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

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#1 precaud

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Posted 18 August 2019 - 03:39 PM

(MODS - PLEASE do not move this thread to the binoviewer forum, just because you think it is a so-called "better fit". I specifically want to hear from 180mm Mak owners, even ones who do not hang out in the BV forum.)

 

Context: I made a brief attempt to use binoviewers a few years ago (the WO ones), only to discover that my dobs would require significant modification, which I wasn't willing to do. So out they went (the bv's, not the dobs!).

 

Now I'm making another attempt, this time armed with a couple scopes that are more likely to be able to accomodate them. One of which is the SW 180 Mak. I got an Omegon BV (same as the TS one) from a CN member. I don't have a matched pair of eyepieces to use with it yet.

 

So while I get the basics in order, I'd like to hear from owners of the SkyWatcher / Orion / Celestron 180mm Maks who use (or used) this class of BV, and get a feel for what works, what doesn't, what you like, what you don't, etc.

 

I am particularly interested to know about viewing without an OCS/barlow (the math says that using a barlow with this scope locks you into very high-magnification territory...)

 

Thanks!

 



#2 GUS.K

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Posted 18 August 2019 - 04:42 PM

I have the SW 180 Mak and use the WO binoviewers without the 1.7x GPC. Works with no issues. I use many different pairs of eyepieces from different brands. Favourite is the nangler 16 T5 and TV 20mm plossls.
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#3 precaud

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Posted 18 August 2019 - 08:00 PM

I have the SW 180 Mak and use the WO binoviewers without the 1.7x GPC. Works with no issues. I use many different pairs of eyepieces from different brands. Favourite is the nangler 16 T5 and TV 20mm plossls.

 

Thanks Gus, that sounds great. Are you using anything special for the visual back and diagonal? Is 20mm the widest eyepieces you can use  before visible vignetting?



#4 GUS.K

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Posted 18 August 2019 - 10:52 PM

I notice vignetting on the 24 panoptics, but not on the 20 plossls. I use a 2 inch visual back and either s TV 2 inch diagonal or a Tak 1.25 inch prism diagonal.

#5 Asbytec

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Posted 18 August 2019 - 11:20 PM

One of my questions concerning MCTs and bino viewing is having adequate back focus without compromising on full aperture. The baffles tend to be tight. My older version barely gets full Illumination at the diagonal, forget back focus required. But, folks seem to be using them without problems.

Edited by Asbytec, 18 August 2019 - 11:22 PM.


#6 precaud

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Posted 20 August 2019 - 08:58 PM

So, no more 180 Mak BV users? Don't be shy...



#7 elwaine

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Posted 22 August 2019 - 08:25 AM

I’ve been thinking of getting a bInoviewer for my 180 MCT. A few years ago I had a 152mm TEC Mak and used a Denkmeier BV with a power switch. It worked OK when the power switch was in the 2x and 1x positions, but the Mak would not come into focus when the power switch was in the wide angle position. — Not sure if that helps you. 

 

With such an inherently narrow f.o.v. and small diameter baffle tube, I’m wondering if it even pays to get another premium BV that has large prisms. A William Optics BV might work just as well in a Mak. But that’s a question for the BV forum. 


Edited by elwaine, 22 August 2019 - 08:27 AM.


#8 precaud

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Posted 23 August 2019 - 07:10 AM

With such an inherently narrow f.o.v. and small diameter baffle tube, I’m wondering if it even pays to get another premium BV that has large prisms. A William Optics BV might work just as well in a Mak.

 

That was my thinking as well. That's why I wanted to hear from actual users, and see how they feel about it after using it. It looks like the useful range of eyepiece FL would be (depending on AFOV) 20-24mm on the low end, to maybe 12-15mm on the high end. Not sure that latter is realistic, though... the BV prisms would all have to be very good to support that...


Edited by precaud, 23 August 2019 - 07:12 AM.


#9 Asbytec

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Posted 23 August 2019 - 11:12 AM

In my experience, commercial MCTs are very tightly baffled. Mine was too tight. You need some amount of back focus to use binos, and I am sure the Mak can accommodate it. But, I presume not without vignetting to the point of reduced effective aperture. Still, I'd like to hear how others fare, as well. There are some users out there doing it. I suspect, by some studies of SCT back focus, SCTs are better equipped for binos. MCTs do tend to be something of a specialty scope for high power, narrow FOV lunar and planetary viewing. And they excel at it, IMO. A handful of folks use them for imaging, so...


