Accessible maser lines for amateur radio astronomers

For amateur-level radio astronomy, the most accessible astrophysical maser lines are those in frequency ranges where equipment is practical, affordable, and atmospheric attenuation is manageable. Here are the best options, in order of practicality:

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⭐ 1. OH Masers (≈ 18 cm band)

Frequencies:

• 1612.231 MHz
• 1665.402 MHz
• 1667.359 MHz
• 1720.530 MHz

Why they’re best for amateurs:

• Easily reachable with L-band antennas (simple Yagi, horn, or small dish).
• Strong and common in star-forming regions and AGB stars.
• Can be observed with inexpensive SDRs.
• Minimal atmospheric absorption.

Ideal for: A first maser-hunting project.

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⭐⭐ 2. Methanol Masers

Frequencies:

• 6.668519 GHz (6.7 GHz) – strongest Class II maser
• 12.178597 GHz – also strong and accessible

Why they’re good:

• Intense signals from high-mass star-forming regions.
• Require a C-band dish (~1–2 m) and low-noise LNA, but still feasible.
• Methanol masers are stable and narrow, excellent for Doppler work.

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⭐⭐⭐ 3. Water Masers (22 GHz)

Frequency:

• 22.23508 GHz

Why they’re harder but possible:

• Very strong astrophysical sources.
• Requires a high-precision K-band LNA and a dish ≥ 1.5–3 m.
• Atmospheric attenuation increases significantly above ~20 GHz.

This is a “next-level” amateur project but entirely achievable with good hardware.

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⭐⭐⭐⭐ 4. Silicon Monoxide (SiO) Masers (~43 GHz, ~86 GHz)

These include:

• 43.122 GHz
• 86.243 GHz

But:

• Not practical for most amateurs due to atmospheric transparency and hardware cost.
• Only advanced amateurs with mm-wave systems attempt these.

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Summary Table

Maser Species	Frequency	Wavelength	Difficulty	Notes
OH	1612–1720 MHz	~18 cm	⭐ Easy	Best starting point
Methanol	6.7 / 12.2 GHz	~4.4 cm / 2.5 cm	⭐⭐ Moderate	Very bright, great for new dishes
Water (H₂O)	22.2 GHz	~1.35 cm	⭐⭐⭐ Hard	Strong sources, but weather-sensitive
SiO	43 / 86 GHz	~7 mm / 3.5 mm	⭐⭐⭐⭐ Very hard	Requires mm-wave setup

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