Shop by Price
Shop by Brand

Skywatcher EQ-AL55i Pro SynScan Astronomy Mount And Tripod

Skywatcher EQ-AL55i Pro SynScan Astronomy Mount And Tripod
Skywatcher EQ-AL55i Pro SynScan Astronomy Mount And TripodSkywatcher EQ-AL55i Pro SynScan Astronomy Mount And TripodSkywatcher EQ-AL55i Pro SynScan Astronomy Mount And Tripod
Price:  £759.00(Inc. 20% VAT)

Model:  20859
Brand:  Skywatcher



Generally In Stock, Please Confirm Before Ordering

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

The exciting and versatile new EQ-AL55i PRO features a dual-position counterweight bar, making it usable at ALL latitudes from 0-90 degrees thus solving the problem for users living in, or travelling to, areas of extreme latitude, beyond the capability of most conventional mounts.

The EQ-AL55i is fully controllable with a smart device via it's built in Wi-Fi module using the free Synscan Pro App for iOS or Android.

The EQ-AL55i PRO mount features a built-in illuminated polar scope for precision alignment, interfaces for USB-C, autoguider, optional SynScan hand controller and SNAP shutter control for your DSLR (programmable via Sky-Watcher’s free SynScan Pro app for iOS and Android).

With its 10kg payload capacity, the EQ-AL55i PRO is well-equipped, via its 45mm dovetail saddle, to handle a wide variety of OTAs and peripheral equipment.
The EQ-AL55i PRO is a great mount for the astro-photographer and visual observer that wants a mount combining excellent performance and good portability. A 200mm tripod extension tube (code 20860) and Synscan computerised handset and cable (code 20948/20193) and 5kg Counterweight (code 20950) are available as an optional accessories.

High Precision DC servo Motors.
RA axis Resolution 0.32 Arc Second
Slewing speed up to 4°/sec (1000X).
Ports: USB, SNAP, Power, ST-4 & Synscan Hand Controller (optional)
Built-in Wi-Fi Module
ST-4 type Autoguider Interface: Supports 0.25x, 0.5x, 0.75x 1x guiding rate
Single Axis Tracking
Tracking Rate: Lunar, Solar or Sidereal
Controller: Synscan Pro App (iOS, Android or PC)
Compatible with Synscan™ Hand Controller (optional accessory) with 42,900+ Object database containing complete Messier, NGC, and IC catalogues.
Supplied with Polarscope with LED illumination
Latitude Adjustment 0° to 90°
R.A. Worm Gear 73.4mm Diameter, 144 Teeth
DEC Worm Gear 51.6mm Diameter, 100 Teeth
R.A. Worm Drive 11mm Diameter
DEC Worm Drive 11mm Diameter
45mm Dovetail Saddle
Payload Capacity 10kg
Counterweight Bar 20mm Diameter, Mountable in 2 x Positions
Counterweights supplied: 1 set of 5.3kg (1.8kg & 3.5kg)
Weight of Mount Head only: 3.8kg
1.75" Diameter Stainless Steel Tripod & Accessory Tray, Weight 5.7kg
Power Requirement DC12V 2A Tip Positive (via external supply)

Be the first to Write a Review for this item!

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


Related Products
Skywatcher CQ350 Pro Equatorial Mount & Tripod

Skywatcher CQ350 Pro Equatorial Mount & Tripod£3,198.00   £2,899.00

With a maximum payload capacity of 35kg, it places the CQ350 PRO squarely between the EQ6-R and the EQ8-R PRO and with its dual-fit 45mm/75mm saddle, makes it a secure and highly capable platform for supporting a wide range of OTAs and peripheral equipment.

Skywatcher EQ8-R Pro SynScan GOTO Mount & Pier Tripod

Skywatcher EQ8-R Pro SynScan GOTO Mount & Pier Tripod£4,199.00

The Sky-Watcher EQ8-R Pro is an exciting evolutionary progression of the popular EQ8 Pro. The EQ8-R Pro is an extra heavy-duty, observatory class German equatorial mount, with a payload capacity of up to 50kg.

Skywatcher EQ8-R Pro SynScan GOTO Mount Head Only

Skywatcher EQ8-R Pro SynScan GOTO Mount Head Only£3,399.00

The Sky-Watcher EQ8-R Pro is an exciting evolutionary progression of the popular EQ8 Pro. The EQ8-R Pro is an extra heavy-duty, observatory class German equatorial mount, with a payload capacity of up to 50kg.