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Takahashi CAA-250 F/5 Corrected Cassegrain Astrograph OTA Package

Takahashi CAA-250 F/5 Corrected Cassegrain Astrograph OTA Package
Takahashi CAA-250 F/5 Corrected Cassegrain Astrograph OTA PackageTakahashi CAA-250 F/5 Corrected Cassegrain Astrograph OTA PackageTakahashi CAA-250 F/5 Corrected Cassegrain Astrograph OTA PackageTakahashi CAA-250 F/5 Corrected Cassegrain Astrograph OTA Package
Price:  £14,795.00(Inc. 20% VAT)

Model:  TCK25000
Brand:  Takahashi



Generally In Stock, Please Confirm Before Ordering

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

This package includes the CAA-250 tube, electic focuser, 7 x 50 finder, finder bracket, finder reticle illuminator and female and male losmandy bars.

Introduced in 1998, the BRC-250 astrograph adopted a totally original optical design, based on Baker-Ritchey-Chrétien, perfectly designed for the imagery at that time. Following the recent evolution of CCD cameras offering larger sensors, Takahashi decided to modify its optical design. To work out this new CCA-250, successor of the BRC-250, the optician engineer Mr Mori Hitoshi opted for a Cassegrain base to lead to this new instrument perfectly adapted for the various objects of the deep sky.

CCA-250 (CCA stands for Corrected Cassegrain Astrograph) offers 3 kinds of focal lengths by the addition of optional reducers and extenders. From F/5 standard focal ratio at primary focus, it is possible to go to F/3.6 by using one of the 2 reducers or to go to F/7.5 by using one of the 2 extenders available. The choice of the model of reducer and extender will depend on the image circle needed, but also according of the size of the sensor of the camera used.

Finally Takahashi carried out a very multi-purpose astrograph offering a extremely high standard product bringing a great optical quality as well as irreproachable mechanics on top of which is added a splendid design associating aluminum and carbon.

Takahashi has chosen a modified optical design based on Cassegrain telescope, with a parabolic primary mirror, a spherical secondary mirror and a neutral field corrector. Collimation is perfectly maintained by using the whole adjustment of the spider instead of having to adjust the secondary mirror.

The main result of this formula is a real increase of the back focus (compared to that of the previous BRC-250), allowing many different possibilities and assemblies, of including those of correctors and reducers. Those will offer you an extreme flexibility to the different possible configurations, neither equipped with a camera with a large sensor or not

The mirror cell and the corrector of the Takahashi CCA-250 astrograph
Thanks to the extenders and the reducers, it is possible to use instrument with 3 different focal lengthes (900mm, 1250mm or 1800mm), with 3 different circles images (40mm, 60mm or 80mm) according to the configurations (see detailed specifications). The telescope is thus not only limited to the large sensors. All the assemblies are screwed at the back of the tube to facilitate the balancing of the instrument.

The focus operation is motorized, using a translation of the secondary mirror. Three fans (coupled with temperature sensors) are installed to accelerate setting of appropriate temperature. All of the commands are centralized inside the Active focuser system and can be either manually controlled of through a compatible interface ASCOM with connector industry USB.

The Takahashi CCA-250 astrograph main accessories
For the very first time, Takahashi has chosen a structure of tube associating both aluminum and carbon fiber. The result is outstanding, both from the esthetic point of view as well as regarding the efficiency of the thermic control.

The carbon fiber is used to maintain the quality of the focus during exposition time as well as to lighten the OTA. Due to the difference of dilatation rate between carbon fiber and aluminium, a compensation system is added to dovetails to keep the integrity of the tube. The photographers will thus use an instrument whose thermal behavior is perfectly known.

The Takahashi CCA-250 EC certification label
In spite of the presence of carbon, the tube is still massive : 23kg without accessories. It is equipped with a male Losmandy-like dovetail (with its female counterpart), as well as a top dovetail accepting TGM mounts. The CCA-250 owns a camera angle adjuster (the CAA) and of a set of extension tubes. The OTA is certified EC, in conformity with the EU law relating to the electricals appliance.

The photographer of the deep sky has, finally, a really general-purpose instrument, without compromise about optical and mechanical.

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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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