Binoviewer or wide FOV EP?

[spaceboy]

Hi All

Sat bored stiff a thought popped into my mind. If you had the choice between a good quality binoviewer (with say BST explorers or Xcel-lx ep's to keep cost down) or a good quality wide FOV EP which would you choose. The advantages of using two eyes over one is with out doubt more comfortable but could become incredibly expensive if your irritated by edge performance in faster scopes. A wide FOV EP allows for higher magnifications on the same objects in turn making for better views due to more detail and better contrast but after several hours of squinting through the lens can become a strain on often already tired eyes. I have read that you get a sense of almost 3D using a binoviewer but with extra travel on the light path there is a slight dulling to the image. No such problem with a single EP but even with the widest FOV I have never felt that immersed in the views to consider it 3 dimensional. Having never used a binoviewer I wondered what members thoughts were.

[Damo636]

I voted wide field eyepiece simply because I have never looked through a binoviewer and enjoy widefield ep's.

[fredster]

Went with binoviewers. I have a set of widefield eyepieces already. So would be nice to add a binoviewer to the set. Used other people's viewers and they are incredible. The eyes just relax, no floaters and the detail pops into view a lot easier than a single eyepiece.

[Odd Thomas]

Binoviewer every time.

[spaceboy]

I found this review interesting which for me sheds some light on the reason for a perceived 3D effect in binoviewers. http://www.cloudynights.com/item.php?item_id=1179

[sunshine185]

Without question, binoviewer. I used mine with a pair of 25mm skywatcher ep's, the type that come with all new sw Scopes, and the view of the moon was incredible. I urge anyone who has not looked through binoviewers to give them a try.

[sunshine185]

Furthermore, I had a x-cel lx as my planetary ep until I got the bv's, once I had looked at Jupiter and m42 through the bv's I never used the x-cel again and sold it on Ebay.

[spaceboy]

I have read that for some scopes a x1.6 or x2 barlow may be required to allow the eyepiece to focus. Stupid question I know but I take it this will effect the focal length of the scope and also the magnification of any given EP ??? While I see this has it's advantages in slowing the scope and helping to clear up any aberrations you might otherwise have suffered in a fast scope with cheaper EP's........ having to then stick to longer focal length EP's would this not effect the eye relief pushing it out ?? Also I assume exit pupil will also be a deciding factor to how long you can go or dose this also change due to the barlowing effect ??

[nightfisher]

I would choose widefield, simply because bino viewer never appealed to me.

good to see you are still posting nick, wondered if you had called it a do

[spaceboy]

good to see you are still posting nick, wondered if you had called it a do

Struggling with the new format TBH Jules. I'm a member on other astronomy sites but always found SGL the easiest to use. Not so the case now

[DirkSteele]

I have read that for some scopes a x1.6 or x2 barlow may be required to allow the eyepiece to focus. Stupid question I know but I take it this will effect the focal length of the scope and also the magnification of any given EP ??? While I see this has it's advantages in slowing the scope and helping to clear up any aberrations you might otherwise have suffered in a fast scope with cheaper EP's........ having to then stick to longer focal length EP's would this not effect the eye relief pushing it out ?? Also I assume exit pupil will also be a deciding factor to how long you can go or dose this also change due to the barlowing effect ??

For any instrument with fixed primary elements (i.e. a refractor front lens or a Newtonian primary mirror), the introduction of a binoviewer can present problems for bringing the image to focus. Regardless of non light-cone altering elements (such as a mirror diagonal in a refractor) that are placed between the scope and your eye, the focal plane (hence focal length of the telescope) remains unchanged. As such the telescope requires a good amount of back focus for the image to brought to focus. This problem does not really apply to compound telescopes such as SCTs which move the primary mirror to focus as they are constantly changing the focal length of the scope and hence the focal plane can be moved substantially beyond the rear of the scope.

A barlow lens will impact the exit pupil which is simply telescope aperture / magnification, regardless of whether that magnification comes from a short focal length EP or a longer one combined with a Barlow. Exit pupils below 0.5mm size can start to become problematic as you will start to become aware of eye-floaters which can interfere with the image.

With regards to Barlow lens and the impact on eye relief, it scales with the focal length of the eyepiece. This is a consequence of the simple negative lens element of a Barlow lens. With short focal length eyepieces the effect is negligible. However, on long focal length eyepieces the exit pupil position moves well beyond the original intended position, resulting in vignetting with many eyepieces. However, if you are prepared for the expense, the Televue Powermates which is a 4 element design completely negates this issue. I have a 2x Powermate and it is a fantastic piece of kit.

[spaceboy]

Thank you for your input Dirk.

In the case of a binoviewer and as far as I understand it, the barlow is only used to aid scopes where the focuser lacks the inward / outward travel to bring the ep's to focus. So using a PM is out of the running as it is only the barlowing element that is used in the 1.25" nose of the binoviewer. Plus the only 1.25" PM I'm aware of is the x2.5 which is going to require even longer FL ep's.

Just for the record if what I have read is true apparently eye floaters are not a problem with binoviewers as your brain cancels them out between using both eyes to view the object.

I'm still not sure how it effects eye relief in this particular situation ???? I think the problem is that to know if the binoviewer will work in a scope with out the need to barlow you would need to try it and with so many cloudy nights it could well be a while to find out. I'm not even sure where you would stand with returning them to a dealer as they do come supplied with a barlow and it is stated in the description that this may be required.????

[DirkSteele]

I may have misunderstood what you have written with regards the binoviewer nose being 1.25" and hence only the 2.5x Powermate would work, but my 2x Powermate came with a 2" to 1.25" adaptor.

Are you able to visit a telescope vendor to try out the binoviewer with your actual scope to see what the outcome is with your set up? This might be the final solution. Unless someone has your particular set up and can offer a view on performance with a binoviewer? What telescope do you have?

[spaceboy]

For the some what huge outlay having to buy 2 off of all eyepieces I was hoping to get my monies worth and use them in each of my scopes, C100ED, 150PDS & Explorer 200P. The more I think about it the less I'm sold on the idea though. The thought of changing ep's that aren't parfocal would be another issue I'm guessing ? needing to focus the bino's and then having to adjust the diopter.

[sunshine185]

What area are you in spaceboy? If you are near to me you can gladly come and test out my bv's

[spaceboy]

Thank you very much for your kind offer sunshine but I live some way away from London. I have also decided to finish of my wide FOV collection instead now. The more I thought about it the bigger the hurdles were getting in my mind. I'm certain the views are superb through binoviewers as I am a big fan of binoculars but the cost is doubled every time I want a different magnification then there is the added weight on the focuser, EP changes becoming a juggling act and a x1.6 barlowing effect has all ended up giving me cold feet on the idea. I'm sure one day I will get one but not until I have had chance to look through some for myself.