"He's your son!!" of APOD

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daveboling
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Omega Sunrise

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Needs to sheet in the jib a bit...
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I teleported home one night
With Ron and Sid and Meg.
Ron stole Meggie's heart away
And I got Sidney's leg.
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Equinox in the Sky

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dave boling
I teleported home one night
With Ron and Sid and Meg.
Ron stole Meggie's heart away
And I got Sidney's leg.
-- Douglas Adams

'Bundinn er bátlaus maðu'.
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ISS Transits Mars

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dave boling
I teleported home one night
With Ron and Sid and Meg.
Ron stole Meggie's heart away
And I got Sidney's leg.
-- Douglas Adams

'Bundinn er bátlaus maðu'.
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Enceladus in Infrared

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dave boling
I teleported home one night
With Ron and Sid and Meg.
Ron stole Meggie's heart away
And I got Sidney's leg.
-- Douglas Adams

'Bundinn er bátlaus maðu'.
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Moon over Andromeda

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dave boling
I teleported home one night
With Ron and Sid and Meg.
Ron stole Meggie's heart away
And I got Sidney's leg.
-- Douglas Adams

'Bundinn er bátlaus maðu'.
david_h
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Re: "He's your son!!" of APOD

Post by david_h »

Can I take this opportunity to ask why astronomical photos so rarely indicate the angular field of view? Is it because the target audience is comprised mainly of people who already know 'how big' things are and those who don't care?
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Re: "He's your son!!" of APOD

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For many of the images posted, the angular field of view is fractions of arc seconds. It doesn't mean much, and astronomers don't commonly use, angular field if it would read 1.3E-5 arc seconds for a galaxy cluster. A good number of the APOD descriptions will give angular field of view for larger objects, particularly those that are faint to the naked (can I say naked on this forum :shock: ) eye. Even Jupiter (and Saturn, both of which are currently prominent in the night sky), as large as it appears, ranges only from 29.8 to 50.1 arc seconds. So, at best, it would take ~72 Jupiter diameters to make one degree in the night sky. If I remember correctly (long odds here), a fist held at arms length is about 10 degrees (could be 15, don't clearly remember), so holding your fist out next to an object in the sky will allow you to "ballpark" the angular field of view.
Does this help or confuse (hint, I'm better at the latter than the former....)?

dave boling
I teleported home one night
With Ron and Sid and Meg.
Ron stole Meggie's heart away
And I got Sidney's leg.
-- Douglas Adams

'Bundinn er bátlaus maðu'.
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daveboling
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Moon Pairs and the Synodic Month

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dave boling
I teleported home one night
With Ron and Sid and Meg.
Ron stole Meggie's heart away
And I got Sidney's leg.
-- Douglas Adams

'Bundinn er bátlaus maðu'.
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Lightning over Colorado

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dave boling
I teleported home one night
With Ron and Sid and Meg.
Ron stole Meggie's heart away
And I got Sidney's leg.
-- Douglas Adams

'Bundinn er bátlaus maðu'.
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Filaments of the Cygnus Loop

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dave boling
I teleported home one night
With Ron and Sid and Meg.
Ron stole Meggie's heart away
And I got Sidney's leg.
-- Douglas Adams

'Bundinn er bátlaus maðu'.
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GW Orionis: A Star System with Tilted Rings

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APOD video
dave boling
I teleported home one night
With Ron and Sid and Meg.
Ron stole Meggie's heart away
And I got Sidney's leg.
-- Douglas Adams

'Bundinn er bátlaus maðu'.
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Sonified: Eagle Nebula Pillars

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Yet another APOD video
dave boling
I teleported home one night
With Ron and Sid and Meg.
Ron stole Meggie's heart away
And I got Sidney's leg.
-- Douglas Adams

'Bundinn er bátlaus maðu'.
david_h
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Re: "He's your son!!" of APOD

Post by david_h »

daveboling wrote:For many of the images posted, the angular field of view is fractions of arc seconds. It doesn't mean much, and astronomers don't commonly use, angular field if it would read 1.3E-5 arc seconds for a galaxy cluster. A good number of the APOD descriptions will give angular field of view for larger objects, particularly those that are faint to the naked (can I say naked on this forum :shock: ) eye. Even Jupiter (and Saturn, both of which are currently prominent in the night sky), as large as it appears, ranges only from 29.8 to 50.1 arc seconds. So, at best, it would take ~72 Jupiter diameters to make one degree in the night sky. If I remember correctly (long odds here), a fist held at arms length is about 10 degrees (could be 15, don't clearly remember), so holding your fist out next to an object in the sky will allow you to "ballpark" the angular field of view.
Does this help or confuse (hint, I'm better at the latter than the former....)?

dave boling
Thanks. It's a question I had been thinking of asking on this thread for years. I guess what I actually like to know is what the angular diameter of the things I am being shown. I asked about angular field of view as that seems analogous to a map scale - which by convention is always there to help us tell if we are looking at a contour map of a mountain or a molehill. The trouble with space is that it looks much the same however much we enlarge it. I posted prompted by the Andromeda galaxy image because there we were given a sense of scale. Without the moon it could have been like a picture from Hubble of a speck of light or less to the naked eye rather than something that is actually quite 'big in the sky' but not seen like that without a little image processing.

I guess unless one is an astronomer then for most of us it's just awesome eye candy.
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Solis Lacus: The Eye of Mars

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dave boling
I teleported home one night
With Ron and Sid and Meg.
Ron stole Meggie's heart away
And I got Sidney's leg.
-- Douglas Adams

'Bundinn er bátlaus maðu'.
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daveboling
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Biking to the Moon

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dave boling
I teleported home one night
With Ron and Sid and Meg.
Ron stole Meggie's heart away
And I got Sidney's leg.
-- Douglas Adams

'Bundinn er bátlaus maðu'.
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