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Need Some Binoscope Advice, Ref Eyepieces


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Hi

Last autumn I purchased a binoscope, but have only now got round to using it. The initial experience has been, well. . . decidedly immersive, to put it mildly - all the more so since I'm so used to peering up at the cosmos through single eyepieces.* The scope itself (an APM 70mm SR binos) came with a pair of excellent 18mm eps. But I also have two Panoptic 24mm eps , which offering as they do a TFOV of four degrees at 17x are just the ticket for trawling through the heavens - the main reason for buying the scope in the first place. Nonetheless, I'd like to stretch things a bit in terms of magnification, and this is where my ignorance begins to make itself felt. Assuming that 35x~45x is a reasonable higher magnification range, given the scope's optics (also making due allowance for the UK's miserable climate) I had intended to repeat the Pan 24mm doubling act by purchasing a second ES 82 8.8mm ep to compliment the one l already own. But not having yet closed the deal, I've now had an attack of cold feet, insofar that I understand that ultra-wide field oculars like the ES 82s can be a problem with binoscopes. . . that one shouldn't go beyond the 60 to 65 degree mark for various optical reasons. I do respect such views, of course. All the same, I do wonder if this is true right across the board, and not just based on viewing preferences or personal "ophthalmological" issues. I would, therefore, like to know what the actual truth is, if such a thing exists in this regard. Thanks in advance.

 

* I do also own a pair of 12x36 Cannon stabilsed binoculars, but regard their astro use almost as a different kind of viewing experience.

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Despite having considerable experience of both building and using binoscopes I haven't had the opportunity to use very expensive wide angle eyepieces so my comments are confined to the use of a pair of Meade Super-wide (68*) 24.5mm FL and a pair of Super-Plossl (84*) 20mm FL, both pairs being 1.25" fit. My several binoscopes share these eyepieces and I get good results with them, it's shorter focus higher power eyepieces that give me problems as they make it harder to keep the eyes centred on the exit pupil.  I use the 84* eyepieces on a 300mm F3.5 reflecting binoscope giving 50x magnification.  The outer field images are poor but an advantage of binocular vision is that you can't easily pan your eyes round the view so you tend to concentrate on the good central area whilst still benefitting from the immersive effect of the wide angle.  What is true, is that the characteristics of different wide angle eyepieces do impact on their binoscope performance and can be an expensive experiment if you get it wrong.

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I got a pair of 8.8mm copies of the ES eyepiece. Sources tell me they are excellent copies from Opticstar, rather than cheapo knockoffs. Also the prices were very similar.

I tried them in my TS Optics 82mm Duplet giant bino's and the kidney beaning was horrendous, made them unusable.

I am currently using 2x 24mm APM UFF which are pretty much the same as the panoptics. I also have in the APM in 18mm and have a pair of 10mm on order.

I am waiting to test the bins with 10mm eyepieces before I consider upping the power anymore.

I am of the opinion they will get to circa x60 or maybe a little further before any false colour issues start to show but I am waiting to test with the 10mm before I take it further.

The main reason for this delay in going any further than 10mm (X47) is stability of view.

When using the bins with the 18mm recently outdoors in their first real use in a dark site the parallelogram was a little shaky with the bins on them.  Due at least in part to having too much counterweight on, I wait for a smaller one for a more even balance.

Instead of the extra wide field ES I might be tempted to consider the ES 62 degree version in 9mm or maybe the BST starguiders in 8mm with a 60 degree FOV. 

It is the latter of the two mentioned that I am thinking of as a possible final pair for the bins.

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The benefits of 82degree ep is lost a bit as you can’t easily swivel your eyes to see the whole field. I’ve replaced my 13m Nagler with Morpheus as they are just as immersive, but have more w yet relief and less distortion and I can see the whole field (which I couldn’t quite with the Naglers). I once looked through some (nominally) 90degree field of view Nikon WX, amazing, but i did note that I couldn’t see the edges when viewing- I could “see further” if i deliberately looked “round the corner” of the field.

I’ve used 7mm ep (cheap ultrawide) in my 70mm on the moon fine in the past, might replace them with 6.5mm Morpheus. 

As Peter notes centring your eyes at high powers can be fiddly and as in note above you can’t move your eyes. About too much or you lose the view in one eye… hence the move the bino, not your eyes suggestion.

 

peter

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Thanks for the instructive comments and advice.  Yes, I'm also considering going for the APM UFF 10mm eps, certainly as a default option. They're reasonably priced and with their 60* AFOV they seem a safer bet than some of the ultra-wide ones. 

