binoviewers and dso's

[sunshine185]

Had a quick session tonight to check the accuracy of my levelling base and setting circle. I'm well chuffed, found m13, 57, and 92. Was using a WO 66 degree ep ( these are the only ep's I've got! ) m13 looked great even though I couldn't make out much detail. Put the 1.6x corrector in the ep and tried again, was a bit better, could make out lots of stars. Was about to pack up so I thought I would give the binoviewers a whirl. I wasn't expecting much, I know there's a loss of light on one side so I thought they would struggle with m13, how wrong I was, the gc just came alive, out was bristling with stars. It was right up there with m42, Saturn and Jupiter as one of the most amazing things I've ever seen.

[Monty]

Why is there a loss of light on one side?

[sunshine185]

A bv splits the single view into two and one side is slightly less bright than the other.

[Darkstar_1]

I was contermplating on getting a bino viewer, how noticable is the difference in brightness?, do they give a better view of DSO's? finally are they worth the outlay? thanks.

[sunshine185]

Apart from the 250px, they are the best thing I ever bought, m81,82 is VERY feint from my garden, the bv had trouble with that, but on m13 last night it was stunning. You won't notice the loss of brightness on planets, the moon etc.

[Peter Drew]

The light loss from the beamsplitter is somewhat mitigated by the brain recieving two signals rather than one plus one of noise. The brighter DSO's do exhibit a 3D effect with binoviewers, for lunar and planetary viewing they are unbeatable.

[brantuk]

I'm with Peter on this - bv's are awesome - 3D effect on planets - and deepsky star fields are totally immersive cos you feel like you're in the middle of them. For best effect get a pair of "wing eyeguards" to cut out light interference from the sides.

[sunshine185]

Was looking at getting some eye guards, only place I've seen them advertised is Sherwood's photo.

[jonstarrysky]

Just to chime in with the crowd about the virtues of binoviewing. I have two pairs and swear by it. You can stay at the eyepiece for longer, being comfortable and immersed in the view. By being able to concenrate better with 2 eyes means the loss in brightness by the beam being split is not really noticable, at least to me on most objects. I've seen plenty of feint DSOs in my binos.

I actually have 2 pairs including the quite expensive Denk II supersystem (top end kit handmade in USA) which I might sell if anyones keen on that. Yep, wing eyeguards rock too with binos as mentioned above. Cant remember where I got mine. Baader planetarium perhaps.

[Monty]

Wow I need to do some investigating and look at some prices.

[Stevie816]

Just to add my vote for Williams binoviewers, Rarely use anything else for Planets and DSO's, And also I would like to mention, I made my own eyeguards from an old cardboard tube. real easy and cheap. don't really need rubber as you can get an exact fit by trimming them. (really proud of myself might try something more ambitious next.)

Stevie816

[sunshine185]

Stevie, put a tutorial in the diy section, anything that saves me a few quid is worth the effort. When you say cardboard tube I presume you mean toilet roll tubes?

[Stevie816]

Hi Sunshine a tutorial sounds rather grand and would take longer than making the shrouds.

I just found a cardboard tube in the kitchen cupboard with some foil on it. It fitted over the ep,s perfectly. So then I just cut off two pieces about 4 cms long at an ange and slid them over the ep's. So I now have angled shrouds that with a bit of trimming fit my eyes perfectly.

What seperates me from mere DIY is I then painted them black ! .

Watch out for the autograph versions in exclusive stores soon.

They work really well I used to wear a hoody but my breath tended to fog up the ep's.

next week the cardboard Dob.

Regards

Steve

[L8-Nite]

A bv splits the single view into two and one side is slightly less bright than the other.

I don't have that issue with my binoviewer.

Does the same side remain slightly less bright if you switch the eyepieces from one side to the other ?

[sunshine185]

the cheaper bv split the light cone and I think one side gets a little less light than the other, it isn't noticeable on anything bright but on a very feint object that I can barely see with one eye,I can't see through the other, but one side is definitely dimmer than the other .

[sunshine185]

Here is a bit of technical jargon " "A perfect beam splitter coating would let 50% of light through for transmission and reflect 50% of the light. Each beamsplitter contains a 45 degree angle glass wall internally that passes 50% of the light through, and reflects 50% of the light 90 degrees. After all is processed with other optical components, it is these beams that exit the system. The right eyepiece receives the reflected portion of light and the left eyepiece receives the transmitted portion"

[Stevie816]

I often worried that with only one Ep I always use my right eye, and I got to wondering, What if my left eye was better !.

I couldn't easily change from one eye to the other so I tried the WO Binovierwers and WoW. Even the floaters in my eyes dissapear. I presume my brain can ignore them in stereo mode.

I have never noticed the slight disparity in light levels. But whenever I check against other EPs I quickly return to my Binoviewers.

Not sure about the science of it but even my novice friends prefer the Bino's

Stevie816

[Pappy Nick]

I vaguely remember somebody on this forum mentioning that sometimes people have problems obtaining focus with some BV/Scope combinations. Has anybody got any experience/comments regarding this ???

[sunshine185]

I can only speak from experience using bv on an 8" and 10" sw dobsonian, you can achieve enough " in focus" if you take apart the 1.25" holder and screw it together backward, so to speak, the holder then goes in the focusser backwards enabling the "in focus" you need. You need smaller eyepiece screws though, otherwise the holder won't fit in the focusser.

[cantab]

From what I've read it's a common problem. The binoviewer adds several inches of light path, and most Newtonian focusers and some on refractors can't move inwards that much to compensate. That's why binoviewers often have included Barlows, it moves the focal point outwards. Otherwise there are things like sunshine185 mentioned, or physically shortening the scope.

[Saleratus]

Some scopes have tubes with an extra section that can be taken out for binoviewing--like my APM 80/480. This is neat for some wide field applications, but usually I'm happy using a small barlow factor to move the focus back to where it needs to be for the binoviewer.

I think whether one eye is brighter than the other in a binoviewer is a function of the individual equipment. I have not noticed any brightness difference in mine.

[glowjet]

For those wanting eye guards, they are available from Telescope House

John.