5mm-ish eyepiece options for 8" SCT?

[mental4astro]

I all,

I'm looking for people's thoughts on different eyepieces in the 5mm focal length size for use in an 8" SCT.

I have two particular requirements :
A, comfortable eye relief, that being around 20mm;
B, AFOV 58deg to 72deg.

AFOV in 80deg or larger I find eye placement too tricky/critical to be comfortable with my constant to and fro from my sketch pad. But, I am happy to be shown an EP that can prove me wrong! I am happy to keep an open mind with this point.

I do realize that 5mm is a big ask for regular use in a SCT. I currently have a 5mm Hyperion, which I have to say I am happy with, even though I may only get to thrash it once or twice a year. But, on these occasions I sometimes feel I could get a little sharper image... I also have an 8mm LVW which has that focal length covered, so an EP in that fl isn't sought.

Looking for options.

Mental.

[Wavytone]

Alex if image quality is the priority - not wide field - what you want is one of the simpler eyepiece types with relatively few elements - orthoscopic, super monocentric, plossl, etc. - though eye relief will be abysmal...

Or borrow my f/15 mak and put 8mm behind it, this will be similar ...

[Camelopardalis]

Or a 5mm Pentax XW....if you're coming to SPSP you can borrow mine ;)

[Kunama]

Radian or LVW would be my pick.
20mm eye relief and 60º/65º AFOV

[MattT]

Have you still got the 10 XW? If you do get an ES 1.25" 2x focal extender and use that....then on those incredable nights you can drop the LVW in for 4mm :D

[ausastronomer]

Hi Alex,

If you don't have anything between 5mm and 8mm I would be seriously considering a used 6mm TV Radian as it will get a lot more use than a 5mm eyepiece in an 8"/F10 SCT.

If you have your heart set on something at 5mm you could go with a 5mm TV Radian or a 5mm Vixen LVW in the 60 deg AFOV class, or spend a little more and get a 5mm Pentax XW. You can currently land a brand new 5mm Pentax XW at your doorstep for $AUS360 from Barry Gooley at KK in Japan. All 3 are very high quality eyepieces. I like the Radians a lot and in my detailed comparison between the 6mm DELOS and the 6mm Radian the Radian outpointed the DELOS in several criteria. The DELOS had slightly better throughput and contrast and was a fraction sharper on axis but in an F5 Newtonian the Radian had clearly better EOF performance, less scatter and less internal reflection. The 5mm Pentax XW is an outstanding eyepiece in every performance criteria.

Cheers,
John B

[mental4astro]

Ta lads.

Wavy, a mate I think has a 5mm ortho I could try. But yeah, eye relief is cornea scratching stuff.

Dunk, I will be attending SPSP. Taking your C8 or its bigger brother?

Matt 'k', the LVW keeps popping up, and the Radians sound promising. I hadn't thought of those. Have you tried the 5mm Radian in an SCT?

Matt 'T', here's something curious about the 10mm XW - I used it on Jupiter a few days ago in my C8, stunning image and ease to keep my eye on. But I then tried it on the Moon, an eye placement was impossible! Even when seated, the tiny normal pulse induced movement of one's head made it impossible to keep the image from blacking out. Yet I haven't experienced this with a Newtonian. There must be something about the focal plane of the SCT that the 10mm XW just doesn't like. It is a totally unusable eyepiece for the Moon with my C8, unlike anything I've ever used! :shrug: :question: :screwy: Absolutely stunning with Jupiter (really left me stunned how good the image was!), but unusable with the Moon, and not my first experience of the Moon with this scope/EP combo. I can try it with a barlow of ANY description, but I won't hold my breath. 'Barlow lenses' can drastically alter the way an eyepiece works, either good or totally crap. You never know and I could be surprised. I am seeing the XW line as very, very scope focal plane shape sensitive. Great eyepieces, but you NEED to match each to the right scope or they just don't behave.

[Camelopardalis]

As much as I can cram in :lol:

I found the eye placement to be fickle before I started using the wind-up eye guard, was a problem on the shorter focal lengths especially (the 2" ones seem fine without), but now no issues. Prefer it to the Delos with the twist lock that likes to unlock :shrug:

[Waxing_Gibbous]

If you have trouble with eye placement in wider angle EPs, I would suggest something other than Radians or XWs.
I'm not "dissing" the views they offer - the Pentaxes are especially fine -but I found them very fiddly when it came to placing my eye in exactly the right spot. Gave me backache for days! :-)
I had very good views with an Explore Scientific 6.7 82 in my f15 Mak and I didn't have to do much if any 'craning' to get a nice view. Although it was a bit much in anything other than perfect seeing, at f8 one should perform pretty well.
I'll evangelise here for a minute and strongly suggest either Brandon eyepieces (I have a 24mm and a 16mm) or Takahashi LEs (7.5mm).
Both give exceptionally sharp, flat views with excellent contrast. They have fairly narrow FOVs - about 45* - but boy, are they worth it.

Oh yeah - f15 does indeed rule!!

[mental4astro]

Thanks for your input, Peter.

Eye placement can be a problem for me with my constant to-and-fro if the viewing sweet spot is a narrow one. Really more a case of a pain in the neck when you need to always find that spot time-and-time-and-time-and-again. I find most ultrawide eyepieces fall in this category for me. But, I've also found that this also changes with the scope you are using. Scope design has so much to do with eyepiece performance in matching the two for optimal results. This is something Wavy opened my eyes to, and is the least spoken about and can make such a difference to one's wallet and satisfaction. If this was better understood and shared, it would open more options and wisely close others for the individual scope designs.

With this 10mm XW, it is only with the Moon while using my C8 that I have problems. Yet in my fast Newt's, it is magic and I have no problems with my to-and-fro.

This is why I am being very specific with asking for eyepieces to be coupled to an SCT. What works in a fast Newt may not work as well in an SCT, and vice versa.

[Kunama]

Hi Alex,
I used the Radian 5mm and the LVW5 in the Mewlon 210 DK (I haven't had an SCT since the 1980s), the LVW is quite a bit less demanding of eye placement and would be my choice of the two for your 'to & fro' sketching activities. I think the LVWs are excellent eyepieces, my favourites in any focal length.

After trying Nagler, Delos, Radian and some Pentax, I have gone the full circle and just yesterday bought a full set of brand new LVWs. Like PJH, I am not dissing the others, they are fine eyepieces, but the sheer comfort factor of the LVWs just suits my viewing.

I only tried 3 Tak LEs, but found the shorter ones did not have the eye relief I needed so sold them. I would however consider a pair of 24s for the binoviewers.