Seeing versus transparency
Seeing and transparency describe different limitations. Separating them helps choose targets instead of labelling a night simply good or bad.
Seeing: image stability
Seeing concerns atmospheric turbulence and stability of fine detail. In poor seeing stars scintillate and a planetary image ripples or will not hold focus.
Local heat sources matter too: roofs, concrete and observing through an open window.
Transparency: how much light arrives
Transparency describes absorption and scattering by cloud, moisture, dust and bright sky background. It strongly affects faint nebulae and galaxies.
A night can have steady seeing but milky sky, or excellent transparency with strong turbulence.
Match the target to conditions
With good seeing choose planets, the Moon and double stars. With good transparency but weaker stability, use wide fields and extended objects.
Do not automatically increase magnification. The useful range depends on target, aperture and current stability.
Build a personal comparison scale
Rate both independently from 1–5 using a consistent method. Add observing direction and target altitude.
After several entries compare sessions from the same site. Consistency matters more than false laboratory precision.
Common mistakes
- Using one general “conditions” value.
- Observing over a warm roof and blaming the upper atmosphere.
- Choosing faint galaxies through hazy transparency.
- Comparing ratings made with changing criteria.
What to record in TelescopeTo
- Separate seeing and transparency scores.
- Direction, target altitude and local heat sources.
- Highest useful magnification for the specific target.
Guide limits
A 1–5 rating is a subjective log, not a meteorological measurement. The service does not retrieve weather data.