Shop by Price
Shop by Brand

William Optics Pleiades 181 APO Refractor

William Optics Pleiades 181 APO Refractor
William Optics Pleiades 181 APO RefractorWilliam Optics Pleiades 181 APO RefractorWilliam Optics Pleiades 181 APO Refractor
Price:  £18,999.00(Inc. 20% VAT)

Model:  T-P-181RD
Brand:  William Optics



Special order, delayed despatch

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

Introducing the William Optics Pleiades 181 – The Ultimate Imaging Telescope for Medium Format Astrophotography

Elevate your stargazing and astrophotography experience with the newly launched Pleiades 181 by William Optics, a masterpiece exclusively designed for imaging with medium format cameras. This state-of-the-art telescope boasts a substantial 181mm diameter and a 998mm focal length, encapsulated in a sleek, robust design with a 3.7” R&P focuser for precise control.

Key Features:

  • High-Performance Optics: The Pleiades 181 features a seven-element, temperature-compensated lens system, ensuring minimal thermal distortion and a Strehl ratio minimum of 0.96 for sharp, clear images across a greater than 55mm image circle.
  • Designed for Medium Format Cameras: Engineered specifically for medium format imaging, the Pleiades 181 accommodates cameras with an M68x1 thread, capturing expansive celestial scenes with unmatched clarity and color accuracy, making it an ideal choice for serious astrophotographers.
  • Unique Cosmos Steering Wheel: A pioneering addition, the Cosmos Steering Wheel allows for effortless handling, rotating, and precise positioning of the telescope, enhancing both comfort and functional ease during prolonged observation sessions.
  • Durable and Portable: Despite its large aperture, the Pleiades 181 remains relatively portable with a weight of 33.07 lbs (OTA only) and 41.23 lbs fully equipped with ring, dovetail, and saddle. The retracted and extended lengths are 1231mm and 1496mm respectively, with a dew shield diameter of φ230mm.

Why Choose Pleiades 181?

Designed with the specific needs of advanced astrophotographers in mind, the Pleiades 181 is not just a telescope, but a dedicated imaging gateway to exploring the cosmos with exceptional detail and depth. Whether you are capturing distant galaxies or the intricate patterns of nebulae, the Pleiades 181 brings the universe closer to you with unparalleled precision.

Explore the heavens with precision and elegance with the new Pleiades 181 from William Optics, where innovation meets the art of celestial imaging.

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
William Optics Fluorostar FLT 120 Triplet APO Refractor OTA

William Optics Fluorostar FLT 120 Triplet APO Refractor OTA£3,249.00

The brand new Fluorostar 120 APO by William Optics meets the demands of the modern astrophotographer with high quality glass, 3.3" heavy duty focuser with rotator and bahtinov mask.

William Optics RedCat 61 f/4.9 Petzval Apo Refractor Telescope

William Optics RedCat 61 f/4.9 Petzval Apo Refractor Telescope£1,629.00

The brand new William Optics RedCat 61 is the latest Cat to join the family. Featuring high quality glass in a Petzval design for a flat field edge to edge, plus the brand new internal focusing mechanism.

William Optics Zenithstar 73 III APO Refractor OTA

William Optics Zenithstar 73 III APO Refractor OTA£629.00


Zenithstar 73 is a greatly versatile and portable refractor telescope for beginners and veterans alike. Designed for both astrophotography and wildlife photography, high power visual observing through the Zenithstar 73 is also hugely satisfying.