astronomik.gif (3506 Byte)

GSO Dobsonians
GSO is one of today's well known premium quality manufacturers for Newtonians and Dobsonians. The telescopes have an excellent value for money and a quality comparable with other more expensive manufacturers.

Dobsonians are ideal for visual observers with no interest in astrophotography, but who wish to get the best out of their money in terms of visual performance.
Sooner or later all amateur astronomers face the same dilemma: They want the biggest telescope they can get their hands on (since, as they say, "Aperture can only be replaced by even more aperture"), but their finances draw the line terribly soon.

This is partially due to the inherent expenses for high-quality optics, but also due to the fact that a large telescope also requires a heavy - and expensive! - mount to carry it.

John Dobson (being in a monastery) faced a similar problem in the 1970's and therefore constructed and built several telescopes of a radically new design. To put it all in a nutshell, he cut out everything the telescope could spare and still remain a functional telescope. The result was the "Dobsonian telescope": A large Newtonian optical tube (Dobson actually ground and figured the mirrors himself!) mounted in what is little more than a box of wood. There are no fancy setting circles, worm gears or motor drives. You basically put all your money into big, good quality optics.

The result are very large aperture telescopes at a fraction of the cost of most conventional models!

The Dobsonian telescope design is by many considered to be the ultimate, no-nonsense telescope. It will show you extraordinary details in all fields of visual astronomy, especially deep-sky observations (that is: observations of faint objects like galaxies, gas nebulae and the like).

Still, you have to be aware that there is (in fact, that there must be!) also a limitation: Dobsonian telescopes are by design not suited for any kind of astronomical photography.

Fortunately there is a way to make your dobsonian telescope fit for astronomical photography. You take the optical tube and put it on an equatorial mount. The drawback: Obviously this means that you will need a big and heavy, and therefore expensive, mount to do that. Consider this whenever you want to buy a Dobsonian telescope and do not rule out astronomical imaging!

C-Line Dobsonians
The GSO C-line Dobsonians offer an outstanding value for money and performance. The low prices are achieved mainly by cutting costs on the accessory side, the optical performance is not compromised!
TS1021000.jpg (7818 Byte)
TS127v.jpg (21047 Byte)
TS150.jpg (24627 Byte)
C-Line - Aperture 200mm / Focal Length 1200mm
2" focuser, good quality optics, top price offer
C-Line - Aperture 250mm / Focal Length 1250mm
2" Crayford focuser, 8x50 finderscope, 2" eyepiece
C-Line - Aperture 300mm / Focal Length 1500mm
Excellent value for money
2" focuser, 8x50 finderscope, 2" eyepiece
BCR / SCR Line Dobsonians
These Dobsonians have the same great optical performance of the economy line, but have more and better accessories.
TS1021000.jpg (7818 Byte)
TS127v.jpg (21047 Byte)
TS150.jpg (24627 Byte)
Aperture 200mm / Focal Length 1200mm
2" Crayford focuser, 2" wide angle eyepiece, cooling fan, 8x50 finderscope, ...
Aperture 250mm / Focal Length 1250mm
2" Crayford focuser, 2" wide angle eyepiece, cooling fan, 8x50 finderscope, ...
Aperture 300mm / Focal Length 1500mm
The Flagship of our GSO Dobsonians: 2" Crayford focuser, 2" wide angle eyepiece, cooling fan, 8x50 finderscope, ...
GSO Truss Tube Dobsonians
Above a certain size closed tube Dobsonians are no longer portable. The new GSO Truss Tube design solves this problem!
Aperture 400mm / Focal Length 1800mm
2" Crayford focuser, 2" wide angle eyepiece, cooling fan, 8x50 finderscope, ...


Please send requests or online orders to: sales@telescope-service.com



GSO Dobsonian 200E and C - Aperture 200mm - Focal Length 1200mm
A low-budget, excellent quality entry into the world of 20cm telescopes!




