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Binoviewer Performance Questions


John

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5 hours ago, Gavster said:

I got mine from telescope express where they are currently 1200 euros. On astrobuysell they seem to be about £800 when they come up for sale. Not cheap I agree. Then you probably also want at least one gpc and preferably both the 1.25 and 2.6 which would add another £150.

Thanks Gavin,

Even buying used I'm going to need a budget of around £1K then plus some eyepiece pairs. 

I've got to prove to myself that binoviewing has a place in my astronomy hobby before I invest that sort of sum I feel. I'll be looking out for ways to try before I buy :icon_biggrin:

Thanks very much for all the feedback folks - much appreciated :icon_salut:

 

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52 minutes ago, John said:

Thanks Gavin,

Even buying used I'm going to need a budget of around £1K then plus some eyepiece pairs. 

I've got to prove to myself that binoviewing has a place in my astronomy hobby before I invest that sort of sum I feel. I'll be looking out for ways to try before I buy :icon_biggrin:

Thanks very much for all the feedback folks - much appreciated :icon_salut:

 

I picked up a pair of Mark IVs for a lot less than than John. If ever we get to meet up with a clear sky you can try them!

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2 hours ago, YKSE said:

Thanks for pointing out the mistake, it's Harry Siebert who did the analysis.

As it's done with ray trace, which many optical engineers should be able to verify quite easily, so I'd treat it as valid as being done by Mel until the opposite is proven.:wink:

I think that discussing the fully illuminated field issue is worthy of another thread. I use Bartels program quite a bit and the results can be, well, illuminating!:icon_biggrin: Calculating ones own newt's FIF is interesting and the effect of binoviewers that much more possibly.

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1 hour ago, jetstream said:

I think that discussing the fully illuminated field issue is worthy of another thread. I use Bartels program quite a bit and the results can be, well, illuminating!:icon_biggrin: Calculating ones own newt's FIF is interesting and the effect of binoviewers that much more possibly.

Go ahead Gerry, I'm listening :) 

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First off I like open minded discussion which can hopefully lead us to make good choices in equipment. If you run Bartels program or calculate the fully illuminated field out for newts (others) it becomes apparent that many if not all common reflectors have limited illumination. But will it really matter? Mel suggests that a drop to 70% is OK for visual near the edge.

Here is my 15" with an approx 10mm FIF


Off-Axis	Illum.	Light Loss
0.00 mm	100.0%	0.00 mag
2.00 mm	100.0%	0.00 mag
4.00 mm	100.0%	0.00 mag
6.00 mm	100.0%	0.00 mag
8.00 mm	100.0%	0.00 mag
10.0 mm	100.0%	0.00 mag
12.0 mm	99.16%	0.00 mag
14.0 mm	96.91%	0.03 mag
16.0 mm	94.13%	0.06 mag
18.0 mm	91.06%	0.10 mag
20.0 mm	87.82%	0.14 mag
22.0 mm	84.46%	0.18 mag
24.0 mm	81.03%	0.22 mag
26.0 mm	77.55%	0.27 mag

Max field for visual use with 68 deg eyepiece and 7mm exit pupil = 19.92 mm radius.

offset = -3.82 mm parallel to focal plane.

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On 2016-11-17 at 19:31, Stu said:

I was only teasing John! I have actual found my (collimated) pair to be pretty good for doubles.

I'm on my fifth pair by the way!

Not to want to confuse things further, but I found bv's disappointing on doubles. I really like looking at double stars Cyclops style, but in BVs they look (to me) rather "woolly" or soft and on pairs like Delta Cygni which are a good test for a 4", where the companion sits right on the first diffraction ring of the primary, I just couldn't distinguish the faint star with binoviewers. Could be my eyes (or BVs) though..

My personal opinion is that lunar, Jupiter and Saturn look great in binoviewers (I don't do solar), for all other objects I prefer Cyclops..YMMV as our US friends would say?.

Dave

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1 hour ago, F15Rules said:

but in BVs they look (to me) rather "woolly" or soft

I have to say that the Binotrons offer very sharp stars, doubles or not- I'm not a doubles observer really but the the ones I look at are VG in the 15"/Binos.

 

1 hour ago, Moonshane said:

I cannot get on with them for deep space stuff.

If we keep the "false exit pupil" thing in mind binos can offer great views on brighter DSO in my experience eventhough filter use is out. The binos/15" carve out the dust lane of NGC 3628 in the Leo triplet like no get out...

 

What I like about the Denkmeier Binotrons is that I was sold a complete system that I can use in any scope and just put them in and observe, Russ figured everything out for me including an extra spacer for the 15" which he made for me free. No doubt all other binos work but for me an engineered system was the way to go. All the talk about illumination etc is just for fun and interest, my binos just plain old work.

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The stakes are rising - Binotrons seem to cost a wee bit more than Baader Mk V's :rolleyes2:

Too many "Fifs and buts" about these things (including my own limited experience with lesser ones) for me to contemplate that sort of outlay I'm afraid, especially if I've now got some maths to do as well to calculate my FIF's :shocked:

Oh for the simple life ! :happy11:

Thanks for sharing your experiences though - very "illuminating" even if cheap BV's are not ! :smiley:

 

 

 

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