Monday, March 26, 2012

"I see no ships" Maybe you need a new telescope then Horatio?

After a good pair of binoculars a telescope is the next most important tool for the birdwatcher, offering higher magnifications for detailed and long-range viewing.
Out in the field.
Scope, tripod and Mule Pack ready for action.

Here I will be focusing on telescopes for birdwatching which are almost exclusively of the refracting type with an objective lens at the end and use prisms to fit a long focal length in a compact body in the same way as binoculars do. The other kind of telescope often seen is the reflecting type which uses a two mirrors, a large one at the back and a smaller secondary mirror at the front to focus the light into an eyepiece. This type of scope is favoured for astronomy because it is easier to make very large high-quality mirrors for good light gathering than it is to make large lenses of the same quality. Amateur astronomer will use scopes with mirrors of 8 inches (200mm) or bigger, something that would be extremely expensive if not nearly impossible with a refracting scope. Astronomical scopes are typically set up semi-permanently in one place, birdwatchers however require scopes to be rugged, weather resistant or waterproof and portable, making the refracting type a much better option.
Reflecting and refracting astronomical telescopes.

A typical birdwatching scope.
This also shows the two types of body available with
straight and angled eyepieces
So what do telescopes do that binoculars can't?
Binoculars are mostly between seven and twelve times magnification with eight and ten times being the most common and versatile. Scopes however, typically have magnification between 15 and 75 times depending on the eyepiece. As with binoculars the brightness of the image is determined by the magnification and the diameter of the front (objective) lens. Our video on binocular specifications is worth a look because the same principles apply to telescopes. Basically the larger the objective lens, the brighter the image will be, but the higher the magnification, the darker the image becomes.

Larger scopes, typically with a 77mm-100mm objective lens, are the best for a bright image and higher magnifications, but are heavier and less portable than mid-sized scopes, typically with 60mm-70mm objective lenses. The smallest and lightest are scopes like the Nikon ED50 and the Opticron GS52 ED, which with objective lenses of 50mm and 52mm respectively making them ideal for travel and carrying long distances, but compromised in poor light. Whilst the brightest image and highest magnifications may be appealing, I have known people with large heavy scopes that they often leave at home or in the car because of the inconvenience carrying them.

After you have settled on a size of scope suitable for your needs the next decision is between a straight or angled eyepiece mount on the scope body. This is a matter of personal preference, but it is usually easier for two people to share an angled scope because straight scopes need to be positioned at exactly the right height. the eyepiece.
Then we come to the eyepiece itself  Most cheaper scopes come supplied with a zoom eyepiece usually covering the range 15-45x magnification on 60-65mm scopes and 20-60x on 80-85mm scopes. Higher up the price range there is often a choice between a zoom and a range of fixed magnification eyepieces (for example 20x, 30x and 45x). These are more restricted than a zoom in that you cannot change magnification without changing eyepiece, but they are still popular with some birders because you get a wider field of view and often a slightly brighter and sharper image compared with a zoom at the same magnification. At the top of the range Leica and Swarovski make wide angle zooms covering the 25-50x range which offer a field of view similar to the fixed magnification eyepieces.

As with binoculars the main improvement as you go up the price range is the quality of the glass. The build quality does increase too, but this is not a criticism of the construction of the budget and mid-range scopes, which are designed very well to cope with use in field.

The same terminology referring to glass types and quality in binoculars applies here too, there is a short glossary of commonly used terms and acronyms at the end of this blog.

Another feature that varies between manufactures and models is the focusing control. There are basically two main types: a wheel mounted on the prism housing and a ring around the whole body like you would find on a camera lens. Some scopes with the wheel type have two wheels, one high geared and one low geared, for fast and precise focusing. The Zeiss Diascopes are unique in having this feature built into one control that responds to how fast you turn the wheel. Which one of these is right for you is a mater of personal preference and both systems are quickly adapted to.

Hawke Naturetrek showing wheel type focusing
Nikon ED82 showing ring type focuing

While most scopes are waterproof and fairly rugged, another popular accessory is a stay-on-case. These add an extra layer of protection to the scope and eyepiece keeping the outside in better condition and, as the name suggest, stay on the scope when in use.

With the high magnifications offered by telescopes a suitable tripod is essential to get a steady view. All telescopes and cameras use a standardised screw thread size to fit them to a tripod. Most modern tripods have a quick release system that allows you to remove and refit the scope without having to unscrew it. These work by having a small metal plate that screws into the foot of the scope which then clips into the tripod head. Some tripods come as a complete kit of legs and head, others you can choose the best combination for you requirements. The size of your scope influences the tripod you need, smaller scopes can use lighter tripods than larger scopes and still be steady. Another factor that effects the weight of a tripod is the material it is made from. Most low to mid range tripods are made from light-weight aluminium tubing, but the top of the range are carbon fibre. The same qualities that make this material ideal for sports cars and aircraft make for strong, ridged and light tripods.

