MMT Blue Channel


This file summarizes several instrument specific items for the MMTO’s Blue Channel spectrograph.

Wavelength Calibration

Templates were created in 2023 that cover the usable range for each of the following gratings:

  • 300GPM

  • 500GPM

  • 800GPM

  • 832GPM, both 1st and 2nd order

  • 1200GPM

These templates have been tested against a wide range of archived data and have proven to be reliable. If there is an issue for some reason, the Holy Grail algorithm has also proven to work in many cases, especially with the 300GPM and 800GPM gratings.

Observation and Reduction Setup

A few notes on setting up observations to work optimally with pypeit and what to watch out for in your PypeIt Reduction File:

  • pypeit_setup will group data by grating angle. Sometimes continuum flats can be shared between different grating angles and this will need to be edited by hand.

  • If a spectrograph component is in motion while an image is acquired, the position will be reported as moving in the image header. These images will get included in a PypeIt Reduction File with those moving values set to None. Users will want to inspect those files and either remove them or edit the missing information by hand.

  • Images that are intended to be used as sky flats should have target set to skyflat in their headers so pypeit can identify them automatically. Otherwise they will need to be manually configured.

  • On-sky images that use the 5.0x180 slit are assumed to be standard star observations. Edit the resulting PypeIt Reduction File if this is not the case or otherwise define which observations are standard stars.

  • Images taken as part of spectrograph focus runs are automatically identified and configured as tilt images, but not arc. This is because their line widths can vary by quite a bit and thus shouldn’t be coadded to/averaged with in-focus arc images.