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I went for a UO Ortho (Volcano top) 12.5mm. Glad to hear that it barlows well too, because I wouldn't have much fun trying to look through the eyelens of any FL's < the 12.5mm.

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I went for a UO Ortho (Volcano top) 12.5mm. Glad to hear that it barlows well too, because I wouldn't have much fun trying to look through the eyelens of any FL's < the 12.5mm.

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Actually the 9mm has plenty of eye relief for a non-eyeglass wearer. It is the 7mm where things start getting tight.

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That is good to know, seriously speaking. However, my reference was in regards to the shrinking eyelens diameter as you go lower in FL.

On a side note, as far as the 12.5 is concerned, I just called UO and found out it has 10.5mm ER, which is a pleasant suprise--I was guessing an Ortho would have Plossl like ER or worse, but it shows that I have much to learn.

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I went for a UO Ortho (Volcano top) 12.5mm. Glad to hear that it barlows well too, because I wouldn't have much fun trying to look through the eyelens of any FL's < the 12.5mm.

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Actually the 9mm has plenty of eye relief for a non-eyeglass wearer. It is the 7mm where things start getting tight.

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That is good to know, seriously speaking. However, my reference was in regards to the shrinking eyelens diameter as you go lower in FL.

On a side note, as far as the 12.5 is concerned, I just called UO and found out it has 10.5mm ER, which is a pleasant suprise--I was guessing an Ortho would have Plossl like ER or worse, but it shows that I have much to learn.

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True, the UO 9mm is still comfortable to use, although the eye lens is smaller than that of the 12mm's:



But not as tiny as the 5mm!

Best,

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I went for a UO Ortho (Volcano top) 12.5mm. Glad to hear that it barlows well too, because I wouldn't have much fun trying to look through the eyelens of any FL's < the 12.5mm.

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Actually the 9mm has plenty of eye relief for a non-eyeglass wearer. It is the 7mm where things start getting tight.

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That is good to know, seriously speaking. However, my reference was in regards to the shrinking eyelens diameter as you go lower in FL.

On a side note, as far as the 12.5 is concerned, I just called UO and found out it has 10.5mm ER, which is a pleasant suprise--I was guessing an Ortho would have Plossl like ER or worse, but it shows that I have much to learn.

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the "usable" eye relief of the eyepieces has been previously published in this forum. Regardless what the retailer tells you about eye relief, you still need to measure the "usable" eye relief by subtracting the un-usable recess from the top of the housing to the eye lens. One good thing to keep in mind, more recess keeps eye lens cleaner from eyelash gunk. But for eyeglass wearers, it reduces ability to accomodate the user.

usable eye relief
1st is the total eye relief
2nd is the depth of lens recess
3rd is the net usable eye relief.

UO (vol top) ortho 18mm 15.7-3.0 = 12.7
UO (vol top) ortho 12.5mm 11.0-3.3 = 7.7
UO (vol top) ortho 9mm 8.0-1.7 = 6.3
UO (vol top) ortho 7mm 6.0-1.3 = 4.7

here's a selection of various brands in the 9mm-7mm range

TV 8mm plossl 6.4-3 = 3.4
Tak LE 7.5mm 11.0-1.2 = 9.8
TMB Plan II 8mm 16.7-3.5 = 13.2
TMB Plan II 7mm 16.0-3.5 = 12.5
TMB Supermono 8mm 7.1-3.1 = 4.0
Cel Ultima 7.5mm 6.3-2.8 = 3.5
UO (vol top) ortho 9mm 8.0-1.7 = 6.3
UO (vol top) ortho 7mm 6.0-1.3 = 4.7

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On a side note, as far as the 12.5 is concerned, I just called UO and found out it has 10.5mm ER, which is a pleasant suprise--I was guessing an Ortho would have Plossl like ER or worse, but it shows that I have much to learn.

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