So does anyone else not even think about exit pupil? In my world, it isnt even a consideration. I am so seeing limited that getting to the perfect exit pupil for my scope just doesn’t happen all that often. What i worry about is magnification or eyepiece choice. Far and away i spend most of my nights using a 13 or 21mm eyepiece in my 16 inch which is 140 or 90x. That is all the math I really need to know. Anything else is just more math that isnt really necessary
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I have exclusive eyepiece sets for each of my scopes . On the barrel cases I have the focal length of the eyepieces and the magnification of what that eyepiece will yield in that particular scope . Then I made up a laminated card that gives the eye relief and exit pupil of each eyepiece in the set for that particular scope . Not that it’s a big deal but it’s kinda nice to have that pre calculated information at hand . The only time I’ve ever had a problem with exit pupil is with my 32mm Plossl in my 8” f4 Schmidt Newt which IIRC is at 7mm . If my eyes aren’t fully dilated due to starting to view earlier than full darkness , the shadow of the secondary mirror is on full display . Once my eyes are fully dilated , that phenomenon disappears .
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@Starrancher i have everything written down on one sheet of paper. Sounds like it is the same info you have except i add a mag limit. The only eyepiece i have, well that i notice a secondary blackout on, is the 56mm and it is exclusively used on my SCT
So when you see that , the exit pupil of the eyepiece is larger than your eyes pupil .
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With a SCT I’m assuming it’s f10 . What magnification is that yielding in your scope ?
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@Starrancher . First i am one of the lucky people who’s pupil gets really big. The last time i was at the eye doctor I had him measure them. I am just shy of 8mm at normal dark adaptation. So i can use about any eyepiece i want and be good to go, the only exception i notice is the 56mm, i only notice it during the day. At night it is gone. The SCT is F10 and while it can go to 500x I rarely take it past 200x because my skies generally suck. I spend a lot of nights between 80 and 140x
So what magnification are you at using the 56mm in the SCT ?
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@Starrancher it only gets me 45x. Its my low power and go wide eyepiece in my SCT
I use a 26mm Plossl in my 8” f4 Schmidt Newt and get 31x . Under a dark desert sky I get the entire Andromeda galaxy in the 52 degree apparent FOV . The far reaching faint edges might spill over ever so slightly . With a 32mm Plossl I can get down to 25x but the exit pupil exceeds my dark adapted eyes some .
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@Starrancher yeah i guess I am one of the lucky people that have freaky large pupils at night. It does explain my exceptionally good night vision in general
Right . If you can get to 6mm you’re doing pretty good . Last I checked I could get there but last I checked was 15 years ago .
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@Starrancher i have mine checked every year or two when i have my eye doctors appointment. Last November he measured me at a strong 7mm, bot quite 8mm. So i am doing good
Is that with the drops they put in your eyes to dilate them ?
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@Starrancher no chemical additives required. That is my normal dark adaptation without any assistance.
Now that’s pretty amazing .
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@Starrancher i have had it measured every year for the last three years. Just hangs between 7 and 8mm.
8mm is like the maximum with young healthy eyes . At my age I might still be able to get there . Even if not , the only problem I would have is a couple long focal length eyepieces in my short focal length scope and at powers down in the Sub 30x magnification range . At that point it’s time for binoculars . But what do you get other than being able to fit M45 into the FOV . That and maybe a few other open clusters is about all I’d use binoculars for in the celestial realm .
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@Starrancher i don’t really get that eyepiece out unless i have to. When the SCT is up i usually also have something else out that goes wider
@Starrancher been meaning to update this thread for a while now since i have had the SCT out. For grins i slapped the 56mm Meade in way early in the evening just to see how my eye reacted to it in the slowly darkening evening. As usual there was a small blacked out area in the middle was there but as it got darker the black spot went away fairly quickly. At 58 years old its nice to have eyes that still work well.
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Well , I’ve got 9 years on ya and astigmatism. The focus knob usually takes care of that until I get to the low power pieces and the seagulls come out in the outer edges toward the field stop . The center shadow goes away once it gets dark enough for dilation to occur on my longest focal length pieces . I’ve only seen it once as I must have just been checking something before it got dark enough . At first I thought there was something wrong with the scope but it was only because my pupils weren’t dilated enough . I was relieved when it got a bit darker and I kinda figured out what caused it . Then I read up on it a bit after that weekend star party when I got home . Yeah , it was totally normal .
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