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Baader Mark V vs Denkmeier Binotron binoviewer ?

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#26 Eddgie

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Posted 07 September 2013 - 11:09 AM

I love my mrk5s perfect fov in 24pans. Denki, I dislike the way in lower power arm you get vignetting plus you can see uneven brightness around one edge of the fov... caused by the power switch lens getting in the way! Really annoying


This is why when I talk about the Binotron or Denks, I always reference the D21s. These eyepecies have the largest field stop that you can use in the Denks without vignetting in low power.

Don't get me wrong, I really like the Binotrons and hope to buy a pair one day. I am bothered by the field illumination falloff, but I still feel like in the Dob, the ability to use all three modes of the powerwsitch make it a far better fit than in a large SCT where it is almost impossible to ever use the high power arm due to excessive magnificaiton.

I think for Dobs and Newts though, the value proposition is much better. The only real tradeoff with the Binotron/D21 is the illumination falloff in low power mode, but this may have something to do with having to have the OCS screwed out some to reachfocus. I was wondering if the probelm would be less if the OCS could be fully retracted on the OCS.

I would rather have a little intrusion of the OCS into the light cone in low power mode than have the light fall off so much. The intrusion at low power doesn't matter, and it is out of the way at medium and high power.

But I stick to what I said earlier. If you made me pick just one, it would be the Mark V because it works best with the EdgeHD 8" and I can get pretty close to the same low power in the Newt with the Mark Vs even with the 1.7x GPC because of the ability to run the Ultimas without meaningful off axis ray interception.

Just because I had not done it before, I checked the Mark V with the 1.7x GPC last night on Vega. I mean in normal focus, it i shard to see that the off axis rays are being affected in Mark V/1.7x combo.

I put in the 35mm Ultimas and defocused about 10 waves, and then slewed the pattern to the edge of the field.

About 70% out from the edge, I could see that there was some very slight slicing of the off axis rays. One edge of the pattern started to slightly flatten and I would estimate that at the edge of the field, the flattening would have accounted for about 15% to 20% of the pattern, and this is why it is hard to see in focus. The brighness (or darkness to be exact) of the edge of the field is not easy to see.

The Binotron though was more like 40% of the pattern being cut, and it is clear to see that the sky darkens considerably well before the field stop even of 20mm ES68s in the low power mode of the Denks.

Under a very dark sky, it might go unnoticed though, and it only seemeed to happen in the low power mode.

Again, I wonder is some of this was not caused by the need to have to extend the OCS so much to reach focus (over half an inch).

Now that I have a lower profile focuser, I would like to re-try. I am guessing I could now reach focus with the OCS fully retracted, which might make a big improvement.

It will only cost me $1250 to find out.

#27 Eddgie

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Posted 07 September 2013 - 12:39 PM

The low power arm is not really intended for eyepeices with this big a field stop.

The D21s are the best match for the aperture of the low power arm.

This is why when I write these notes I always say "using the D21s in the Binotron." This is the optimal eyepiece for low power function in the Binotron without vignetting.

If someone does not mind the vignetting then of course they can use lower power eyepieces with bigger field stops.

And if you use the Denk with 26mm Plossl you get about the same magnification in my dob as using the Mark V with the 35mm Ultima.

As it turns out, when you push things to the extreme ends, the Mark V actually holds up better than most people realize. The 1.7x GPC sounds like a big handicap, but for getting the lowest power field without vignetting, the big prisms of the Mark V allows you to use something like the 35mm Ultimas, and suddenly you are in the same game.

And the Baader GPC was designed as a coma corrector as well, and it is very effective. Even using Hyperions, the field is very sharp right to the edge in the 17 and 13s.

In fact, the performance is so good that I think I may have made an error rushing to the 24 ES eyepeices. I would like to try the 24 Hyperions with this setup. The 24mm Hyperions have a full 28mm field stop, so the true field would be almost as big as the Denks using the D21s.

Once again though, I love the powerswitch in a Dob or Newt. In that type of scope it is at its very best. The off axis illumination is not great with low power arm in (The Mark V with 1.7x GPC is better here too) but under darker skies this is harder to see and less of a bother, and the ability to so easily change powers is hard to dismiss.

And the Binotron is a first class unit optically and mechanically. There is a great deal to love there, and I can completely understand it when people say they love their Binotron.

#28 crazyqban

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Posted 07 September 2013 - 06:32 PM

I would like to try the Binotrons but I think that it will be difficult for me to leave the Mark Vs. I had adapted a Denk Power Switch to use with my Mark Vs and was put off by the amount of re-focusing required when I would change the Power Switch arms. I find it easier to to swap out the eyepieces since most of the ones I have are parfocal. The one thing that I did miss from the Power Switch was the low power setting but I am able to get the same low power with the Mark Vs by using a Siebert 1.3X Multi OCA. I have been using this setup for a few years now and I am very happy with it.

#29 Eddgie

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Posted 08 September 2013 - 09:11 AM

I did not like refocusing, but I do prefer it to changing eyepeices. At the dob, I generally have to get out of my chair and go get the eyepecies.

