About FOV Astro

1) Select Telescope

Choose a telescope brand and model. The telescope defines aperture and focal length. Focal length controls magnification and field size: longer focal length → smaller field of view.

2) Select Camera

Choose your camera model. The camera defines pixel size (µm) and resolution (sensor width/height in pixels), which determine the sensor’s physical size and your pixel scale.

3) Select Reducer / Barlow

Pick an optical factor that multiplies the effective focal length. Reducers (e.g., 0.8×, 0.63×) reduce focal length and widen the field; Barlows (e.g., 2×, 3×) increase focal length and narrow the field.

4) Select Object

Choose a target to center the sky background and frame overlay. Use the preview to confirm your target fits (and to plan a pleasing composition).

5) Rotation

Rotation changes only the orientation of the blue frame. Use it to match how your camera is mounted or to rotate the composition for best framing (for example, aligning a galaxy’s major axis diagonally).

6) Seeing (FWHM)

Seeing is atmospheric blur, expressed as the full width at half maximum (FWHM) of star images in arcseconds. Typical values: 2–3″ (good), 3–4″ (average), 4–6″ (poor). This tool uses seeing to estimate sampling quality.

FOV Astro calculates key imaging metrics:

• Effective focal length (EFL): telescope focal length × reducer/barlow factor.
• Focal ratio (f/): EFL divided by aperture. Lower f/ is “faster” for extended targets.
• Pixel scale: arcseconds per pixel, computed from pixel size and EFL.
• Sensor size: physical dimensions derived from pixel size × pixel count.
• Frame FOV: total field of view across sensor width/height.

The sampling indicator is based on pixels per seeing FWHM. It estimates whether your pixel scale matches your sky conditions:

• UNDER: stars span too few pixels (loss of fine detail; blocky stars).
• GOOD: balanced sampling for detail vs noise and typical guiding errors.
• OVER: very fine sampling (can be useful in excellent seeing, but often increases noise and demands on tracking).

Increasing seeing FWHM (worse seeing) increases the number of pixels across a star’s blur profile, so the indicator moves accordingly. Changing focal length or pixel size also shifts sampling.

FOV Astro loads a sky background for visual context. If you have a local cache configured, it attempts to load the cached image first. If no cache image is found, it falls back to downloading a survey image via NASA SkyView.

• Local cache: fast, consistent, works offline if bundled with the app.
• SkyView fallback: convenient, but requires internet and may be slower.

Attribution: Background imagery retrieved via NASA SkyView Virtual Observatory (NASA/GSFC), including DSS survey data (when using the SkyView fallback).

• Wide nebulae: try reducers or shorter focal lengths; slight undersampling is often fine.
• Small galaxies: longer focal lengths help framing; aim for GOOD sampling when possible.
• Rotation: use it to avoid clipping corners of your target and to improve composition.
• Compare setups: switch camera models to compare sensor size and pixel scale quickly.
• Save a reference: take screenshots of your preferred framing for the field.

Clear Skies is a lightweight astro-weather planning tool integrated with FOV Astro. It analyzes cloud layers, transparency, precipitation, wind, and solar altitude to estimate how suitable the upcoming nights are for astronomy and astrophotography.

Location entry methods

1) Search by city / town / postcode

• Start typing a location in the search box.
• A dropdown list of suggestions will appear.
• Select the correct match (country and region shown for clarity).
• Click Forecast to load the 7-day astro forecast.

2) Use GPS (automatic detection)

• Click Use GPS.
• Your browser will request location permission.
• Once approved, your coordinates are used to fetch the forecast.
• This requires HTTPS (secure connection) to work properly.

3) Manual entry (advanced users)

• You may enter a specific town near your observing site.
• This is useful for remote dark-sky locations.
• Choose the closest listed location for best accuracy.

Understanding the 7-Day Summary

Each day receives an astro suitability score based on:

• Total cloud cover (most important factor)
• High / mid / low clouds (affect deep-sky differently)
• Visibility (transparency proxy)
• Precipitation probability & amount
• Wind speed (important for guiding stability)
• Solar altitude (night weighting)

The color scale typically runs:

• Red – Poor (cloudy or unsuitable)
• Yellow / Orange – Moderate
• Green – Good to excellent astro conditions

Tonight Details Panel

The Tonight section shows a breakdown of the current or upcoming night:

• Cloud distribution by altitude
• Wind and precipitation conditions
• Visibility estimates
• Sunset / sunrise times
• Astronomical darkness window

This helps you decide:

• When to start imaging
• Whether transparency supports broadband vs narrowband
• If wind may affect guiding performance

Hourly Forecast

The hourly chart provides a detailed astro score through the night. This is useful for:

• Identifying clear windows between cloud bands
• Planning meridian flips and target switches
• Deciding when to run longer exposures

Darker green hours indicate stronger observing conditions. Red periods suggest clouds or unsuitable conditions.

Best practices

• Check forecast 24–48 hours before imaging.
• Re-check on the same day for updates.
• Combine Clear Skies with FOV Astro to confirm framing + weather.
• For planetary imaging, prioritize seeing conditions over total cloud cover.
• For deep-sky imaging, transparency and high clouds matter most.