Rob

Could launch a XP VM?..

Wayne's adapter is fantastic.. such a quality product... big thumbs up from me also.

I use Craterlet

Rob

Thats good.. bring on the 880 image fest!!!

And with my 2x Shorty barlow

Sorry the 200P.. with a washing line 20% through the image!!!

Flashed my first Cam tonight and grabbed a quick image. I have no IR cut, and it was very gusty.. also no registax whiz. sorry for my lack expertise!. Used my 3x Vixen barlow. only had my RA drive on also. Not great, but an insight to where / how good the cam maybe??

First cam delivered & flashed!..

Still waiting!.. so I maybe the last!

Indeed Eddy.. it will come to those that wait!.. and wait, and wait lol

Lets hope I can grab some of your skies then!!.. 100% cloud in Soton

I ordered a second today!.. bet I get that before the first...

so im the only 1?! lmfao are they hating or what?! lol

Apparently it went out on Friday 10th aswell so should have been here today!

Me too!!

I only ordered mine yesterday 2pm and they were both here this morning!

Blimey luck of the draw I guess!.. beats me how I can order stuff from the US and it can be with me within 7 days del by mr postie.. but some thing 50 miles away can take 4/5 days!!

Not rec mine yet.. ordered them Friday. Never mind they will turn up soon I'm sure

Not received my cam yet.. hoping it arrives monday so I can give the flash a go!!

Thanks for the info Russ

Well I have to share with you the super service from this up and coming telescope supplier. I went to Astrofest and OVL were offering 10% on the whole range. I had an issue that meant I could not place my order on the day (My new Credit Card had not come through). I spoke to the guys at OVL on the stand and explained i could not place my order, as only Paypal offered. They claimed speak to a retailer to see if they could help!.

Came back thinking this was a loss. Anyway spoke to the guys at Harrison Telescopes on Saturday at 5pm.. yes 5pm. They claim to work 7 days a week, and they sure do!. I explained the issue with the 10% and lack of card at Astrofest.. within 45mins the deal was done... on trust to provide the 10% discount. They asked me to pay by Paypal then refunded me the 10% discount with 20 mins at 7pm Saturday!!.

This is first class service.. I have no hesitation to use them again, and regard them as providing service from astronomers, to astronomers.

Thanks Harrison Telescopes!.

Regards

Rob

Telescope Types

Ok, there are three principal telescope types. These being

Refractors

These are based on a straight lens system. Refractors have long, thin tubes with an objective lens at the front that collects and focuses the light. The earliest of this type of telescope was used by Galileo to study planets.

They are now used mostly for lunar, planetary, globular cluster, and binary star observing, they can perform admirably on brighter* Messier & NGC objects. Many amateur astronomers prefer the crisp, high contrast, diffraction free images of a good refractor.

A useful rule of thumb in astronomy is that a good 3" to 4" refractor will usually perform as well as an average 6" to 8" reflector or catadioptric for seeing details on the Moon and planets.

Refractors do not have a secondary mirrors or multiple optical paths to introduce light scattering or diffraction. These brighten the sky background and reduce contrast.

Refractors also have the highest light transmission, ie the percentage of the light gathered by the scope that actually reaches your eye and can transmit 90% or more of the light they collect, compared with the 77% to 80% transmission of reflectors and 64% to 75% typical of catadioptrics.

The light transmission of a refractor rarely deteriorates with age, as do reflectors and catadioptrics, since their mirrors slowly oxidise and lose reflectivity over a period of time.

With good seeing conditions, refractors can reveal subtle lunar and planetary detail within a good contrast range.

Diffraction spikes on a reflector's star images, caused by its secondary mirror spider vanes, are absent in an unobstructed refractor. With no diffraction spikes to hide faint binary star components or smear globular clusters, refractors can resolve closely spaced binary stars more easily than a typical reflector.

