WATCHING SEABIRDS WITH VINTAGE OPTICS – A DIY APPROACH

In the decades gone by I used several telescopes to study seabirds. These included, among other things, two good 80mm spotting scopes (on loan from a conservation organisation) and a small 40 mm vintage (53-year-old) terrestrial refractor or ‘Spyglass’. The two spotting scopes were returned in due course so I have now fallen back on my old spyglass. Some birders seeing this prehistoric looking instrument often look at me with barely disguised contempt: that is until they look through it. The vintage instrument gives sharp high-resolution images of high contrast with an, admittedly, rather small field of view. So what is the secret? Very simple, as it is not ‘nitrogen filled’ I can easily dismantle the scope into its individual components without the use of tools, for cleaning, servicing etc. An exception being the objective and ocular retaining rings which require a small screwdriver, toothpick or ballpoint pen tip for removal. When something is easy to maintain, the chances are high that it will be properly maintained which, in this case, is mainly cleaning of the lenses internally with proper lens cleaning equipment and methods.

I have modified the scope somewhat. To improve image contrast, I lined the interior surface of the optical tube with black velvet and blackened the objective edge with indelible ink. Furthermore, I always carefully tighten the objective retaining ring so that it holds the lens securely but never too tight, as overtightening sets up stresses in the glass which, to some extent, can adversely affect the image. Of course gross overtightening can crack the lens rendering the instrument useless.

 

Accessories can sometimes assist observations. For example, the use of filters can improve visibility during misty or foggy conditions. To cite an example: in Colombo mist occurs offshore on November mornings making observation difficult. A suitable filter can help here. As my scope is not threaded for filters I constructed an adapter out of a short piece of plastic water pipe to enable the use of HOYA glass photographic filters in front of the objective cell. The use of a minus-violet (Y44) or a yellow (K2) filter have permitted me to glimpse birds which would otherwise have been lost in the fog. I also occasionally use a linear polarizing filter (PL) to reduce reflections off the sea surface and a UV filter for permanent lens protection.

 

Lastly, the scope is best mounted on a steady tripod. The professional video tripods are ideal, but these are usually too heavy and also very expensive. I therefore modified a normal camera tripod with tubular legs by loading the bottom section of each leg with weights. Lead shot is ideal but I used nails (with a little engine oil to prevent rusting). A cork plug in each leg ensures that the weights do not move. I have fitted a snap swivel to the bottom of the tripod's centre column; weights can be hung from this when extra stability is required. 

©Rex I. De Silva