WR-137 waveguide covers roughly 5.8–8.2 GHz, which puts you squarely in C-band.
That is an excellent range for amateur radio astronomy, because it includes one of the brightest and most accessible astrophysical maser lines.

Below are the best targets you can observe with WR-137 hardware.

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⭐ Top Target: 6.668 GHz Methanol Masers (CH₃OH)

Frequency: 6.668519 GHz
In WR-137 band: YES – perfect match
Why they’re ideal:

• Extremely bright Class II masers
• Located in active star-forming regions
• Narrow lines that show Doppler velocity beautifully
• Detectable with 1–2 m dishes and a low-noise C-band LNA
• Many sources observable from mid-latitudes

Strong, Amateur-Detectable Methanol Maser Targets

Here are some of the best ones:

Source	RA / Dec	Notes
W3(OH)	02h 27m / +61° 52′	One of the brightest 6.7 GHz masers in the sky
W51	19h 23m / +14° 31′	Very strong; excellent target for smaller dishes
W49N	19h 10m / 09° 06′	Extremely powerful; good for velocity structure
Orion KL	05h 35m / −05° 22′	Classic star-forming region; bright masers
Cep A	22h 56m / +62° 01′	Compact, strong source
NGC 7538	23h 13m / +61° 28′	Stable, bright maser emission

These are the best C-band targets for amateur maser detection worldwide.

With a WR-137 waveguide feed and a good LNA (<1 dB NF if possible), you can definitely detect several of these.

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⭐ Additional Targets in WR-137 band

Beyond the methanol masers, there are a few other areas of interest within the 5.8–8.2 GHz range:

1. Radio Continuum

Useful for calibrating your system or doing mapping:

• Galactic H II regions (W3, W49, W51, Orion)
• Supernova remnants such as Cassiopeia A, Cygnus A
• The Galactic plane (broadband synchrotron and thermal emission)

All very strong in C-band.

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2. Recombination lines

There are several hydrogen recombination lines near 6–8 GHz (Hnα, e.g., H109α ~5.99 GHz).
These are weaker than masers but can be detected with longer integrations.

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⭐ What You Cannot Do With WR-137

Just to clarify expectations:

Line	Freq	In band?
Hydrogen 21 cm	1420 MHz	❌ Not in WR-137
OH masers	1.6 GHz	❌ Not in WR-137
Water maser	22 GHz	❌ Not in WR-137
SiO masers	43/86 GHz	❌ Not in WR-137

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