Edited by Asbytec, 23 August 2019 - 11:16 AM.


#10 precaud

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Posted 23 August 2019 - 11:56 AM

Still, I'd like to hear how others fare, as well. There are some users out there doing it.

 

Yeah, we know they're out there...

 

I just got a pair of the 23mm Vite / Svbony Aspherics to play with, should be fine at F/15, so maybe I'll have a chance to try it out this weekend.


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#11 precaud

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Posted 27 August 2019 - 08:53 AM

Sunday nite was the "maiden voyage" for the Omegon BV with a pair of 23mm Aspherics in the SW180. It was only fitting to invite over a maiden for assistance and a second perspective.

 

The good news is, using a 1.25" prism diagonal, there was no problem at all coming to focus.

 

Unfortunately, in other respects, night 1 was a bust. We couldn't get the images to merge. No amount of fiddling helped bring together the two Saturns, one sitting a couple diameters away on top of the other. I punted and contemplated the letter I was going to write to the prior owner of the BV's.

 

Yesterday, it occured to me to examine the twist-locks more carefully. The collet is fairly narrow, and high in the barrel. I inserted one of the eyepieces, tightened the collet, and felt it hang on the edge of the blasted undercut. Tightening further lifted up one side of the eyepiece before it snugged into place, leaving a tipped eyepiece. That was the cause.

 

Why don't we boycott all eyepiece manufacturers until they get rid of these cursed things?

 

So I used some 0.20" wide tape I had laying around, and filled the undercuts. Last night I set up again, sans maiden, to check it out. The images merged.

 

Overall impressions:

: The pseudo-stereo effect is compelling, even with a dimmer image. It appears one can use less magnification to get the same perceived detail.

: There is some mild vignetting visible with the 23mm Aspherics. Not objectionable, but noticeable if you look for it. So this FL/AFOV combo represents the outer limit of useable low-magnification and widest FOV possible observing with this setup.

: Eye placement is very finicky.

: Eyepieces with less eye relief and/or good eyecups would help steady the head and let in less ambient light.

: Besides loss of brightness, detaill also suffers through the BVers. This was especially noticed on M22. Comparing mono vs bino with the same eyepiece showed the clear superiority of the monocular with the BV out of the optical chain. This would only be worse with shorter FL eyepieces.

 

This latter causes me to want to use the BV's at lower magnifications. But we're already at the lower limit with this scope.

 

So that's where it rests. Yes, it works. Yes, its interesting. But it's not an ideal combo. A scope with half the focal length would deliver a more usable range of magnifications. And bring along its own bag o' worms.


Edited by precaud, 27 August 2019 - 08:57 AM.

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#12 fcathell

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Posted 28 August 2019 - 04:59 PM

I just recently acquired the Arcturus binoviewer and have been using it in my 102, 127 and 150 Maks. It comes with 30mm eyepieces and 1.85X and  3X Barlows which will screw into the base after removing the standard eyepiece barrel.  All I can say is "fantastic"!  No issues at all and the views are stunning.  Even with the 3X Barlow (equivalent to a 10mm eyepiece) Saturn is unbelievable. I will need to add tape to my undercut barrel eyepieces that I plan to use in the binoviewer so they will seat properly into the viewer. I wish I could find some straight, smooth barrels that had compatible threads for the specific eyepieces I plan to ultimately use. 

 

Frank

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#13 Asbytec

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Posted 28 August 2019 - 09:32 PM

No vignetting? Nice. My fears may be unfounded.

One way to tell, if its possible to do so, is visually look for the secondary mirror through the eyepeice end of the binos. Without an eyepiece. If you can see the entire secondary on axis, then there is no vignetting. Check by moving your eye off axis. It may be the field lens(?) of the bino or Barlow sit well into the diagonal enough to avoid vignetting.

