Conditional Alignment

 Gawd, that sounds like some form of sexual psychoanalytic technique! But, its actually a way to fix buggered binoculars!

Binoculars, like other optical systems, have a number of parameters that have to be in tip top alignment  for them to work properly. Some, such as chromatic aberation, coma, etc, are inherent to the glass itself and can only be solved by buying the best. But others are a physical alignment issue. In particular - collimation.

Ive come this because I decided to give away one of my pairs of 10x50 binos. Back-yard astronomy is a great and relatively simple hobby to get into for a youngster, but many people make the mistake of jumping straight to a telescope and are disappointed when the images they see are nothing remotely like what the press tell us they should be. Sorry, but nothing you can buy at amateur level is going to give you views like what are published in magazines and on the web from the Hubble space telescope or the myriad of astrophotographs created by allowing software to 'stack' hundred upon hundreds of long time exposures! Buy the biggest possible mirror in your budget, lets say thats a 8" dobsonian - and Andromeda will still be a vague fuzzy oblong! Sorry, thats how it is! Combined with the tiny field of view which makes actually finding the thing you want to see difficult in the first place, and its no wonder so many give up!

But it shouldnt be like this. The night sky is amazing - even if all you can see are the brighter navigational starts from a light polluted city. Its the way people are introduced to it that makes all the difference! Dont go out and buy a telescope! Go out, and buy - a planisphere! Or a simple, beginners level star atlas. Then - simply go out, and look up!

Of course, just looking denies you some of the more easily found wonders. But a pair of binoculars will reveal a plethora of amazing sights. Even for me, the sheer background of the starfield when using a pair of simple binos to look into the Milky Way is astonishing.

So when a work mate mentioned their daughter was interested in the night sky and wanted a telescope, I asked if they had any binos. With the answer being no, I decided my spare pair would perhaps give the young person a much better start into the hobby.

Now, This left me with my ancient Miranda 10x50s, that I bought when I was about Sams age, and still at school, and the cheap Bressers of Sams. This is when, in deciding to check them over, I found that Sams had been sat beside a bottle of aftershave, and all the rubber had gone sticky! I also found that the collimation was so far out that there may as well have been two of everything! So, how to fix?

Well, the sticky rubber was solved by rubbing a load of talc into it! Its not perfect, but pretty much the best I can do without the impossibility of replacing the rubber parts.

The collimation is something that I dont have the equipment to do fully, but it is relatively simple to do what is called 'conditional alignment', this is where the collimation is corrected, for the specific interpupilary distance in use. In other words, it fixes it for anyone whos eyes are the same distance apart. This is done by very carefully adjusting the prism adjustment screws hidden just under the rubber covers! I have done a 'rough and ready' job on these, entirely by trial and error with them focused on a pylon some 10 miles away. A more accurate alignment could be done using specialist Bahtinov masks, which are a form of grating, but I cant be bothered with the expense or difficulty in making my own, for a cheap pair of binos.

Anyway, these are the pair Tom was using up on the hill, and he assures me the images were sharp and not doubled, so it seems to be good enough for now.