Since the Moon and planets are all brightly lit by the Sun, high light gathering power is not as important as high magnification within the solar system. The relatively small aperture of a refractor is therefore often an advantage for this kind of observing.

For lunar, planetary, binary and star cluster observing, a refractor may be perfectly adequate.

Shortcomings.

Refractors suffer from chromatic aberration, or false colours. This is an optical defect that produces a faint coloured 'halo' around bright stars, the limb of the Moon, and the planets. Chromatic aberration becomes more visible as the aperture increases and the focal ratio decreases, although modern optical systems can minimize the problem in two element achromatic refractors and virtually eliminate it in three to four lens apochromatic systems. Of course a price to fit this quality of lens step also applies

While they are light weight in smaller sizes, refractors become bulkier than reflectors or catadioptrics for apertures approaching 100mm (4"). A 100mm (4") refractor typically costs and weighs 2 to 6 times as much as a 115mm (4.5") reflector or 90mm (3.5") Maksutov-Cassegrain.

If high light grasp is not essential, ie for observing faint galaxies, where a larger reflector would have the edge, the clarity, contrast, and good image quality of a refractor is worth considering.

Newtonian Reflector

These are based on mirror systems, the most popular of which is the Newtonian invented by Isaac Newton in 1668. Newtonian reflectors offer more performance for your money than any other telescope type. Reflectors have no lens at the front. Instead, the light is collected by a parabolic mirror at the bottom of the telescope tube, which reflects light onto a secondary mirror near the top of the tube. This secondary mirror (called the flat) is used to reflect the light from the main mirror into the eyepiece at the side of the tube.

The reflector's large light gathering area and relatively short focal length can provide bright images of deep space objects that are too faint for any small aperture refractor. And the reflector's large aperture can resolve details within those objects with a precision that not many small scopes can match.

The penalty you pay for this performance is typically one of large size and weight, although not one of high cost, as reflectors cost the least per millimetre (inch) of aperture of any telescope type.

The reason is because a Newtonian reflector has only one mirror to grind and polish to a precise curve (with an accuracy of around 100 nanometres [100 x 10-9m ]( 4 millionths of an inch) or better.). A refractor, on the other hand, has two to four lenses ( not including the eyepiece ), with four to eight precision surfaces to shape. And those lenses might have to be expensive and esoteric formulations in order to provide satisfactory images. Similarly, a catadioptric scope has three or four curved optical elements to shape to a high degree of accuracy.

All that extra mirror, lens grinding and costly optical glasses in refractors and catadioptrics isn't cheap. It makes the one parabolic mirror and one flat mirror optics of the Newtonian reflector the least expensive to make, hence its lowest cost.

For the same money you get more aperture with a reflector than with any other type of telescope. All other things being equal, the bigger the aperture, the better the performance. An 8" reflector typically costs 50% less than a 4" refractor, and little more than 4" catadioptric, but will have four times the light grasp of either.

For purely visual deep space observing, Dobsonian reflectors are very cost effective and a good choice. These are Newtonian types with a simplified mount. With huge mirrors (up to 16" in diameter) to gather light, and inexpensive wood mounts, these new Newtonians have brought about the age of the "light bucket" in amateur astronomy. The deep space observer on a budget has never had it so good.

If astrophotography is going to be your thing, a large aperture equatorial mounted reflector is excellent for recording deep space objects in detail, as well as visual observing.

Shortcomings.

There are five:- diffraction, coma, size, weight, and added maintenance.

Light diffracted, or scattered, by a reflector's diagonal mirror reduces image contrast in lunar and planetary observing, and can mask subtle surface details. In addition, diffraction spikes on star images, due to the spider vanes that hold the diagonal mirror, can hide faint binary star components and smear globular cluster detail.

Because of the parabolic shape of their primary mirrors, all reflectors have coma, an optical defect in which stars appear triangular or wedge shaped at the edge of the field. The faster the focal ratio, the smaller the coma free field. This can be annoying in photos, where the entire field is available for leisurely inspection. It is usually unobjectionable visually, however, since objects of interest are normally kept in the centre of the field, where eyes and eyepieces are sharpest and coma is not a factor.

