It would be possible in a scope with a focal ratio of f/3.33. I do not know of any scope made with that ratio, but it is possible.
It would be possible in a scope with a focal ratio of f/3.33. I do not know of any scope made with that ratio, but it is possible.
LX200 ACF 8"SCT, Apertura AD12, SkyWatcher 120, ES 102CF Apo triplet, ES AR102, ST100, ST90, Apex 90mm Mak, ST80, ETX60,
Oberwerk BT-82XL-ED, 25x100s, 15x70s, 8x56s, Kasai 2.3x40s, Celestron AVX, CG4, SLT, LCM, Obie HD Parallel Bino mount
Explore Scientific 82 degree and 68 degree EPs, Baader 9mm Ortho, Meade 5000 SWA EP set, many more various EPs, Baader Moon&SkyGlow, FringeKiller, SemiApo filters, Celestron UHC, Meade 4000 Nebular Filter, Kson OIII, DGM NPB and lots of astro stuff.
Mike.
100% beginner.
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with telrad. Tasco galaxsee 45 on an equitorial mount. Vivitar 2inch refractor on basic tripod.
Eyepieces: Apertura 30mm 2" superview. Apertura 9mm plossl. GSO 32mm plossl. GSO 1.25" 2x shorty
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Photography: coolpixl110 on a basic tripod.
Not quite...
Camelhat is correct, but so is AntennaGuy. If you cancel out various parameters to simplify the equation, the easiest formula for the exit pupil of any given eyepiece ends up being the focal length of the eyepiece divided by the f-ratio of the telescope. If you have a 30mm eyepiece and a 3x barlow, that gives you an effective focal length for the combination of 30/3=10mm. If you have a focal ratio of f5, as in the Apertura 12 scope, then the exit pupil with the barlow is 10/5=2mm.
(Using Camelhat's formula the magnification would be 1520(focal length of the telescope)/10(focal length of the combined eyepiece)=152x, and exit pupil would be 304(the diameter of the mirror)/152(magnification)=2mm Voila!)
If you had a very fast scope with an f-ratio of 3.33 as suggested above, the exit pupil of this combination would be 10/3.3=3.3mm...
A 5.5mm eyepiece in your f5 scope will have an exit pupil of 5.5/5=1.1mm
Using the alternative formula of mirror diameter/magnification: the 5.5mm eyepiece gives you a magnification of 1520/5.5=276, and the exit pupil then is 304/276=1.1mm...
Have fun!
Dean
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: 12" home-made dob, Celestron 150 f5, Tak TSA102, TV 76, Celestron 800CPC, ETX 125
Mounts:
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MiniTower, HEQ5Pro
Binos: 25x100FB, Carton 11x80, Vanguard Endeavour 1045, Takahashi 22x60, Swarovski Habicht 8x30
Eyepieces: My favourites are my Televue 32mm plossl, Nagler 13mm T6, Nagler 3-6mm
Hey Mike - Fun with math time!
Here is an older thread you might have some fun with:
Darth Fractor's EP kit calculator
The .xls spread sheet will let you plug in numbers and yield the resulting magnification, FOV & Exit Pupil. Check
the formula section & you'll find the formulas mentioned in the previous posts.
Side note - apologies as Darth Fraktor is misspelled in the title of the thread.
I've been reliably informed we Americans have difficulty speling correctly, but
believe I've finally got that one down.
Moving on.......
And keep in mind that, while you love your GSO 30 mm superview (as do I), it might not be nearly as enjoyable with a faster scope because the faster the scope, the more stringent the eyepiece match is. I added a 24 mm 2" ES eyepiece that is slightly better but not by a whole lot. For the money the GSO superview is hard to beat so long as the scope is not faster than F/5.
... Henk. Telescopes: 6" Mak-Newt (Comet Hunter), ES ED127CF, ES ED80, Zhumell Z12, Coulter Odyssey 10, AT6RC, Venture RX-7, Celestron Skymaster 20x80, Mounts and tripod: Losmandy G11S, AVX, LXD55, Tiltall, Cameras: Fuji X-a1, Canon SX40, Xt, XSi, T6, ELPH 100HS, DIY: Dob and camera barndoor trackers, afocal adapter, Dob with foldable base and Az/Alt setting circles, Accessories: SSAG, Plossls, Barlows, Telrad, laser collimators (Seben LK1, Z12, Howie Glatter), Cheshire, 2 Orion RACIs 8x50, Software: DSS, ImageMagick, PHD, Nebulosity, Photo Gallery, Gimp, CHDK
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Thanks for the link! Okay I got it so that's pretty crazy...if I was at Max mag at 600x or 2.5mm would have an exit pupil of .5mm hahaha... How can you even see through that lol
Mike.
100% beginner.
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with telrad. Tasco galaxsee 45 on an equitorial mount. Vivitar 2inch refractor on basic tripod.
Eyepieces: Apertura 30mm 2" superview. Apertura 9mm plossl. GSO 32mm plossl. GSO 1.25" 2x shorty
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Photography: coolpixl110 on a basic tripod.
Surprisingly you can! The problem with such a small exit pupil is that you start to see "floaters", or small particles (bits of protein?) that slowly move across your eyeball. This can be a bit annoying when they cross the direct field of view.
Generally 1mm is probably the smallest exit pupil that most people would recommend for high-power viewing of bright objects like the moon and planets, and around 2-4mm is probably optimum for higher power viewing of deep-sky objects. 0.5mm is possible on a good night.
All the best,
Dean
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: 12" home-made dob, Celestron 150 f5, Tak TSA102, TV 76, Celestron 800CPC, ETX 125
Mounts:
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MiniTower, HEQ5Pro
Binos: 25x100FB, Carton 11x80, Vanguard Endeavour 1045, Takahashi 22x60, Swarovski Habicht 8x30
Eyepieces: My favourites are my Televue 32mm plossl, Nagler 13mm T6, Nagler 3-6mm
PS: The 0.5mm exit pupil is what you get when you push a telescope to the "2x per mm of aperture" or "50x per inch" that many say defines a good quality telescope: so 200x for a 100mm scope etc. If a scope is not capable of a good image at that magnification under excellent seeing conditions then one would have to question how good the scope really is...
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: 12" home-made dob, Celestron 150 f5, Tak TSA102, TV 76, Celestron 800CPC, ETX 125
Mounts:
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MiniTower, HEQ5Pro
Binos: 25x100FB, Carton 11x80, Vanguard Endeavour 1045, Takahashi 22x60, Swarovski Habicht 8x30
Eyepieces: My favourites are my Televue 32mm plossl, Nagler 13mm T6, Nagler 3-6mm