Image: GSD 200 C - The GSD 200 E is similar in appearance, but has a different focuser.
This image shows the smaller 6x30 finderscope. Now the Dobsonian comes with the larger 8x50 finderscope.


GSD 200E and C - Aperture 200mm - Focal Length 1200mm

Within our GSO Dobsonian line this particular model serves a very clear purpose: To offer a large aperture and an excellent image quality at as low a price as possible. The value for money is fabulous.

At the same time the optical and mechanical quality is at the same high standard that our customers have learned to respect in all GSO Dobsonians!

Innovative features like the primary mirror cooling fan and azimuth roller bearing top off the excellent package of our 8" GSO Dobsonian.

Gas Nebulae and Galaxies in Detail
With this telescope you will be able to see fine details in planetary nebulae - remnants of old, dying stars. You will see the spiral arms in many galaxies. Large nebulae like the Veil nebula in Cygnus can be seen with many beautiful details.

The Moon and the Planets
Sharp images of the moon and the planets require excellent optics. The GSO Dobsonian has a precisely figured parabolical primary mirror for superb images. The small secondary mirror and the four thin secondary spider vanes bring along even sharper and more detailed images than would be possible with a large secondary mirror that is held by three thick spider vanes.

Grab-And-Go Setup
The simple and intuitive way to use this telescope makes it much easier for beginners to spend their first joyful hours under the starry sky. Set-up is as easy as you can imagine: Just put the rocker box on the ground, insert the telescope tube and put the springs in position and you're ready to go!

Further Information: Visit our new Online Shop!


Recommended Accessories
Here you can find accessories that are important and helpful for almost any telescope. Cleaning tools, filters, star charts, ...


Please send requests or online orders to: sales@telescope-service.com


GSO Dobsonian 200 BCR - Aperture 200mm - Focal Length 1200mm
High quality accessories: 2" Crayford focuser, wide angle eyepiece, roller bearing, ...





Gas Nebulae and Galaxies in Detail
With this telescope you will be able to see fine details in planetary nebulae - remnants of old, dying stars. You will see the spiral arms in many galaxies. Large nebulae like the Veil nebula in Cygnus can be seen with many beautiful details.

The Moon and the Planets
Sharp images of the moon and the planets require excellent optics. The GSO Dobsonian has a precisely figured parabolical primary mirror for superb images. The small secondary mirror and the four thin secondary spider vanes bring along even sharper and more detailed images than would be possible with a large secondary mirror that is held by three thick spider vanes.

Grab-And-Go Setup
The simple and intuitive way to use this telescope makes it much easier for beginners to spend their first joyful hours under the starry sky. Set-up is as easy as you can imagine: Just put the rocker box on the ground, insert the telescope tube and put the springs in position and you're ready to go!

GSD 200 - Aperture 200mm - Focal Length 1200mm

This is the instrument that probably gets closest to the ideal "allround" visual telescope. It's high-quality mirror shows astonishing details on the moon and the planets while its large aperture of 203mm (8") gathers enough light to show virtually hundreds or thousands of faint galaxies and nebulae. This may well be the only telescope you will ever need!

Features of this telescope:
- high quality 2" Crayford focuser - zero image shift
- azimuth roller bearing for smoother tracking of the stars
- primary mirror cooling fan for quicker cool-down
- multi-coated 8x50mm finderscope
- eyepieces and accessories worth approximately 150 Euros

A comparable telescope got excellent results in a review in Sky and Telescope (January 2000, the model name was Orion Sky-Quest).

Please see the General Notes on Dobsonian Telescopes to find out why a Dobsonian might be just the telescope for you!

As focal length and mirror diameter suggest this is not a small telescope by a margin, but it is still small and portable enough not to pose any problems getting it wherever you want to set it up to observe. It will fit even in small cars.

Set up is extremely easy, as is actually using the telescope. Just push the telescope into whatever direction you want to look. You do not have to release clutches or turn any slow-motion knobs in order to slew it.

