Rodstar
31-10-2006, 10:29 PM
How can we maximise what we can perceive with our eyes? :eyepop:
I found the following web resources of interest. Hope you like them too.
1. At www.fortunecity.com/roswell/borley/49/visual.htm there is an excellent summary, drawing on various articles from astronomy journals from the mid 1980s to mid 1990s, regarding how to maximise what your eyes are capable of seeing. Amongst other things, the point is made that, contrary to astronomical folklore, it is often beneficial to increase magnification to better detect faint deep sky objects because the background will be darker, meaning the fainter object will still contrast against the background, while, at the same time, the human eye is more capable of seeing a larger faint object.
2. Mel Bartels provides a good summary of the subject, "Visual Astronomy: An investigation into the visual optimum detection magnification", at his website www.bbastrodesigns.com/visual.html. Of particular interest to me is Mel's comment, after describing how the cones and rods in the retina operate, that the best spot on the retina to use averted vision is found by looking at a point 15 degreees away from the object, slightly above it and with the object aimed at your nose. He also discussed the fact that the best magnification, in any situation, is that which gives the best eye detection contract value for a given apparent object size and sky background. Mel also provides a table (author undisclosed) which indicates that our eyes are capable of detecting much fainter magnitude objects in the right circumstances with sufficient mental discipline. For example, the table indicates that there is a 5% probability of detection of a magnitude 17.4 star with a 10 inch telescope. I understand from this it is suggested that if I observe carefully for 60 seconds, I might, on the basis of probabilities, see the 17.4 magnitude star for 3 seconds. Sounds a bit far fetched to me.....;)
3. Of course one of the gurus of the science of visual observing is Roger N Clark. On his site www.clarkvision.com/visastro/omva1/index.html, Clark summarises data collected from a World War 2 study of soldiers to help them see better at night to assist in an understanding of the elements of better visual detection. Interestingly, he notes that when an object is magnified in a telescope, the contrast between object and background does not change since both are magnified equally. However, his studies reveal that at a certain point there is a deterioration in visual detection of faint objects if magnifying any further. The best observing strategy, says Clark, is to magnify deep sky objects , or the details within them which interest you, to about 100 arc-minutes in size. He gives the example that if you are trying to detect a dark nebula in a spiral galaxy are, magnify that dark nebula so that appears about a degree across or more. He recommends a magnification sequence increasing by a factor of 1.5x with the following being a good magnification sequence: 35x, 50x, 80x, 80x, 120x, 180x, 270x 400x.
Happy visual observing! ;)
I found the following web resources of interest. Hope you like them too.
1. At www.fortunecity.com/roswell/borley/49/visual.htm there is an excellent summary, drawing on various articles from astronomy journals from the mid 1980s to mid 1990s, regarding how to maximise what your eyes are capable of seeing. Amongst other things, the point is made that, contrary to astronomical folklore, it is often beneficial to increase magnification to better detect faint deep sky objects because the background will be darker, meaning the fainter object will still contrast against the background, while, at the same time, the human eye is more capable of seeing a larger faint object.
2. Mel Bartels provides a good summary of the subject, "Visual Astronomy: An investigation into the visual optimum detection magnification", at his website www.bbastrodesigns.com/visual.html. Of particular interest to me is Mel's comment, after describing how the cones and rods in the retina operate, that the best spot on the retina to use averted vision is found by looking at a point 15 degreees away from the object, slightly above it and with the object aimed at your nose. He also discussed the fact that the best magnification, in any situation, is that which gives the best eye detection contract value for a given apparent object size and sky background. Mel also provides a table (author undisclosed) which indicates that our eyes are capable of detecting much fainter magnitude objects in the right circumstances with sufficient mental discipline. For example, the table indicates that there is a 5% probability of detection of a magnitude 17.4 star with a 10 inch telescope. I understand from this it is suggested that if I observe carefully for 60 seconds, I might, on the basis of probabilities, see the 17.4 magnitude star for 3 seconds. Sounds a bit far fetched to me.....;)
3. Of course one of the gurus of the science of visual observing is Roger N Clark. On his site www.clarkvision.com/visastro/omva1/index.html, Clark summarises data collected from a World War 2 study of soldiers to help them see better at night to assist in an understanding of the elements of better visual detection. Interestingly, he notes that when an object is magnified in a telescope, the contrast between object and background does not change since both are magnified equally. However, his studies reveal that at a certain point there is a deterioration in visual detection of faint objects if magnifying any further. The best observing strategy, says Clark, is to magnify deep sky objects , or the details within them which interest you, to about 100 arc-minutes in size. He gives the example that if you are trying to detect a dark nebula in a spiral galaxy are, magnify that dark nebula so that appears about a degree across or more. He recommends a magnification sequence increasing by a factor of 1.5x with the following being a good magnification sequence: 35x, 50x, 80x, 80x, 120x, 180x, 270x 400x.
Happy visual observing! ;)