Since an 8" reflector can weigh 50% more than an 8" catadioptric, and its 48" long optical tube is not the easiest thing in the world to manage in an apartment / flat elevator / lift. A large reflector usually requires the elbow room afforded by a suburban environment. Also, since city light pollution compromises deep space performance by washing out faint nebulae and galaxies, dark sky observing sites are always recommended with large reflectors.

In addition, unlike refractors or catadioptric telescopes, a reflector can require frequent re-collimation or alignment of its optics. However, this maintenance typically averages only a few additional minutes of work per observing session.

These drawbacks aside, for serious visual observing of faint galaxies and nebulae, as well as for lunar and planetary observing, you'd be hard-pressed to equal, much less surpass, the price / performance ratio of a Newtonian reflector.

Catadioptric Reflectors

These are modern compound, or lens/mirror combination telescopes and combine many of the best features of refractors and reflectors into one package, with few of their drawbacks. Catadioptrics include Schmidts, Maksutovs and Schmidt-Cassegrains (SCT).

They allow the performance of a large aperture, long focal length scope to be folded into a reasonably lightweight and transportable package which can be very useful if the telescope is transported to dark sky sites.

Because of their optical design, catadioptrics are almost completely free of the coma found in reflectors and the chromatic

aberration found in refractors. Stars are point-like and coma free across the visual field of a catadioptric telescope, and there is no trace of coloured fringes around bright stars and planets to mask faint detail and colours. Some curvature of field is often visible in catadioptrics, particularly in fast focal ratio models, but it usually shows more at the edges of wide field photo's than in visual observing.

A catadioptric's setup and takedown time is short, due to its lighter weight, and compact size.

Shortcomings.

An 8" Schmidt-Cassegrain costs 50% to 300% more than an 8" reflector (although about the same as many 4" refractors).

Schmidt-Cassegrain catadioptrics do not have as wide a contrast range on the moon and planets as a refractor or most f/6 to f/8 reflectors, because of the extra light scattered by its more complex optics and folded light path, nor will it be able to resolve close binary stars as easily. However, a Schmidt-Cassegrain will usually outperform a fast (f/4.5) focal ratio reflector of similar aperture on the planets and binary stars due to the absence of secondary mirror spider vanes, which usually cause diffraction effects in Newtonian types.

A Maksutov-Cassegrain has better contrast than a Schmidt-Cassegrain, often equalling that of a refractor of similar aperture, because it has a smaller secondary mirror obstruction.

Although their large apertures allow detailed deep space observing, catadioptrics generally do not have as bright an image as other telescope types of similar aperture and power. A catadioptric can have a light transmission of 64% before secondary obstruction light losses are allowed for ( 70% to 75% with multicoated optics ), compared to 90% of a similar aperture multi-coated refractor and the 77% to 80% of a reflector.

Despite these shortcomings, if it fits your budget and you need a portability, then a good catadioptric is a wise investment

Clear Skies

Rob

Source: R.M. Clarke. The salopain web - edited by R Hughes. 2005

Choosing a Telescope

1: Avoid buying a low cost "beginners", or "starter" type telescopes from high street stores / tv shopping channels. You will almost certainly be disappointed and discouraged. Most of these inexpensive telescopes have poor optics, with flimsy mounts that will be of no use and provide you with shaky images.

A good start telescope range such as the Skywatcher / Celestron will give the amateur astronomer a great start in the hobby. As with binoculars, the most important factor is the light gathering power of the telescope, this of course depends on the lens / mirror diameter, known as aperture. The bigger the aperture, the more light is gathered by the telescope.

2: When buying a telescope, you need to consider portability.

