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Shelyak Grating module for the Lhires III - 1800 l/mm

Shelyak Grating module for the Lhires III - 1800 l/mm

by Shelyak
SKU SHK-SE0121
CA$1,099.00 - CA$1,099.00
CA$1,099.00
CA$1,099.00 - CA$1,099.00
CA$1,099.00
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  • Grating Ruling: 1800 lines/mm
  • Compatibility: Shelyak Lhires III Spectroscope
  • Function: Alternative module to change native resolution
  • Use Case: Wider spectral coverage at lower resolution
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  • Description
  • FAQ
  • Specifications
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  • Grating module for the Lhires III - 1800 l/mm

    This interchangeable grating module provides a ruling of 1800 lines/mm, specifically designed to alter the native high-resolution capabilities of the Shelyak Lhires III spectroscope. It allows you to trade the maximum resolving power of the standard 2400 l/mm grating for a somewhat wider spectral window in a single exposure.

    The 1800 l/mm Grating: Trading Resolution for Spectral Range

    In spectroscopy, there is a fundamental trade-off between resolution and spectral coverage. This 1800 l/mm grating module for the Lhires III is engineered for situations where capturing a broader range of wavelengths is more critical than achieving the highest possible resolution. By decreasing the line density from the standard 2400 l/mm, this grating disperses light less, fitting more of the spectrum onto your camera sensor.

    This makes it useful when you want a wider window around a chosen line than the 2400 l/mm gives. With limiting magnitudes of 5.0 (2400 l/mm) and 6.8 (1200 l/mm) in Shelyak's table for a 200 mm telescope and a 1 h exposure, it is suited to bright stars and bright novae.

    Lhires III 1800 l/mm vs. Standard 2400 l/mm Grating

    The Lhires III spectroscope ships with a 2400 l/mm grating, which is optimized for high-resolution studies of specific, narrow spectral regions. This alternate 1800 l/mm module extends the instrument's capabilities, turning it into a more adaptable research tool.

    • Standard 2400 l/mm Grating: Use this for maximum resolving power. It excels at splitting close binary star lines, measuring the Doppler shift in stellar spectra, or studying the fine structure of nebular emission lines like H-alpha and OIII.
    • Optional 1800 l/mm Grating: Choose this module for survey work or for targets where context is key. It covers a wider window around a chosen line than the standard grating, at lower resolution.

  • Why would I choose the 1800 l/mm grating for my Lhires III instead of the standard 2400 l/mm?

    You would choose the 1800 l/mm grating when your primary goal is to capture a wider range of wavelengths in a single exposure. The standard 2400 l/mm grating offers higher resolution but sees a smaller piece of the spectrum. The 1800 l/mm module suits bright stars and bright novae when a wider window around a line matters more than the finest detail.

    What astronomical targets are best for the Lhires III with the 1800 l/mm grating?

    The 1800 l/mm grating suits bright targets where a wider window around one line helps. Good examples include:

    • Bright novae: To follow a broad emission line such as H-alpha as the outburst evolves.
    • Be Stars: To observe the profile of a hydrogen Balmer line such as H-alpha.

    Is the 1800 l/mm grating a direct replacement for the Lhires III's original grating?

    Yes, this is a fully compatible, interchangeable module designed by Shelyak specifically for the Lhires III spectroscope. It is intended to be swapped with the standard 2400 l/mm grating to change the instrument's optical characteristics based on your observing target.

    Will the Lhires III 1800 l/mm grating let me capture the spectrum of a star like Vega (Alpha Lyrae) in one shot?

    No. Shelyak's Lhires III figures give a field of about 8.5 nm per image with the standard 2400 l/mm grating and about 25 nm with the 1200 l/mm grating, so the 1800 l/mm grating sits between the two. The Balmer lines of Vega run from H-gamma (434 nm) to H-alpha (656 nm), so each line needs its own exposure.

    How does the 1800 l/mm grating affect the brightness of the spectrum from my Lhires III?

    By dispersing starlight over a smaller area (lower dispersion), the 1800 l/mm grating can produce a brighter continuum in the resulting spectrum compared to the 2400 l/mm grating, assuming equal exposure time and conditions. This can be advantageous for obtaining a better signal-to-noise ratio on the overall spectrum of fainter objects.

    Does installing the 1800 l/mm grating on the Lhires III require recalibration?

    Yes, absolutely. Any time you change the diffraction grating in a spectroscope, you change the instrument's dispersion (how many angstroms per pixel). You will need to perform a new spectral calibration using a calibration lamp to accurately measure wavelengths with the 1800 l/mm grating installed.

  • Fits (mount / scope) Shelyak Lhires III
    Fits Spectrograph Shelyak Lhires III

    • Grating module 1800 l/mm

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