ep's for binoviewer

[davekelley]

I am buying a WO binoviewer used, without the 2 20mm ep's.  I believe that you can't exceed 66deg fov with one of these binoviewers.  I am torn between buying 2x15mm bst explorer ep's or one 16mm Nirvanah, since I have one Nirvanah already.  Is there any reason not to buy the 2nd Nirvanah even though the fov is 82 degs?  I almost only do planets and moon, m13, due to light pollution.   I also have a 7mm Nirvanah so should I also think about getting a 2nd one?  (assuming that I actually like the whole bino viewing thing).  Thanks everyone (skywatcher 127 mak, azgti wifi).

Dave

[banjaxed]

A lot depends on what type of telescope you are using because some scopes need a barlow to reach focus. There is a section on the CN forum dedicated to binoviewers which will tell you all you need to know.

[Timebandit]

 

 

Personally for binoviewing you can get away with half decent inexpensive plossl or Orthos. I use these to great effect in my frac and get really good views. I would keep a look out for some used plossl or Ortho in the for sale adds on SGL. I personally use some second hand BGO , but the baader classic Ortho would be just as good. Hope this helps

 

 

 

[davekelley]

45 minutes ago, Timebandit said:

 

 

Personally for binoviewing you can get away with half decent inexpensive plossl or Orthos. I use these to great effect in my frac and get really good views. I would keep a look out for some used plossl or Ortho in the for sale adds on SGL. I personally use some second hand BGO , but the baader classic Ortho would be just as good. Hope this helps

 

 

 

I was looking at 2 15mm bst starguiders at £41 each, or for £120, I could buy a 16mm Nirvanah and have 2 of them.  I do love plossls though, except for the 52 deg afov.  I am hoping to use in 127 mak, without barlow......thanks

 

[Floater]

I suggest you wait and see:

a) how you get on with binoviewing (some folks just don’t enjoy the experience)

b) how your setup works (Barlow, or not; glass path corrector, or not; is magnification/FOV suitable).

Knowing these things will help you choose any other EPs.

Hope you have fun. I enjoy BVs, especially for solar and lunar.

 

Edited March 17, 2020 by Floater

[Louis D]

It's not the apparent field of view that matters, it's the field stop that matters.  The max field stop supported on these binoviewers is around 22mm, give or take a millimeter.  I'm not sure what the field stop diameter is on the 16mm Nirvana, but it's 22mm for the TV 16mm NT5, so you should be okay.  This assumes you can fit your nose between the eyepieces.  I use a pair of 23mm Svbony/Vite 62 degree aspherics from ebay in my binoviewer most of the time.  They're pretty good at f/12 in my 127 Mak.  Keep in mind that you generally won't be able to look off axis without losing the view in at least one of the eyepieces, so on-axis sharpness out to about 50 degrees is the main thing to look for.  Also, look at the weight and width of the eyepieces.  I find 60 degree eyepieces look more like 65 to 70 degree eyepieces in a binoviewer.

[Stu]

I find that you observe differently when binoviewing vs cyclops observing. With a single widefield eyepiece, you tend to look around the field to take in what's there off axis. With binoviewers I tend to focus on axis, and just take in the rest with peripheral vision. This is largely because you need to keep you head and eyes aligned with the binoviewers in order to avoid losing one channel or the other. Looking around the field just doesn't work for me, so I prefer to pan the scope.

For this reason, I think Plossls and orthos work well provided they are not so short focal length that the eye relief is too short. I don't see too much point in paying for a wide field of view you don't really use properly, so 60 degrees is plenty I think. I use 25mm orthos in mine and Barlow them up to get the required mag.

[JTEC]

As Stu says ...  

I’m fortunate to own a Baader MkV bino and a TEC140. I’ve tried various eyepiece pairs in the combo, including a pair of 13mm Ethos (not mine!), a pair of 24mm 68degree Ex Sci (same numbers, if not quality, as 24mm Pans) and a pair of 17.5mm Morpheus. The 100degree Ethos pair was visually confusing. I kept one of the 24mm and one of the Morpheus because I like both eyepieces but didn’t like them that much in the bino - others will have had a different impression perhaps. Those are the eyepieces I no longer use or aspire to using for binoviewing though I like them for mono.

The ones I much prefer have narrower apparent fields of view. After lots of trialling and testing, the best performing eyepiece pairs in my combo are: 

20mm Long Perng Plössl 

18mm Tak LE

9 and 12.5 mm Tak orthos

11mm  Televue Plössl 

Also spare a thought for the pretty much unique 28mm Edmund RKEs, which work well Barlowed in the bino.

There’s a pattern here 🙂 I can’t be sure but I don’t think it’s just down to viewing tastes because many others say something similar.  A welcome advantage is that premium price eyepieces are not required.

I think it was Roland Christen who advised against using any eyepiece shorter than 10mm in a bino and advised using longer fls and Barlowing up.  FWIW, this is what I do, Barlowing with either the TV Powermate ahead of the prism or the Baader x1.7 (really closer to x 1.5 I think) GPC.

 

 

 

 

[Space Hopper]

Almost the same set up JTEC !!

24 Panoptics         * Can't fault. Perfect in every way. They set a benchmark.

19 Panoptics          

13 Naglers

These are my 3 main 'workhorse' pairs. A costly investment, but some were purchased used. Still cheaper though than premium 2" cyclops glass.

