Best eyepieces for binoviewers

[Prickly]

Evening all,

I am considering getting some binoviewers and was interested in feedback about what would be a good choice of eyepiece / barlow combinations for planetary observation (approx 250 - 350x mag) for my telescope. My scope is a 140mm f5.8 refractor 800mm focal length.

Some points I have gleamed from reading other points.

-Most binoviewers allow a max usable field of 60 degrees
-Mostly binoviewers need a barlow (around 1.6x seems common) to enable focus to be met
-Barlows used in front of the star diagonal (say a 2x barlow) may end up resulting in closer to a 3x barlow effect [maybe not the case with the powermates]
-The effect of using the barlow increases the eyerelief so that 20mm eye relief eyepieces may end up more like 30-40mm depending on barlow used I guess
- The preferred eyepiece range is 10-20mm and less than 10mm can be hard to fuse.
- I dont want to get too heavy with the diagonal, eyepieces and binoviewers which may cause focussing problems.

One thought has been a 8-24 zoom eyepiece with around 12-15mm eye relief (post barlow maybe around 24mm?). Allowing for the barlow effect it might be possible to have a nice range to dial in the right focal length.

Another though would be just a nice high quality fixed focal length eyepiece eg. 5mm ortho or similar with short eye relief that barlowed might increase to around 10-15mm. At present Im thinking this may be the way to go.

So over to everyone. What do you find works well. Appreciate feedback from those of you who have experimented with binoviewers/eyepiece/barlow combos. Im thinking the williams optics unit looks quite a good binoviewer.

Thanks in anticipation.

David

[PhilW]

David/Prickly,
My standard eyepiece set on the binoscope is a pair of 11mm type 6 Naglers. They are great: light, compact, wide field & adequate eye relief. In your scope that would only produce 72x magnification, but you could use a shorty barlow & still have a compact setup.

Phil

[Prickly]

Hi Phil,

Thanks - around the 11mm mark does sound pretty safe and you cant beat those naglers. I have a 4.7mm nagler type 1 which is great too. Was considering maybe another of these but maybe this could be too high powered? To some extent maybe the 82 degree field is a little wasted if the max is around 60 degrees.

Dont know whether you or others have found problems using shorter focal length eyepieces. I think I read that the 3-6mm zoom televue can be used with binoviewers but I do wonder how well this would work with the short focal length.

Cheers
David

[wavelandscott (Scott)]

While I do not have an over abundance of experience with binoviewing, I am quite fond of my Denkmier 14 mm and 21 mm. I have used them in my 8 inch dob and also in my ED80 to good effect.

They have ample eye relief and 68 degree FOV...there are nice eyepieces and I would highly recommend them (depending on your budget). I consider them to be in the same league as the other "premium" eyepieces I own (compared mono mode only) and I do own and use some Naglers (13 T6 and 16 T5) and Pentax XW (7 and 10 mm) along with an assortment of TV Plossls. I think they are that good.

I have also used TV plossls in my Denkmier Binoviewer which also work well until the eye relief gets a little tight in the shorter focal lengths. When I am going for max magnification I move to my 8 mm TMB Planetary eyepieces...while not as nice as the Denks in terms of overall build quality (my opinion), they are good value for money...no they are not Naglers but they are not priced like Naglers either.

Good Luck!

[gbeal]

I've deviated somewhat from those above, going budget, and longer. My Denk standards have really only seen the pair of old, and not too pretty Celestron 20mm Erfles. They work, and well. The 10" newt and 2" OCS only ups the mag by about 1.3x and I can also use the OCS in a configuration that gives 3x. If I need more, then I use the 5x Powermate.

[Prickly]

Hi,

Thanks for this. I understande the denkmeiers are pretty much top of the line binoviewers. Have you compared them to other binoviewers out there? How do you find them?

Interesting that a standard 20mm works so well with the 3x barlow. The WO binoviewer comes with 2x 20mm eyepieces so maybe barlowing / powermating is the way to go.

Have you ever tried lower power eyepieces in the binoviewers in comparison to the 20mm and barlow? If so did you have any problems merging the images. Guess Im a little sceptical / unclear of the basis for why there should be a problem fusing the images as I have read elsewhere.

