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Bresser Messier NT-203s/800 Optical Tube Assembly

Bresser Messier NT-203s/800 Optical Tube Assembly
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Price:  £574.00(Inc. 20% VAT)
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Model:  4803800
Brand:  Bresser

Availability  

  

Generally In Stock, Please Confirm Before Ordering



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



203 mm f/3.9 Newtonian telescope (optics only)

Fotonewtonian f/3.9 with 2.5" Hexafoc
Aperture: 203 mm; Focal Length: 800 mm f/3.9; large 85 mm secondary mirror
Excellent 2.5" Hexafoc Focuser with possibility to upgrade to a 10:1 reduction
Ready for the HR Coma Corrector (part No. 0510330)
Scope of delivery: OTA + Finder + Tuberings + SPL26 mm
Elaborate 6 point flotation system for mirror support
Universal 44 mm Dovetail plate with stainless steel rail (fits LXD75/Great Polaris/EQ5)
Telescope for night and solar observation
Cradle rings with handle and camera holder included
Aperture Solar-filter and smartphone adapter for celestial navigation included

NEW – now including a high-quality aperture Solar-filter for safe observation of sunspots, eclipses and planet transits. Great telescope for night and solar observation.

In the past few years the Bresser Newton telescopes have become the standard workhorse for Deep Sky astrophotography. We now proudly present the second generation of this telescope, the Bresser NT-203s/800 with Hexafoc and a fast parabolic main mirror. The Bresser NT-203s/800 f3.9 will deliver you deeper images due to its - compared to 8" f/5 systems - oversized primary mirror and therefore faster optical system with the same exposure time. The big 85 mm secondary prevents vignetting for optimal illumination The excellent 2.5" Hexafoc focuser also does not cause vignetting due to its large diameter and makes focussing a joy - the smoothness and shifting-free operation sets new standards in this price class. This groundbreaking focuser, tube rings with 44mm universal standard dovetail and camera mounting feature and a high-end finderscope with haircross and laser-engraved scale leave nothing to desire even for demanding astrophotographers. The NT-203s/800 Hexafoc has a classical tube construction with an aluminium tube. The focuser can be upgraded with a 10:1 reduction (part No. 0625720) without problems. Ready to use with the HR Coma Corrector (part No. 0510330) which eliminates coma, field-curvature and astigmatism.

Please note: Reflector telescopes with optical design Newton are very good for astronomical observing at the starry night sky. But these telescopes are not well usable for observing landscape and nature during daylight. Therefore we suggest BRESSER refractor (lens) telescopes for landscape and nature observing.

CHARCTERISTICS
Optical design: reflector telescope
Mirror diameter: 203 mm / focal length: 800 mm / F/3.9
Maximum recommended magnification: 406x
Telescope for night and solar observing
Very high quality Hexafoc focuser with 2.5" free inner diameter
Diffraction limited optics with parabolic main mirror
8x50 straight through viewfinder with reticle
Optimized finder socket for comfortable use
Cradle rings with handle and integrated piggyback camera holder (1/4 thread)
Smartphone adapter for celestial navigation included
Dovetail plate with stainless steel rail
Can be connected to SLR cameras (optional T2 ring required)
50.8mm (2) to 31.7mm (1.25) adapter with integrated T2 thread (T2-adapter ring for your camera is needed)
Aperture 203 mm
Focal length 800 mm
Focal ratio f/3.9
Backfocus fully inward focused: 60 mm
85 mm secondary mirror for optimal illumination
Large knobs for primary and secondary mirror adjustment
Tube without accessories: 8.7 kg - Tube with all accessories mounted: 11.5 kg

SCOPE OF DELIVERY
Optical tube
26 mm Super Plössl eyepiece 31,7 mm (1.25")
Integrated 31,7 mm and T2 adapter
Prism rail with stainless steel clamping surface
Adapter for 50.8 mm (2") eyepieces
8x50 optical viewfinder
Rotatable star map
Aperture solar filter
Tube clamp with handle and camera holder
Smartphone adapter for celestial navigation
Software Stellarium (via download)

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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 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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