I tried all sorts, but i've found these pretty much tick all the boxes.

The 13s have eye relief thats a little on the tight side for my liking. They also have abnormally long barrels that don't sit flush in the Mk 5

I like the 82º fov at max power (196x) with the 2.6x gpc, especially using manual alt-az

I like my binoviewer eyepieces to be small and manageable. I've tried Delos, but they were way too big.

For the same reason i've never pushed the button on a Docter 12.5 (now Noblex) although i'd love to look through a pair.

 

 

[davekelley]

I am reading that if you don't use a barlow with the binoviewer you effectively lose aperture?  I was hoping to use it without barlow (my scope is already 1500mm f/l I don't want any more).  I know that the WO bino comes with a x1.3 barlow but I bought mine used and without the barlow.  Am I going to have to purchase a barlow or will this loss os aperture not matter on objects like the moon and planets?  I understand that eyepieces below 10mm won't work in binoviewers but x150 - 200 is as high as I can really go anyway before images start to breakdown.  Would I even be able to reach focus in the Mak without some sort of Barlow?  

[Ricochet]

3 hours ago, davekelley said:

I am reading that if you don't use a barlow with the binoviewer you effectively lose aperture? 

I don't think so. You might see some vignetting with long focal length eyepieces but that only dims the edge of field. 

3 hours ago, davekelley said:

Would I even be able to reach focus in the Mak without some sort of Barlow?

There is a lot of focuser travel in a Mak so you can probably focus natively, but doing so will move the primary a long way and increase spherical aberration. You will probably get better performance with a barlow and longer focal eyepieces than without and short eyepieces. 

[joe aguiar]

I just use 3 pairs of super plossls 

26, 17,10

Remember the binos add maybe 300 to 500 mm fl depending which one u have and if u have the Barlow that adds more plus then that turns my eps into 26 are really then 13,8.5,5 which is high enough 

Joejaguar 

[davekelley]

Thanks!  OMG these things add 300mm focal length!  Strictly for high power viewing.  I can't wait to try them out on the moon.  It's a very bad year for planets here in the UK!  We don't get to see them till early hours of the morning all the way through summer so I might have a long wait!

 

[Louis D]

I've used my Arcturus binoviewers with my 127 Mak natively, and I didn't notice any vignetting.  I've read that the focal length does increase somewhat, along with spherical aberration, but for casual viewing, I never noticed anything.  If I put my 3x (effective) barlow nosepiece on it, I'd be at 4500mm, so that would be a total non-starter.

As far as losing aperture, 127mm Maks have a measured 118mm of clear aperture due to the undersized meniscus corrector, so you're already down on aperture before you start moving the mirror, so don't fret it and just enjoy the views.

[davekelley]

I put one of my Nirvanah 16mm ep's into the binoviewer, just to test if I can get focus without the barlow and very easily can, not just focus but a very comfortable amount of eye relief and a really pleasing wide fov, which will be more pleasing when I've got a 2nd Nirvanah and I can use both eyes.  I am certainly going to purchase a 2nd Nirvanah.  The barrel of the ep is long and seems to sit a bit proud of the holder but it doesn't seem to be an issue.  I am wondering what the effective focal length/power is that I am working with?  The 127mak is 1500ml and I use a tak prism diagonal and I think the 16mm ep sits about 5mm or so proud of the holder.  Overall though so far, very exciting.  I will post back after I try it out properly with two eyes.  

Clear skies

Dave.

[Louis D]

38 minutes ago, davekelley said:

I put one of my Nirvanah 16mm ep's into the binoviewer, just to test if I can get focus without the barlow and very easily can, not just focus but a very comfortable amount of eye relief and a really pleasing wide fov, which will be more pleasing when I've got a 2nd Nirvanah and I can use both eyes.  I am certainly going to purchase a 2nd Nirvanah.  The barrel of the ep is long and seems to sit a bit proud of the holder but it doesn't seem to be an issue.  I am wondering what the effective focal length/power is that I am working with?  The 127mak is 1500ml and I use a tak prism diagonal and I think the 16mm ep sits about 5mm or so proud of the holder.  Overall though so far, very exciting.  I will post back after I try it out properly with two eyes.  

Clear skies

Dave.

You're probably operating up around 2000mm to 2200mm or so for focal length with the binoviewers in the path, or about 1.4x nominal.  You're also losing some clear aperture as well as adding some spherical aberration and increasing the percentage of central obstruction by diameter.

[davekelley]

OMG you make that sound really bad!  I haven't been able to test it out on the night sky I was just testing the ability to focus in the daytime.  I had a look through a 32mm plossl and I thought the Nirvanah was 100% nicer.....

 

 

[Louis D]

3 hours ago, davekelley said:

OMG you make that sound really bad!  I haven't been able to test it out on the night sky I was just testing the ability to focus in the daytime.  I had a look through a 32mm plossl and I thought the Nirvanah was 100% nicer.....

 

 

Don't worry about it.  I've done the same with my 127 Mak and the results look spectacular to the eye.  It's way better than operating at 3x with a Barlow element to reach focus which works out to 4500mm, unless you're trying to go for planetary views with 32mm Plossls (11mm equivalent), then it's fine.