762 replies to this topic

[jrazz]

I've been playing with folding down the eyecups before committing to surgery 

 

The only problem with that is that the original ocular covers don't fit. So that's why there's 3D printing!

(seriously, making stuff at home is so fun - directed at someone who in in the process of building a 3D printer  )

 

 

Not particularly relevant to the team (even though it's on my 20x65) but I thought it was relevant to the conversation.

 

 

 

 

p.s. Glow in the dark filament so you can find it after you drop it.... I'm sure none have you have ever dropped these covers in the dark though...

Edited by jrazz, 10 June 2022 - 05:03 PM.

[Mark Y.]

MT4....You probably missed your calling,because you should have been a vascular surgeon.

[Fiske]

The only problem with that is that the original ocular covers don't fit. So that's why there's 3D printing!

(seriously, making stuff at home is so fun - directed at someone who in in the process of building a 3D printer  )

  

 

[Fiske]

Okay optical theory geniuses, what limiting magnitude advantage should a 15x70 binocular theoretically have over a 15x56 instrument?

 

Edited by Fiske, 10 June 2022 - 09:58 PM.

[Rich V.]

Fourteen millimeters?    

[jrazz]

So this is from something I found out trying to do optical math (which I'm not qualified for)

 

I found that at a reasonably dark site the difference in limiting magnitude between the 15x70 Ultra and the Maven 15x56 is only about 0.1 or 0.2. To me it looks like when calculating LM the magnification dominates while the aperture is far less important. So I'm assuming that while the view is brighter the difference is actually not that great. 

 

 

Point source optics is weird.

[Rich V.]

Seriously, I'd say less than 0.1 magnitudes between 56mm and 70mm.

 

You say you see a noticeable difference in star brightness between 10x42s and 10x50s which is a bit less than the ratio between 56-70mm but close; a factor of 1.42x vs 1.56x in exit pupil area.

 

Rich

[Fiske]

Thank you Jordan and Rich! 

 

I am still a little skeptical the difference is so small. 

 

Here is an observation report I did in Team 10x responding to the assertion that one could not see more in a 10x50mm binocular versus a 10x25mm binocular, which some of you may recall.  And here is a subsequent post where I estimated the limiting magnitude difference between the two apertures (really the same binocular with aperture masks) as 8.3 versus 9.5, so a 1.2 magnitude difference, which sounds like quite a bit more than 0.1 mag / 14mm of difference.

 

And yes, I most certainly see a brightness/vividness difference between a 10x42mm binocular and a 10x50.

 

I'm intrigued by the math and will do some observations comparing the 15x56 and 15x70 to estimate the limiting magnitude difference between them. 

[ckwastro]

It has been a long, long time since I’ve run these calculations, but if memory serves, a factor of 2.52 per magnitude between the radius squared is a simplified method for calculating how much deeper an optic will go. Emphasis on simplified. 

 

For instance, it is generally accepted that a 12.5 inch telescope will go one magnitude deeper than an 8 inch telescope. The radius squared difference on those two is 2.44 so it’s not quite a full magnitude but close enough. Also a 20” should go one magnitude deeper than a 12.5. That factor is 2.56. Keep in mind with each magnitude deeper the increase in the number of stars visible is exponential, so going between 8th & 9th magnitude is nowhere near the same thing as going between 14th and 15th magnitudes. 

 

With a 70mm objective and a 56mm objective the radius squared in millimeters is 1225÷784 which equals 1.56. 1.56÷2.52 equals approximately 0.62 magnitude. So the 70mm should go 0.62 magnitudes deeper than a 56mm in theory, but at these small apertures it is probably noticeable, but it’s not going to be a “wow factor”.  

Edited by ckwastro, 10 June 2022 - 08:02 PM.

[Fiske]

Yeah. This is more consistent with the observations I made last December.

 

But I am planning to make more observations with the 15x56 and the 15x70. Not to mention the 20x65ED and the 20x80 Deluxe. There is going to be some difference due to optical quality differences between the instruments, but my experience suggests that doesn't have as much of an impact as aperture does.

 

I will share my observations here for sure.

 

Regardless of the magnitude question, I can say that the Maven 15x56 binocular is a fantastic astronomy instrument. I am delighted with it.

 

And I appreciate the analysis Jordan and Rich have shared. I just want to test it against what I actually see at the eyepieces. 

 

Edited by Fiske, 10 June 2022 - 08:55 PM.

[MrZoomZoom2017]

You all might find this CN Report to be helpful:  https://www.cloudyni...binoculars-r590

 

With that said I do like Rich's answer !

