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[Trinoc]

You're correct about the depth of field, but the minimum spatial resolution is proportional to the f-number.  So f-number does influence spatial resolution, but I got it backwards.  Lower f-numbers mean better spatial resolution.

Isn't there a problem with dimensionality here? The f-number is dimensionless whereas (I think) spatial resolution has dimensions of length^-1.

[DoctorAtlantis]

They're not fish. Have you not heard, they're Sea Kittens!

I just threw up in my mouth. 

This is like Peta's "Joe Camel" only instead of selling cigarettes, it's selling stupid.

On the other hand, my kids seem to have no trouble with the idea that cartoon pigs are funny and cute, but that BBQ and sausage are tasty.  Cognitive Dis-tastes-too-good-not-to-eat. Num-num-yom-num-yom-yom.

(My favorite country breakfast wit is "The chicken contributes to breakfast, but the pig is committed.)

[scottishlass]

not very scientific or skeptical comment but....I had a wee smile to myself when the swan discussion was taking place and someone said (couldn't make out who) 'to blaaaave' (reference to the most excellent film Princess Bride) It made me dig out the DVD and enjoy it all over again.

Also, my three year old son has been running around saying 'Whos that noisy' in his little Scottish Lad accent. If I had a mic I would submit it! 

[dhawk]

You're correct about the depth of field, but the minimum spatial resolution is proportional to the f-number.  So f-number does influence spatial resolution, but I got it backwards.  Lower f-numbers mean better spatial resolution.

Isn't there a problem with dimensionality here? The f-number is dimensionless whereas (I think) spatial resolution has dimensions of length^-1.

Spatial resolution just has units of length, not 1/length. And when I said that spatial resolution is proportional to the f-number, that was not to the exclusion of other variables. It's also proportional to the wavelength, hence the units of length.

[dhawk]

Also, my three year old son has been running around saying 'Whos that noisy' in his little Scottish Lad accent. If I had a mic I would submit it! 

You gotta record that. I'm pretty sure they'd play it if you sent it in.

[Opcn]

Two systems with the same focal length (size in an observatory or a fish head)and different diameters will have different F-numbers and let in different amounts of light.

[dhawk]

Two systems with the same focal length (size in an observatory or a fish head)and different diameters will have different F-numbers and let in different amounts of light.

Erm... I'm not sure why you thought this needed to be said.  My response to your last post already included that the f-number is the ratio of the focal length to the diameter.  I thought it was obvious that the diameter was all that matters in determining how much light enters.

You said:

I think we use mirrors [instead of lenses] in telescopes for two reasons, one they don't cause a shift in the light and two they have lower F numbers (let in more light).

The problem I had with that was 1) lenses don't shift the wavelength, although chromatic aberration may have been what you were talking about, 2) it doesn't make sense to say mirrors have lower f-numbers than lenses, because you can create mirror and lens systems with arbitrary diameters and focal lengths, and 3) having a lower f-number is not equivalent to letting in more light, which is why I wrote the following:

The f-number does not (directly) determine how much light enters.  The f-number is the ratio of the focal length to the diameter.  You can have two systems with the same f-number that let in different amounts of light, or two systems with different f-numbers that let in the same amount of light.

The only thing that matters is the diameter.

[rev_matt_y]

So where do I send my audio files for Who's That Noisy?

[Trinoc]

So where do I send my audio files for Who's That Noisy?

Email to Steve, perhaps?

[dacyebd]

Wanted to take the opportunity to apologise to the SGU presenters and listeners for writing a drunk email that directly lead to the loudest, longest Dick Van Dyke in Mary Poppins impression in living memory.

Come on Jay, try another accent next time Steven introduces you. Nail a northern irish accent by the weekend.

[Opcn]

Wanted to take the opportunity to apologise to the SGU presenters and listeners for writing a drunk email that directly lead to the loudest, longest Dick Van Dyke in Mary Poppins impression in living memory.

Come on Jay, try another accent next time Steven introduces you. Nail a northern irish accent by the weekend.

Or nail someone with a northern irish accent, that's probably more fun anyways.

[Eustace H Plimsoll]

As an Englishman (wow, writing that made me feel very 19th century for some reason) I would like to say that I am a big fan of the accents - keep 'em coming.

One thing that does annoy me (just a little) is the conflation of "English" and "British". Your "British accents" are always English. At one point you even talked about British as opposed to Scottish accents, whereas, as I'm sure you know, Scotland is part of Britain. I know a lot of Scots probably don't want consider themselves "British", but that doesn't mean it should be used as a synonym for "English". You'd never hear anyone over here refer to a "British accent" - there just isn't any such thing. Of course, accents vary widely within England itself too, but talk of British accents just sounds weird...

 Not hugely important, I know, but it does wind me up ever so slightly. 

But like I said - the accents are great, Jay. Don't let this put you off letting rip with a few "cor blimey guvnor"s when you feel the urge.


I also agree that Randi speaks was poor. And as much respect as I have for the man, and as likeable a character as he seems to be, I don't generally look forward to his segments.

[Evil Eye]

Yeah... well people from Greenland don't generally think of themselves as from North America either. But they are.

[Eustace H Plimsoll]

Yeah... well people from Greenland don't generally think of themselves as from North America either. But they are.

Yes, so doing an English accent and calling it a "British accent" is the same as doing a USA Accent and calling it a North American accent, even though North America includes Canada, Greenland and Mexico... Technically a USA accent is North American, just as an English accent is British, but it is confusing to refer to either of them by the same name as the broader group in which they belong, and it also just sounds weird. And it would be plain wrong to talk of North American accents and Canadian accents as if the the latter was not included in the former group.

Like I said, I'm not really annoyed by this, and neither do I expect foreigners to be well versed in the national and political distinctions of  the British Isles, which can be confusing even for a native.

I am right though 

[Zeno Izen]

I also agree that Randi speaks was poor. And as much respect as I have for the man, and as likeable a character as he seems to be, I don't generally look forward to his segments.

We dug it over here.  Taste! You never know.