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can I use a binoviewer with my reflectors?

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#1 observing1

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Posted 16 October 2013 - 02:12 PM

I have the orion skyquest 4.5 and 8, will the binoviewer work with them?

I was reading about the Celestron Stereo binocular viewer from Amazom. It says it doesn't work well with reflectors, only refractors and SCTs. Why is this?

#2 REC

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Posted 16 October 2013 - 02:42 PM

You are gong to need a barlow of some type to get it to focus. Best way I know how to do it would be the Baader Maxbright BV system...about $350 area.

Worth doing in the 8" Dob. The views of the moon are excellent!

Good Luck!

#3 Eddgie

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Posted 16 October 2013 - 04:29 PM

For a reflector, you really need the Baader 1.7x Newtonian GPC. The standard GPCs may not allow reaching focus...

#4 Eddgie

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Posted 16 October 2013 - 04:38 PM

You can use a binoviewer, but most likely not the common inexpensive ones unless you use a Barlow lens.

The reason is that the light has to travel about 110mm inside the binoviewer before it gets to the field stop of the eyepiece.

There really isn't a Newt or Dob made that will allow you to rack in the focuser 4.5" so this is why a regular binoviewer won't work.

The 1.6 GPC that comes with these is really there for refractors because most refractors have a lot more focuser travel, and the 1.6 barlow often (but not always) gives just enough light path savings to allow many refractor to reach focus.

There are three things you can do.

The first is to modify the telescope by moving the mirror forward about 4 inches, but then you also need to make the secondary mirror a bit bigger so the light cone does not miss the outside edge.

Second option is to go to a Denkmeier system This uses an OCS that goes inside the focuser system but you can also get a powerswitch that allows you to change magnification easily.

When you factor in that you can do most of your observing with a single pair of eyepieces (rather than buy multiple pairs) the value proposition is actually very good.

The last option is the Baader Maxbright, Televue Binovue, or Mark V, used with the Baader 1.7x GPC which is also a coma corrector. The Maxbright is a fraction of the cost of the Mark V and half the cost of the televue, but it only works with shorter focal length widefield eyepieces like the 19mm Pans or the 20mm ES eyepeices.


This is why the Denkmeier system is a pretty good value. You can get low, medium, and high powers with one pair of eyepeices, and while the costs seems high, it really isn't that bad vs buying the Maxbright with a 1.7GPC and you get lower powers too.

#5 Sarkikos

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Posted 16 October 2013 - 09:02 PM

All a Newt needs to come to focus for binoviewing is an OCS or Barlow. I do this for my 10" f/4.8 and 8" f/5.9 Dobs with a simple, old-school Burgess Binoviewer and a 1.9x OCS or a Barlow or a Barlow lens cell. You don't need a fancy new binoviewer or a special OCS. Any old binoviewer should work as long as it's used with an OCS or Barlow.

Of course, a Baader Mark V or Denkmeier Binotron would be very nice with a reflector. I'm thinking about getting one of those two myself. But it's not necessary.

Mike

#6 dvb

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Posted 16 October 2013 - 10:59 PM

You might want to check out Siebert - I have a zero mag OCS from him that can be adjusted for refractor or reflector.

#7 Eddgie

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Posted 17 October 2013 - 08:31 AM

I have a zero mag OCS from them and could not get it to work with low power wide field eyepeices without some pretty severel vignetting.

Tried and tried, but gave up.

Maybe they would be OK with small apeture binos, but simply unusable with the Mark V and 24mm ES eyepeices.

#8 Sarkikos

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Posted 17 October 2013 - 08:42 AM

I doubt very much if a zero mag OCS - or native magnification - could work with any binoviewer in a Newt/Dob without incurring some problems: vignetting, over-sized secondary (with loss of contrast), instability in primary cell collimation due to raising screws. If these problems don't bother the observer, then go for it. For myself, I still think that in some cases monoviewing is better.

Mike

#9 SkyGibbon

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Posted 22 October 2013 - 05:18 PM

I have an 10" classic dob and my WO binoviewers work fine with the 1.6" corrector, but I have to put it farther down the drawtube than screwing it directly to the nosepiece. I use an old barlow barrel with gender changer. Screw corrector to one end, then screw the other end directly onto the nosepiece. Works good, with just a tad bit of mag.






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