 

Cheers,

Tim

[scroff]

Okay optical theory geniuses, what aperture advantage should a 15x70 binocular theoretically have over a 15x56 instrument?

 

Well, here's a shot at it...

The difference in light flux through the two apertures is simply the ratio of the two areas...as you mentioned that is 1.5625.

(From wiki), magnitude is ma-mb = -2.5log(Ia/Ib) such that ma is magnitude of object a, mb is magnitude of object b, Ia is intensity a, Ib is intensity b.

If one takes the light flux through the aperture as Intensity, then -2.5log(1.56) gives -0.48 which I believe will be the difference in limiting magnitude. The number is negative to mean that a magnitude 8 star viewed through 56mm lens would appear as magnitude 7.52 through 70mm lens.

Does that seem correct? 

 

This should only hold true for all else being equal, including magnification.

 

Disclaimer: I am in no way attempting to claim any sort of optical genius.

Edited by scroff, 10 June 2022 - 09:18 PM.

[Fiske]

I did find this online binocular calculator that accepts various specifications like aperture, magnification, FOV, and then calculates various figures, Adler Index, etc. An estimated limiting magnitude is included, which is going to be highly variable depending on many factors that aren't calculated. I wouldn't expect to get close to the limiting magnitudes stated below from my 18.30ish mpsas yard, but the difference it is showing between the two instruments is 0.5 magnitudes. 

 

15x70

 

• Exit Pupil Diameter: 4.7 mm
• Relative Brightness: 21.8
• Luminosity: 9
• Apparent FOV: 60.0°
• Linear FOV: 70 meters
• Twilight Factor: 32.4
• Adler Index: 125
• Limiting Magnitude: 11.7
• Light Gathering Power: 100x
• Angular Resolution: 1.7 arc sec
• Star Transit Time: 64 sec

 

15x56

 

• Exit Pupil Diameter: 3.7 mm
• Relative Brightness: 13.9
• Luminosity: 7
• Apparent FOV: 60.0°
• Linear FOV: 70 meters
• Twilight Factor: 29.0
• Adler Index: 112
• Limiting Magnitude: 11.2
• Light Gathering Power: 64x
• Angular Resolution: 2.1 arc sec
• Star Transit Time: 64 sec

Edited by Fiske, 10 June 2022 - 09:46 PM.

[Fiske]

Sky conditions last night were not great, but were clear enough to do some observing. I recorded 17.99 mpsas from my driveway, the worst value I have seen so far, no doubt from the combination of hazy skies and an 84% illuminated waxing gibbous moon. 

 

A series of observations were made with the Maven 15x56 and the Oberwerk 15x70 Ultra. I was unable to see a single star with the Ultra that could not also be seen with the Maven. In fact, the Maven seemed to show more stars in averted, though I could not pin any down specifically. This is consistent with Jordan and Rich's calculations, I must admit. 

 

The significant differences between observations with the two instruments is that M57 in Lyra was slightly more conspicuous as a non-stellar, nebulous ball with the Ultra. It could still be seen with the Maven, but wasn't as apparent in averted vision and required more concentration to view. The other difference is that the Maven is noticeably sharper, which may partially account for why the aperture advantage of the larger binocular didn't translate into a fainter limiting magnitude. The Maven may have been able to reach as deep because the additional sharpness increased the visibility of fainter stars. The effect was conspicuous and frankly made the Maven views more enjoyable. 

 

I had anticipated that the Ultra views would be brighter than the Maven's, but that was not the case last night. 

 

Whether the poor transparency was a factor, I am not sure, but plan to do additional comparisons on a clearer evening. Limiting magnitude for either instrument was between 9.5 and 10.0.

 

 

[MT4]

If Maven were to come out with a B.5 18x65 / 20x65 / 20x70 / 22x70 with the same fluorite-crystal objectives and AK prism design, I'd be among the first to pre-order.   

 

I'd probably forget about trying to find that elusive Takahashi Astronomer 22x60, though if one were to magically show up I don't know what I'd do

[Mark Y.]

I'm not feeling too sorry for ya' MT4!

 

You've got a plethora of amazing binoculars already.

[MT4]

I'm not feeling too sorry for ya' MT4!

 

You've got a plethora of amazing binoculars already.

