# Should we update definitions and remove the 100 GHz hard limits on radio astronomy related tags?

I just noticed that some of the following tag definitions include upper limits on frequency:

• : Questions about the part of the electromagnetic spectrum between 10 MHz and 100 GHz.
• : Questions related to the instruments used to perform observations in the radio frequency range (10 MHz to 100 GHz)
• : Questions about observation performed in the radio frequency range of the electromagnetic spectrum (between 10 MHz and 100 GHz).

Questions:

1. Should we update those definitions and remove the 100 GHz hard limits?
2. Considering that these days astronomers will comfortably use the word "light" in the context of what has been traditionally called radio astronomy and there is instrumental capability on Earth or in space at so many points in the radio, millimeter wave, far infrared and infrared realms, how should tags for these best be distinguished going forward?
3. What is the tag for? Is it redundant?
• radio by itself is useful in a narrow set of cases. For example, questions about theory (not observation) that discuss radio emissions. Since observation wouldn't be part of the question, radio-astronomy wouldn't really apply.
– called2voyage Mod
Apr 8 '20 at 17:29
• @called2voyage I see, I'm not sure if radio-astronomy applies to How do we know that comets definitely mase and not just fluoresce? or not, so I've added both tags, and I've removed radio from Is there work underway to push the long baseline capabilities of the Event Horizon Telescope to sub-millimeter wavelengths?
– uhoh
Apr 8 '20 at 19:07
• @called2voyage see this comment does this ring a bell?
– uhoh
Apr 30 '20 at 1:24
• It looks like from James K's analysis that the radio tag is not used on any questions that really need it right now, so I agree with his assessment that we could just discard it. If we need it in the future for the cases I mentioned above, we could always create it.
– called2voyage Mod
May 1 '20 at 15:26
• @called2voyage oh goodness, that's the conversation I was looking for! Yikes, thanks, etc.
– uhoh
May 1 '20 at 15:30

Absorption by the atmosphere increases from 100GHz to 1Thz, which can be partially avoided by putting telescopes at high, dry places.

But any line is going to be arbitrary. I don't see any real benefit in writing any particular number. "radio" should be synonymous with "radio astronomy" (I don't care which way the synonym works, but there are 13 [radio] questions and [178] radio astronomy ones) And the hard limits should just be removed to leave:

Questions about observation performed in the radio frequency range of the electromagnetic spectrum.

Of the 13 questions tagged "radio", 12 are about radio astronomy, and one is a misplaced space exploration question "what was the transmission time of Mars insight probe"

I may be bold.

• Okay I guess we agree that specifying a frequency is not a good idea. About the radio tag, I remember having a conversation recently about it with someone (one of the mods?) but I can't find it now. It may have been in association with How do we know that comets definitely mase and not just fluoresce? I felt it was redundant but the other conversant felt it had a narrow but unique space and was useful as a separate tag. Maybe there's a (now invisible) chat about it?
– uhoh
Apr 29 '20 at 8:49
• I don't think that is enough reason to keep the tag. You could argue that "astronomy" is redundant in "radio-astronomy" as all questions but the weighting (178 - 13) makes it easier to keep radio astronomy. wrt comets masing, cometary masars are known through radio telescopes, so I see no issue with that being tagged "radio astronomy". May 2 '20 at 7:46
• Perhaps then everyone is in agreement. I found the conversation I mentioned and it was right up there under my question.
– uhoh
May 2 '20 at 9:03

update: I checked and discovered that following this answer there's been an unmentioned edit to the two tags with frequency specifications, so I'm mentioning it now.

Should we update definitions and remove the 100 GHz hard limits on radio astronomy related tags?

## Yes

There are plenty of dishes that focus into waveguides or horns that feed antennas connected to electronic amplifiers using transistor amplifiers connected to heterodyne down-conversion with balanced mixers and then analog-to-digital conversion, where intensity images are produced by interference implemented mathematically in a computer (rather than in wavefronts incident on material producing intensity signals in the form of electrons (CCDs) or phonons (bolometers)) which work up to circa 1,000 GHz, so the 100 GHz limit is obviously wrong!

But what's a better definition?

Hmm...

to go further I've just asked What's the highest frequency that's been imaged by a radio telescope?