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Synta 7" (180) Mak owners - what's your binoviewer experience?

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#26 elwaine

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Posted 05 September 2019 - 04:46 AM

Your explanation of the issues is reasonable. How much of it applies here? I don't think that this setup was that far away from the stock path length, though. A good chunk of the needed ~100mm was gotten by the change from stock 2" mirror diagonal to a 1.25" prism. I'd have to measure their focal length difference to be certain, but I was surprised how few turns of the focus knob were required make up the difference with the BV. There's even more to be had by using a shorter visual back on the scope.

 

An easy way to normalize out the magnification difference caused by the configuration would be to put an extension tube on an eyepiece to match its path length with that of the BV. Then compare the two.

Excellent points!!! I was wondering about that. 

 

Ed, what do you think?



#27 Joe1950

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Posted 05 September 2019 - 09:23 AM

I've done some experimenting with binoviewing due to some of the issues.

 

I don't have a 180mm Mak, but do have a Bresser 127mm. I have used two different binoviewers on the Mak, a 6" F/6 DOB and a 100 and 80mm refractors.

 

Here is some of what I found, with help from Eddgie on the merging issue, that may be of use/interest to others. On some of the things, I have no idea why they act as they do. Anyway...

 

1. I have an Astromania binoviewer. It is the exact same as the Arcturus. I was having a lot of merging problems and couldn't merge stars at all. The smaller the object the harder it is to merge. I thought it was collimation/alignment of the binoviewer, but Eddgie told me the real issue and I was able to get them to work.

 

The problem with the Arcturus and other moderately priced binoviewers is the eyepiece holders. The way they are constructed getting the eyepieces centered and aligned is difficult.

 

First off, I use only eyepieces with no undercuts. The two Plossl 32mm EPs that came with the viewer and three other sets I have are Meade Series 4000 Plossls and none have undercuts. This helps.

 

The other and very important thing I did was to arrive at a way so as not have the eyepiece holders and their collets throw the centering and alignment off. One thing, so far worked for me.

 

When I put the eyepieces in the holder tubes I tighten the collets so that they just touch the eyepiece barrels. And that is, just touch. Tightening the collets was the problem with my binoviewer.

 

By just touching the eyepiece barrels, the collets center the eyepieces well enough but don't tilt them. The eyepieces essentially sit, by gravity, on the interior stop ring and are well aligned. I've been able to merge stars at all powers as well as everything else.

 

Having the eyepieces like this requires that the binoviewer itself is not tilted to a degree where the EPs will fall out or move. With an Alt-Az this is no problem. With an EQ mount the binoviewer should always be adjusted to be as vertical as possible. 

 

This has worked wonders for me for merging and I suspect it would for others having the problem also.

 

2. I have several nose piece Barlows I use. Two came with the binoviewer, a 2.88X and a 3X. Additionally, I took the front Barlow assembly off a 2X and 3X Shorty Meade Barlows, so I just had the lens with its cell. The 2x threads into the front silver nosepiece of the binoviewer. I had to modify the 3x by attaching it to an empty filter holder, and it too will thread into the silver nose piece.

 

Also, I have a 1.9X Burgess Barlow attachment and a 2X William Optics attachment.

 

All these will work with my refractors and the Mak. The two Meade Barlow's will work with my DOB, and there is an important reason for this.

 

All the Barlow nose pieces except for the Meade pieces, require the binoviewer to move inward a substantial distance to focus. This is normal and a problem with most Newtonians. There isn't enough in-focus travel to reach focus with Newts. There is enough for the refractors and the Mak.

 

But, using the Meade 2X and 3X pieces the Binoviewer/Barlow combination focus right about at the point where mono eyepieces do!

 

So in this configuration, the binoviewer works fine and focuses in the DOB. Also, the focus of the binoviewer is very close to the optimum spot of the Mak.

 

Why? I haven't any idea.

 

In all situations I don't notice any vignetting. I don't, however use any wide angle eyepieces, just the Plossls mentioned before. 