Another concern may be the amount of primary mirror travel required to reach focus. This may or may not change things. You can check this by dropping a ruler in front of the meniscus and seeing how far the ruler is protruding into the light path at the point it is seen in a defocused star. If the ruler is just inside the edge of the meniscus aperture, then you're fine.

Edited by Asbytec, 28 August 2019 - 09:34 PM.


#14 precaud

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Posted 28 August 2019 - 10:05 PM

OK, thanks, I'lll try that next time I set it up.

 

But, if the vignetting is not readily visible, does it matter?



#15 Asbytec

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Posted 29 August 2019 - 02:07 AM

No, unless you're losing aperture. Even then, maybe not. It may be the bino experience, itself, makes it unimportant.

Edited by Asbytec, 29 August 2019 - 02:07 AM.

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#16 elwaine

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Posted 29 August 2019 - 02:29 AM

Overall impressions:

: The pseudo-stereo effect is compelling, even with a dimmer image. It appears one can use less magnification to get the same perceived detail.

: There is some mild vignetting visible with the 23mm Aspherics. Not objectionable, but noticeable if you look for it. So this FL/AFOV combo represents the outer limit of useable low-magnification and widest FOV possible observing with this setup.

: Eye placement is very finicky.

: Eyepieces with less eye relief and/or good eyecups would help steady the head and let in less ambient light.

: Besides loss of brightness, detaill also suffers through the BVers. This was especially noticed on M22. Comparing mono vs bino with the same eyepiece showed the clear superiority of the monocular with the BV out of the optical chain. This would only be worse with shorter FL eyepieces.

 

This latter causes me to want to use the BV's at lower magnifications. But we're already at the lower limit with this scope.

 

So that's where it rests. Yes, it works. Yes, its interesting. But it's not an ideal combo. A scope with half the focal length would deliver a more usable range of magnifications. And bring along its own bag o' worms.

 

Interesting report. Thank you,

 

We need to keep in mind that your report is specific to one combination of BV, eyepieces, viewing conditions and choice of targets. That could explain why Cali and Frank are enamored with their BV experience using smaller aperture Maks,  while your experience seems rather luke warm. (BTW, that is not meant as a criticism in any respect.)

 

Years ago I used a Denkmeier BV with a power switch, Denkmeier 14mm eyepieces, a Zeiss prism diagonal with a 150mm Mak. Views of the Moon, Jupiter, and Saturn were outstanding... much more detailed than monoviewing with Ethos eyepieces. Looking at  star clusters and most nebulae from my backyard is an exercise in frustration with or without a BV.

 

I’ve read that the quality of the prism in BVs have a significant impact on performance: not only with regards to the f.o.v., but also with perceived contrast and visual details. So I’m starting to leave little hints for my CEO to pick up on... like internet ads for a new Baader Mark V Binoviewer and a pair of Noblex 12mm eyepieces. That way she’ll be real happy when I buy a pre-owned quality BV and a pair of Baader Mark IV 8-24mm zoom eyepieces. grin.gif


Edited by elwaine, 29 August 2019 - 02:32 AM.

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#17 precaud

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Posted 29 August 2019 - 08:19 AM

We need to keep in mind that your report is specific to one combination of BV, eyepieces, viewing conditions and choice of targets.

 

That's true for everything posted on this forum. As the duke in the Phantom Tollbooth said, "it goes without saying". Reminding others of it is a subtle way of minimizing the value of content or conclusions one doesn't agree with.

 

Looking at  star clusters and most nebulae from my backyard is an exercise in frustration with or without a BV.

 

Nebulae, I can understand; LP renders most of them undetectable without filtering. But star clusters? Pls explain.



#18 precaud

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Posted 29 August 2019 - 08:37 AM

. I wish I could find some straight, smooth barrels that had compatible threads for the specific eyepieces I plan to ultimately use. 

 

Yeah, I wish Scopestuff or Agena would address this need...



#19 fcathell

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Posted 29 August 2019 - 05:04 PM

I checked the Arcturus binoviewer and there is no pirmary vignetting when looking down either of the eyepiece holders on either my 102 or 127 Maks. Eye was centered in the opening (optical axis) and the full mirror was visable, but there is essentially no margin.  I also noticed that if you take a given eyepiece and focus it without the viewer then insert the viewer with the same eyepiece, it takes about 6 full turns of the focuser to bring it back in focus. Based on this I think they are actually using some form of relay lenses (??).

