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Bresser Sirius 70/900 AZ Refractor Telescope

Bresser Sirius 70/900 AZ Refractor Telescope
 Bresser Sirius 70/900 AZ Refractor TelescopeBresser Sirius 70/900 AZ Refractor Telescope 
Price  £114.99
List Price  £138.00
Saving Of  £23.01
(Inc. 20% VAT)
Add Accessory Bundle

Model:  4512001
Brand:  Bresser



Generally In Stock, Please Confirm Before Ordering

2 Year Warranty On All New Items
(Excluding Batteries & Globes)

Embark on the adventure of astronomy: with the entry-level telescope including extensive astronomy accessories , starting out in celestial observation is child's play.

Complete set of telescope, tripod, mount and accessories
Easy-to-use refracting telescope for beginners
Telescope aperture: 70 mm / focal length: 900 mm
Ideal for Sun, Moon, planets and star clusters
Astrophotos possible with smartphone
Plenty of accessories to get started straight away
With safe lens solar filter

Set off on your personal journey to the stars with the BRESSER Sirius 70/900 AZ lens telescope. The complete astronomy set already includes everything you need to start observing the sky: the astronomical lens telescope with 70 mm aperture and 900 mm focal length, the azimuthal mount, the tripod and a wide range of accessories for fascinating discoveries. At the same time, it is very easy to operate - ideal to amaze even children with a view of the night sky.

Simply a stargazing classic - the telescope
With this lens telescope - a so-called Fraunhofer achromatic refractor - even total astro-beginners and children can easily explore the secrets of our night sky. Because this classic design impresses with its special user-friendliness and easy handling. To ensure that you enjoy good imaging properties when looking at the Moon, Sun, planets and star clusters, the entry-level telescope has been equipped with modern, precisely coated optics. The 70 mm aperture collects a total of 100 times more light than the human eye. And it is also convincing compared to a comparable 60 mm telescope: the light gathering capacity is 36 % higher and the resolving power is also better. Thus, with the 70 mm lens telescope, significantly more details are visible at the same magnification, e.g. on Saturn's rings or the two main cloud bands of Jupiter.

But how big do the celestial objects appear then? The resolution of the 70 mm lens lets you enjoy really sharp images at magnifications up to about 140x. For comparison: with a 60 mm aperture, this is only possible up to 120x. Technically, of course, the starter telescope can do even more - theoretically up to 675x with the included accessories. However, with increasing magnification, the image can slowly become more and more blurred. And how big you can really see the planets, star clusters and co. depends not only on the telescope. Another important factor: the air turbulence in the atmosphere (seeing conditions).

A sharp image with good contrast - this is what the starter telescope achieves with its large focal ratio of about 1 to 12.9 (F/12.9), which is calculated from the ratio of the 70 mm aperture to the 900 mm focal length. And you will see: Due to the long focal length, especially the Sun, Moon, planets, open star clusters and globular clusters become absolute eye-catchers.

Solid base for your stargazing hours - mount and tripod
Found the ideal location for your nocturnal explorations? Then attach the telescope tube to the height-adjustable aluminium tripod with azimuthal mount. And this azimuthal mount is particularly compelling due to one quality: operation is really child's play. Simply swing the telescope by hand to the left or right, up or down, as with a common photo tripod. This way you can quickly move your gaze from one celestial highlight to the next. And where are the accessories? Simply place them on the storage plate between the tripod legs. This way, eyepieces, solar filter and co. stay always within reach.

All the trimmings - the accessories
The beginner’s telescope comes with everything you need for a quick start in stargazing. When searching for celestial bodies worth seeing, take your first look through the included LED viewfinder. Because the direction finder helps you to align the telescope precisely and find astronomical objects. It works like this: The LED finder is mounted in parallel on the telescope tube. It projects a red dot onto a small ground-glass screen that appears to float in front of the sky when you look through it. And that is exactly where the aperture of your telescope points. This way, you can always keep an overview of the night sky - before focusing your attention on the details through the magnification of the telescope.

And you decide how high this magnification is by choosing the eyepiece. You will be amazed: the two eyepieces included in the set (4 mm, 20 mm) allow you to admire completely different images of the same object. If you one day want a change of perspective, you can expand your astronomy set with a large selection of eyepieces. For this purpose, the socket diameter is 1.25 inches (31.7 mm), which corresponds to an international, manufacturer-independent standard.
You like what you see, but would love more detail? Then simply insert the 3x Barlow lens between the telescope and the eyepiece. And you have tripled the magnification of the eyepiece!

Observation comfort and a pleasant view - this is what the 90-degree star diagonal mirror is made for. Even if your starter telescope is pointed vertically into the sky, you don't need to lie down underneath it to see anything. Instead, simply look in comfortably from the side and enjoy the view.

But it's not only at night that we should look skywards. For only during the day you can see a very special star: our Sun. So put the solar filter in front of the lens and safely look at sunspots and granulation on the Sun.
CAUTION: Never point the telescope at the Sun without the solar filter!

Would you like to share your discoveries with friends and family? Then take your first steps in astrophotography right away - and those are done in no time with the smartphone camera adapter for your beginner's telescope. The Moon, Sun, planets, open star clusters and globular clusters always make a good picture.

Discover what our night sky has to offer with the BRESSER Sirius 70/900 AZ refracting telescope.