Secondary mirror obstruction is only 25%, four thin spider vanes (each only 1mm thin) keep the secondary mirror in place. Consequently contrast and definition are very good, more so than one might imagine. The GSD 200 will actually show more detail on the moon and the planets than many apochromatic refractors!


Using the Dobsonian Mount
The mount of a Dobsonian telescope is called "Rocker-Box", a fitting name for the uniquely simple and well-working design. The rocker allows you to point the telescope at any point in the sky and allows for comfortable, intuitive movement.

Moving the telescope is very simple, just push the telescope into the right direction – no need to use clamps or motors, it doesn't get more simple than this!

Despite its simple design you will be able to track objects precisely even at high magnifications. With a little experience 250x is no problem at all.

Back-Focus
The Dobsonian was designed for visual applications. It is sometimes not possible to find focus with SLR cameras. In such cases we recommend to refit the telescope with the low profile Crayford focuser.

Some eyepieces with a low field stop might need to be pulled out of the focuser by a little margin in order to reach focus. If you do not wish to do that you can buy the optional 35mm extension tube.

Specifications:
 
Aperture / Focal Length 200 mm / 1200 mm
Focal Ratio f/6
Secondary Mirror 50mm diameter
Tube Dimensions approx. 115cm x diameter 23cm
Tube Weight approx. 9.5kgs
Rocker Box Dimensions approx. diameter 50cm x 60cm
Rocker Box Weight approx. 11.2kgs
Focuser 2" Crayford focuser with 1.25" adaptor
Finderscope 8x50 quick release finderscope
Primary Mirror very precisely figured parabolical primary mirror. Better than diffraction limited. BK-7 optical glass.
Accessories 2" wide angle eyepiece TS WA 42mm (Erfle design) - fully multi-coated
1.25" Super Plossl - fully multi-coated
Moon filter
Cooling fan
Roller bearing in azimuth


The active cooling fan reduces cool-down time of this telescope significantly.

Excellent Crayford 2" Focuser & Red. 1.25" - with 1:10 microfocuser
the Crayford focuser has zero image shift and offers very smooth focus motion. Including 1.25" adaptor. Both 2" and 1.25" with brass compression ring...... further information

High Quality Accessories & Eyepiece Tray
TS WA 42
 - 2" Erfle wide angle ......  further information

TS Super Plossl 12mm ..................  further information
Moon Filter ..... more contrast for lunar viewing

8x50 Finderscope with Quick Release Bracket
The achromatic objective is multi-coated for a brighter image.

Thin 4-Vane Spider - More Contrast
The less diffraction the better the contrast. Thin secondary spider vanes improve contrast compared with cheap three vane or thick four vane spiders - important for the moon and the planets
Industrial Roller Bearing for Azimuth - Not Just a Simple Friction Bearing
The roller bearing makes moving the telescope in azimuth much easier. If you want more friction simple felt pads will do the trick.
Spring Tension System
The spring tension system prevents the telescope from moving on its own when exchanging eyepieces.


Optional Tube Rings
GSO Dobsonians are no one-way street!

Dobsonian telescopes are ideally suited for visual use - with no other telescope design will you get this amount of observing fun for your budget!

Astronomical imaging on the other hand is barely possible with any Dobsonian telescope. Only the very brightest objects (the sun with the proper filter, the moon, the brightest planets) can be photographed without a tracking motor.

Deep-sky objects (galaxies, gas nebulae) require long exposure times and consequently a solid equatorial mount.

Two Telescopes in One

Our idea was quite simple: As long as you desire just to enjoy the beauty of the various celestial objects and joyful hours behind your eyepiece you should set up the GSO Dobsonian as it is - as a Dobsonian telescope. Setup takes only a few seconds and you will be observing in no time. Also, this combination is very portable.