 

Frank


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#20 elwaine

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Posted 29 August 2019 - 06:39 PM

That's true for everything posted on this forum. As the duke in the Phantom Tollbooth said, "it goes without saying". Reminding others of it is a subtle way of minimizing the value of content or conclusions one doesn't agree with.

 

 

Nebulae, I can understand; LP renders most of them undetectable without filtering. But star clusters? Pls explain.

 

First of all, I did not disagree with your conclusions. In fact, as I stated, I found your report interesting, and I thanked you for it (because I learned from your experience, and isn’t that what this forum is about?). Pointing out that your experience could be related to your choice of equipment and targets is not intuitively obvious to those who have no binoviewing experience of their own. I mentioned it to be helpful. There was no hidden agenda in my post. 

 

Under markedly light polluted skies (red and white zones), even bright open star clusters lose there pizazz. Faint globular clusters, such as M13, appear to be nothing more that an ill defined, barely discernible patch of fuzz — even in a 7” Mak.  That was also true trying to see M13 and M3 in my former 4” Traveler. I was able to see a few individual stars in M13 when I used my 130mm refractor, but it lost its charm and fascinating features that stand out under dark skies.


Edited by elwaine, 29 August 2019 - 06:40 PM.


#21 denis0007dl

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Posted 03 September 2019 - 02:38 PM

Always wanted to try SW 180mm Mak vs đy 6" APO....
Never had opportunity, so far...

#22 precaud

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Posted 03 September 2019 - 08:36 PM

Always wanted to try SW 180mm Mak vs đy 6" APO....
Never had opportunity, so far...

 

Please do! And report back!



#23 denis0007dl

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Posted 04 September 2019 - 03:33 AM

Maybie one day.
Wondering how 180mm mak works with Pans 24mm with binoviewers.

#24 Eddgie

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Posted 04 September 2019 - 08:54 AM

There are three issues and one has been mentioned, but the others maybe not.

 

The first is the potential for aperture reduction and this hornet stings twice.  The first sting is the reduction itself, and the second is the fact that when the aperture is reduced, the remaining obstruction now becomes larger in terms of percentage.

 

To next is the increase in focal length.  This will give your eyepieces a much higher power than the simple numbers would suggest, meaning that if you did not account of this, you would have a smaller exit pupil than if you used a 23mm eyepiece in mono-mode.  So, not only does the image start dimmer, but it is at higher power.

 

The last is that in systems like MCTs and SCTs, the correction of the system is only perfect at one mirror spacing and this spacing is usually the one that is provided by the manufacturer using the supplied diagonal and visual back. In other words, if the manufacterer provides a 1.25" diagonal, then chances are that the system will give it's best performance with a 1.25" diagonal, and changing the mirror spacing to accommodate a longer visual back, a 2" diagonal, and an additional 100mm of light path means that in all likelyhood, the system was experiencing some amount of optical degradation.

 

Now I don't have a 180 MCT, so I have never measured any of these things on one, but this is typical of the design characteristics and my guess is that you had a reduced aperture, larger obstructed, optically degraded (spacing) system working at too high a power for the reduce exit pupil to provide a fair comparison.

 

I have seen this so many times. People use a scope that is badly degraded by the configuration and think that binoviewing is not all it is cracked up to be.  

 

To get the most out of binoviewers, the configuration has to be optimized. 

 

Sadly, that optimization in an MCT requires glass path correction, and by the time this is done, the powers, when using an MCTs, are far too high or general astronomy use, though they may be excellent for planetary observing. 


Edited by Eddgie, 04 September 2019 - 09:04 AM.

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#25 precaud

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Posted 04 September 2019 - 08:17 PM

I have seen this so many times. People use a scope that is badly degraded by the configuration and think that binoviewing is not all it is cracked up to be.  

 

To get the most out of binoviewers, the configuration has to be optimized. 

 

Sadly, that optimization in an MCT requires glass path correction, and by the time this is done, the powers, when using an MCTs, are far too high or general astronomy use, though they may be excellent for planetary observing. 

 

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.


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