which EP's for Binoviewers, advice please

[Chris]

Hi,

I struck gold today on the FLO clearence thread and was lucky enough to get in first on a pair of WO Binoviewers!. These were reduced considerably due to not having the original box or the WO wide field 20mm EP's. I therefore need to buy another EP to match one of the ones in my sig or buy a suitable pair, the only problem is I haven't got that much of a clue when it comes to EP's, I've not long caught the bug for them but I think the bug may become bad

I would really appreciate some advice on what characteristics I need to look out for when buying a pair of EP's for Binoviewers, at a guess this would include things like apparant FOV, lens design, size, eye relief, and focal length.

I plan on using the binoviewers with my f/6 200p Dob.

I reckon a can spend about 80-90 quid on a pair of EP's by selling one or two bits, or as said I could buy one to match my existing EP's such as the TV 15mm Plossl or Vixen NLV 12mm. I also have a ES Maxvision 20mm and a Skywatcher extra flat 19mm on there way so maybe another one of those?

What should I do??

Thanks

Chris

[Johnboy]

Hi,

I have the WO binoviewer. My advice is to make sure the eyepieces you buy are not to wide (in size), as the space between them side by side may not be wide enough for your nose. It sounds silly but can be a real problem if you can't get your eyes close enough to the eyepieces because your nose doesn't fit between them. I like the TMB's from Skys The Limit. http://www.skysthelimit.org.uk/telescope%20eyepieces.html

Hope this helps.

John

[Mark at Beaufort]

Chris your first decision is the scope that will be used with the binoviewers. You got to remember that the barlow will increase the magnification and my experience shows that it will be greater than the stated figure on the barlow.

I use the binoviewers on two of my scopes. The 180 Mak/Cass has a FL of 2700 and I don't need the barlow so I use the 25mm Plossls, 15mm Skywatcher wide and William Optics 12.5 planetary. Although I have the complete range of Ethos EPs these cheaper EPs provide excellent views on Planets and the Moon.

THe second scope is my 4" Astro Tech APO f6.95 frac. With the 1.6x barlow the view of the Sun with the 25mm Plossls is fantastic.

So my advice is initially buy EPs in the 20mm to 25mm range and then if that suits your scope maybe something in the 12mm to 15mm range. Don't buy large EPs like Hyperion or the Hyperion Zoom because your nose (unless its very small) won't fit between them.

Mark

[Chris]

Hi guys, thanks for the advice so far, so narrow EP's like the Plossl are the way to go then I have a 20mm Revelation Plossl, I could buy another one of those to begin with. alternatively I notice that FLO do Skywatcher Super Plossl's for 40 quid a pair which seems like good value as it would cost me 29 pounds for another Rev Plossl.

I'll be using My 200p f/6 with a focal length of 1200mm, would 20-25mm be a good allrounder focal length EP for this scope to start with? 20mm will give 60x and 96+ with the 1.6 barlow and 25mm will give 48x and 77x +.

EDIT: I'm leaning towards a pair of these between 17mm and 25mm, would the 25mm suffer from vignetting with the WO binoviewers 20mm clear aperture??

http://www.firstligh...-eyepieces.html

Thanks

Chris

[Chris]

2 x 25mm Skywatcher SP's ordered, also ordered a Telrad whilst I was at it

[Mark in Macc]

Good advice so far. I have the WO binos and have a pair of TV 25mm plossls, the 20 mm WO EPs that come with the binos and a pair of 15mm NLVs. The WO EPs are surprisingly good. The NLVs are the widest at 45 mm and I wouldn't buy anything wider. All of these have good eye relief, which I think is important with binos, as one of the reasons I have them is for comfort and ease of viewing. Some people do use BSTs, which should also be OK as they are narrower than the NLVs. Ultra wide EPs may vignette, depending on the diameter of the effective field stop vs the field stop of the binos. Plossls and 60 deg EPs should be OK at 25 mm or below. I wouldn't use an 82 deg EP in a binoviewer as I have to move my head to take in the view of my ES 82 30 mm and this isn't possible with binos. Good luck and enjoy! You'll never leave binoland now that you have arrived!