For astronomical imaging or the comfort of a tracking motor just attach the cradle rings and put the tube on an equatorial mount. (see image to the left)

Our recommendation: The Celestron ADM is a solid mount that will carry your 200mm "Newtonian" with good stability. For astro-imaging we offer a well working dual axis motor-drive. This combination will bring much joy to your astrophotographical ambitions.

More details on the ADM

Many other interesting mounts can be found here.

Primary Mirror Substrates BK-7 and Suprax

The image quality itself is not affected by the mirror substrate. Likewise cooldown-time is nearly the same regardless of which of these substrates you choose. The integrated cooling fan shortens the cool-down time considerably.

The only difference between the mirrors is the image quality during cool-down (between 15 and 45 minutes, depending on the ambient temperature).

BK-7 reacts about twice as strongly as Suprax. This means that you can use higher magnifications sooner with a Suprax mirror. Suprax has roughly comparable thermic properties as Pyrex. Once cool-down is complete there is no difference in optical quality.

Useful Links:
Eyepieces
A broad selection of 1.25" eyepieces can be used with this telescope.

Item No Short description Price - Euro incl. VAT
GSD 200 BCR GSO Dobsonian 200/1200 - 2" Crayford focuser - BK-7 primary mirror 378.-
limited special offer
only as long as supply lasts!
GSD 200 SCR GSO Dobsonian 200/1200 - 2" Crayford focuser - Suprax primary mirror 648.-
GSD 200 LX Limited Edition - GSO Dobsonian 200/1200 with Low Expansion primary mirror. See special offers section for details. 398.- / 598.-
CR 230 Cradle rings for the Dobsonian 89.-

Recommended Accessories
Here you can find accessories that are important and helpful for almost any telescope. Cleaning tools, filters, star charts, ...

The TS Eyepiece and Accessory Case isn't just an assortment of randomly picked eyepieces, we have put a lot of thoughts into choosing a fine range of eyepieces that will work with nearly all telescopes. These great eyepieces are included in the TS eyepiece and accessory case:

- three excellent quality TS Super Plossl eyepieces
- one TS wide angle eyepiece
- our excellent TS Barlow lens (2x/1.5x)
- five carefully chosen TS colour filters and one grey moon filter (not just a cheap green filter)
- an adaptor for focal and eyepiece projection astro-imaging

All comes in a beautiful, foam-lined aluminium case .......... Link to further information


Please send requests or online orders to: sales@telescope-service.com


GSO Dobsonian 250C - Aperture 250mm - Focal Length 1250mm
Economy line GSO Dobsonian with good 2" accessories



GSD 250 C - a powerful and very affordable telescope not only for observing the deep sky objects, but also for observing the planets with high contrast.


Now the GSD 250 C comes with a good quality Crayford focuser for extra-smooth focus motion.
GSD 250 C

Why should you sacrifice quality only because you want to save money? The GSO Economy line was created to offer Dobsonian telescopes as cheap as possible without reducing the quality of the optics. In our opinion the result is an excellent telescope at an exceptional value for money.

Optical Performance

The telescope is equipped with the same high quality GSO parabolical primary mirror as the GSD 250 BCR and SCR. We guarantee a diffraction limited performance.

As a result you get sharp and contrasty images of the moon and the planets as well as impressive views of countless deep sky nebulae and galaxies. Many details can be seen in these nebulae.

Simple Operation

The telescope is operated with ease by a single person. The weight and dimensions are small enough to be handled by one person as well. The tube will fit on the back seats of most cars.

Using a Dobsonian is very simple. The telescope is moved manually around a horizontal (azimuth) and vertical (altitude) axis. An azimuth roller bearing and an altitude Teflon friction bearing are used to offer good motion smoothness.

Further Information: Visit our new Online Shop!
Recommended Accessories
Here you can find accessories that are important and helpful for almost any telescope. Cleaning tools, filters, star charts, ...