 

There was a time not too long ago when I was trying to kid myself thinking that I would never become a binocular collector.  I think I've crossed that line and there's no way back.   The only thing I can do now is to "collect" high-quality instruments only and observe with them all.  The different instruments in my collection do provide different perspectives of the heavens above and some may be more suitable for certain viewing conditions than others.   That's what keeps the business of collecting and observing fun for me 

 

By the way, once I got past three instruments, it was a lot easier to add another, then another, then yet another, etc.  If you catch my drift 

[MT4]

I just came back in from a 2-hour lunar observing fest.   It was almost-clear tonight, a rarity for me nowadays, and so I couldn't let such a golden opportunity to observe go to waste.

 

I had a total of 8 binos with me:   Nikon EDG 7x42, Nikon Ell 8x30, Nikon MHG 10x42, Fujinon FMT-SX 10x50, Maven B.5 15x56, Zeiss 15x60 BGAT*, Nikon 18x70, APM MS ED 20x70.

 

Aside from the exceedingly bright moon, I looked at the star field around Libra and Scorpius.   I came away with the following general takeaways:

 

(1) In the center of the view, the Maven B.5 15x56 was the sharpest and had the best contrast.  Stunning was the first thought that popped into my head when I first looked through the Maven.  (The only other binocular in my collection that was an equal to the Maven in this respect is the Kowa Highlander Prominar BT.   It's no coincidence that these two instruments feature fluorite-crystal objectives.)

(2) Overall, the Zeiss 15x60 BGAT* had the best presentation of the star field.  The view was simply put addictive.  I could have looked through the Zeiss for hours on end but since I had 7 other instruments with me I had to make an effort to take the Zeiss off the p-gram mount and put something else on.  Nevertheless, the Zeiss got the most attention out of all my binos tonight.

(3) For my observing taste and for lunar viewing, the Nikon 18x70 easily won against the APM MS ED 20x70.  It was really a battle of 4 degrees at 18x vs. 3.3 degrees at 20x.  (It should be noted that the APM has ED glass and its field is a lot flatter compared to the Nikon's.)

(4) 15x vs. 18x is very tricky for me.   I've compared my Maven 15x vs. my Nikon 18x many times and I still can't declare that one is definitely better than the other.  While the Maven has the better optics by a mile, the Nikon has the mag advantage as well as the AFOV advantage.  In my opinion, 4 degree TFOV at 18x is pure magic and it's a shame that Nikon hasn't made any effort to come up with an upgraded version of their 18x70 instrument.

[Rich V.]

I would love to see an upgraded Nikon 18x70 with long ER, flat field eyepieces and ED glass.  If only Nikon would embrace the 21st century and modernize their optical design instead of resting on their 20th century laurels.

 

I'm happy to hear the level of performance of the Maven 15x56 is so high.  It looks to be a great, relatively compact roof prism addition to the 15x field.

 

Rich

[MT4]

I would love to see an upgraded Nikon 18x70 with long ER, flat field eyepieces and ED glass.  If only Nikon would embrace the 21st century and modernize their optical design instead of resting on their 20th century laurels.

 

I'm happy to hear the level of performance of the Maven 15x56 is so high.  It looks to be a great, relatively compact roof prism addition to the 15x field.

 

Rich

 

Nikon did embrace the 21st century when creating the WX binoculars in 2017 but too bad they are too much binoculars for most and besides they are still only 50mm instruments.  An upgraded 18x70 as you outlined above would be an instant modern hit in my opinion.    (This is not to say that the current, old-school Nikon 18x70 isn't still great, it's just that it's dated.)

 

The Maven is indeed quite compact and lightweight at around 1250g.

 

The Zeiss 15x60 is much heavier at a little over 1600g but I've found that I can handhold the Zeiss a bit more steady compared to the Maven.   (I sometimes use the Zeiss to develop my arm muscles.  After holding the Zeiss for a while, switching to the Nikon MHG 10x42 and Ell 8x30 feels like holding toy binoculars )

[jrazz]

My shiny new addition...

Soooo pretty. Really nice on the inside too. The 24mm UFFs are a perfect fit. I can merge the fields with about 2mm between the barrels. Feels very comfortable.

 

Do not be alarmed by the tripod choice. It's just so I could lift it off the grass!

It's so unsteady I can barely look through it right now

 

What I see is awesome but I'm going to have to improve that.

 

[lookoutmtn17]

Jordan, that is one good looking BT! I believe you have passed the "budding binoholic" stage.

Tim

[jrazz]

Fair... Let me change that.

[Rich V.]

Ooh, I like the pretty pearly white.  That would have been my choice, too.

 

No strong winds forecast tonight, I hope.  

 

Rich

[jrazz]

No winds but haze from the Arizona fires

 

And it's like a million degrees outside!