 

3. Finally, using these different nose piece Barlows works well giving great sharp images, high contrast and little scatter. I only view the planets and the moon. There is no good DSO observing where I live. Anyway, most who use binoviewers say, monoviewing is best for DSOs especially with a wide angle and premium eyepiece.

 

But, I've found that the stated magnification stamped on the nose-piece/Bralows is not what you get using them in a binoviewer. It seems the actual magnification is higher, significantly so with the 3X Meade. I don't know what each nose-piece Barlow gives, but I will be doing drift timing tests to find out.

 

Both Meade nose-piece Barlows seem to be significantly more magnification than stated, but all the Barlows are apparently more.

 

I have to say that not using a Barlow at all with the Mak or using the Burgess and William Optics nosepiece-Barlows, which do shift the focal point from the Mak's nominal position does not seem to have any negative effect on the quality of the view. And there is no visible vignetting.

 

These are just my observations with the binoviewer. everything was done, trial and error. At this point, binoviewing the moon and planets and double stars is superior in all instances over monovision. 

 

Thanks. Hope this is helpful.


Edited by Joe1950, 05 September 2019 - 09:24 AM.

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#28 elwaine

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Posted 05 September 2019 - 03:42 PM

Excellent info, Joe. Thank you for sharing!


Edited by elwaine, 05 September 2019 - 03:43 PM.

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#29 precaud

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Posted 05 September 2019 - 08:47 PM

Thanks for sharing your experience, Joe. And for affirming that the eyepiece holders are indeed the cause of the major problems with these things.

 

My priorities are at the opposite end of yours. I'm not really all that interested in BV's for lunar and planetary. I want them for DSO and wider-field views. Like binoculars, but with more mag and some aperture behind them. So having them perform well without barlow or OCS is primary to me.

 

I read with interest in another thread that someone was using their BV's with a C102 frac. I never thought of doing that, assuming that it would not give bright enough images for me. But maybe my 5 incher will.


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#30 Asbytec

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Posted 05 September 2019 - 10:03 PM

Hi Joe, 

 

"All the Barlow nose pieces except for the Meade pieces, require the binoviewer to move inward a substantial distance to focus. This is normal and a problem with most Newtonians. There isn't enough in-focus travel to reach focus with Newts. There is enough for the refractors and the Mak.

 

But, using the Meade 2X and 3X pieces the Binoviewer/Barlow combination focus right about at the point where mono eyepieces do!

 

So in this configuration, the binoviewer works fine and focuses in the DOB. Also, the focus of the binoviewer is very close to the optimum spot of the Mak."

 

Focus travel required was the crux of my concern above. If a lot of focus travel is required, we run the risk of vignetting on the baffles (unless you cut them to size smile.gif ). In my experience, MCT baffles are pretty tight. It's less about the field stop of wide fields, though there may be some vignetting, you'll have to tell me. But, a large amount of back focus can vignette in a moving mirror system. However, if the binos focus about where mono eyepieces do, then you should be fine. That was my question. Most Barlows I am aware of require some focus travel, inward focus in a Newt and back focus in a moving mirror system, in order to intercept the light path. The way I see it, once the Barlow captures the light path, it extends the light path up the binocular so the oculars and reach focus. I mean, that's how we focus with a Barlow, yea? 


Edited by Asbytec, 05 September 2019 - 10:05 PM.

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#31 Joe1950

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Posted 05 September 2019 - 11:33 PM

Thanks Larry, John and Norme!

 

It's all very odd to me, concerning how the different Barlows behave. The Meade Barlows are both the 'Shorty' types so that may have some influence on how they act, but I really don't know.

 

On the DOB, there was not enough in-focus for the majority of the Barlows, but the Meade 2X and 3X worked and the focus tube was right about where it usually is for mono eyepieces. I'm sure the magnification of these Barlows is more than 2X and 3X though, so I will have to do timing tests to see exactly where they land.

