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Useful wide-ish EP for C 9.25 for spectacles users


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I'm planning to get a 7-21mm or 8-24mm Zoom and just wondering if there is something a bit wider, perhaps around 30-40mm  (in 1.25") that would be friendlier towards family users who all wear glasses (general sky surfing/viewing, etc.). I'd read somewhere that Revelation and Celestron EP's offer good value. Budgetwise, under £100, preferably in the £60-70 range or up to budget limit if it makes sense. Something that would work for the same general purposes on a 60mm F6 would be good. Emphasis on comfort at the eyepiece (else I'll never be able to persuade to stretch the budget and landscape the garden).

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There's the new SVBONY zoom eyepieces getting a lot of chatter on Cloudy Nights these days.  All seem to be well thought of according to early adopter reports.  They're available in 7-21mm, 8-24mm, and 10-30mm focal ranges via ebay, Amazon, AliExpress, and the SVBONY website.  The 8-24mm is probably going to have the best eye relief for eyeglass wearers.

It's uncertain how much additional true field of view you'd gain going with the 10-30mm over the 8-24mm.  Neither is going to be particularly wide at the long end.

Edited by Louis D
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I find that even if I can get a decent view with my glasses on, that I'll then often be left with smudges on my glasses from the experience.  My glasses are for distance, my close-up vision is very good, so I tend to take my glasses off at the eyepiece and it gives me a far better view as I can get right in there with the eyeball.  Can't say I've come across any eyepiece that provides a truly equal view for glasses or no glasses, I expect that to get the best for glasses wearers an eyepiece would have to be designed for it, meaning that non-glasses wearers would be at a disadvantage. 

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Thanks. I can deal with smudges. Viewers include elderly persons and their eyesight/eye health is not too good.  It's really ease of use/comfort with glasses on that I'm after. Shame there is not a telescope shop where I could go and browse and try out some EP's. The online option is buy more than one and return the one's I don't like (subject to postage and potential restocking fees).

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2 hours ago, jonathan said:

... I expect that to get the best for glasses wearers an eyepiece would have to be designed for it, meaning that non-glasses wearers would be at a disadvantage. 

Tele Vue designed the 40mm version of their plossl expressly for glasses wearers I believe.

To some extent I feel that the Explore Scientific 92 degree eyepieces favour the glasses wearer, especially the 12mm.

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I've got the 40mm Celestron Plossl and it works well for me and my wife. I've got glasses like jam jar bottoms and she doesn't wear any. It's got AFOV of 40 degrees giving a TFOV of about .68 degrees in my 9.25. It has an eyerelief of 28mm, which is crucial to me as I've got astigmatism so can't use long focal length eyepieces without glasses.

I also have a 32mm Bresser Plossl that's got a AFOV of 50 degrees and gives the exact same TFOV.

Edited by Starwatcher2001
typo
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5 hours ago, jonathan said:

I find that even if I can get a decent view with my glasses on, that I'll then often be left with smudges on my glasses from the experience.

Carefully clean off all face grease from the top of the eyepiece, generally a folded down eyecup, and you won't have this issue.  I never swap between glasses on and off with the same eyepiece because I know I'll get smudged eyeglasses.

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Having cylindrical astigmatism, I have to wear glasses, and many modern EPs have 16mm or more eye relief, which I have found sufficient for my needs, although 18-20mm is ideal. Longer focal lengths are generally OK, as even the Plossl or Ortho designs have generous eye relief at long focal lengths.

The main issue for wide-field observing with the C9.25 (likewise for my C8) is the limitation posed by the 1.25" visual back. This means either a 32 mm Plossl or 24 mm super wide angle (like the MaxVision 24mm 68 deg EPs) give you the maximal field of view. Going to even longer focal lengths gives nothing in terms of FOV. There are two ways around this: If the scope is not an Edge HD type, get the 0.63x focal reducer and insert it between the scope and the visual back. They pop up second hand for little and extend the FOV by 1.58x linearly (or 2.5x in terms of surface area on the sky). This should work well with all your existing kit. The other alternative is to get a 2" visual back, along with a 2" star diagonal, and 2" EPs. More expensive, but certainly worthwhile, I have found. I should add I happily used the focal reducer method for years, it is just that once I needed a 2" visual back for my Vixen flip-mirror, I got lured down the path of 2" EPs.

 

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Decent glasses friendly 30-40mm eyepieces:

Pentax XW 40

Pentax XW 30

TeleVue Panoptic (41mm)

TeleVue Nagler 31

Explore Scientific 40mm 68°

Explore Scientific 40mm 62°

Explore Scientific 40mm 52°

Explore Scientific 30mm 82°

APM or Altair 30mm Ultra Flat field

TeleVue Plössl 40mm

TeleVue Plössl 32mm

Lower prices 30-40mm long eye relief eyepieces will be astigmatic in about the outer 50% of the field.

If this is just a finder eyepiece, then maybe that's OK.

If this is an eyepiece you plan to view with often, then I suggest saving your pence and paying a bit more.

 

 

 

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In 1.25", as you requested, a 32mm Plössl is about as wide with long eye relief as you are going to get. Though quite a few of the 65° to 68° 24mm eyepieces would give the same field of view but with higher magnification.

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9 hours ago, Don Pensack said:

Decent glasses friendly 30-40mm eyepieces:

Pentax XW 40

Pentax XW 30

TeleVue Panoptic (41mm)

TeleVue Nagler 31

Explore Scientific 40mm 68°

Explore Scientific 40mm 62°

Explore Scientific 40mm 52°

Explore Scientific 30mm 82°

APM or Altair 30mm Ultra Flat field

TeleVue Plössl 40mm

TeleVue Plössl 32mm

Lower prices 30-40mm long eye relief eyepieces will be astigmatic in about the outer 50% of the field.

If this is just a finder eyepiece, then maybe that's OK.

If this is an eyepiece you plan to view with often, then I suggest saving your pence and paying a bit more.

 

 

 

That's a helpful list, thank you.

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I've just ordered the SVBONY 7-21mm. Chose this over the 8-24mm based on size/weight (not really a major issue just a slight preference) as it will be easier to use on my smaller OTA's (refractors) and will suffice for now as well as being a cheap experiment to help determine what EP's I need in future.

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