bino question

[doug mc]

Working on a budget and needing advice on a bino unit. I have a c8 so reaching focus will be ok. Is the budget Andrews unit ok? I have floaters in my old eyes and have heard using binos reduces them. I understand that low power views with these units is limited by there smaller prisms. That is no problem as most of my viewing is on the moon and planets. Any comments please.

[glend]

I had the Andrews binos unit and it was fine with 20mm EPs, I also have old eyes with floaters. I didn't notice any floater issues with the binos. I sold my bino unit simply because I had too much stuff and it was not getting used much but there's nothing wrong with that unit.

[doug mc]

Floaters become a problem with high power views. Anyone used these binos at higer powers.

[dannat]

they should be fine but try not to push the power too much -you can get away with less mag. using binoviewers.
note your c8 will operate at more than 2000mm f/l with the binoviewer at prime focus, closer to 2120mm -what diagonal are you using with it? the 2" units will add a bit more to the focal length
to avoid prism cut off a 19mm ep is a good choice, maybe a 15mm giving ~140x (i would check cheap ep's first to see the binoviewer can merge at high magnifications -some cheaper units can be out a touch)

[Tinderboxsky]

I suffer floaters at powers above 100 when mono viewing. However, they completely disappear when using my binoviewer. The maximum power I use with the binoviewer is 151X - this is using 9mm eyepieces with 1.7 glass path corrector and 800mm focal length.
I use a Baadar Maxbright binoviewer, however the reasoning floaters disappear or are minimized is a function of the binoviewer concept rather than being attributable to a particular brand. So hopefully the same result would apply for me if I was using the Andrews' binoviewer instead of the Baadar Maxbright.
Have you read this review? It is excellent introduction to all of the issues and contains some excellent reference sources at the end.
http://www.iceinspace.com.au/42-717-0-0-1-0.html

Cheers

Steve.

[doug mc]

Thanks, i think i will go ahead with the Andrews binos and get a pair of 20mm plossls to experiment with. If all goes ahead i will post my findings here. I have both 2inch and 1.25 diagonals, also a few barlows.

[Starlite]

Hi Doug mc, I just bought a Williams binoviewer from Andrews last week complete with barlow and a pair of 20 mm, 66 fov for $399 +15 postage. Looking at the full moon last night, not much difference if any compared to my Denkmeiers.They worked with all my Skywatcher telescopes. 8" dob,102 f500, 102 f1000, 120 f1000, 127 mak, Lunt 60 ha solar scope.Still got to try on a 16" sw and 20" Obsession. I live just down the hill from you at Stone Creek Estate.PM me if you would like to try them. Cheers John.:)169737

169738 Just checked the 16" SW Dob and they work great, just ordered another set from Andrews today.

169739

169740

[Renato1]

How did it work out for you Doug?

I love using binoculars, but never warmed much to my binoviewers.
Regards,
Renato

[doug mc]

Going back to mono will most likely be a rarity for me now. Should have done this years ago :thumbsup:

[Renato1]

Interesting thanks. I may have to revisit my binoviewers.
Regards,
Renato

[doug mc]

For those who are interested and use a bino with a schmidt cas scope and are concerned about back focus issues. My bino is a Andrews unit, it works very well indeed. It has a light path of 100mm. I bought a William Optics 1.6x barlow nosepiece to use with it. I have two 1.25 inch diagonals. The standard Celestron prism and a Long Perng dielectric. The Celestron prism has a light path of 65mm, the dielectric 95mm. Using the 1.6 barlow screwed into the bino with the prism diagonal, you need an extra 59mm of infocus, or backfocus depending how you want to look at it. If you place the barlow in the front of that diagonal, it negates the light path of the bino almost spot on. So it places the focal plane of my C8 back to the standard f/10 position. By pushing the barlow further into the lightpath this way its power is increased to about 1.8x. The increased contrast on luna detail is much better for me using a bino than mono, much more noticeable than using more expensive eyepieces in mono. Please note I am 62 years young and have more floaters than when younger, but am sure those with more youth would see improvements as well.

[Starlite]

Thanks for the info Doug, I put the bino barlow in front of the diagonal on my 127 SW Mak and it really increases the mag of the binoviewer, I also tested the 127 SW Mak mono with a Televue 5mm with no barlow which gave 300x. 5mm into 1500= 300x.Amazingly the binoviewer had more mag looking at a microwave tower 6 km away and the view was crystal clear. Could home in to just the top of the tower.:thumbsup: thanks Doug, cheers John. The pic of the towers was taken with a camera,not with the scope.

[doug mc]

I could be wrong about the increase from 1.6x to 1.8x in my C8 by placing the barlow in the front of the diagonal instead of the bino. With the lens in the front of the diagonal it extends the focal plane further out. To compensate for this you need to back the mirror off to reach focus again. This changes the focal length of the scope by reducing it, thus negating the effect of increasing the focal length with the barlow placed in that position. These changes do not hapen in a fixed focal length scope like a standard refractor or newtonion. Will check to see if this works out when the sky clears. I am expecting that if I focus a star using a diagonal, then placing the 1.6x barlow in the front of it then the bino into the diagonal, there should be minimal refocusing needed. The overall effect amplification of this setup should still be close to 1.6x.

[Starlite]

My Williams bino works in my Lunt 60 solar scope only if I swap barlows. I have to use the barlow out of my Orion bino which is physically shorter.I need about 3mm of forward travel with the Williams to get focus.Just swap barlows and I have 5mm to play with.:)