The Baader GPC though does provide a better off axis illumination than I was getting with the Binotron.

I think it is just a consequence of the long light path of the Binotron/Powerswtich. This configuration is maybe 25mm longer than the Mark V, and the OCS is a couple of millimeters less clear apeture (45 vs 47 for the Baader), and I think it is difficult to get all of the off axis ray bundle to make it to the field stop in such a long light path, and especially using smaller prisms.

And that is my struggle. I love my Mark Vs and they work well in all of my scopes.

But I love the powerswitch on the Binotron and the ability to easliy dial in multiple magnificaitons.

Even if I get the Binotron (and I want one), I don't know if I could bring myself to sell the Mark V.

And that now has become the issue. I have so much money invested in telescope stuff that somethign would have to go. I have enough money to buy a pair of binotrons right now out of pocket, but my ethic has been that this is a hobby, and these days, I try not to throw any more money into it.. If I want something new, I have told myself that I have to sell something to finance the new purchase.

And for now, I am not willing to do that. So the Binotron is on hold.

If the 12" dob works out, I will sell the C14 and either the LXD-750 mount (and move the 5" APO to the CGE) or the CGE.

But until I am ready to let something else go, the Binotron has to wait.

Maybe Santa will bring me a Binotron though... LOL.

#30 George9

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Posted 13 September 2013 - 03:21 PM

I think for a new binoviewer owner, the Denk Supersystem is a really great, high-quality way to get into it. I added a 1.25" OCS and an extra adaptor for a Lunt diagonal, and I can reach focus with all my scopes and all the scopes I visit (refractors, small to large reflectors, solar scopes, Herschel wedges, etc.). There is always some way to come to focus with the available parts. And, because of the PowerSwitch, you can start off with just one high-quality eyepiece pair (e.g., D21s). Add a 2" Barlow and you have 6 magnifications. And if you drop it, which is not uncommon in the first week, it is back like new in another week.

If I wanted to spend the money, long term I would end up with the Baader Mark V. But then I would be figuring out which OTAs I have to cut, which scopes have to be replaced, etc. Not that you couldn't just mimic the Denk's optical train, but you wouldn't do that because the point of getting the Baader is to produce the cleanest path without all the correction lens (like the low power reducer).

George

#31 SteveH

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Posted 16 October 2013 - 12:35 PM

Off topic a bit, but does anyone have experience with how these two compare to the TeleVue BinoVue?

#32 Eddgie

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Posted 16 October 2013 - 04:54 PM

The Televue Bino has several pluses and minuses.

Pros:

Very high quality

Fully compatiable with the Baader T2 system, so you can use components like the Baader T2 Prism which has a very short light path, allowing full aperture in SCTs and the Baader Coma corrector for Newts (which works nicely). It can also be fitted with a Quick Connect ring to make swapping it back and forth very easy. I have two Mark Vs and I have four telescopes I use them on, and all are equipped with T2 Prisms or the Newt GPC, so I can swap the binoviewers very easily.

And finally, they have a 27mm prism to allow completely unvignetted operation with 24m Pans or ES 24/68s. This is compared to the 26mm of the Denk IIs (28mm for the Mark Vs, and yes there are eyepieces out there with 28mm field stops, so this is indeed a real advantage for the Mark V).

The downside. A longer light path than the Maxbright or the Mark V. If you are using it in a refractor, the shorter the light path, the more likely you are to reach focus without requiring a GPC, or if you do need the GPC, the shorter the light path, the less GPC you may need (lower magnification).

Next, while the quality is excellent, I don't think they have coatings that are in the same league as the Binotron or Mark V. There is a lot of glass in a binoviewer and coatings can make a difference.

Finally, they do not have adjustable diopters. This does not sound like all that big a deal, but then again, this means that you use them by slipping one eyepiece out 4mm or 5mm, then focusing the scope with that one eyepiece. Then you have to slip the other eyepiece in and out of its holder to reach focus for the other eye.

This is not all that hard to do, but the Binotron and Mark V allow you to set the proper focus for each eye once, then not have to mess with it. With the Binovue, every time you change eyepeices, you have to do this dance.

My biggest objection to the Binovue is the diopters (or lack of).

I love the big prism and the T2 compatibility.

If using a refractor though, the Maxbright with a T2 Prism may reach focus without a GPC, where the Binovue will almost always require one.

And if the Maxbight only needs a 1.25x GPC, the Binovue might need 1.5x due to the longer light path.

So, you pay more for a bigger prism so you can use a lower power wide field, but at the end of the day, you might get as big a true field using the Maxbright with shorter focal length eyepeices because it might not need a GPC or might need a less powerful one.

For an SCT though, I would go with the Binovue over the Maxbright because of the ability to use 24mm Pans with no vignetting.

#33 junomike

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Posted 16 October 2013 - 06:07 PM

Also, The TV's allow for easy use of eyepieces whether under-cut or not. This is due to the "splines" that clamp down on the eyepiece.