 

I'll do more testing when the weather clears and try to get better data. If I use the 32mm Plossl that came with the binoviewer in my 127 Mak and use the 2X Meade, thinking it is operating at about 3x in reality, that results in 178X, with a 32mm eyepiece!

 

Anyway it's strange.

 

Probably it would be best to get those glass path correction units Eddgie mentions, but I can't afford one at this time. I'm not sure how they work concerning the placement of the focal plane.

 

 

Right now I'm using the binovierer and finding that whatever I use as a Barlow, the view is not noticeably degraded for any issues. Even without a Barlow, I get a very nice, sharp and detailed look. All this with the moon and planets, with me.

 

I've used the binoviewer and different Barlows on a ETX-90. And I used the binowiewer on it without a Barlow. The view of Jupiter was outstanding in all cases. All better than monovision. The planet was bright appearing and contrast was especially good. I was surprised, frankly, how good it looked.

 

Still a work in progress to optimize things as best as possible. But, from my point of view, all the views with the binoviewer are an improvement.


Edited by Joe1950, 05 September 2019 - 11:34 PM.


#32 Joe1950

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Posted 06 September 2019 - 02:06 AM

I also recall someone (can’t recall who) telling me that to effect a given change in focal point, the main mirror moves very little. And, the reduction in performance, expressed in a change in wavelength accuracy, is also rather small.

 

So, in effect, moving the focal point 100mm would have a minor effect on image quality. Again I can’t recall where I heard it or how accurate it is.

 

Of course it doesn’t take vignetting into account.

 

The only thing I can go by is that with both the ETX-90 and the Bresser 127, the images at focus without a Barlow are not visibly degraded to any degree I can detect and are still significantly better than monovision... this on the moon, planets and double stars.



#33 Asbytec

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Posted 06 September 2019 - 02:48 AM

Joe, in my experience, the MCT mirror barely moves at all, it's hardly perceptible as I recall. I tore mine apart to do some measurements and I remember being stunned by how little it moves. Check yours someday. Nothing like the large movement of a Newt focuser. Yet, the effect on focus is easily seen. So, even with a tiny bit of movement between the mirrors, the affects are much larger as they are when focusing a Newt. I'm unclear on how this might result in vignetting, just have to test it by dropping a ruler in front of the meniscus and see where it obstructs a defocused star. If the ruler intrusion is well over the meniscus, we're losing aperture.

 

I believe for an SCT, maybe MCT too, the correction changes by about 1/24 wave over correction for each inch of back focus. I added as much back focus as I could muster to see if there is a noticeable degradation in the image. Degradation or improvement was not immediately apparent. We'd probably have to observe that way for a long time to notice it. For a SCT, if 1/6th under corrected, then 100mm of back focus should be perfect. Unfortunately, I don't believe it's that simple in a complex design with a lot going on. 


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#34 elwaine

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Posted 06 September 2019 - 03:40 AM

NI read with interest in another thread that someone was using their BV's with a C102 frac. I never thought of doing that, assuming that it would not give bright enough images for me. But maybe my 5 incher will.

 

That’s what I was getting at in a post I made earlier. Sky conditions play a major role in what we can see with any given set up. I used my A-P Traveler under skies that varied markedly with regards to levels of darkness. I used to think that New Hampshire skies were dark until I went to the Grand Canyon. I saw more through that 105mm aperture refractor in the National Parks out West than I could see under NH skies using a C8. Blew me away. 

 

Binoviewing does cut the light to each eye in half. But the ability to detect details is not halved because of the way the brain processes visual input. The loss is considerably less than 50%. That said, for DSOs, we will always see more with mono-vision than with Binoviewing. So as I originally tried to point out, one’s level of satisfaction with Binoviewing will depend on one’s intended targets, for a given telescope, binoviewer, and eps,  under specific sky conditions. Unfortunately, the only way to know if one wil be pleased with Binoviewing is to try it with one’s own setup under one’s own skies. 

