Quote:
Originally Posted by ngcles
Hi Rod & All,
Rod wrote:
"As I understand it, the effect of the Paracorr is to transform the 31 Nagler into having an actual focal length of about 26.35mm. I am assuming the exit pupil is similarly adjusted, and would end up being about 5.2mm?"
Well Rod if you're using the Paracorr, you'll be sweet.
Les D
Contributing Editor
AS&T
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Hi Les,
I use a 31mm Nagler in my 18"/F4.5 Obsession with and without a Paracorr. I am also at least 10 yrs older than Rod, who is but a pup. I am 48. Although he
"ALMOST" has less hair than me already
Without parracor the exit pupil is 6.88mm
With parracor the exit pupil is 6.00mm
I also have a 27mm Televue Panoptic which gives the following exit pupils:
Without paracorr the exit pupil is 6.00mm
With paracorr the exit pupil is 5.2mm.
I have spent quite a bit of time comparing the exit pupil/contrast/background sky brightness issues under a number of different scenarios and sky conditions. Ultimately I don't have a problem with the 31mm Nagler under any circumstances with the exception of almost city sky conditions. Even then it is still very useable. Under rural and dark skies the 31mm Nagler works very well for me without the paracorr at F4.5 for a 6.88mm exit pupil. Although, I usually do use the paracorr as it cleans up the EOF nicely. It is worth adding the following. I haven't smoked in almost 10 years, drink very little alcohol, take no medications on an ongoing basis and I am in very good health. These things can have an enormous effect on ones ability for their pupil to fully dilate. Take it as an absolute given that someone who smokes, drinks alcohol, or is in a poor state of health, will not have anywhere near the pupil dilation of someone who abstains and is in good health. On top of these external influences everyones physiological composition and abilities are different and their pupil dilation abilities vary. Age is also a significant factor. The older you are the less pupil dilation you will have. Rod observes regularly with me under reasonable sky conditions, he doesn't smoke and drinks very little. He will be fine with a 31mm Nagler in his F5 scope, for a 6.2mm exit pupil. With a paracorr which he has, it's a no brainer.
Cheers
John B