Cheers.
David

[astropolak (Joe)]

Hi
I suppose the cost of Denk binoviewer needs to be kept down to be affordable and I can see many shortcomings in my Big Easy package. I think we spend too much time reading equipment reviews on US web sites.
I find the Denks quite usable but doubt they are a class ahead of binos like WO or Burges.
As mentioned in previous posts the Denk eyepieces are good, so are my 24mm Panoptics (if you ignore slight vignetting ) or my KK Erfles 20mm. You will find that you will spend a lot more time comfortably studying objects so it pays to get eyepieces with a decent eye relief.
I treat the Denks as a stepping stone to my future 14" bino telescope project. (just dreaming for now and reading all literature on the subject).

Personally if I had to do it again I would choose a cheaper brand of binoviewer as the Denk failed to live up to the promise. I am not saying it's a bad product I just do not think it's any better than the rest of them.

Joe

[Prickly]

Hi,

Thanks for that - interesting there doesnt seem to be too much difference between them. Interested to hear about what others think of the cheaper binoviewers. Nothing like practical experience looking through them.

The previous post on using cheaper 20mm eyepieces was along the same lines as my thinking about using some cheaper zoom eyepieces.

Cheers
David

[wavelandscott (Scott)]

Originally Posted by astropolak

Hi

Personally if I had to do it again I would choose a cheaper brand of binoviewer as the Denk failed to live up to the promise. I am not saying it's a bad product I just do not think it's any better than the rest of them.

Joe

While I have not tried any other binoviewers except the Denk Big Easy package, I am happy with their performance in my different scopes. Of course your mileage may vary

[gbeal]

While as I stated my eyepiece selection has been limited to the 20mm Erfles, I wonder how the zooms will work. The focal lengths will have to be exact of the images will suffer, surely?

[Prickly]

Yes, not sure how accurate the focal length are but a number have click stops. They can be adjusted too up and down marginally but that would be messy of course. The meades, televue, vixen and zhumell 8-24 all seem to share a similar design, although the vixen have an additional element and use lanthanum. I think I read somewhere that some of these might be made in Taiwan. Usually televue and vixen are pretty accurate in terms of QC.

Probably a burgess planetary or UO ortho might be safer and better quality wise at around the same price but the zooms get a pretty good rap, have good eye relief, reasonble weight and field and would be handy being able to go in and out to locate objects. So not the perfect eyepiece but might have a couple of handy features in practice - maybe. Have heard rotating zooms can be a pain though because of the helical eyepiece adjusters.

[casstony]

The Chinese binoviewers will do most of what the premium bino's will do, in a similar way that a decent plossl will do most of what a several hundred dollar eyepiece will do. However when pushed to the limit, as you will be doing by observing at 300x, you might run into eyestrain problems with the Chinese units since they are not as well collimated as the Denk's. An exception to this might be the University Optics unit since they are apparently re-collimated before being sold. Even then the prism surface accuracy is greater on the premium Denk's which may(?) be noticeable at high power.

I'd be interested to hear of any experiences with the Chinese bino's at high power - my skies don't allow me to go much over 100x most of the time.

[skies2clear]

I found Joes comments about his Denks interesting, and of course others may have different opinions. For some time I've considered upgrading from the WO BV'er. I have assumed the Denks are better units.

My opinion of the WO unit is it has given me taste of what binoviewing is about, for not too much money. To be really honest and try and put things into perspective for me and my viewing preferences/idiosynchrosies, they have been fun, but not a serious observing tool. They are Ok at lower powers, but when I want high contrast, high magnification and sharp views, I forget about them. I keep reading how great BV'ers are on planets, but with the WO unit, I have to say the performance at high powers is pretty ordinary. I have no trouble merging views, and am using very high quality ancillaries, but they just don't have the resolution at high powers, that mono viewing gives. Planets never really snap in compared with cyclops vision, and the image is noticeably dimmer. The loss of image brightness is a bigger problem though with DSO's.

I find the BV'er is good on the moon though, and gives comfortable views. This is the great advantage with my unit, in that 2 eyed viewing in general has less strain. So, I have been researching into better BV'ers lately, trying to see which ones have higher optical accuracy to satisfy my high power needs.

The supplied 20mm eyepiece pairs do a good job though, but not up to the better premium types. I have a pair of Pentax 14XW's and a pair of Tak LE 7.5's, that are superb in mono viewing, but as I've said, the BV'er holds things back at high powers. I also acquired a Seibert Multimag OCS, which improved things over the WO 1.6X OCA quite noticeably. I don't believe anything is wrong with my WO unit, just isn't up to the optical accuracy I would like.

If I stay around 100X they are fine, but when venturing into 300X or higher territory, it ain't pretty!

So for me, where to from here? I am reluctant to purchase any other afordable BV'er because I feel the improvement will be a waste of time. My shortlist now is Denk II's or the very expensive Baader MkV (I'll be saving for a long time it seems).