Please send requests or online orders to: sales@telescope-service.com


GSO Dobsonian 250 BCR - Aperture 250mm - Focal Length 1250mm
With an aperture of 250mm this telescope is a very popular combination of light-gathering power and portability.







The GSD 250 is a well made telescope with excellent optics and a very smooth Crayford focuser. The focuser has zero image shift.
The telescope now includes a dual speed 1:10 microfocuser (not yet shown on the image)

10 inches (250mm) of aperture make this telescope a Deep-Sky big gun.

The TS WA 30mm 2" wide angle eyepiece
offers a far larger true field of view than is possible with any 1.25" eyepiece. That is particularly important for viewing gas nebulae and galaxies.

The secondary mirror obstruction is around 25%. This means that the GSD 250 is also well suited for lunar and planetary observations. Under good seeing conditions you will see plenty of craters, ridges and mountain ranges on the moon in finest detail. Planets, too, will make for innumerable joyful observing hours. You will see finest structures in Saturn's rings and many surface details on Mars. The telescope's large aperture brings along much easier to see colours, e.g. on Jupiter. The 12mm Super Plossl eyepiece which is in the standard scope of delivery offers an excellent contrast.

Despite all the telescope can easily be handled by one person - it will fit on the backseats of most small cars.

The GSD 250 is another sample of what I call "astronomical plug and play". Set-up and collimation take less than five minutes for experienced amateurs, you can launch into the observing session right away.

Please see the General Notes on Dobsonian Telescopes to find out why a Dobsonian might be just the telescope for you!

Using the Dobsonian Mount
The mount of a Dobsonian telescope is called "Rocker-Box", a fitting name for the uniquely simple and well-working design. The rocker allows you to point the telescope at any point in the sky and allows for comfortable, intuitive movement.

Moving the telescope is very simple, just push the telescope into the right direction – no need to use clamps or motors, it doesn't get more simple than this!

Despite its simple design you will be able to track objects precisely even at high magnifications. With a little experience 250x is no problem at all.

Back-Focus
The Dobsonian was designed for visual applications. It is sometimes not possible to find focus with SLR cameras. In such cases we recommend to refit the telescope with the low profile Crayford focuser.

Some eyepieces with a low field stop might need to be pulled out of the focuser by a little margin in order to reach focus. If you do not wish to do that you can buy the optional 35mm extension tube.

Specifications:
 
Aperture / Focal Length 250 mm / 1250 mm
Focal Ratio f/5
Secondary Mirror 63mm diameter
Tube Dimensions approx. 121cm x diameter 30.3cm
Tube Weight approx. 15.5kgs
Rocker Box Dimensions approx. diameter 54cm x 64cm
Rocker Box Weight approx. 12.2kgs
Focuser 2" Crayford focuser with dual speed 1:10 microfocuser, with 1.25" adaptor
Finderscope 8x50 quick release finderscope
Primary Mirror very precisely figured parabolical primary mirror. Better than diffraction limited. BK-7 or Suprax optical glass.
Accessories 2" wide angle eyepiece TS WA 30mm (Erfle design) - fully multi-coated
1.25" Super Plossl - fully multi-coated
Moon filter
Cooling fan
Roller bearing in azimuth


The active cooling fan reduces cool-down time of this telescope significantly.

Excellent Dual Speed 1:10 Crayford 2" Focuser
the Crayford focuser has zero image shift and offers very smooth focus motion. Including 1.25" adaptor. Both 2" and 1.25" with brass compression ring...... further information

High Quality Accessories & Eyepiece Tray
TS WA 30
 - 2" Erfle wide angle ....  further information

TS Super Plossl 12mm ..................  further information
Moon Filter ..... more contrast for lunar viewing

8x50 Finderscope with Quick Release Bracket
The achromatic objective is multi-coated for a brighter image.