Peter(W), about these Morpheus eyepieces of yours: are they the 76* wide field ones, by chance? I mention this because I seem to recall reading somewhere that their compact build lends them highly suitable for binoviewers (and possibly binoscopes too?) I've never looked into a Morpheus as yet, but I'm impressed by what people say about them. I also like their long eye-relief.  Thanks again.

PS. I'm bound to say that gazing up at the Pleiades the other night, both through the UFF 18mms and the Pans, was quite an experience. . .  :)

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My 13mm Naglers were lovely and compact, but there is some distortion, I am beginning to appreciate reading glasses and couldn’t quite see the whole of the 82degree field, so I moved over to Morpheus. They’re narrow enough for bino use, but much bigger than the Naglers, eye placement can be a little harder due to the longer eye relief.  They have a good following, the APM 12.5 ultrawide more so, but they’re a bit more expensive.

Peter

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23 hours ago, bomberbaz said:

I got a pair of 8.8mm copies of the ES eyepiece. Sources tell me they are excellent copies from Opticstar, rather than cheapo knockoffs. Also the prices were very similar.

I tried them in my TS Optics 82mm Duplet giant bino's and the kidney beaning was horrendous, made them unusable.

I am currently using 2x 24mm APM UFF which are pretty much the same as the panoptics. I also have in the APM in 18mm and have a pair of 10mm on order.

I am waiting to test the bins with 10mm eyepieces before I consider upping the power anymore.

I am of the opinion they will get to circa x60 or maybe a little further before any false colour issues start to show but I am waiting to test with the 10mm before I take it further.

The main reason for this delay in going any further than 10mm (X47) is stability of view.

When using the bins with the 18mm recently outdoors in their first real use in a dark site the parallelogram was a little shaky with the bins on them.  Due at least in part to having too much counterweight on, I wait for a smaller one for a more even balance.

Instead of the extra wide field ES I might be tempted to consider the ES 62 degree version in 9mm or maybe the BST starguiders in 8mm with a 60 degree FOV. 

It is the latter of the two mentioned that I am thinking of as a possible final pair for the bins.

 

44 minutes ago, Photonic Nights said:

Thanks for the instructive comments and advice.  Yes, I'm also considering going for the APM UFF 10mm eps, certainly as a default option. They're reasonably priced and with their 60* AFOV they seem a safer bet than some of the ultra-wide ones. 

I am thinking that the APM 10mm will be fine. I picked up my 1.35KG weight today and swapped it out for the 3.5kg that I previously used.  The difference in weight seems to have made a significant difference in stability so I will let you know how I get on with the 10mm eyepieces when they arrive as in how comfortable they are and performance.

I think though they will be fine in both of our respective bins. 

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Steve, thanks for your comments about the 10mm UFF eps. I await with interest your thoughts on them. By the way you don't think 10mm would be too much mag (40x) for my scope? Your TS 82mm rig does have some 27% more aperture than my 70mm one, after all. And the Morpheus 76* range does include a useful 12.5mm ep, but they're not cheap. On balance, I think it best to practice patience for now and use the time (weather permitting) to see what my still newish and largely untested binos is capable of delivering. . . even if it does mean sticking single higher power eps in it for occasional mono viewing. Talking of which, I made the elementary mistake of accidentally putting two different eps in the scope (ES 82* 8.8mm & Pan 68* 24mm). Even now the resulting eyestorm is hard to put into words and I don't think I'll ever see Orion's Belt in quite the same light again. Worse still it took a surprisingly long time before I saw the error of my ways. Live and learn. . .

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All these binoculars are pretty f5.6, so the same exit pupil and brightness. The bigger models show rain the e stars and have a more zoomed in view….. more light, but more spread out.

 

peter

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5 hours ago, Photonic Nights said:

Steve, thanks for your comments about the 10mm UFF eps. I await with interest your thoughts on them. By the way you don't think 10mm would be too much mag (40x) for my scope? Your TS 82mm rig does have some 27% more aperture than my 70mm one, after all. And the Morpheus 76* range does include a useful 12.5mm ep, but they're not cheap. On balance, I think it best to practice patience for now and use the time (weather permitting) to see what my still newish and largely untested binos is capable of delivering. . . even if it does mean sticking single higher power eps in it for occasional mono viewing. Talking of which, I made the elementary mistake of accidentally putting two different eps in the scope (ES 82* 8.8mm & Pan 68* 24mm). Even now the resulting eyestorm is hard to put into words and I don't think I'll ever see Orion's Belt in quite the same light again. Worse still it took a surprisingly long time before I saw the error of my ways. Live and learn. . .