A 16" Dobsonian or (light bucket as some may say) might be appealing if you're interested in deep space observing, but not if you live in a flat on the 4th floor!!. Carrying around a telescope of that weight 80 kilos (176 lbs) which could be around 67 inches long, can be daunting + put you off the hobby in one easy step! (oh yes, it can also put your back out!). So match your ambitions to your main observing site. Its easy to get aperture fever!. Don't overdo size, weight, or price. Choose a telescope you can carry and set up by yourself, just in case a family member or friend can't or won't go with you.

3: What kind of telescope?

Many telescopes are capable, with varying degrees of success of showing you virtually everything in the night sky. But no one telescope does it all perfectly. This is the hardest part of telescope selection. Every telescope excels in particular areas, and others where it's only adequate. Refractors, for example, are usually better at high power lunar and planetary observing than they are at finding faint fuzzy nebulae and galaxies. Reflectors are the reverse.

4: What magnification should you use?

Any telescope can magnify to any extent, however, the highest useful power of a telescope under ideal seeing conditions is only 50 to 60 times per inch (25mm) of aperture. Under average seeing conditions, atmospheric turbulence limits the highest useful magnification to 25 to 30 times per inch (25mm) of aperture.

So, how much power do you really need? High magnifications are OK when viewing the solar system, as there is plenty of light available, although you don't always need to use high magnification as there is plenty of lunar and planetary detail to see at 50 to 100 times.

Except for resolving close binary stars and globular clusters, very high magnifications are not usually needed outside the solar system either as stars always look like points of light, no matter what the magnification. Many planetary nebulae, like the Ring, Nebula, M57, look great at 100 times, but are too dim to see well if you increase the magnification. The Andromeda Galaxy is over 3° across, or six times the diameter of the moon. You don't need high magnification to see something that big!

Clear Skies

Rob

Source: R.M. Clarke. The salopain web - edited by R Hughes. 2005

[glow=red,2,300]Choosing Binoculars[/glow]

Binoculars (or bino's as their affectionately known) are often ignored by beginners, yet they offer a low cost start to the hobby. Portability and a wide field of view can often be a great place to start, Bino's offer this. One of the disadvantages is that, being hand held, they can give unsteady images. Obviously this is due to hand shake however can be overcome by using a tripod. Some recent binoculars have an image steadying mechanism, but this comes at a price!.

The performance of binoculars is specified using a two number system, such as 6×30 or 8×50. The first number represents the magnification, and the second the diameter of the objective lens in millimetres.

The object lens is the one at the front of the binoculars. The larger the diameter (or aperture as its know), the better the light gathering power. This is the most important property for observing the night sky. Beginners usually assume that the higher the magnification the better. In general it is often better to choose a pair of binoculars with a wide field of view, i.e. a lower magnification. Higher magnifications can resolve double stars, but narrows the field of view, making it difficult to find your way around the sky. It is important to note that higher magnifications also magnify the atmospheric instability. This causes stars to twinkle, and, of course, it also magnifies hand shake, making stars appear to jump around in the field of view. For this reason, 10 times magnification is considered the maximum for hand-held bino's.

The bigger the aperture of the objective lens the brighter the image. Most astronomical objects are hard to see not because they are small, or distant, and need more magnification, but because they are faint and need a larger aperture to gather more light. A pair of 8×50s collects twice the amount of light as 8×35s, and hence everything appears to be brighter.

Suitable binoculars are 10x50; 15x70 and 20x100 giving magnifications of 10 times, 15 times and 20 times with lens diameters of 50mm; 70mm and 100mm ( 2 inches; 2.75 inches and 4 inches) respectively. For best results, the ratio of aperture to magnification should not exceed 5, that is lens size (in millimetres) divided by the magnification should be no more than 5.

Bino's are good start point to the hobby, but equally an essential part of your kit bag even if you have a telescope!.

Clear skies

Rob

Source: R.M. Clarke. The salopain web - edited by R Hughes. 2005