Thin 4-Vane Spider - More Contrast
The less diffraction the better the contrast. Thin secondary spider vanes improve contrast compared with cheap three vane or thick four vane spiders - important for the moon and the planets
Industrial Roller Bearing for Azimuth - Not Just a Simple Friction Bearing
The roller bearing makes moving the telescope in azimuth much easier. If you want more friction simple felt pads will do the trick.
Spring Tension System
The spring tension system prevents the telescope from moving on its own when exchanging eyepieces.


Optional Tube Rings
GSO Dobsonians are no one-way street!

Dobsonian telescopes are ideally suited for visual use - with no other telescope design will you get this amount of observing fun for your budget!

Astronomical imaging on the other hand is barely possible with any Dobsonian telescope. Only the very brightest objects (the sun with the proper filter, the moon, the brightest planets) can be photographed without a tracking motor.

Deep-sky objects (galaxies, gas nebulae) require long exposure times and consequently a solid equatorial mount.

Two Telescopes in One

Our idea was quite simple: As long as you desire just to enjoy the beauty of the various celestial objects and joyful hours behind your eyepiece you should set up the GSO Dobsonian as it is - as a Dobsonian telescope. Setup takes only a few seconds and you will be observing in no time. Also, this combination is very portable.

For astronomical imaging or the comfort of a tracking motor just attach the cradle rings and put the tube on an equatorial mount. (see image to the left)

Our recommendation: The EQ-6 is a solid mount that will carry your 250mm "Newtonian" with good stability. A photographical variant of this mount is available. It offers a better tracking precision. This combination will bring much joy to your astrophotographical ambitions.

More details on the EQ-6

Primary Mirror Substrate BK-7

The image quality itself is not affected by the mirror substrate. Likewise cooldown-time is nearly the same regardless of which of these substrates you choose. The integrated cooling fan shortens the cool-down time considerably.

The only remaining difference between different mirror substrates is the image quality during cool-down (between 30 and 45 minutes, depending on the ambient temperature).

BK-7 reacts about twice as strongly as Suprax or Pyrex. However, this is only one side of the truth. The other side is that warm air will rise from the still warm mirror and cause "local seeing" that affects the image even more. It doesn't matter whether the mirror is made of BK-7, Suprax or solid gold - it will always suffer from this effect until it is fully cooled down. Considering how expensive exotic mirror substrates are we favour a cooling fan rather than "better" substrates!

Useful Links:
Eyepieces
A broad selection of 1.25" eyepieces can be used with this telescope.

Item No Short description Price - Euro incl. VAT
GSD 250 BCR GSO Dobsonian 250/1250 - 2" Crayford focuser with 1:10 microfocuser - BK-7 primary mirror 498.-
limited special offer
only as long as supply lasts!
CR 303 Cradle rings for the Dobsonian 99.-

Recommended Accessories
Here you can find accessories that are important and helpful for almost any telescope. Cleaning tools, filters, star charts, ...

The TS Eyepiece and Accessory Case isn't just an assortment of randomly picked eyepieces, we have put a lot of thoughts into choosing a fine range of eyepieces that will work with nearly all telescopes. These great eyepieces are included in the TS eyepiece and accessory case:

- three excellent quality TS Super Plossl eyepieces
- one TS wide angle eyepiece
- our excellent TS Barlow lens (2x/1.5x)
- five carefully chosen TS colour filters and one grey moon filter (not just a cheap green filter)
- an adaptor for focal and eyepiece projection astro-imaging

All comes in a beautiful, foam-lined aluminium case .......... Link to further information


Please send requests or online orders to: sales@telescope-service.com


GSO Dobsonian 300C - Aperture 300mm - Focal Length 1500mm
Economy line GSO Dobsonian with good 2" accessories



GSD 300 C Dobsonian with good 2" accessories - the image shows an older model of the telescope with rack and pinion focuser. Now the telescope comes with a better Crayford focuser.

Optical Performance

The telescope is equipped with the same high quality GSO parabolical primary mirror as the GSD 300 BCR. We guarantee a diffraction limited performance.