I wouldn't have thought so no, As Peter says the exit pupil will be the same as mine at 1.8mm and only x40. The thing we are really aiming to avoid is chromatic aberrations and at F5.7 you should be fine at that magnification.

post-2597-14073834301145_thumb.jpg.7e19c836557db320ae5aca70d22b4984.jpg

I think more importantly is how do you intend mounting the bins for stability. As I said above mine are on a parallelogram and now it is better balanced it seems to be perfect.

Every time I see this chart it makes me wonder about the Startravel 120! Come to think of it, they also do a 150mm aperture one at F5. 

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Note I have the ED 70mm bins, so CA isn’t a concern, useful as I would get the semi-apo if I got a larger model. I had an ST120 and  used to observe the moon with a yellow filter, didn’t do much star observing, I sold it ages ago (sometimes wish I hadn’t).

Peter

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2 hours ago, PeterW said:

Note I have the ED 70mm bins, so CA isn’t a concern, useful as I would get the semi-apo if I got a larger model. I had an ST120 and  used to observe the moon with a yellow filter, didn’t do much star observing, I sold it ages ago (sometimes wish I hadn’t).

Peter

What kind of magnification do you get up to peter. The sales blurb ref my bins say up to x60 will be CA free although I would need 8mm to hit that. No plans to buy any just yet but just wondered what your own experience is?

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Yes, I too regard mounts to be of prime importance. No point having a great scope if the views are off the Richter scale! Having to do my astronomy out of town due to limited views and locally heavy light pollution, I own a (reasonably portable) Skytee 2 for my 4" refractor, a rock-steady tripod, certainly for my needs. It can even take without complaint my ES 6" Mak-Newt "Comet Hunter", though hoisting it to the zenith can at times be a bit of a fan dance (though well worth the effort). For the binos I have a CF Manfrotto 055, upon which sits a chunky APM Centre Mount. No instability issues to report there, that's for sure. That same tripod, together with a Scopetech Zero Mount (and a wonderful piece of kit that mount is too - I simply can't praise it enough) also does service for my trusty little ES "Essentials" 80mm triplet - a flight-friendly setup originally intended for a stargazing holiday down in La Palma, planned, would you believe, for summer 2020? Needless to say that adventure quickly hit the buffers, what with Covid and volcanic eruptions :(  

Steve, thanks for that chart. . . very interesting! By the way is there any difference in exit pupil size between standard telescopic viewing and looking through binoculars, say?

Gray

 

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Not sure what you mean as a difference buddy, the view through 70mm bins will certainly be a lot brighter than looking through a 70mm frac.

Think it was @PeterW who gave me a link to a CNights thread about how binoculars and scopes work as far as light gathering and brain perception. It was a little involved but an excellent read and to give you the gist here goes.

A 70mm set of bins give you the equivalent light gathering capacity to the brain (not eyes) of 70mm x1.41 max. This is what your brain perceives of the two images it receives from the bins although this is maximum, it can be as low as 1.2x depending on the individual.   In area size that is 1 element of 70mm bins gives 38.5 CMsq x 1.4 = 53.9 CMsq or a little higher than an 80mm scope (As a maximum).

My 82mm bins are a little under the equivalent of a 100mm scope. Again as a maximum.

Hope this helps.

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Hi Peter,

I can't agree more fully about the contrasty image using two eyes. Despite the near-full moon , despite too all the light-pollution in my back garden, even the Double Cluster, washed out as it was, nonetheless showed a surprising degree of contrast through the binos last night. (So relaxing as well, using two eyes instead of one - all the difference between watching and squinting, it seems to me). Incidentally there were no chromatic issues with the Moon to report either. Not a trace. All in all then, I can't wait to see what transpires at my local dark-sky location.

Just to make sure we're on the same page here, what I have is the 70/82mm equivalent of the 100mm centre mount shown in the link below, not the basic cheapo mount that came bundled with the scope. Personally I have absolutely no problems with it. It's smooth and predictable without being either over-tight or (horrors) sloppy. It tells me that the sweet spot in the adjustment lever has the right amount of forgive. It's worth point out too that the scope fully loaded is bang-on 4.5 kg. That and its length (39 cm) means it doesn't put the mount under too much stress. Financial considerations aside, I would like to have bought one of APM's bigger brothers; but as my sadly under-used 6" mak-newt makes clear, the trade-off between aperture and portability is always going to be a live issue for me. Hell, even my NP101 is starting to look a tad bloated! Hope this helps.

Gray 

https://astromart.com/classifieds/astromart-classifieds/mounts-alt-az/show/apm-center-mount-for-100-mm-apm-sa-and-apo-binoculars

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