Choose a target
Select the Moon, Sun, a planet or a deep-sky object.
Interactive telescope simulator
What will you see through your telescope?
Choose a target and equipment combination. See whether the object fits, how large it appears and what changing the focal length really does.
Try the simulator
NASA, ESA and STScI · OPAL 2024
How to use the tool
Build and explore your view
The red outline represents what the selected camera or eyepiece can see.
Select observing mode
Use Imaging for a camera, or Eyepiece for the Celestron 8SE.
Choose the equipment
The field size and object scale are calculated automatically.
Explore the framing
Drag to move the red frame. Use the arrows to move the object, and Display zoom to inspect narrow views.
Build your view
Choose a setup
Select one of the Show Me The Sky telescope and camera combinations.
Horizontal field—
Vertical field—
Pixel scale—
Target in frame—
Understand the result
Why does the view change?
Longer focal length
Produces a narrower field and makes a target occupy more of the frame.
Larger sensor
Captures a wider area of sky at the same telescope focal length.
Target angular size
Determines how much of the available field the object actually occupies.
The imaging field-of-view formula
FOV = 2 × atan(sensor size ÷ (2 × effective focal length))The preview compares the calculated field with the target's apparent angular size on your selected date. The images show framing and scale; they do not simulate atmospheric seeing, exposure, detail or brightness.
See it for real
Want to observe through one of these telescopes?
Join a live, guided Show Me The Sky session from home.
Comments