As a result you get sharp and contrasty images of the moon and the planets as well as impressive views of countless deep sky nebulae and galaxies. Many details can be seen in these nebulae.

Simple Operation

The telescope is operated by a single person.

Using a Dobsonian is very simple. The telescope is moved manually around a horizontal (azimuth) and vertical (altitude) axis. Teflon friction bearings are used to offer good motion smoothness.

GSD 300 C

Why should you sacrifice quality only because you want to save money? The GSO C-line was created to offer Dobsonian telescopes as cheap as possible without reducing the quality of the optics. In our opinion the result is an excellent telescope at an exceptional value for money.
Further Information: Visit our new Online Shop!
Recommended Accessories
Here you can find accessories that are important and helpful for almost any telescope. Cleaning tools, filters, star charts, ...


Please send requests or online orders to: sales@telescope-service.com


Der GSD 300 bietet durch seine große Öffnung spektakuläre Ausblicke ins All.

Observing with the GSD 300
Fine structures in galaxies and gas nebulae are visible that are otherwise only seen in photographs. Objects even begin to show colour!

In galaxy clusters you will be able to see several galaxies in your field of view, each of the galaxies consisting of billions of stars.

Globular clusters are resolved to the center in single stars. Fine filaments can be seen in supernova remnants like the veil nebula.

Under good seeing conditions the telescope will show splendid details also on the moon and planets. The cassini division in Saturn's rings is an easy target, as are fine structures in Jupiter's atmosphere and on Mars' surface. You only need to consider that with 300mm aperture the performance is often limited by turbulences in our own atmosphere - the telescope itself is not the limit to what you can see!

Operation is still possible by a single person. For transportation you will need a station wagon or SUV at least, but the single parts are light enough to be carried by one person.

Setting up the telescope is very easy and done within minutes.

Using the Dobsonian Mount
The mount of a Dobsonian telescope is called "Rocker-Box", a fitting name for the uniquely simple and well-working design. The rocker allows you to point the telescope at any point in the sky and allows for comfortable, intuitive movement.

Moving the telescope is very simple, just push the telescope into the right direction – no need to use clamps or motors, it doesn't get more simple than this!

Despite its simple design you will be able to track objects precisely even at high magnifications. With a little experience 250x is no problem at all.

Back-Focus
The Dobsonian was designed for visual applications. It is sometimes not possible to find focus with SLR cameras. In such cases we recommend to refit the telescope with the low profile Crayford focuser.

Some eyepieces with a low field stop might need to be pulled out of the focuser by a little margin in order to reach focus. If you do not wish to do that you can buy the optional 35mm extension tube.

Specifications:
 
Aperture / Focal Length 300 mm / 1500 mm
Focal Ratio f/5
Secondary Mirror 70mm diameter
Tube Dimensions approx. 145cm x diameter 36.5cm
Tube Weight approx. 19.5kgs
Rocker Box Dimensions approx. diameter 63.5cm x 64cm
Rocker Box Weight approx. 13.5kgs
Focuser 2" Crayford focuser with dual speed 1:10 microfocuser, with 1.25" adaptor
Finderscope 8x50 quick release finderscope
Primary Mirror very precisely figured parabolical primary mirror. Better than diffraction limited. BK-7 or Suprax optical glass.
Accessories 2" wide angle eyepiece TS WA 30mm (Erfle design) - fully multi-coated
1.25" Super Plossl - fully multi-coated
Moon filter
Cooling fan
Roller bearing in azimuth


The active cooling fan reduces cool-down time of this telescope significantly.

Note the 9-point flotation mirror cell!

Excellent dual speed (1:10) Crayford 2" Focuser
the Crayford focuser has zero image shift and offers very smooth focus motion. Including 1.25" adaptor. Both 2" and 1.25" with brass compression ring...... further information

High Quality Accessories & Eyepiece Tray
TS WA 30
 - 2" Erfle wide angle ....  further information

TS Super Plossl 12mm ..................  further information
Moon Filter ..... more contrast for lunar viewing

8x50 Finderscope with Quick Release Bracket
The achromatic objective is multi-coated for a brighter image.