Cheers
Nick

[astropolak (Joe)]

Hmmmm
To be fair, the Denkmeier Big Easy does give me around 200 -250 mag with improved detail when compared to a single eyepiece. It is less sharp by a small margin compared to monocular viewing but the brain processes two eyes with ease and allows me to spend more time viewing with the bino thus allowing to discern more detail...
It may be a good time to clearly state what I do not like about the Denk Big Easy:
Lack of grip (ANY grip) on the body makes it easy to drop...
The OCS uses bright retaining rings for the lenses causing reflections especially in the focal reducer.
It claims the highest clear aperture yet vignettes with the Pan 24's
Bright stars or planets cause reflections from my eyes back into the bino and the bino combines the reflections - this may be a common problem with all binoviewers...
Most recently I have discovered that my new Denk is out of collimation without dropping it or even shaking it. It does not hold collimation and I do not know what is worse - not collimated properly from factory or loosing collimation in use. The unit is only few months old.
The eyepiece locking mechanism is crude and flimsy (but it works).
That is all for now...
I use it on 10" SCT with the 1 /1/4" OCS.

Joe

[casstony]

Originally Posted by astropolak

Most recently I have discovered that my new Denk is out of collimation without dropping it or even shaking it.
Joe

Joe, what indication is there that your unit is out of collimation?

[astropolak (Joe)]

Tony, and everyone else listening...
The out of collimation was picked by one of my learned colleagues at our latest star party. He stated that he could not merge the image. Now, I had disagreed with him at that time but took a note of it.
Few nights ago I set up for observing but I was more tired than usual from looking at computer screens all day long. Centered on a single star and guess what... two of them. It turns out that when I am fresh and not tired I can merge just about anything but when my eyes are more lazy than usual I can see that there is a problem, basically we can easily accommodate small horizontal shift but can not tolerate any vertical shift and this is what I've got...
There is no doubt that the bino is out of collimation as I saw it before in binoculars that I had to collimate myself so I know how to test for it..

Joe

[casstony]

Thanks Joe. If you get the time, could you try looking through the bino's at a calender with no eyepieces - try holding them at different distances and see if you can merge the image.

[Prickly]

The Denkmeier would sound the shot if it werent for the collimation issue. One think Im trying to get around is to avoid constantly blinking to even out the tear film with high power viewing and also being generally more relaxed using 2 eyes for viewing.

Nick, have you tried the WO unit without the screw-in barlow using instead a high quality barlow / powermate with your tak eyepieces. Be interested to hear what the outcome was if you have.

Pity to have to jump up to the higher price bracket viewers but perhaps this is not possible with the lower priced bino viewers.

[Satchmo]

Originally Posted by Prickly

Pity to have to jump up to the higher price bracket viewers but perhaps this is not possible with the lower priced bino viewers.

Interesting thread.

Theres no magic bullet with binoviewers. Your adding lots of glass and surfaces into the light path which all scatter and abberate the light as well as a long light path which only amplification solves. I've viewed through a $2000 Televue unit a number of times and still find them interesting but not a serious solution to full time binocular viewing. The brain is never really fooled enough into complete action by them IMHO.

I'm getting out a Baader Maxbright unit ( $259 USD )to play with on my 14" Mono-Newt: I'm particularly interested that they are end - user collimatable . For 1.25X amplification I need 92mm in travel so I'll use a larger secondary, shift the primary forward and two Bintel 2" extension tubes stacked into the focusser for Mono viewing.

Neverthless I am still collecting parts feverishly for my 14" F4.5 Bi-Newt, the binoviewer is for fun and education and will always go well for solar viewing on my 6" F8 refracter.
Have also ordered two 14.5" fast cooling Conical shape mirror blanks for another matched binocular optical set for sale.

[Prickly]

Hi Mark,

Keen to hear how the Baader Maxbrights go. I also noticed a new burgess optical binoviewer. This one has 24mm diameter barrel to avoid vignetting on 1.25 inch eyepieces 27mm prisms and 3 screws to centre the eyepeices. Also sells for about $300 US. Havent seen any reviews.

Interested to hear if anyone else has been able to use binoviewers sucessfully for detailed planetary viewing and if so what binoviewer / barlow/eyepiece combination.

The idea of planetary viewing with a binoviewer seems very attractive but its hard to see the point forking out the money if they images arent too great. Agree minimising optical surfaces would have to be a key factor. Some ortho eyepieces might go some way to achieving this and use of a high quality barlow?

Cheers
David