Beginner’s telescope for astronomy
70 mm aperture; 900 mm focal length
Achromatic refractor type Fraunhofer
Ideal for observing the Sun, Moon, planets and star clusters
Height-adjustable tripod with azimuthal mount
Easy to use, also very suitable for children
Focal ratio F/12.9, therefore very sharp image and high contrast
Two eyepieces and one Barlow lens with 31.7 mm (1.25 inch) sockets for different magnifications
Safe solar observation with the included solar filter
Entry into astrophotography with smartphone camera adapter

Starter lens telescope
Aluminium tripod
Azimuthal mount
Eyepieces: 4 mm and 20 mm (1.25 inch socket)
Barlow lens 3x (1.25 inch socket)
Star diagonal mirror
LED illuminated dot finder
Solar filter
Smartphone camera adapter
Accessory tray
Astronomy software via download
Instruction manual

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Some items that are showing as in stock are in stock at our holding warehouses, not at the shop. To double check the stock levels at the shop, please contact us on 01909774369 or

The delivery times for most items is 1 - 2 days but again, please double check stock levels on important orders before placing an order via the website.

The delivery costs for courier next day are for mainland UK only. If you live in the Scottish Highlands/Islands, Channel Islands or Northern Ireland, then a shipping surchage will apply. please contact us for prices. Smaller items can still go 1st class via Royal Mail.

Please note that if you are wanting to take advantage of our Saturday and Sunday timed services or next day pre 12 or pre 10:30 services, you MUST check that the stock is here at the shop before placing orders. Also, orders using the Saturday and Sunday services must be placed before 1pm the previous working day. Also, please remember to check that the stock is here at the shop before placing orders. If the stock is not at the shop, we won't be able to ship on any of the timed services. 

Please note International customers will need to contact us for a shipping price prior to ordering via the website. We don't ship all items internationally. It is at our discretion what we ship outside of the UK. This all depends on the size and weight of the items. Please get in touch with us for any postage costs. Please note we do NOT ship telescopes or heavy items outside of the UK. This is due to massive postage costs and problems regarding returns.

If you have any questions regarding stock levels or delivery, please get in touch.

Zygo Interferometer Testing For ED Refractor Telescopes!

We are extremely pleased to announce our Zygo Interferometer is now installed and ready for use! Our experienced staff can test refractor lenses up to 120mm aperture and provide a comprehensive 2 page report showing the optical quality and Strehl ratio, plus much more information. We are using the very latest Zygo MX software to provide a more detailed report compared to other standard reports.


The interferometer is essentially a measuring instrument. Within the interferometer is a calibrated laser that is pointed through the optical test surface, then onto a high quality reference sphere, then back through the test subject then to an internal camera which gives us the measurement on the screen. From this, we can adjust the position of the test optic and the reference sphere to obtain a perfectly calibrated system. The more central the laser to the test optic and then on return, the better and more accurate reading and measurement we can take. This takes a lot of adjustment to get the best results from the optical surface. Once the measurement has been taken, we are provided with a series of results that show the optical quality of the surface plus other information. Continue reading for an explanation of the individual values and you can also see a test report that was done on one of our RVO Horizon 60 OTAs. 

We are offering certain telescopes with a Zygo test at an extra cost. Mainly ED doublets and triplets. All available telescopes with a Zygo test report are listed here. Just select Zygo Test Report from the drop down box at the top of the listing and we will test the optics in house and provide a full 2 page report with your scope. This will show you the optical quality of your telescope optics. We can also offer this service on your refractor telescope. Please get in touch for more details about this. 

At Rother Valley Optics, one thing we pride ourselves on is customer service and quality of our equipment. When we test your telescope, we will ensure that it is of the highest quality otherwise, we will reject the scope under our strict quality control and test another model for your peace of mind. One of the main values to look at when testing a refractor is the Strehl ratio. The higher this number, the higher quality lens you have. At Rother Valley Optics, we will guarantee the highest possible Strehl ratio for your telescope.  We will aim to provide 0.95 Strehl or higher on Takahashi, RVO Horizon, William Optics and many more! Generally, the higher the Strehl ratio, the lower the Astigmatism and Coma meaning a better image quality from your instrument. 

Other measurements such as the PV and RMS are important too. With these measurements, the lower the number the better as it shows less curvature on the lens. The flatter an optical lens, the better it will perform. The PV rating (Peak To Valley) is a measurement from the highest point (Peak) to the lowest point (Valley). From this we get the RMS (Root, Mean, Square). This is a similar figure to the PV and measured exactly the same way. The RMS is basically an average height difference from the PV so again, the lower the better. As you can see form the example below, we measured an RMS of just 0.027 wave which is a very good value.

We also measure the Power with our systems which is essentially the error from the reference sphere to the test optic. The reference sphere we use on our system is a very high quality sphere so the closer to zero the Power, the less error between the 2 elements thus ensuring a higher quality optical surface. 

You will also see some more values such as Astigmatism and Coma. Again, these are measured by the interferometer when we take measurements of the optical surface after adjustment. These are values which ideally would be at 0 but as our test optics are all curved lenses, there will always be astigmatism and coma present. The lower the number, the less of these aberations you will effectively see but with most refractors, you can buy field flatteners which will compensate for the coma anyway. The astigmatisms value is explaining the error between the symmetrical curvature of the lens. Basically, no lens will be perfectly symmetrical, the lower the astigmatism, the more symmetrical the lens surface is. 

Once the Zygo test report has been completed, the optical alignment is thoroughly tested and tuned to ensure they are spot on before they leave us. 

All available telescopes are on the website at the link below and ones we've tested already that are available straight away are also listed.

Here is an example of the test what we provide. This was a test on one of our Horizon 60 ED OTA's.

For any questions about this amazing new service, please either call 01909774369 or email


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