So you just landed your first, second or what-so-ever number binoculars.
Perhaps its the best binoculars you could get for yourself. But I have a question for you. The very piece you got, the one delivered to you, is that the best one? Are you sure its not defective?
Not meant to scare you but you have to be sure on this. Thats what I am here for; to show you the tests you can perform on your pair to make sure its in good condition.
When you have the binocular in hands, do these 3 simple tests to determine the quality and proper functionality of your pair. [Well, all those easily observable checks, like ‘scratches on lens, dust from the inner side or damaged body etc’ are not going to be talked about here. You are smart enough for that.]
If you don’t have your binoculars yet, here are my 11 recommended binoculars to get you headstarted!
So without any further ado, lets jigsaw in the topic. Act upon and see if the binocular is best or you need to arrange a return – thank me later for saving your money. :p
1. Collimation of binoculars
Collimation refers to the alignment of the optical axis. The best performance is reached when the optical axis of the objective lens passes through the optical center of all lenses and prisms.
This should hold true for both optical barrel assemblies.
For most binoculars, poor collimation is not immediately obvious when you first pick it up and view through it. This is because your eyeball will adjust to compensate for misalignment in the optical instrument. Of course, if you let your eye muscle strain like this for a few minutes, you will feel the pain soon.
Here is a simple way to check for collimation.
First, look at a target ~100 yards away with the binocular. Be sure to adjust the center focus as well as the right eyepiece.
Now, relax your eye for a minute by taking the binoculars down. Look at the target again with the left objective lens blocked by your hand.
After a minute, quickly remove your hand which covers the objective lens. If the target appears to be out of focus immediately but becomes in focus after a second or two, the binocular is not collimated.
Your eye is doing the hard work to adjust collimation and focus.
Choose a different binocular.
Resolution determines how sharp the image is and how much fine detail you can see.
You can usually check this by comparing a few different binoculars and look at the same target ~100 yards away.
The manufacturer usually specifies resolution by a number, e.g., 5 seconds of arc. This means that the binocular should be able to resolve two fine features at an angle of 5″ apart.
Professionals use standard test charts very much like the one used in an eye doctor’s office.
You usually do not need to bother with this kind of tests, unless you are talking about a 20 or 30 thousand rupee instrument.
These test charts are available in the references I cited earlier. But, your common sense is sufficient for most purposes.
3. Star testing binoculars
The ultimate test of an optical instrument is the so-called “star test“. This is done by looking at the image of a distant star in the night sky.
To do this, locate a bright star at the center of the field-of-view.
The perfect image should appear as a round disk, with a few weak, concentric rings due to diffraction.
Almost all binoculars will show some deviation from this perfect image.
Some asymmetry is acceptable, but if your binocular’s star test yields an image which is something like a triangle or a stick, try to get rid of it.
Summing it up. So this is how you can find out if your brand new binocular is doing perfectly. All these tests may sound simple but are just as effective. Congratulations if yours passes it all – Enjoy it!
Don’t worry if it fails, there can be a lot of factors involved for that. Just try a few more times before concluding. But if there’s still no difference – Get hang of it. Replace it or just return it!
And do ask me any question if you have in the comments below. It so awesome talking to you.