NL focus question (1 Viewer)

[tx2ad]

Howdy!

I've got the NL 8x32. If I'm not able to get tack sharp focus of planets/stars at night (say, of Jupiter) - does that indicate that there is an issue with the focus that I might want to have serviced? What I see through the NL is a slight smear or a small spike or two. So, if one of Jupiter's moons is fairly close to the planet, I'm not able to see it b/c the focus issue obscures the moon (it gets smeared/blended into the planet). I also have a Leica 10x25 with which I have no trouble getting perfect focus of planets/stars.

For birding or other daytime activities - I don't discern any issues/problems with the NL at all.

Thanks for the input!

Cheers,
Mike

 

[dorubird]

From what you say, maybe binoculars can't focus at infinity! Can you focus beyond infinity?
Or it can also be some astigmatism or coma. What do the stars look like?

 

[[email protected]]

It is probably astigmatism due to the large exit pupil of the binocular. Try stopping it down to 20mm and see if it makes a difference.

pin point with Binos - Binoculars - Cloudy Nights

pin point with Binos - posted in Binoculars: I just started astro early this year and I started with TV85. All stars look pin point. Today I received my first binocular (Canon 10x42L IS) but I am not getting pin point star. Is this common with binos having fairly short F ratio.I think what I...

www.cloudynights.com

 

[Dominique B.]

It is probably astigmatism due to the large exit pupil of the binocular. Try stopping it down to 20mm and see if it makes a difference.

pin point with Binos - Binoculars - Cloudy Nights

pin point with Binos - posted in Binoculars: I just started astro early this year and I started with TV85. All stars look pin point. Today I received my first binocular (Canon 10x42L IS) but I am not getting pin point star. Is this common with binos having fairly short F ratio.I think what I...

www.cloudynights.com

an 8x32 has an exit pupil of 4mm. This size is an ideal, very suitable size for astronomy.
One SLC 15x56 - ~4mm / one EL 10x50 - 5mm / SLC 10x42 - 4.2mm - glasses that show excellent star imaging. My EL 8x32 also shows this quality.

It could also be due to the large field of view of the NL and the prism, the roof edge of the glass.

 

[exup]

Is this not a roof prism diffraction spike, not uncommon when using roof bins and one of the reasons sky watchers often prefer porros.

Here is Neill English discussing it:

Product Review: Pentax Papilio II 6.5 x 21. | Neil English.net

 

[[email protected]]

an 8x32 has an exit pupil of 4mm. This size is an ideal, very suitable size for astronomy.
One SLC 15x56 - ~4mm / one EL 10x50 - 5mm / SLC 10x42 - 4.2mm - glasses that show excellent star imaging. My EL 8x32 also shows this quality.

It could also be due to the large field of view of the NL and the prism, the roof edge of the glass.

From Cloudy Night's.

"Cutting masks to 20mm for testing a 42mm binocular would eliminate a lot more than astigmatism. First, it would change your ~f/4 binocular to an ~f/8. This would reduce any chromatic aberration and produce an on-axis image with a much smaller chromatic blur. Also, it would eliminate any spherical aberration if it were present. This would reduce the size of the least circle of confusion. True the mask would reduce astigmatism, but it would be near impossible to separate the effects of reduction of astigmatism in an on-axis image from other aberrations that would also be reduced, especially from spherical aberration.

Astigmatism generally becomes more of an issue off-axis. As the image is moved away from the center of the view, the image will tend to elongate. With the image positioned off-axis, astigmatism can be observed by racking focus just inside and outside of best focus. If astigmatism is present, the elongated image will flip from horizontal to vertical. The effects of astigmatism are minimized on-axis.

If astigmatism is present and is so severe that you can observe an on-axis image flip from horizontal to vertical when racking in and out of focus, the binocular is to be rejected as defective. However, I would add, it is not likely you are observing astigmatism in the on-axis image in a 10x binocular. I have minor astigmatism present in one barrel of my BT100. It is easily seen at 60x. It can barely be detected in the on-axis focused image at 37x to 44x. At 25x, it cannot be seen at all.