So, that's a round up of what telescopes are all about, have a look at our website or visit us at Glandford or Cley for our full range of telescopes and tripod.

Cley Spy


APO. Abbreviation of apochromatic. A completely apochromatic lens system corrects all chromatic aberration (colour fringing). Leica's APO-Televid scopes also have fluorite lens elements.

BK-7 and BAK-4 prisms. These are two grades of glass, boroscilicate BK-7 (generally in cheaper optics) and barium crown BAK-4 (delivering better sharpness)

ED, HD, HR, Prominar. Terms used to denote higher-quality glass models, HD standing for High Definition, ED usually standing for Extra-low Dispersion, and HR standing for High Resolution. These terms are not standardised, one companies standard glass can sometimes be as good as another's HD. With Swarovski HD denotes models with fluorite lenses. Prominar is a term unique to Kowa and again denotes the higher quality glass versions, including the impressive fluorite-lensed TSN-883 with its 88mm objectives.

Eye relief. This is the distance that your eye should be from the eyepiece lens to get the optimum image. Spectacle wearers often need a longer eye relief when using a scope or binoculars with there glasses on.

Nitrogen filled. Waterproof scopes and binoculars are often filled with a dry, inert gas (most commonly nitrogen or argon) to prevent internal fogging.

SOC. Stay-on-case.

Sunday, March 25, 2012

Pond Life

Before pond

Taking advantage of the continuing warm sunny weather we have been very busy in the garden. The pond has been dug, lined, filled and fruit trees and shrubs have been planted. The Pond is still looking a bit new, but we've done our best to make it look natural and blend the edges into the surroundings. In the middle there are some water lilly pads and around the edge in the boggy areas we put in some sedge, yellow flag iris, forget-me-not and figwort.

The finished pond in all its glory.
Three of the locals.
The pond has already attracted six ducks and a pond skater within hours of being filled, so it's looking promising! The water level will be topped up every time it rains not only in the obvious way, but also via the gutters on the shop which we have connected to the pond.

Ornamental pile of railway sleepers.
We have also created two platforms in the long grass near by out of old railway sleepers which will provide sheltering and basking places for reptiles and amphibians. The untidy areas of a garden are often the most attractive to wildlife and require the least effort to maintain.

The cherry tree.

The fruit trees are primarily for the insects in spring and summer and birds later in the year. We have two varieties of apple, Snadringham and Saturn, both later fruiting to coincide with the migrating thrushes arriving, a cherry which the blackbirds will like, and a hazel to tempt the great-spotted woodpeckers down from the woods. Planting these trees tested our endurance because the dry ground had become like concrete, requiring a pick axe to start the holes. With a big hole filled with lots of compost and a bit of watering these should do well in spite of the soil conditions.

The latest Cley Spy bird news is red kites at both the Glandford and Cley reserve shops, Mediterranean gull at Glandford and a black redstart at Cley. Also one of the nest boxes has been occupied by blue tits.
We'll keep you posted on all the sighting here and on our Twitter and there are more photos on our Flickr too.
Cley Spy

Monday, March 12, 2012

Spring has sprung, the grass is ris. I wonder where the birdies is?

With a little work they could be encouraged to your garden.

With the glorious sunshine this weekend we have been getting outside and making plans for our back garden at Glandford. We are fortunate in having a half acre field as a back garden, but you can still do a lot for the wildlife with a much smaller plot.

Out the back.
The best place to start is assessing what you already have. Here there is an open area of rough grass with a ragged hawthorn hedge at one end and along the boundary with the seed crop field mentioned in the Glandford Finch Invasion blog post a few weeks ago. There is a short section of soil bank topped with a few bushes and two small willow trees. The far north end is a patch of low hawthorn and bramble scrub and there are a few old railway sleepers in a heap.

Barren Srawberry
(Potentilla sterilis)
Common field speedwell
(Veronica persica)
Looking in a bit more detail there are a few wild flowers already coming through including common field speedwell (Veronica persica), barren strawberry (Potentilla sterilis), colt's-foot (Tussilago farfara) and some other interesting looking stuff coming up that is too small for me to commit myself to positively identifying yet! Not a bad start really, but lots more to be done.

(Tussilago farfara)
First of all the pond. Water in the garden is always a big draw, especially if it varies in depth and has muddy, stony and sandy edges. As well as the plants, invertebrates and hopefully amphibians, a pond should help the birds too, providing a drink and a place for a wash and brush up. Even a very small area of water can get a surprising variety of species if it does not dry out in the summer.
The site for the pond.
Our area designated to be the pond should be big enough to get a good variety of plants established and attract dragonflies and have a good diversity of nooks and crannies in the water and around the edge for other invertebrates.

