Astronomical Refractor

Astronomical Refractor

astronomical telescope advice plz!?

I got a star 70060 starter astronomical telescope from telescopeplanet.co.uk for christmas and i need some advice on how to get the best results from it, it's a
60mm Refractor Telescope with
3 Eyepieces (SR4mm, H12.5mm, H20mm, 1.5X erecting eyepiece & 3x barlow Lens)

which is the best lens combination to view the planets in the night sky? all i've managed so far is a view of the crescent moon and the REALLY bright star that's visible beside it just after dusk, anything else is blurry and impossible to get in focus any kind of help would be ace as i really want to get some use out of this wonderful present!
any advice on things to look out for too would be great!
many thanks in advance

Your scope will ideally support a maximum magnification of around 120x; that would depend on the quality of the optic and the prevailing conditions.

We should begin by losing your barlow lens and your erecting eyepiece. They are useless and the quality on these (provided with cheap starter scopes) is usually so low that they would be useless on any scope, of any size.

Then you should adjust your finder scope so that it is aligned with your main scope. Just aim the main scope at some conspicuous target (like a sign or tower in the distance, and adjust the finder until it points at exactly the same spot. You have a very poor excuse for a finder; but, if you align it correctly you should be able to get some help from it. The finder serves as a wide angle targeting device; the idea is to get it close enough so that you can see the object in the main tube.

Once you get that done, insert your diagonal into the focuser, and then your 20mm eyepiece. This should yield around 35x which is plenty to make out the brighter planets. Also, be aware that objects which are higher up in the sky will look much clearer then those near the horizon; you have to cut through more atmosphere when looking at the lower angle.

Today, both Jupiter and Mercury were very low on the Western Horizon at dusk; the season for Jupiter has passed and we will not be seeing much of it again until again until late spring. Mercury is Always an elusive target; it is never more then 15 degrees or so from the Sun. So, unless you have installed a full aperture solar filter, you are limited to catching periodic glimpses of Mercury at dusk or dawn.

Venus was that very bright star like object that you saw near the Moon, it will be back again tommorow, so you will have another chance to look at it. At 35x you should be able to make out what looks like a tiny version of our Moon during first quarter. If you look closely, both mercury and Venus go through phases.

Saturn comes up from the due east at around midnight. The ring alignment right now is at a right angle to us so they are edge-on to us. At 35x you should be able to see a small sphere with a line through it; if not, switch to the 12.5mm eyepiece and try it again at 56x. If the conditions are right you will see Satirn's giant moon Titan as a small point of light out beyond the end of the rings.

As you wait for Saturn to climb to a good position, you can turn your scope toward Orion. The Nebula is bright enough to be seen as a dim grey cloud with a 60mm; you should also be able to make out Trapesium, the four bright stars that sit as a tight little square right in the middle of the nebula.

Clear Skies!

For More Astronomical Refractor Info Click On The Links Below

The development of building a telescope was greatly aided by the construction of the achromatic lens.

The Achromatic Refractor

In 1733, the achromatic lens was invented by Chester Moore Hall, an English barrister. This was accomplished by combining a convex crown and a concave flint lens in such a way that their focal lengths were inversely proportional to their dispersions.

Although a number of telescopes were made according to Hall's instructions, the benefits of the achromatic lens do not appear to have been made available to the public until John Dollond invented it independently in 1758, and patented it. Dollond's efforts led to a demand for clearer glasses of more varied densities and of less equal dispersions, needed to improve achromatism, and chemists pursued experiments in learning how to control the refractive indices of melts, and in the pouring of large disks of limpid, homogeneous glass.

Altogether, excellent progress began to be made, and by 1800 achromatic objectives 6" in diameter were being turned out. Some of the best glass had been manufactured by Guinand, a Swiss who worked with Fraunhofer from 1805 to 1814. Fraunhofer produced a number of splendid achromats up to 9" in diameter.

Dollond was making refractors (spyglasses) with single-lens objectives as early as 1742, his price for a 2-foot telescope then being 7s 6d. In comparison, in 1762 he sold a 2-foot telescope with a two-lens objective (achromat) for 2 guineas. The lens diameters in each case were just under 2".

In 1783, with a view to combining the benefits of the wide field of Huygens' eyepiece with a means of making micrometric measurements of an image in the focal plane, Jesse Ramsden, an English optician, designed the compound eyepiece. Building a telescope was becoming more like the process undertaken today.It can be seen that a measuring device, such as adjustable parallel wires, set in the focal plane would be magnified along with the image. Measurement of an image in the focal plane was by no means a new idea; probably this had been first accomplished by Gascoigne, an Englishman, about 1638.

With the advent of the achromatic lens, the erecting or terrestrial eyepiece assumed considerable importance. This type of eyepiece was first suggested and used by Kepler, and improved in design about 1645 by Antonios Maria v. Schyrle, a Capuchin monk better known as Rheita. It is mentioned here because it spelled the rise of the refractor and the decline of the Gregorian for terrestrial use

In the early part of the 19th century, small achromatic refractors were being manufactured by several concerns. For those not having the means to buy achromats, telescopes with single-lens objectives continued to be made. Enterprising opticians were also offering lens sets that could be assembled into simple refractors.

The Modern Era

The method of chemically depositing silver on glass discovered about 1840 by Justus von Liebig, of Nuremberg, was successfully applied to a small glass telescope mirror in 1856 by Karl Steinheil, a German physicist, and independently in the following year by Jean Foucault, the famous French physicist.

Various processes of plating glass with metal for the making of mirrors had been known and practiced for centuries, but for one reason or another, the coatings were unsuited for front-surface reflection.

Then, in 1858, Foucault announced the development of his amazingly delicate and simple test for a concave reflecting surface, using an illuminated pinhole and a straightedge placed in the vicinity of the center of curvature of the mirror. The pinhole and straightedge were the outgrowth of earlier experiments in which simultaneous microscopic comparison was made of a pin point, likewise placed at the center of curvature of a mirror, and its reflected image, which was caused to fall alongside.

The last speculum of note to be constructed was one four feet in diameter, made by Grubb in 1870 for the Melbourne Observatory. Silver-on-glass mirrors replaced the more expensive and difficult-to-work speculum. It tarnished, but not nearly so quickly as speculum, and it could be removed by chemical means and a new coating applied without upsetting the figure of the glass surface.

Building a telescope was becoming closer to being constructed in the style we know it today.

You'll Soon Be Gazing At The Stars Through Your Very Own Telescopes

Visit: http://www.maketelescopes.net

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Many thanks for reading our Astronomical Refractor article

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