The two most likely aberrations to be detected in an on-axis image that will not come to a pinpoint focus are spherical and chromatic aberration."

edz

 

[Foss]

Howdy!

I've got the NL 8x32. If I'm not able to get tack sharp focus of planets/stars at night (say, of Jupiter) - does that indicate that there is an issue with the focus that I might want to have serviced? What I see through the NL is a slight smear or a small spike or two. So, if one of Jupiter's moons is fairly close to the planet, I'm not able to see it b/c the focus issue obscures the moon (it gets smeared/blended into the planet). I also have a Leica 10x25 with which I have no trouble getting perfect focus of planets/stars.

For birding or other daytime activities - I don't discern any issues/problems with the NL at all.

Thanks for the input!

Cheers,
Mike

Next time you're stargazing, you might see if the out-of-focus issue is present in both barrels (IE: using your dominant eye, achieve best focus in left barrel, then do the right barrel). This probably wouldn't help with other issues mentioned above, but it may isolate a problem for Swaro service to look into. Wouldn't hurt to check that the barrels focus beyond infinity at the same time.
Good luck,
~ Foss

 

[tx2ad]

Its been cloudy/rainy since I posted - so I am not yetable to do follow-up looks and respond to everyone.

My initial thoughts based on use of my NL and 6.5 Kowa was - my eyes have just gone south with age and I can't get a perfect image. When I tried out the Leica UV 10x25 and all of the night sky objects were perfect crisp circles (with some discernible and appropriate color casts) I then started to question the optics instead of my eyes. Not knowing enough, it could very well still be my eyes and not the optics. My wife is also unable to get perfect views of night sky objects - but its also possible that's due to her eyes as well.

I have put in an effort to adjust the diopter while looking at planets/stars trying to get the crispest images possible out of the NL. Using the UV I haven't needed any diopter adjustment at all for my viewing.

I can say for sure that the NL appears to be focusing on Moon, Jupiter, and deeper sky objects - its possible to get a sharper focus on each object starting from a shorter focus point, and then to move the focus beyond the object and watch the focus degrade.

When the skies clear up, will do more viewing and report back my results.

 

[Scott98]

What you describe sounds very much like a diopter mismatch to me. Bright astronomical objects with tiny disks like Jupiter will show tiny diopter mis-focus when you won't notice it during the day. Sometimes your biology changes a little bit and the diopter that was perfect last night is a tiny bit off tonight.

It usually takes me quite a bit of fussing around, focusing and de-focusing, opening and closing each eye, etc, to get it just right.

 

[dorubird]

Its been cloudy/rainy since I posted - so I am not yetable to do follow-up looks and respond to everyone.

My initial thoughts based on use of my NL and 6.5 Kowa was - my eyes have just gone south with age and I can't get a perfect image. When I tried out the Leica UV 10x25 and all of the night sky objects were perfect crisp circles (with some discernible and appropriate color casts) I then started to question the optics instead of my eyes. Not knowing enough, it could very well still be my eyes and not the optics. My wife is also unable to get perfect views of night sky objects - but its also possible that's due to her eyes as well.

I have put in an effort to adjust the diopter while looking at planets/stars trying to get the crispest images possible out of the NL. Using the UV I haven't needed any diopter adjustment at all for my viewing.

I can say for sure that the NL appears to be focusing on Moon, Jupiter, and deeper sky objects - its possible to get a sharper focus on each object starting from a shorter focus point, and then to move the focus beyond the object and watch the focus degrade.

When the skies clear up, will do more viewing and report back my results.

Now, with this information, things become a little clearer: it could be from the astigmatism of your eyes. That's why you see the stars more point-like with the little Leica 10x25 due the smaller exit pupil that doesn't have such big problems with the astigmatism of your eyes. You must wear glasses if you have astigmatism to see the stars well with binoculars with larger exit pupils.

 

[tx2ad]

I do wear reading glasses, my spouse does not wear glasses at all.
We could have undiagnosed/untreated eye issues.

With the NL's stopped down to 7/8" objective - nearly perfect; at 3/4" objective - perfect.
Also, 1" objective gave no discernible improvement.