<p>With a 50mm full frame lens and a 35mm sensor (or film), how far should I be to shoot Earth with earth’s edge just inside top and bottom edge of the resulting image? I don't want any cropping.</p>
<p>Earth diameter: 13,000 km</p>
<p>Same question for shooting the largest black hole, Phoenix A, with diameter of 600billion kilometers. How far should I be? In case of a black hole, would I be sucked in by its gravity at that shooting distance?</p>
<p>I would like to make an online calculator for it so that all I have to do is put in object's diameter and then it would tell me minimum distance (including whether it's safe or not at that distance in case of a black-hole object).</p>

CC BY-SA 4.0
2022-07-04T03:17:01.447Z
This has the two equations you'll need: https://shuttermuse.com/calculate-field-of-view-camera-lens/
Greg Miller
CC BY-SA 4.0
2022-07-04T06:12:29.717Z
Gravity doesn't "suck".  Black holes have very strong gravity, but it never works like suction, it always works like gravity. If you are outside the black hole it is possible to escape.
James K
CC BY-SA 4.0
2022-07-05T08:07:38.177Z
For the visibility part of the question, basic geometry plus https://en.wikipedia.org/wiki/Pythagorean_theorem is sufficient. For better approximations of the earth diameter, see https://en.wikipedia.org/wiki/Earth_radius#Extrema:_equatorial_and_polar_radii
Ralf Kleberhoff
<photography><positional-astronomy>
How to calculate shooting distance for an astronomical object
Ariel Narboada
# How to calculate shooting distance for an astronomical object

(Asked by: username_0 on 2022-07-04)

With a 50mm full frame lens and a 35mm sensor (or film), how far should I be to shoot Earth with earth’s edge just inside top and bottom edge of the resulting image? I don't want any cropping.

Earth diameter: 13,000 km

Same question for shooting the largest black hole, Phoenix A, with diameter of 600billion kilometers. How far should I be? In case of a black hole, would I be sucked in by its gravity at that shooting distance?

I would like to make an online calculator for it so that all I have to do is put in object's diameter and then it would tell me minimum distance (including whether it's safe or not at that distance in case of a black-hole object).

**Tags:** photography, positional-astronomy

> **Comments:**
> **username_1**: This has the two equations you'll need: https://shuttermuse.com/calculate-field-of-view-camera-lens/  
> **username_2**: Gravity doesn't "suck".  Black holes have very strong gravity, but it never works like suction, it always works like gravity. If you are outside the black hole it is possible to escape.  
> **username_3**: For the visibility part of the question, basic geometry plus https://en.wikipedia.org/wiki/Pythagorean_theorem is sufficient. For better approximations of the earth diameter, see https://en.wikipedia.org/wiki/Earth_radius#Extrema:_equatorial_and_polar_radii  

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## 0 answers

