Sensor Coverage Calculator
Enter your camera's resolution and pixel size with your telescope's focal length to find the sensor size, the patch of sky it covers and which well-known targets will fit.
Sensor coverage
Sensor size, pixel scale and sky coverage from your camera's specs.
From the camera's spec sheet.
Include any reducer or Barlow.
The defaults match a ZWO ASI2600 (Sony IMX571 sensor) on a 600 mm refractor.
Field of view
2° 14.6′ x 1° 30′
3.363 square degrees of sky
- Sensor size
- 23.49 x 15.70 mm
- Sensor diagonal
- 28.26 mm
- Resolution
- 26.1 MP
- Pixel scale
- 1.29″ per pixel
- Diagonal field
- 2° 41.9′
Will it fit?
- Full Moon (31.2′)Fits, 23% of frame
- Andromeda Galaxy (M31) (3° 12′ x 1°)Too large
- Orion Nebula (M42) (1° 6′ x 1°)Fits, 49% of frame
- Pleiades (M45) (2°)Too large
- Ring Nebula (M57) (1.4′ x 1′)Fits, 65 px across
Sizes are approximate and assume you can turn the camera 90°. Faint outer halos can make galaxies and nebulae look bigger in long exposures.
How this is calculated
- 1
Sensor size
Width in mm = pixels across × pixel size in µm ÷ 1000, and the same for the height. A 6248 x 4176 sensor with 3.76 µm pixels measures 23.49 x 15.70 mm.
- 2
Pixel scale
Arcseconds per pixel = 206.265 × pixel size in µm ÷ focal length in mm. With 3.76 µm pixels at 600 mm that is 1.29″ per pixel.
- 3
Field of view
Each side is 2 × atan(sensor side ÷ (2 × focal length)). The example above at 600 mm covers about 2.24° x 1.50°, or 3.36 square degrees.
- 4
Target check
Each target's approximate size is compared with the field, allowing the camera to be turned 90°. Small targets show how many pixels they span, which tells you how much detail to expect.
Frequently asked questions
How do I find my camera's sensor size from its resolution?
Multiply the number of pixels by the pixel size in micrometres and divide by 1000 to get millimetres. Do this for both width and height. For example, 4144 pixels at 3.76 µm is 15.58 mm.
Will the Andromeda Galaxy fit in my camera's field of view?
The bright part of Andromeda is about 3.2° by 1°, so you need a field at least that wide. An APS-C sensor needs a focal length of about 420 mm or less, and a full frame sensor about 640 mm or less.
What focal length do I need for the Orion Nebula?
The bright core of M42 and M43 spans just over 1°. On an APS-C sensor anything from about 500 to 800 mm frames it well. The fainter outer loops of nebulosity need a wider field.
Why do more megapixels not always give more detail?
Detail is limited by the telescope and the atmosphere as well as the sensor. If the pixel scale is already finer than the seeing allows, more pixels only oversample the same blur.