Visual Perspective

The cosmos at our fingertips.
RedGriffinDiver
Asternaut
Posts: 1
Joined: Tue Nov 24, 2020 1:05 pm

Visual Perspective

Post by RedGriffinDiver » Tue Nov 24, 2020 2:47 pm

When I look at a picture on APOD I visualize myself in a spaceship looking out the window/viewscreen. Would there be a way to notate the pictures with something like this view would be XX light-years/million miles from the center of the object? Or do I need to figure it out based on the description of this picture shows a field of X light-years across?

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Chris Peterson
Abominable Snowman
Posts: 15525
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: Visual Perspective

Post by Chris Peterson » Tue Nov 24, 2020 2:54 pm

RedGriffinDiver wrote:
Tue Nov 24, 2020 2:47 pm
When I look at a picture on APOD I visualize myself in a spaceship looking out the window/viewscreen. Would there be a way to notate the pictures with something like this view would be XX light-years/million miles from the center of the object? Or do I need to figure it out based on the description of this picture shows a field of X light-years across?
Consider that the equivalent distance is dependent upon your display device and how far you are from it. You are much "closer" if you're sitting in front of a 30-inch monitor than if you're viewing the APOD on a phone in your lap.

Sometimes the angular size of an object is given in the APOD caption. Otherwise you can usually look it up. You can use that to calculate the apparent distance. If an object subtends 1° and is 1000 ly distant, and you estimate that it fills 30° of your field when you view the image, that means you are effectively 30 times closer, or its apparent distance is 1000 ly / 30 = 33 ly.
Chris

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Chris L Peterson
Cloudbait Observatory
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