[Bender]

I would advise on a pair of 25mm (and maybe 20) TV plossl as well. Given the excellent QC of Televue it is no problem to by 2 Plossl independent second hand and be sure they will match. Plus they are light. I went through quite a few TV plossl pairs and they always matched.

Unfortunately i cant say the same of BGO's. Theid 3 pairs, one of them bought new especially for my binoviewer, and the field stops nover perfectly matched. Your tolerance might differ, i find i distracting and send them back.

[Chris]

Good advice so far. I have the WO binos and have a pair of TV 25mm plossls, the 20 mm WO EPs that come with the binos and a pair of 15mm NLVs. The WO EPs are surprisingly good. The NLVs are the widest at 45 mm and I wouldn't buy anything wider. All of these have good eye relief, which I think is important with binos, as one of the reasons I have them is for comfort and ease of viewing. Some people do use BSTs, which should also be OK as they are narrower than the NLVs. Ultra wide EPs may vignette, depending on the diameter of the effective field stop vs the field stop of the binos. Plossls and 60 deg EPs should be OK at 25 mm or below. I wouldn't use an 82 deg EP in a binoviewer as I have to move my head to take in the view of my ES 82 30 mm and this isn't possible with binos. Good luck and enjoy! You'll never leave binoland now that you have arrived!

I think you've hit on something with the BST's they taper down to the top and have good ER plus 60 degree FOV! I'll be interested to see how the 25mm Skywatcher SP's perform beings they are the budget choice and I think BST's or TV plossls are definately on the list for future pairs, Thanks

[Chris]

I would advise on a pair of 25mm (and maybe 20) TV plossl as well. Given the excellent QC of Televue it is no problem to by 2 Plossl independent second hand and be sure they will match. Plus they are light. I went through quite a few TV plossl pairs and they always matched.

Unfortunately i cant say the same of BGO's. Theid 3 pairs, one of them bought new especially for my binoviewer, and the field stops nover perfectly matched. Your tolerance might differ, i find i distracting and send them back.

I do like my 15mm TV plossl, I think I'll see how much of an issue any mismatching is for me when I try my 25mm SP's which I'm expecting to be mismatched as they are 20 pounds a pop. If it really bugs me I'll go down the same root as yourself, although I hope it doesn't bother me else things could get expensive!

I'm surprised that the BGO's don't match well considering there rep!

Thanks

Chris

[Mark in Macc]

I sold my 15mm TV plossl and went for the 15 mm NLVs mainly due to eye relief. The eye lens of the TV plossl is also quite small and I didn't find it comfortable to observe with. The NLVs are the exact opposite and are highly rated but expensive. I picked up a pair in the US but haven't really been able to test them in anger yet. The BSTs are also very comfortable to use and would be worth a punt. You might even be able to get Alan at Skysthelimit to loan you a pair. They offer legendary customer service.

[Mark in Macc]

I just remembered that Angusb1 on here uses a pair of 25mm BSTs in his binos. He commented to me that he gets some vignetting but nothing too serious and that he considers them to be awesome in binos. I strongly suspect that he is correct :-)

[Mark at Beaufort]

These are the EPs that I use -

http://www.green-witch.com/acatalog/Ultra_Wide_Range.html - 15mm small and give a good FOV no vignetting

http://www.green-witch.com/acatalog/LER_Eyepieces.html - 20mm gets criticism in some quarters but not too bad in the binoviwers

http://www.scopesnskies.com/prod/eyepieces/plossl-eyepieces/25mm-plossl-eyepiece.html - I have 3 Antares 25mm Plossls and they are all the same. Great in binos - no vignetting and I get fantastic views of the Sun with my Herschel Wedge

http://www.firstlightoptics.com/william-optics-eyepieces/william-optics-spl-eyepiece.html - fantastic, sharp and good contrast especially good on Saturn

This gives you an idea what I have just for the binoviewers. For DSOs on my Dod and 6" Newt I use my 8mm, 13mm and 21mm Ethos EPs.

Mark