Although we have a good number of fruit-baring bushes with the hawthorn, a bit more choice is always desirable. Cherry and elder trees provide a good sugar-rich feast in the summer and apples, especially late fruiting varieties, are popular with thrushes in the autumn. For the insect-eating birds flowering and evergreen shrubs are a good idea as well as log piles and areas of bare soil. Attracting incests is good for the birds, but they are also fascinating in themselves. One of the best ways to observe the more flighty insects like butterflies, moths and dragonflies is with a close-focusing binocular. A lot of modern 8x32 binoculars focus down to less than 2m (6'6''), but the best are the Pentax Papilio 6.5x21 and 8.5x21 both with a minimum focusing distance of 50cm (1'8''). Not only are these bins good for seeing fine detail on a butterflies wings for example, they can also be quite handy for inspecting the contents of a pond without getting wet!  Our plant shopping list includes lavender for moths and bees, a buddleia bush or two, a guelder rose and maybe a rowan tree (mountain ash).

The old wood burner.
One of the best ways to make a garden a haven for wildlife is to be untidy.   If you have the space to let a part of your garden run wild, long grass, brambles, old flower pots and log piles provide hiding, nesting and foraging places for insects, slugs and snails, small mammals, reptiles and amphibians and birds. The old wood burning stove from our old shop has got a new lease of life in the long grass where we hope in time a robin or wren may decide to nest.
With the addition of a pile of big stones, some decoratively arranged railway sleepers and few nest boxes we'll be sorted for the spring.

Lots more to do, but that should keep us busy for now. We'll keep you up dated.

Cley Spy

Monday, March 5, 2012

A birder's best friend. A short history of bioculars

Old and New.  An 1890s 12x30
field glass next to a current
Zeiss 8x30.
We have recently filmed a short video guide to understanding the specifications of binoculars (Click here to view), so as a follow up this is a (very) brief history of binoculars with some additional information on types and specifications. 
Binoculars are the one essential piece of equipment for the birdwatcher and are a great boon to most other outdoor activities. The history of these elegantly simple instruments started in 1608 when the Dutch spectacle  maker Hans Lipperhey built a “telescope for both eyes”.
This was essentially two telescopes joined together, producing an inverted image.  Significant advances in the technology beyond the basic Galilean design of two lenses at either end of a tube came later in the Seventeenth Century with the addition of erecting lenses to correct the inverted image. These additional lenses made the glasses much more practical for terrestrial use but increased the length significantly.

Ernst Abbe 1840-1905.
Father of the prismatic binocular.
The Porro prism design.
In 1854 the Italian artillery officer Ignazio Porro developed a telescope that erected the image by using two prisms. The Porro prism design (and other arrangements of prisms) effectively folds the light-path allowing much shorter instruments to be made. When independently reinvented by Ernst Abbe in 1870 (who worked in association with optics company Carl Zeiss in Jena) this much more compact design formed the basis of modern prismatic binoculars. During the Twentieth Century advances in optical understanding and technology included coated lenses to increase light transmission and colour fidelity, nitrogen filling for fog and water proofing and more recently fluorite crystal lenses with their very low dispersion and excellent light transmission.

These days there are essentially two types of binocular widely available: roof prisms and Porro prisms. The majority of modern binoculars are of the roof prism design which has a more slim-line shape and when combined with internal focusing gives good waterproofing and shock resistance.  Schmidt type roof prisms are the most commonly used

The Nikon E II 8x30
Dialyt (left) and Schimidt (right) type roof prisms

Top of the range.
A cut away Zeiss Victory FL 8x42 with
Schmidt type roof prism

Although Porro prisms are mostly at the cheaper end of the market due to there simpler construction, there are still some high-quality examples available such as the Nikon E II and the Swarovski Habicht. Modern top of the range binoculars are ultra-precise and constructed under laboratory conditions using exotic materials, complex and time-consuming process and rigorous testing.

Here are some of the terms associated with binoculars that you might come across and what they mean.

APO. Abbreviation of apochromatic. A completely apochromatic lens system corrects all chromatic aberration (colour fringing).  Leica's APO-Televid scopes also have fluorite lens elements.

BK-7 and BAK-4 prisms. These are two grades of glass, boroscilicate BK-7 (generally in cheaper optics) and barium crown BAK-4 (delivering better sharpness)

ED, HD, HR. Terms used to denote higher-quality glass models, HD standing for High Definition, ED usually standing for Extra-low Dispersion, and HR standing for High Resolution. These terms are not standardised, one companies standard glass can sometimes be as good as another's HD. With Leica and Swarovski HD denotes models with fluorite lenses.

Eye relief. This is the distance that your eye should be from the eyepiece lens to get the optimum image. Spectacle wearers often need a longer eye relief when using binoculars with there glasses on.

Nitrogen filled. Waterproof binoculars are often filled with a dry, inert gas (most commonly nitrogen or argon) to prevent internal fogging.

Phase correction. Coatings applied to the surfaces of roofprisms to reduce dispersion, giving sharper images with better contrast and reduced chromatic aberration (colour fringing).

For any more information please contact us through our website or drop in and see us at Glandford or Cley Marshes.

Cley Spy