 

 


Edited by elwaine, 06 September 2019 - 03:49 AM.

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#35 Joe1950

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Posted 06 September 2019 - 04:59 AM

Joe, in my experience, the MCT mirror barely moves at all, it's hardly perceptible as I recall. I tore mine apart to do some measurements and I remember being stunned by how little it moves. Check yours someday. Nothing like the large movement of a Newt focuser. Yet, the effect on focus is easily seen. So, even with a tiny bit of movement between the mirrors, the affects are much larger as they are when focusing a Newt. I'm unclear on how this might result in vignetting, just have to test it by dropping a ruler in front of the meniscus and see where it obstructs a defocused star. If the ruler intrusion is well over the meniscus, we're losing aperture.

 

I believe for an SCT, maybe MCT too, the correction changes by about 1/24 wave over correction for each inch of back focus. I added as much back focus as I could muster to see if there is a noticeable degradation in the image. Degradation or improvement was not immediately apparent. We'd probably have to observe that way for a long time to notice it. For a SCT, if 1/6th under corrected, then 100mm of back focus should be perfect. Unfortunately, I don't believe it's that simple in a complex design with a lot going on. 

Now I remember, Norme! You may have told me the info in a PM!

 

I’d think, from what I’ve seen with all configurations with Barlow’s and even without, those figures are valid or close. I really don’t see any loss of detail or contrast. In all cases, the binoviewer advantage over monoviewing remains.

 

Just to test, I think I’ll do some viewing without any Barlow in the binoviewer and check it at different magnifications. 

 

Thanks, Norme!


Edited by Joe1950, 06 September 2019 - 05:01 AM.

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#36 Joe1950

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Posted 06 September 2019 - 05:22 AM

That’s what I was getting at in a post I made earlier. Sky conditions play a major role in what we can see with any given set up. I used my A-P Traveler under skies that varied markedly with regards to levels of darkness. I used to think that New Hampshire skies were dark until I went to the Grand Canyon. I saw more through that 105mm aperture refractor in the National Parks out West than I could see under NH skies using a C8. Blew me away. 

 

Binoviewing does cut the light to each eye in half. But the ability to detect details is not halved because of the way the brain processes visual input. The loss is considerably less than 50%. That said, for DSOs, we will always see more with mono-vision than with Binoviewing. So as I originally tried to point out, one’s level of satisfaction with Binoviewing will depend on one’s intended targets, for a given telescope, binoviewer, and eps,  under specific sky conditions. Unfortunately, the only way to know if one wil be pleased with Binoviewing is to try it with one’s own setup under one’s own skies. 

 

If the targets are the moon and planets, along with brighter doubles, I’ve used the binoviewer on my 80mm scope in Bortel 8 conditions and it gave images that were plenty bright enough. 

 

It certainly doesn't appear to be 50% of the brightness. If you switch back and forth between mono and bino, you can see a brightness difference, but not enough to call the bino view dim. In fact, not being overly bright seems more comfortable to me in trying to pick out detail.

 

I really thought binoviewing with the ETX-90 would be difficult. You know the saying about 90mm Maks - They run out of light before running out of magnification. About a week ago I thought I’d give it a try. I had the ETX-90 and the binoviewer set up on a light weight tripod with slo-mo controls. By the time I got out, Jupiter was down to 15 degrees off the deck.

 

Everything was against it, but the view was anything but dim! And most surprising was the contrast between the main belts and lighter regions. I really did not expect to see what I did, and my conditions here are bad. I cannot see 3.3 magnitude Megrez in the bowl of Ursa Major, unaided.


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#37 elwaine

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Posted 06 September 2019 - 07:59 AM

I agree, Joe. The light loss with binoviewers isn't very noticeable. But when you swap out bino for mono, and do a direct comparison, it should be done at the same exit pupils. You can't just remove the binoviewer and use one of the eyepieces from the binoviewer for mono use, because in mono mode, there could be a difference in magnification using the same eyepiece, and hence a difference in exit pupils. 