Thin 4-Vane Spider - More Contrast
The less diffraction the better the contrast. Thin secondary spider vanes improve contrast compared with cheap three vane or thick four vane spiders - important for the moon and the planets
Industrial Roller Bearing for Azimuth - Not Just a Simple Friction Bearing
The roller bearing makes moving the telescope in azimuth much easier. If you want more friction simple felt pads will do the trick.
Spring Tension System
The spring tension system prevents the telescope from moving on its own when exchanging eyepieces.



Tube rings Made in Germany - they are made of birch plywood and offer an excellent stability and even vibration dampening properties.
GSO Dobsonians are no one-way street!

Dobsonian telescopes are ideally suited for visual use - with no other telescope design will you get this amount of observing fun for your budget!

Astronomical imaging on the other hand is barely possible with any Dobsonian telescope. Only the very brightest objects (the sun with the proper filter, the moon, the brightest planets) can be photographed without a tracking motor.

Deep-sky objects (galaxies, gas nebulae) require long exposure times and consequently a solid equatorial mount.

Two Telescopes in One

Our idea was quite simple: As long as you desire just to enjoy the beauty of the various celestial objects and joyful hours behind your eyepiece you should set up the GSO Dobsonian as it is - as a Dobsonian telescope. Setup takes only a few seconds and you will be observing in no time. Also, this combination is very portable.

For astronomical imaging or the comfort of a tracking motor just attach the cradle rings and put the tube on an equatorial mount. (see image to the left)

Primary Mirror Substrate BK-7

The image quality itself is not affected by the mirror substrate. Likewise cooldown-time is nearly the same regardless of which of these substrates you choose. The integrated cooling fan shortens the cool-down time considerably.

The only remaining difference between different mirror substrates is the image quality during cool-down (between 30 and 45 minutes, depending on the ambient temperature).

BK-7 reacts about twice as strongly as Suprax or Pyrex. However, this is only one side of the truth. The other side is that warm air will rise from the still warm mirror and cause "local seeing" that affects the image even more. It doesn't matter whether the mirror is made of BK-7, Suprax or solid gold - it will always suffer from this effect until it is fully cooled down. Considering how expensive exotic mirror substrates are we favour a cooling fan rather than "better" substrates!

Useful Links:
Eyepieces
A broad selection of 1.25" eyepieces can be used with this telescope.

Item No Short description Price - Euro incl. VAT
GSD 300 BCR GSO Dobsonian 300/1500 - 2" Crayford focuser - BK-7 primary mirror 668.-
limited special offer
only as long as supply lasts!
Rohrschellen Plywood tube rings for the GSD 300. For mounting it on an equatorial mount. 168.-

Recommended Accessories
Here you can find accessories that are important and helpful for almost any telescope. Cleaning tools, filters, star charts, ...

The TS Eyepiece and Accessory Case isn't just an assortment of randomly picked eyepieces, we have put a lot of thoughts into choosing a fine range of eyepieces that will work with nearly all telescopes. These great eyepieces are included in the TS eyepiece and accessory case:

- three excellent quality TS Super Plossl eyepieces
- one TS wide angle eyepiece
- our excellent TS Barlow lens (2x/1.5x)
- five carefully chosen TS colour filters and one grey moon filter (not just a cheap green filter)
- an adaptor for focal and eyepiece projection astro-imaging

All comes in a beautiful, foam-lined aluminium case .......... Link to further information


Please send requests or online orders to: sales@telescope-service.com


GSO Truss Tube Dobsonian 400 TDI - Aperture 400mm - Focal Length 1800mm
The Flagship of our GSO Dobsonian line: The GSD 400.




The tube and rocker box are actually in black colour.