(TV's on left, WO on right)

Mike

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#34 Eddgie

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Posted 16 October 2013 - 06:23 PM

In fact this could be a big Plus. I use the ES 68s and they do not sit square always in the Mark V. They want to tilt into the stupid taper on the barrel. I have to hold the tops down when I tighten the eyepiece clamps on the Mark V or they may not bottom and then they won't be always be at the right focus and then I have trouble merging.

I hate those tapered undercuts. May go to 24mm Pans just for that reason.

Anyway, yes, this is a big plus...

#35 junomike

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Posted 16 October 2013 - 06:29 PM

Ah, Eddgie, My 24mm Pans HAVE under-cuts as well as most I've seen for sale used? :question:

Even the New versions look to have tapered under-cuts?

Mike

#36 SteveH

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Posted 17 October 2013 - 06:20 AM

Guys,
thanks for the comments. Being I more of a refractor junkie (TV102 & TEC140) your comments in regards to use in refractors were most helpful.

Steve

#37 Eddgie

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Posted 17 October 2013 - 08:28 AM

If the Televue has a shoulder above the taper then it will still be better than the ES 24.

The ES 24 has a reduced diameter at the top of the barrel, and this allows it to tip over to the side in the Mark V.


If the BVs are not vertical with respect to the ground, the weight of the eyepiece can cause it to not lay flat in the eyeppiece holder of the BV.

The bottom will be not flush aginst the eyepeice stop of the BV, and when you tighten, it tends to lift the barrel of the EP and pull it away from the EP stop, and unevenely. One eyepiece might come to rest a half millimeter above the stop, while the other might come to rest 1mm above the stop.

Most eyepeices with undercuts have exactly that. The undercut is a grove in the barrel but there is still a top, full width ring. When you insert the eyepeice, it is still supported in the eyepeice holder by that top ring.

When I use Hyperions, which are heavier than the ES eyepeices, I have no problem. I push them in until they stop and when I tighten, they star in position.

But the ES eyepeices simply don't do this. They tilt into the undercut and don't stay put when you tighten.

I hate this about them.

If Televue now has the same issue then of course I would not want them anymore than the ES.

But I believe they have simply beveled the bottom edge fo the groove and still maintain a top, full diameter ring.

I am sorry if I have done a poor job of explaining it, but you have to trust me on this. The taper does not work well with the Mark V, especially in a dob where the BV is always leaned over at a prett steep angle.

I really like the performance of the ES eyepeices, but the tapered undercut makes for some fussing about that I don't have with eyepeices that have a fill diameter ring at the top of the barrel.

In fact, the Mark V really doesn't care about traditionsl undercuts. There is noting to snag them.

#38 RAKing

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Posted 17 October 2013 - 10:04 AM

The 24 Pans have a shoulder and drop into the Mark V with no issues. They were my favorite eyepieces with the binos. :)

Cheers,

Ron

#39 Eddgie

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Posted 17 October 2013 - 10:18 AM

Yes, the Mark V works great with traditional undercuts.

I know many hate undercuts, but they have saved my bacon many times.

I could do without then on 1.25" eyepieces, but not on 2".

I am sure that for most use though, the beveled style is fine, but I had trouble with this design in both the Maxbright bino (three screw model) and the Mark V.

They are excellent tough, and unless used prices for 24mm Pans fall, I will just stick with them.

Also, I hope to go to a Binotron for the dob, and if I do, using the 20mm ES with the slope won't matter because in a perfect world, I would not change eyepeices....

#40 Dex Wolfram

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Posted 15 December 2013 - 11:30 PM

Yes, the power switch can be removed. It unscrews from the bino body. The nose can then be threaded directly into the bino body.


Hey Eddgie, can you tell me what kind of threading this is? Need to know in advance!

#41 Eddgie

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Posted 16 December 2013 - 09:33 AM

I'm sorry, I don't know the tread pitch.

#42 Dex Wolfram

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Posted 16 December 2013 - 08:22 PM

Nor the diameter?

#43 Eddgie

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Posted 17 December 2013 - 08:51 AM

Neither.

But the end of the OCS 2" nose has the same diapeter and pitch.

At leset it did on the Denk II.

You could unscrew the powerswitch and screw the nose directly into the base of the binoviewer body.

Just so you know, I don't currently own either the Denk or the Binotron so I can't measure it for you.

Sorry.

But if you have a caliper and you have a thread guage, you can measure it on the 2" nose and have your answer.

#44 Dex Wolfram

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Posted 17 December 2013 - 11:23 AM

Don't own one (yet).

#45 EuropaWill

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Posted 18 October 2014 - 08:17 AM

Well, I think that it will be a much fairer test to compare the Denk to the WO with a bit more similar light path.

As for binoviewing the 80ED, I mean you can, but I don't know what the point would be. You are turning your wonderful wide field scope into a fairly narrow AFOV 70mm telescope (just figuring the dimming factor).
 

The best Saturn I've ever seen was through my AR5 masked down to 76mm though my lomo binoviewer and gso  20mm plossls @2.5x. I counted 7 distinct regions in the rings and will never forget the view. Yes i was operating at over f14.75. A well corrected 80mm scope can do amazingly well provided the conditions permit and your equipment optical train is well matched. 








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