 

As the OP stated, the Moon and Planets are a special case, and his interest lies in binoviewing DSOs with a 180mm Mak. I think it will work just fine... if his skies are dark enough. To some degree it will also depend on the size of the prisms in the binoviewer, and on the eps used. 

 

Trying before buying isn't always possible. But making wise purchases via the CN Classifieds, or on A-mart, is a great way to "rent" equipment for a while and try it out for one's self. I usually can re-sell good, used equipment for what I paid for them on the aftermarket. The "rental" fee equates to the shipping I have to pay for. Not a bad way to go to try something new.


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#38 Chuck Hards

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Posted 06 September 2019 - 08:50 AM

I have one of these Maks, the Orion branded version.  Got it used for $700 from the daughter of the original owner, her dad, who bought it new and only got to use it once before he passed-on.  I got it for Mars last year, but the dust storm never let me really put it through it's paces on that planet.  Configured for mono viewing, it puts up images on-par with my home-made 6" f/8 Newt of known high-quality, but at over twice the magnification with any given eyepiece.   I have not looked at it under DPAC yet.  I'm enjoying the views too much and don't want to ruin it (see my sig).

 

I own an older 1.25" binoviewer and half a dozen eyepiece pairs, but I can't recall ever trying it on the Mak.  I do use the Mak for DSO as well as solar system objects, it excels at the task if the object fits in the FOV.  Contrast is very good, which helps.   The field is certainly narrower than a shorter focal-length instrument but isn't as restricted as one would be led to believe from the focal length alone.

 

Now that the idea is planted in my brain, I'll give the binoviewer a try with this scope next time I take it out. I don't really use the binoviewer much so it tends to be forgotten about.  Which is odd because I use standard binoculars regularly, up to a Swift 20x80mm.   I sold my 25x100mm bino because it didn't do much for me that the Swift didn't, and was five times the mass.

 

Will report when I give the Mak & B.V. a try.


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#39 Joe1950

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Posted 06 September 2019 - 09:30 AM

Chuck, your signature quotes are spot on! I too have given up all testing and my scopes work far better. The only thing that counts is what I see at focus.



#40 elwaine

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Posted 06 September 2019 - 12:36 PM

Love your signature quotes, Chuck. But seeking perfection is one of mankind’s greatest attributes. — Just ask the guys in the refractor forum. lol.gif


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#41 Joe1950

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Posted 06 September 2019 - 01:16 PM

Larry, I own two nice, moderately priced refractors, but I stay out of the Takahashi er, refractor forum!



#42 precaud

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Posted 06 September 2019 - 01:28 PM

Chuck, your signature quotes are spot on! I too have given up all testing and my scopes work far better. The only thing that counts is what I see at focus.

Yes, but you'll notice he said "I have not looked at it under DPAC yet."

 

Which is to say; resistance is futile.  :)


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#43 Joe1950

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Posted 06 September 2019 - 04:17 PM

There is always that remaining urge to do so. I know that feeling all too well.



#44 Ptkacik

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Posted 07 September 2019 - 04:35 PM

FWIW, I use a WO binoviewer on a 180 Mak and find it works so well, it is my go to telescope. I have the Orion Mak and have adapted it to use a Meade Micro-Focuser plus a Meade 2" mirror diagonal. This just barely allows the 0.63 nose piece Barlow thingy to make higher power for planetary viewing. There is not much space between the nose piece and the mirror though but it does not touch.

Negatives? I bought a pair of Meade HD-60 eyepiece cases for more variety on power and found my fat nose doesn't allow my eyes to line up. So I stick to the 20mm WO eyepieces. Also the collimation of the eyepieces isn't perfect and works best when both are screwed down to the minimum focus. Maybe not good for you but works just fine in my setup. Additional collimation adjustments would be nice. Maybe like the little screw things on binoculars.

So in summary, I love the combination. I just need to get out more often.

Clear skies,
Peter
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