Perhaps something around 60x, with wide field of view. I don't know anything about that Celestron EP. What are uou doing with this scope, DSOs, planetary?
From your 16 T5 down you have exit pupils of - 2.5, 1.7, 1.4, 1.0, 0.7, 0.6.
I don't think you can jamb another eyepiece in the middle of that lineup because you have got it all covered. Opinion is your best eyepiece should be twice your f/ratio. So 6.3 x 2 is 12.6, and you have that pretty well covered with either your 16 or 11 Naglers.
Your Celestron Plossl has a 52 degree AFOV. So you might consider buying a wide field eyepiece to replace or complement that. But that means going to a 2" eyepiece. A 41 Panoptic would be nice, giving 30x and 6.6mm exit pupil and 2.2 degree TFOV with your reducer in.
If you only want to use 1.25" eyepieces I would say you have already got a well covered lineup.
Depends on what you want to achieve, you've got a nice spread of quality eyepieces there already
You might want to try removing the reducer sometime for views with your 11 and 9 at least, if you're interested in planetary viewing. Unless you have one of those rare invisible reducers, you're introducing extra glass and with the exception of the rare "Made in Japan" models the reducers have somewhat of a reputation for not necessarily improving the overall image quality. I'm trying to be gentle, but what's going through my mind is that you're not doing your scope justice by using the reducer all the time
With it removed, and on a good night, the 9 will show you more than the 11. The Naglers can be lovely and sharp at the native focal length in the C8. Unless you're out in the desert with excellent seeing, you're not going to benefit much from more magnification than that, if at all.
For pushing the widest FOV, stick the reducer on and the 16T5 should do a lovely job, but you can go wider with 2" eyepieces as Allan says. I use a 40mm SWA for example, good for about 1.35 degrees. I haven't -yet - tried that one with the reducer, but I'd expect the light drop off to be noticeable...but might be still worth a laugh
Thanks all, this is very helpful. To answer a few follow up questions:
1. I do a mix of DSO and planetary work, but I'm a little more inclined these days to getting the best of my scope for DSOs, so that would be my principle focus.
I was thinking of replacing it, either with a 32mm Televue Plossl, or, more attractively (but more $$), a 24mm TV Panoptic (with a 3.8 mm exit pupil, though both will yield the same TVOF). My main hesitation for the Panoptic is, will it overall give more visual "bang for the buck" compared to the TV Plossl ($379 vs $175 at Bintel)?
3. I had thought long and hard about going to 2", but I'm not convinced that it's a good fit for the C8 because of baffle tube clearance (restricting my effective aperature from 8" to 6.8" due to the light cone path), and the risk of vignetting much beyond 1.5 degrees TFOV. I also don't like the weight
Dunk, I think it's time to do a few nights of experimentation with my f/6.3 corrector, in and out. Beyond making my C8 faster with wider FOV, it offers superb field flattening and edge correction. One of the reasons I don't take it out much (at all) is that it goes on before the visual back, so is a bit of a pain to swap. I guess I could have "in and out nights"
My other thoughts, beyond the Panoptic 24mm, were to either:
1) Squeeze in a T6 13mm EP, which would give me a 98x magnification at 50' TFOV, and 246x at 20' with the Powermate (on those nice occasions when the seeing allows).
or
2) Add a T6 7mm, for 183x and 27' TFOV. I doubt I'd ever Barlow it, though!
For planetary, definitely try removing it. It wasn't designed for that purpose, and I've heard stories where it generally flattens the field but you lose a little sharpness and contrast. IMO, throwing money down for a shorter focal length Nagler to use with the (cheap) reducer screwed on is throwing good money after bad Just take the reducer off and you get pretty much the same magnification from your 11mm. 2 minutes saves you nearly $400
For the majority of DSOs that will fit in your current setup, they'll also fit in the FOV without reducer (of course, there will be some exceptions). For the others, use the reducer, if that's what makes you happy
The C8 is not a wide field scope...but there's plenty of options for getting wide enough for most things without reducing aperture, contrast or sharpness. Look for a SCT diagonal, such as the GSO or Bintel one, it screws directly on the rear thread to keep the focal length under control.
The light drop off is an interesting subject, and in theory the 38mm baffle tube diameter should be more limiting than it appears in practice. I use an eyepiece with a 46mm field stop and I've not noticed a dramatic light fall off...just as wide a FOV as my scope can give. An SCT can show a little coma right out toward the edge but it's pretty minor. I don't recommend you go looking for it, as you can never unsee it afterwards
Another way of looking at it is that if you only ever use the 1.25" for wide, you are cutting out a large proportion of the light because 38mm baffle tube is larger diameter than 27
The Omni is an OK eyepiece...an upgrade to a TV plossl is going to be fairly subtle, and especially with the reducer you may not notice any difference.
The 24mm Panaoptic is a lovely eyepiece but not perfect. Have a read of this review and decide if it's for you. The Meade and ES equivalents can be found for a lot less money (about the same as the TV plossl). A 35 or 41mm Panoptic or 40mm Paragon is a better "wide" solution for a C8...IMO The Baader Hyperion Aspheric work well at f10 also and are less expensive, as are the ES 68 or Meade SWA equivalents (but they're a lot heavier than the Baader)
Regarding the weight, you can easily shuffle the scope up through the clamp a bit so it can still clear the base and balances the scope better too.
I avoid the faff mid-session through target selection and planning, by only taking it off/putting on once (if at all). The next few months for me will be heavily dominated by planetary and so I probably won't use it again until winter comes
But try it and see for yourself and please report back. Ideally choose the same object under comparable magnification with and without the reducer. 47 Tuc might be a good candidate although it's starting to get a bit low in the sky now.
