimate the light to a fixed solid angle value. The alt-az mount provides an accurate pointing in the AltAz system. The filter wheel stores the 6 LSST filters, ugrizy.

Optics Layout

This setup comprises a manual filter wheel, some thorlab parts for adjustment of the light beam, an optical bench with an Alt-Az mount on a Vixen bar.

Parts List

Aug, 7, 2024

The deliveries from Agena Astro did not arrive on time, we are still waiting (Aug 13)

Keysight Electrometer (B2983B) Connection Setup

Step-by-step for connection setup

Connect a USB Type B on the back of the electrometer to the laptop
The USB cable is connected to a USB hub that goes into the USB-C power entry of the laptop. This step is needed because the laptop does not accept a high-voltage entry through USB.
Turn on the keysight electrometer (see apparatus manual for instructions)
After that, the electrometer should pop-up as an external driver (hard disk)
Make sure you have install keysight commander
With keysight commander discover what is the name of the instrument USB
Run the python script keysight_usb_connection.py

AltAz iOptron - Python Interface

https://www.ioptron.com/product-p/3700az.htm

The AltAz mount has an easy connection to windows os. But it has no straightforward to mac os.

link

After some deep dive on some forums, I found out that is possible to have a python interface through RS-232 scripts

https://groups.io/g/iOptron/topic/controlling_cem26_mount_from/97702939

https://github.com/chimerasaurus/ioptron-python

Chris found that we can use the indi library to connect to the iOptron mount. I should check only if they have the driver for the Skyhunter mount.

https://www.indilib.org/

TwilightMonitorDatabase

The TwilightMonitorDatabase class is designed to manage and organize data collected by a twilight monitor. This class allows you to create a structured database for each day, storing information such as exposure times, mount positions, and electrometer data.

http://github.com/estevesjh/twmdb-python

Features

Initialization: Automatically sets up the required directory structure and loads or creates a database file for the specified date.
Adding Exposures: Easily add new exposures with relevant data such as timestamp, altitude, azimuth, and electrometer readings.
Updating Exposures: Update existing exposures by specifying the seq_id and the fields to modify.
Data Persistence: Automatically saves the database to a CSV file, ensuring that your data is preserved between sessions.

Example Usage

Initialization

To initialize the database for a specific date:

from datetime import datetime
from twilight_monitor import TwilightMonitorDatabase

# Initialize the database for July 21, 2024
db = TwilightMonitorDatabase(21, 7, 2024)

Add a new exposure

To add a exposure you can simply enter the following information.

# Add a new exposure
db.add_exposure(
    timestamp=datetime.utcnow(),
    alt=45.0,
    az=90.0,
    exp_time_cmd=30,
    filter_type='SDSSr',
    current_mean=0.5,
    current_std=0.01
)

Updating an Exposure

To update an existing exposure, use the update_exposure method by specifying the seq_id and the fields you want to update:

# Update an existing exposure
db.update_exposure(seq_id=1, current_mean=0.55, current_std=0.02)

Data Structure

The database will be rooted in a twmdb-python folder with the following file tree.

.
├── README.txt
├── twmdb.py
└── DATA
    ├── YYYYMM
    │   ├── YYYYMMDD.csv
    │   ├── notes.txt
    │   └── tmp
    │       └── seq_id_XXXXX.csv

Database CSV file information

Every time you close or save the database, a CSV file with panda data frame format is saved. The description of the the CSV file columns is:

tmid: Twilight monitor unique IDs defined by the date and time of exposure start, i.e., YYYYMMDDHHMMSS
date: Timestamp with date and time in UTC.
seq_id: sequence id of the exposure number of the day.
exp_time_cmd: Exposure time commanded (exp_time_commanded).
exp_time: Actual exposure time.
filter: the filter used in the exposure (options include: SDSS{u/g/r/i/z/y} and Empty)
alt: commanded elevation in deg with the format of 0.5f
az: commanded azimuth in def with the format of 0.5f
current_mean: mean current measured by the electrometer during the exposure period. The units are in nano ampere.
current_std: current standard deviation of the electrometer output during the exposure period. The units are in nano ampere.
alt_std: standard deviation of the altitude values in degrees during the exposure period.
az_std: standard deviation of the azimuth values in degrees during the exposure period.
electrometer_filename: filename of the electrometer output.
flag: TBD

Documents

https://drive.google.com/drive/folders/1sVX5E0UK0jYq_DHZrAbwoV0uhllU9BdI?usp=drive_link