Askar 120 ED APO Triplet f/7 Refractor Telescope OTA

The aperture of 120mm gives it an inherent advantage in terms of light-gathering power, resolution and contrast, allowing the photographer to gather more light and present more details and brighter objects in the image. The aperture area of the Askar 120APO enlarged by 36% compared to that of the 103APO.

Along with the more light coming into the astrograph, the limiting magnitude can reach 12.2.

Askar 120APO adopts a triplet air-spaced APO lens design, including one piece of ED glass.

In the refractor's element structure, increasing the number of lens elements and designing lens combinations can effectively improve chromatic aberration correction. However, this also means increased production costs and design complexity.Askar APO series employs special optical designs and multiple lens elements to correct chromatic aberration, naturally providing higher-quality object details and color accuracy.ED glass, also known as low-dispersion glass, is a type of optical glass specifically designed to reduce chromatic aberration.

In addition to the dedicated optical design, the Askar 120APO is well-considered in the mechanical design.

Askar 120APO is light and compact with a total weight of 6.5kg (including the tube rings). So it is suitable for outdoor shooting.

Each piece of Askar 120APO is equipped with a unique name ring for identification.

The retractable design of the dew shield, along with the enlarged locking screws, provides convenient usage. The dew shield serves the purpose of protecting the lens from the impact of external and internal light and protecting the lens itself.

The Askar 120APO has two finder bases, one on each side. Many users have some concerns about the limited space for installing additional astronomical accessories along the use. To address this, we have specially set finder bases on both sides of the focuser. This not only eliminates the need for disassembly when changing the position of the finder scope but also provides additional mounting positions for other astronomical accessories.

The handle of the Askar 120APO has a special slot design, making it also a base for installing a finder scope. The handle itself has been extended by 60mm, which makes the tube rings more convenient to fix the astrograph.

The total weight of the tube ring is only 780g. The thumb screws enable easy opening and locking of the tube rings. Meanwhile, the base of the tube rings is heightened, providing more space.

The standard Vixen dovetail plate is compatible with most equatorial mounts and bases on the market. We extended the length and added screw holes, making the plate becoming 290mm which is more easy to balance on the mounts. With the slot on the handle, the spacing between the tube ring can be adjusted as desired. Additionally, there is also a Losmandy dovetail plate available for purchase, to be used with different equatorial mounts.

The Askar 120APO has two optional accessories(now): a 1x flattener, and a 0.8x reducer. Both of them have built-in filter threads which allow direct filter mounting. Also, they have M54/M48 adapters which are convenient for attaching accessories.

The 1x flattener does not change the telescope's focal ratio itself. After connecting with the Askar 120APO, it still maintains a focal ratio of f/7. The flattener corrects field curvature and coma, resulting in flatter field edges and finer star points.

The 0.8x reducer can bring the Askar 120APO's focal ratio down to f/5.6. This is a standard reducer with field flattening capabilities as well. A shorter focal ratio allows the OTA to have a wider field of view and faster exposure times, making it suitable for capturing large areas of nebulae, star clusters, and faint, fast-moving celestial objects.

In terms of visual observations, the Askar 120APO pays great attention to observation quality. It can easily achieve focus when connected to 1.25" or 2" diagonals or various eyepieces. Because of the segmented lens tube design, it can also be attached to binoviewer for visual observation.

In terms of the focuser, Askar 120APO is equipped with a dual-speed rack and pinion large 3.3-inch rigid focuser, which can be compatible with most motorized focusers on the market. There is a high-precision scale on the 10cm focusing travel. The entire focuser barrel is CNC machined with an anti-reflective internal design and matting paint, providing extra measures to eliminate stray light.

The rear of the focuser features a 360° high-precision big rotator, along with precise scales for convenient adjustment and saving of rotation angles, enabling precise rotation. It is also equipped with an enlarged rotator locking screw that can easily secure even under high loads.

The telescope interface at the rear comes with a 1.25"/2" adapter.

The entire Askar 120APO tube is crafted using high-quality CNC machining, with anodized and surface spray paint treatment. The orange accents on the ivory-white tube add a bright and eye-catching touch, presenting a stylish and elegant overall appearance.

Let the Askar 120APO accompany you in exploring the magnificent landscapes of the universe and create unforgettable memories. Take action now and embark on your astronomical adventure with the Askar 120APO!

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 sales@rothervalleyoptics.co.uk.

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.

https://www.rothervalleyoptics.co.uk/zygo-tested-refractors.html

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 sales@rothervalleyoptics.co.uk.

Are you interested in this product but would like to speak to someone with some more information? Simply fill in the form below and we will get back to you as soon as we can!

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