Planetary telescope night vision.
The minimum magnification for full resolution of an astro telescope at night is 13.5x to 14x per inch of aperture.
So, for a 100mm scope 54x, but actually a higher magnification is needed in practice of 100x or a little more.
For a 60mm scope 33x or actually 65x in practice.
I have seen slightly different figures mentioned, but these are the magnifications I personally use.
The biggest factor, though, is the observer's eyesight.
This varies from military pilots at 20/8 to 20/40 for driving licence eyesight requirements.
There are exceptions, such as the best recorded that I have seen of 20/4.7 to 20/60 or 20/80 for eyesight good enough for many tasks.
As to the highest magnifications used for the finest detail.
From 1940s data 50x per inch of aperture or 2x per mm.
This is often mentioned nowadays.
However, more modern data indicates 67x per inch or 2.5x per mm.
This agrees with planetary observers over the last 200 years.
With planetary observation one needs to start at 80x or 100x to see any detail on a planet's surface.
This is provided with a 60mm refractor or easily with a 75mm refractor.
Then one increases the magnification to fill in fine detail on the drawing.
If Seeing is good enough, the final magnification is 260x with a 4 inch refractor and 400x with a 6 inch refractor.
As to spotting scopes in the day.
The separation of artificial stars in daylight is about 2/3 of the result at night.
Principally because of the pupil size differences.
In addition, from results posted on the forum, 1.5x per mm is the highest normally used.
Spotting scopes are compact telescopes with prisms that do not take well to the very high magnification of excellent astro scopes.
With spotting scopes the chosen magnification is very personal to the observer and a compromise between field size and detail seen.
Regards,
B.
The minimum magnification for full resolution of an astro telescope at night is 13.5x to 14x per inch of aperture.
So, for a 100mm scope 54x, but actually a higher magnification is needed in practice of 100x or a little more.
For a 60mm scope 33x or actually 65x in practice.
I have seen slightly different figures mentioned, but these are the magnifications I personally use.
The biggest factor, though, is the observer's eyesight.
This varies from military pilots at 20/8 to 20/40 for driving licence eyesight requirements.
There are exceptions, such as the best recorded that I have seen of 20/4.7 to 20/60 or 20/80 for eyesight good enough for many tasks.
As to the highest magnifications used for the finest detail.
From 1940s data 50x per inch of aperture or 2x per mm.
This is often mentioned nowadays.
However, more modern data indicates 67x per inch or 2.5x per mm.
This agrees with planetary observers over the last 200 years.
With planetary observation one needs to start at 80x or 100x to see any detail on a planet's surface.
This is provided with a 60mm refractor or easily with a 75mm refractor.
Then one increases the magnification to fill in fine detail on the drawing.
If Seeing is good enough, the final magnification is 260x with a 4 inch refractor and 400x with a 6 inch refractor.
As to spotting scopes in the day.
The separation of artificial stars in daylight is about 2/3 of the result at night.
Principally because of the pupil size differences.
In addition, from results posted on the forum, 1.5x per mm is the highest normally used.
Spotting scopes are compact telescopes with prisms that do not take well to the very high magnification of excellent astro scopes.
With spotting scopes the chosen magnification is very personal to the observer and a compromise between field size and detail seen.
Regards,
B.
