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OVL Dual Speed 2" Low Profile Crayford Focuser For Newtonian Reflectors

OVL Dual Speed 2'' Low Profile Crayford Focuser For Newtonian Reflectors
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Price:  £169.00(Inc. 20% VAT)
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Model:  20170
Brand:  OVL
Select Fit  Reflector

Availability  

  

Generally In Stock, Please Confirm Before Ordering



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


  (2 Reviews)

A Low Profile CNC machined 10:1 dual-speed focuser designed for Newtonian Reflector telescopes of 9" to 15" aperture, and accepts either 1.25" or 2" eyepieces. High quality made focuser.

Provides an exceptionally smooth focusing operation with the utmost precision, with the aid of its fine-focusing facility.

24mm Drawtube.

Average Rating (2 Reviews):  
Write a Review and share your opinions!

Rating:  
OVL performs way beyond its specs, beats the JMI EV in every way
26 May 2022  | 

I needed a new focuser for CCD imaging with my homemade 20" newtonian after my JMI EV motorfocus gave up the ghost after 20 years. According to the specs 15" is the maximum size of telescope, and it does not come with a moto-focus option (essential for CCD). Also my 2kilo CCD camera would be too heavy. Because of the low price I thought I would give it a try, and it perform fantastically way beyond its specs. I added a home made-motor focus off Ebay for 8 (see vid I put on Youtube). and it works better than the JMI at a fraction of the cost. Dunno how they achieve this level of machining for the price, but I could not be happier.
https://youtube.com/shorts/z6IWqjRAqmw

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Rating:  
Excellent upgrade for Meade Lightbridge 16
24 November 2020  | 

Purchased to replace an R&P focuser on a failed Meade Lightbridge 16 restoration so not the original Meade focuser. I did consider a Moonlite but could not justify the cost of the unit and mounting kit. This looked like the next best option and certainly seems to be a winner.

First impression out of the box is that this a very solid good quality focuser, mounted on a heavy CNC base plate. Movement of the focus tube using the "Fast" knob on the Crayford is very smooth and gradual and the fine focus is almost imperceptible. It doesn't say this in the description but the focuser features an additional draw tube about 50mm long for eyepieces needing to be that little bit higher. The description also says tubes up to 15" my Meade 16 is closer to 18" diameter and this seems to sit nicely on the tube, so no issues from a tube size perspective. I did have to drill new holes and at first glance the position of the focuser seems to cover the lower 2 holes. This is easily fixed as base plate has 4 grub screws holding the focuser in place so easy to detach from the plate, mark and drill and then mount the focuser in place.

I'd give this 5 stars but the 2" - 1 1/4" eyepiece adaptor is an odd slotted sprung steel thing which sort of does the job but doesn't fit a 2" filter too well. In order to work it needs to compress slightly which it doesn't do that well with a filter in place, also found it difficult to fit the filter in my nice warm dining room how that would go on a cold night is anyone's guess, fortunately I have a substitute adaptor.

I can't say much about use as the clouds arrived when it did but trying it pointed at the church spire it's very smooth and easy to move but also very solid, looking forward to a clear night and being able to use all of my eyepieces for once,

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5 of 5 people found this review helpful.

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.

 


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  (2)

A high quality CNC machined 10:1 dual-speed focuser designed as an upgrade to Schmidt Cassegrain Telescopes. Accepts either 1.25" or 2" eyepieces. Provides an exceptionally smooth focusing operation with the utmost precision, with the aid of its fine-focusing facility.