Ultimately, if you're worried about width of field combined with image quality, you might be better off channeling the money into a short doublet refractor...a 100mm at f6 should fit just fine on the SE mount and will give you more than double the FOV you can get from a C8.
Btw, I'm not dissing the C8 at all...it's my favourite scope...I have two
Heh, I think Dunk, we've come back to the perennial conclusion "there is no perfect system/eyepiece" But you have convinced me to try my f/10 more often...
I just read an interesting essay by Al Nagler on what he calls the "Majesty Factor" of an eyepiece. Another parameter for the trade-off analysis!
Absolutely - everything is a compromise, it's just a question of satisfying what's important to you.
Personally, I do most of my observing at f/10, busting globs and such is so easy and comfortable...and then whip out the reducer for some of the more extended objects...it's just great to have one in your arsenal and have such a versatile scope having said that, I like to keep a small refractor close to hand for the super sized stuff even if it doesn't as much eye time. It has it's turn, Eta Carina, *MCs, sweeping the MW...winter is coming and having both minimises the compromise
As for Majesty factor....well, I guess they had to come up with something to justify the price tag of the Ethos family
Hi Barry,
Just a couple of comments. I added the GSO 2" diagonal to my CPC 800 scope- and it made a big difference straight away with much better star images than the included 1 1/4 Celestron diagonal, + it gives the option for 2" eyepieces.
I have the Televue 32 Plossl, and it is a very nice eyepiece, but not a quantum jump from the Celestron one you have already. I'm not sure it would be worth getting the 24 Panoptic given it is the same field anyway- but it certainly is a nice eyepiece.
If I were you I would consider upgrading the diagonal, and trying one of the wide-field 2" eyepieces of 32mm or greater fl. The ES 82-degree ones seem good value for money- and they sometimes come up for sale on this forum.
All the best,
Dean
The 24 Panny is a gem of an eyepiece if you are stuck with 1.25" barrels as I am for my portable setup. I find the wide field of view very immersive and a real pleasure to use - It's deservedly considered the Gold standard for its group (which does not mean it is the best in every circumstance, but a top performing all rounder).
Thanks for the suggestion Dean, but I already have a TeleVue Everbrite dielectric 1.25" diagonal - 99% transmission. It runs rings around the original aluminum Celestron one that came with the telescope. See comments above re: not wanting to go the 2" path.
Jonathan, cheers, I'm strongly considering the Panoptic 24 after some additional reading. Good to get an owner's opinion.
Hi,
I have the 24 mm Explore Scientific 68 degree.
I use this as extension to the Delos range I have and it is optically as I would expect a 24 Delos to be (no Delos above 17.3mm). I have the 17.3 mm and 10 mm Delos and with the ES I get in terms of sharpness and transmission comparable results in my two Taks. It has a very good price point too! Eye relieve is sufficient to use with glasses and the EP is very compact.
Barry, the 24 Pan is a great EP if you want to stick with the 1.25". It gives you the same true FOV as the 32 Plössl, but with some of those "majesty factor" components present, i.e. darker background due to smaller EP. I have both, the 32 for sheer exit pupil when I need it. Be aware that the 24 Pan will vignette in the 1.25 diag like the 32, the only remedy to that seems to be going 2" . I asked Don at Bintel whether that was specific to my star diagonal (WO dielectric), his response is below. I do not find it to be too much of a problem though.
Cheers Mirko
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Hi Mirko,
You would need to use a 2" Diagonal,
If you do a simple ray trace it will show that the 1.25" will vignette
regardless of brand.
I bought the 24 Pan for my wide field scope a while back and it is a great eyepiece, but the ES 68 24mm is a tad brighter in both the frac and my C8...and less than half the price.
But you'd be better off with the 35 Pan if you want wide
So, after all this I'm reminded of a line from the movie "Cosmos":
Quote:
S.R. Hadden: First rule in government spending: why build one when you can have two at twice the price?
... as in, I ended up buying BOTH the 24 mm Panoptic and the 13 mm Nagler. And I don't even work for the Govt!
I suspect they'll end up being two of my most used EPs, the Pan for the Max widescreen and the 13 mm because the 2.1 exit pupil is right in the sweet spot.
Thanks for the advice everyone. In a few years time, I might go the 2" route, especially if I get a case of aperture fever and add a larger 'scope to my collection!
I ended up canceling the 13 mm, and only got the 24 mm Panoptic. The 24, 16, 11 and 9 mm Nagler/Pan combo with a 2.5 powermate covers my bases nicely, I figure.
BTW Dunk, you said this:
Quote:
Ultimately, if you're worried about width of field combined with image quality, you might be better off channeling the money into a short doublet refractor...a 100mm at f6 should fit just fine on the SE mount and will give you more than double the FOV you can get from a C8.
Have you tried a rich field refractor on you C8 dovetail? I'm a little worried about the extra weight on my single arm 8SE, so it'd be nice to hear from someone who has experience with this. If you've done it, any models you can recommend?
Yeah the clamp is a standard Vixen-style dovetail, so as long as the frac on rings will clear the clamp shroud (plastic) then you're good to go. My Zenithstar has an attached foot whose end happens to be the same form, so it slots right in (although I usually use a lightweight manual alt az mount as the FOV is nearly 7 degrees!)
I just re-read your post... I mean you could use a wide field scope (a short one) instead if the C8 ota as they're readily switchable. The big brother dual fork CPC could have a piggy back scope, but with the 8SE your limit might be a super lightweight finder, 60mm or so.
Right, I hadn't thought about putting it on the SE mount and taking off the SCT OTA, but you're right, that would definitely be the way to do it if I want tracking/GOTO. What are the specs on your Zenithstar?
. I asked Don at Bintel whether that was specific to my star diagonal (WO dielectric), his response is below. I do not find it to be too much of a problem though. 
