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Mariner 8x40 or 7x50?

binoculars equipment
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#1 Luca Brasi

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Posted 29 May 2020 - 04:50 PM

Long story short...  Would you get a binoculars with 8.4° @ 8x40 or one with 7° @ 7x50?

For some reason Oberwerk makes Mariners in both sizes.  If only they made 7x50s with a 8.5° FOV!

 

My goal is to find a low power binocular that will allow me to observe a few of the brighter DSOs.  At first glance the 7x50s seem like the obvious winner, more aperture and lower power.  But the primary reason I use binoculars is for the immersion factor.  That would lend itself to the 8x40s with a whopping 8.4° FOV... but smaller aperture means less light.

 

I already own a pair of Orion GiantView ED 16x80s and a custom parallelogram mount.  They are amazing under my Bortle 2 sky.  But I'm always adjusting the collimation, I swear just taking them out of the bag moves the prisms!?!  I enjoy the views, but something simpler with half the magnification is what I'm looking for.

 

What are your experiences with low power binoculars under dark skies?  Or maybe I should drop $350 on the 20×80 Deluxe III's and sell my Orion GiantViews!

 

Thanks!



#2 Mark9473

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Posted 29 May 2020 - 06:39 PM

I once tested 7x50 and 8x42 side by side under pristine skies, looking for faint fuzzies; my findings at the time were the following:

 

The 8x42 gives a better view of the North-America nebula, but the 7x50 brings the neighbouring Pelican out a little better.
The 8x42 gives a better view of the Veil, but the 7x50 gives more hints at detecting the other fainter parts.
The 8x42 gives a better view of M101 and the nebulosity around Mel 15 in Perseus.
The 8x42 shows a larger Andromeda nebula as measured against the star background, and shows M110 better too.
The 7x50 is better at the Helix nebula, the Merope nebula in M45, and on M33.
The 7x50 is also better at the dark nebulae in Scutum, Aquila and Cygnus.

 

I call that a tie.

 

Given that on open clusters the 8x40 would be superior, i'd go for the 8x.


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#3 chris charen

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Posted 29 May 2020 - 10:43 PM

The difference of the Afov of 50* vs. 67* is very noticable IMHO. That 67* Afov is very expansive. I  have had several 7x50s and ultimately I find the 50 degree Afov just too restrictive and tube like. The 7x50 has some positives, easy to use eye placement and generally a flat distortion free image to the edge. The 7x50s have an exit pupil of 7mm vs. 5 mm for the 8x40, something you need to take into account. 7mm exit pupil is best suited for 'young' eyes. For me the advantages of a wide angle 8x40 outweigh the 'narrow' image of a 7x50, even taking into account the increased brightness. Others may have a different opinion.


Edited by chris charen, 29 May 2020 - 10:45 PM.


#4 Grimnir

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Posted 30 May 2020 - 04:42 AM

I once tested 7x50 and 8x42 side by side under pristine skies, looking for faint fuzzies; my findings at the time were the following:

 

The 8x42 gives a better view of the North-America nebula, but the 7x50 brings the neighbouring Pelican out a little better.
The 8x42 gives a better view of the Veil, but the 7x50 gives more hints at detecting the other fainter parts.
The 8x42 gives a better view of M101 and the nebulosity around Mel 15 in Perseus.
The 8x42 shows a larger Andromeda nebula as measured against the star background, and shows M110 better too.
The 7x50 is better at the Helix nebula, the Merope nebula in M45, and on M33.
The 7x50 is also better at the dark nebulae in Scutum, Aquila and Cygnus.

 

I call that a tie.

 

Given that on open clusters the 8x40 would be superior, i'd go for the 8x.

Ok, but which 7x50 and which 8x42?

 

Graham



#5 Mark9473

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Posted 30 May 2020 - 05:04 AM

Graham, the 7x50 was a BA8 porro so very large prisms, good off-axis ilumination, good light transmission.

The 8x42 was my Vixen roof prism binocular - small prisms so limited off-axis illumination no doubt, and transmission in the low 80% tier.

Which makes it all the more remarkable how well the 8x42 did.



#6 39.1N84.5W

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Posted 30 May 2020 - 08:08 AM

I've got a super clean Oberwerk Mariner 8x40 for sale, $75 free shipping CONUS. (Thank you)

#7 Grimnir

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Posted 30 May 2020 - 09:02 AM

Long story short...  Would you get a binoculars with 8.4° @ 8x40 or one with 7° @ 7x50?

For some reason Oberwerk makes Mariners in both sizes.  If only they made 7x50s with a 8.5° FOV!

 

My goal is to find a low power binocular that will allow me to observe a few of the brighter DSOs.  At first glance the 7x50s seem like the obvious winner, more aperture and lower power.  But the primary reason I use binoculars is for the immersion factor.  That would lend itself to the 8x40s with a whopping 8.4° FOV... but smaller aperture means less light.

 

I already own a pair of Orion GiantView ED 16x80s and a custom parallelogram mount.  They are amazing under my Bortle 2 sky.  But I'm always adjusting the collimation, I swear just taking them out of the bag moves the prisms!?!  I enjoy the views, but something simpler with half the magnification is what I'm looking for.

 

What are your experiences with low power binoculars under dark skies?  Or maybe I should drop $350 on the 20×80 Deluxe III's and sell my Orion GiantViews!

 

Thanks!

Personally, I wouldn't buy a 7x50 unless your pupils open to 7mm and you're under very dark skies - and probably not even then.

 

Graham


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