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Astronomik ProPlanet 642 BP IR Pass Filter 1.25"

Astronomik ProPlanet 642 BP IR Pass Filter 1.25''
Price:  £71.00(Inc. 20% VAT)

Model:  8H00K8
Brand:  Astronomik



Generally In Stock, Please Confirm Before Ordering

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

The images show the 742 version. Images and the transmission data of the ProPlanet 642 BP will be added soon.

The Astronomik ProPlanet 642 BP is the lastest addition to the family of Astromik ProPlanet IR-pass filters. The filter thrills because of itīs wide range of applications for daylight IR-Photography, high-resolution lunar and planetary imaging and for taking beautifull and deep images of H-alpha regions when used for Astrophotography.

"BP" are short for "Bandpass": The filter gives you a 200nm spectral window from 642nm to 842nm. Contrary to the other two ProPlanet filters it blocks the longer infrared. Together with the Astronmik ProPlanet 742 and the ProPlanet 807 you can now have three choices to match your needs when imaging in the IR. The Astronomik ProPlanet 642 BP will be the right choice for the best image quite often!

Highlight of the Astronomik ProPlanet 642 BP: Three filter in one!

The Astronomik ProPlanet 642 BP will give you three filters in one single product! Depending on your camera, the Astronomik ProPlanet 642 BP is a great tool either for daylight IR-imaging with your digital camera, or it will reduce seeing effects and enhance contrast when used for lunar- and planetary imaging, and third it will be a very good and low-priced H-alpha Filter for getting started in Deep-Sky Astrophotography of H-alpha regions.
Due to our skillfull developement with lotīs of tests we reached the goal to give you a filter which will do a perfect job to deliver amazing images.

Daylight IR-imaging:

contrasty images with a great rendition of colors
Clear "Wood-Effect" images
Not Hot-Spot from longer IR!
Short exposure times, about the same as normal VIS-imaging
perfect choice for Infrared-Videos

High-resolution Lunar and planetary imaging:

short Exposure times
effective reduction of Seeing
enhanced contrast
no ghosts and best sharpness due to blocking the longer IR

Deep-Sky Astrophotography of HII regions:

best transmission of the H-alpha line at 656nm
about 40nm FWHM with astro-modified DSLRs
amazing contrast under lightpolluted skies or moonlight
low priced filter for getting started in H-alpha imaging
easy focussing using camera display plus LiveView!

Guiding for Astrofotography:

installing the 642BP in front of your autoguider-camera dramaticly improves guiding quality, as image-motion from one frame to the next is minimized.

High-Resolution imaging of the moon and the planets is a part of astrophotography which has evolved in the past 20 years at an incredible speed. Amateurs from all over the world can take images which were far beyond reach even for the very best equiped professional observatories 20 years ago.
You will need a low noise video-camera and dedicated image-processing like AstroStakkert, Registax or AviStack plus a infrared-pass filter to enter this field of astrophotography!
Why Infrared? Every observer knows the flickering stars and planetary disks when looking through an eyepiece or at your monitor Slight differences in temperature and preasure result in a different index of refraction for "bubbles" of air. As these bubbles move, the image moves too! This effect is called "Seeing".
This change in the index of refraction becomes smaller the further you go to the infrared (longer wavlengths), and due to that, the Seeing becomes better too!
When observing with the human eye we have no options: The human eye is not sensitive to infrared light. But with the CCD or CMOS sensors from our camera we can go to the infrared part of the spectrum and enjoy the steady air.
An Infrared-Pass filter like the Astronomik ProPlanet 642 BP blocks all unwanted visual light and gives you infrared light only!
The amount of seeing is changeing very fast, so there is no universal filter that will do it every time. So the Astronomik ProPlanet 642 BP is the third filter in this line of Products in addition to the Astronomik ProPlanet 742 and ProPlanet 807! When seeing is no really bad, the ProPlanet 642 BP will be usually the first choice and will give you best results as it blocks the longer IR too!
While we were developing this new filter, several observers had our prototype filters for testing. Most of them reported that the Astronomik ProPlanet 642 BP gave them the very best images compared with filters from other manufacturers. The sharpness and high contrast resulted in the best final images in nearly all situations!

The Astronomik ProPlanet 642 BP has allready reached itīs full transmission of nearly 100% at the famous line of H-alpha at 656nm. -All light coming from the beautifull HII regions can reach the sensor of your camera, while all shorter light and nearly all artifical light pollution is filtered out!
Combined with a typical astro-modified DSLR you will get a spectral window of about 40nm which results in a very dark background and a high contrast. With the Astronomik ProPlanet 642 BP installed in your camera, itīs possible to do nice shoots of H-alpha regions even when the moon is up: Lunar stray light is filtered out very effective!

"How long do I have to expose longer?" -Thatīs a very common question from custmers from all over the world.
The answer is quite easy: You donīt have to expose longer, you MAY expose longer!

Due to the high transmission of nearly 100% you will have the same amound of photons with a wavelength of 656nm on your sensor, wether you have the filter installed or not. But, with the Astronomik ProPlanet 642 BP installed, the background sky will be very dark, while it would be very bright -or even saturated- when imaging without the filter! The filter blocks photons with other energies and give you a higher contrast. With the filter installed you MAY expose longer to collect more photons from your object of desire till the background is getting brighter again!

A narrow band emission-line filter like the Astronomik H-alpha filter with 12nm or 6nm FWHM will do the job much better (it blocks more of the unwanted light), but the lower price of the Astronomik ProPlanet 642 BP is very attractive for beginners in this field of astrophotography! Additional to that the real emission line filters are quite difficult to use for beginners as focusing can be quite difficult with them. With the Astronomik ProPlanet 642 BP you will usually have enough light to use the LiveView monitor on the back of your camera!
Taken all this together the new Astronomik ProPlanet 642 BP is the ideal filter for getting started in H-alpha imaging with your modified DSLR!

Do you use the AstronomikProPlanet 642 BP for H-alpha imaging? Share us you best images with us!

Technical Data
more then 96% transmission for wavelengths of 642nm to 840nm
blocking of wavelengths between 350nm and 630nm
Parfocal with other Astronomik filters
Glass thickness: 1mm
Completely resistant against high humidity, scratches and aging effects
Diffraction limited, the filter will not reduce the optical performance of your telescope!
Astronomik filters are delivered in a high-quality, long lasting, filter box
Since 2008 we do ship filters with a completely new design. Any kind of halo or strange reflection is a matter of past

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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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