Collimation query 10x50's

[Chris]

Hi guys, I've just treated myself to some new Opticron 10x50's for my upcoming birthday from FLO. They arrived today and look great for sum paid but I think there could be an alignment issue.

I don't want to return them unless sure they're not right, so I just wanted a second opinion on my time honored collimation check:

- I pointed them at the roof line across the street to check the vertical collimation, this looked spot on when placing the roof line central in the FOV. Doing the same with horizontal collimation by looking at the edge of the house across the street there is a 4-5mm step/jump when switching between eyes.

I've repeated this at various distances, looking to the end of my short garden, focusing maybe 15 feet away at a wall edge, the horizontal image jumped very noticeably between eyes, maybe more than half the FOV. However, when I focus on the edge of an house 100 yards down the road the jump is hardly noticeable! 

Anyone know what would be a good distance to check collimation? it seems quite effected by distance?

If it's clear tonight I'll get them under the stars and point them at the super Moon to see how they go for Astronomy.

 

I also noticed the diamond shaped exit pupils of the BK7 prisms were not the same, the right hand side had more of a cut off. Also I can't get a really sharp focus unless I close one eye, but there isn't any double image which is why I'm not 100% sure?

 

 

 

 

[Peter Drew]

Assuming you've purchased the binocular for astronomy, the best distance to check for collimation will be infinity. Parallax comes increasingly into play as the viewing distance decreases. 

[Chris]

Ok thanks Peter, I'll get them under the stars when the weather allows, fingers crossed. I've been playing with them some more and they are probably a bit on the soft side when using both eyes for daytime use, although they do sharpen up nicely if I turn my eyes in a bit. Hopefully they will either sharpen up for the astronomy side of things at infinity or reveal any miscollimation on a point source. 

[BinocularSky]

Just to add to what Peter wrote, when testing under the stars, defocus the right eyepiece. This can stop your eye trying to merge out-of-alignment images. If they are OK, the focused star image should appear to be as near as dammit central to the defocused one.

[Chris]

Hi Steve, that's a good tip, thanks  Two days of cloud and rain so far since they arrived, hold on let me just check again....darnit yeah still drizzling  I know a chap on here has just received a Takahashi in the post, so that's probably why! Anyway, when it does clear I'll be keen to try this tip out

[Chris]

On 11/15/2016 at 12:55, BinocularSky said:

Just to add to what Peter wrote, when testing under the stars, defocus the right eyepiece. This can stop your eye trying to merge out-of-alignment images. If they are OK, the focused star image should appear to be as near as dammit central to the defocused one.

Ok, just got the binos under the stars so focused the left eye and defocused the right to give a large airy disc. Opening both eyes showed that the pinpoint star was sitting a distance outside the defocused star at about the 10 O'clock position, so they are indeed a bit out of collimation. Focusing both sides of the bino I was still able to merge the image, so they arn't way way out, but this does explain why they didn't feel right during the day unless I turned my eyes in a touch. I'm sure a well collimated pair would be sharper.

The thought that strikes me is if I hadn't previously owned a number of binos I might have thought this was how they were supposed to be. I wonder how many folks new to binos have been a bit underwhelmed purely because of mild collimation issues? 

[Peter Drew]

If you hold your index finger a foot away from your eye and then focus on it you will notice that objects in the background appear to be double. If you then focus on the background your finger then appears double. This is the parallax effect that a binocular has to deal with. 

[Chris]

19 minutes ago, Peter Drew said:

If you hold your index finger a foot away from your eye and then focus on it you will notice that objects in the background appear to be double. If you then focus on the background your finger then appears double. This is the parallax effect that a binocular has to deal with. 

Hi Pete, nice little experiment, I understand binos have a tough job on their hands, I probably should have waited an extra payday and got something a bit better, all though my last pair of bins were about the same caliber but in a 15x70 and collimation was fine. 

I've done my testing on the star Aldebaran, so nice and bright but effectively at infinity to rule out any parallax. 

[FLO]

Hi Chris, 

We will happily send you a second binocular for comparison. Your binocular might be faulty, need realignment, or it might simply not suit you. Having another to compare will help you determine which. 

HTH, 

Steve 

 

[Chris]

40 minutes ago, FLO said:

Hi Chris, 

We will happily send you a second binocular for comparison. Your binocular might be faulty, need realignment, or it might simply not suit you. Having another to compare will help you determine which. 

HTH, 

Steve 

 

Hi Steve, thanks for your very kind offer  I'm almost certain it's just the collimation that's had a knock - i.e. the packaging was a bit dented when it arrived, the right exit pupil doesn't match the left, and the star test showed the de-focused right hand side didn't merge with the focused left hand side.

I'd be happy to do has you've very kindly suggested, or as I'm sure it's just the collimation I could return them for a replacement. If I hadn't sold my Horizon tripod I could have a go at doing a conditional collimation on them like I've previously done with a couple of pairs of Helios apollo's. I'm sure they will be good once tweaked.

Shall I PM you tomorrow, Steve?

 

 

 

[Chris]

Message sent to questions@firstlightoptics.com

 

[Chris]

@FLO Hi Steve, I've received the second pair of bins and compared them to the first pair during the day, plus tonight under the stars. In a nut shell I'll be keeping the replacement pair and sending back the first pair. I've sent an email going into a bit more detail with the comparison. 

Thanks again for letting me compare two sets of binos to help get to the bottom of things  As always FLO go above and beyond 

 

 

[FLO]

17 minutes ago, Chris Lock said:

Thanks again for letting me compare two sets of binos to help get to the bottom of things  As always FLO go above and beyond 

No problem  

If the first one was faulty we'll happily arrange a DHL collection. 

Steve 

[Astrobits]

On 15/11/2016 at 12:55, BinocularSky said:

Just to add to what Peter wrote, when testing under the stars, defocus the right eyepiece. This can stop your eye trying to merge out-of-alignment images. If they are OK, the focused star image should appear to be as near as dammit central to the defocused one.

Not necessarily so. If you have any wedge in your eyes then the two will not coincide. I know that I have some wedge and allow for it when using and testing binoculars. To me the focussed star appears completely outside of the defocussed one. Years ago, Opticians used to measure wedge but  have not done so the last few times I have had my eyes tested.

Nigel