1. Harrison Telescopes Home PageHome
  2. LoginLogin
  3. Lookup OrdersTRACK ORDERS
  4. View Basket
    View Cart
  5. CheckoutCheckout

Altair Starwave Bahtinov Focusing Masks

Altair Starwave Bahtinov Focusing Masks

Starwave TM bahtinov masks grip the telescope tube gently but firmly with three metal posts covered in non-scratching silicon sleeves. This prevents slippage, whilst allowing the mask to remain perfectly central. This is unlike other masks with two posts, which rely solely on gravity to hold them in position. Because of this 3-post mounting, the Starwave Bahtinov mask remains centred, whilst fitting a wider range of telescopes, saving you money if you decide to change optical tubes. So, all you need to do is measure the outer diameter of your telescope tube or dewshield, and choose a model corresponding to that OD dimension.

Starwave TM Bahtinov masks are made from precision laser cut ABS plastic, which is stiff enough to remain in position, yet has enough “give” to make them tough without being brittle in the cold, unlike acrylic masks which are made from thick, heavy, brittle and hard acrylic plastics.

How does a Bahtinov focusing mask actually work? When in place, the Starwave Bahtinov mask works by forming a diffraction pattern of “spikes” of light around a star or point light source, which is easily visible in your eyepiece or DSLR/CCD camera in live view mode. When the pattern becomes perfectly symmetrical, the telescope is perfectly in focus. Focusing is quick, easy and it saves you time “hunting” back and forth to find the optimum focus, whilst trying to judge the size of a tiny point source of light. A Bahtinov mask useful for a quick focusing re-check if the temperature changes during your imaging session

Do Starwave Bahtinov Masks work with both reflectors and refractors? Yes they do. Even though reflectors have a central obstruction caused by a primary mirror, there is no difference whatsoever in the performance or these masks on a reflector or a refractor. Basically, the reflector secondary mirror just covers the central portion of the mask but the outer clear aperture still carries the pattern.

The following range of sizes are available to fit just about any amateur telescope on the market, as well as DSLR camera lenses:

Starwave TM Bahtinov Mask Size Chart:
80-110mm Starwave Bahtinov Mask to fit 80-110mm OD tubes
85-120mm Starwave Bahtinov Mask to fit 85-120mm OD tubes
100-140mm Starwave Bahtinov Mask to fit 100-140mm OD tubes
125-160mm Starwave Bahtinov Mask to fit 125-160mm OD tubes
150-190mm Starwave Bahtinov Mask to fit 150-190mm OD tubes
175-220mm Starwave Bahtinov Mask to fit 175-220mm OD tubes
195-240mm Starwave Bahtinov Mask to fit 195-240mm OD tubes
215-260mm Starwave Bahtinov Mask to fit 215-260mm OD tubes
250-290mm Starwave Bahtinov Mask to fit 250-290mm OD tubes
290-340mm Starwave Bahtinov Mask to fit 290-340mm OD tubes

Remember to measure your tube or dewshield diameter not the optics size! Please choose a size that sits as close to the centre of the span as possible for best results, for example if your tube diameter is 150mm do not choose the 105-150mm, the better choice would be the 125-160mm.

Customer Reviews

  Great accessory  I always thought these things were a gimmick until I tried one out. Super useful at the start of a session for getting perfect focus.The fact that the mask can sit nice and central regardless of the angle of my tube is a big benefit too.  (09/08/2019) -


  Great product  Good, painless service. Just the way we like it :)   (15/07/2019) Collin - Surrey


    Nice product and a great service.   (12/07/2019) Bruno - London


  No blurred images anymore.  Have to wear reading glasses and photos look blurred to everyone else? Not anymore with the Bahtinov Focusing Mask. Just apply mask and refocus when changing eye pieces. I even saw Messier 3 last night through my cmos camera, which is 33kly away. Looked great. Thanks Mr Bahtinov :)   (24/05/2019) Karl - West Midlands


  Bahtinov focusing mask  Excellent service excellent product as usual Thank you   (15/05/2019) Paul Johnson - Birchwood Warrington


  A Perfect Star.  Excellent focusing mask that just works completely at a great price from Harrison Telescopes. Purchased quite a lot of gear recently and have had no problems with anything. Postage is cheaper than anywhere else and is always very quick. Recommended.   (03/05/2019) Kerry Bloor - Kidsgrove


  Good product does the job.  Item was supplied quickly and well packed to survive the postal service delivery. Definitely helps with the judging of "is it or isn't it" in focus on your scope.   (16/02/2019) -


  Very useful  A very functional and inexpensive addition to the astro set-up. very satisfied.   (08/02/2019) -


  Great buying experience  First time I have purchased from Harrisons Telescopes and certainly not the last...great overall experience from ordering to delivery! Highly recommend.   (25/01/2019) Tony - Preston


  Excellent Service and very responsive  After initially ordering the wrong size mask, my mistake was quickly corrected by Ed and the correct size was sent immediately and arrived promptly the following day. The mask is well made and fits my Starwave 115 perfectly.   (18/01/2019) Keith Charters - Carlisle


  Excellent service. Easy focusing.  Harrison Telescopes offered excellent advice on size of mask required. Very fast delivery. Used last night and corrected previous FWHM focusing giving excellent round stars. No issues with 'brown paper'.   (18/11/2018) Steve - |Hampshire


  nice product, speedy service  Looks good, once I finally got the paper covering off! Haven't tried it yet but will try it on my Starwave 110 to set it up for the scope.   (09/06/2018) robin rice - newton stewart


  A great product at a good price  This simple and inexpensive device takes all the guesswork out of accurately focussing the telescope.   (19/05/2018) -


  Excellent service, time will tell on robustness  Excellent service again. Adjusts and fits easily. Happy that it doesn't look like it will scratch my scope with prolonged use. 4 stars because not convinced about robustness. It's faced with brown card, not clear if this is removable protection or it's laminate construction % removal will damage it?   (19/02/2018) Glynn - Staffordshire
Our Reply: Hi, The brown paper is simply a protective layer for shipping, peels to reveal the nice black finish under it.


  Good item. Simple to use.  Good item simple to assemble and use. Well constructed of quality plastic and precise laser cutting.   (17/11/2017) Bryan -


  Bahtinov Mask  Easy to fit and adjust and makes focusing a lot easier and quicker. A very good product and price.   (28/10/2017) Kevin Langford - Bexley, Kent


  Bahtinov Mask  Easy to fit on the telescope, and easy to learn to use; a great product   (08/09/2017) Anthony Foster - Shawbury, Shropshire


  Made such a difference - Quick delivery  Until I purchased the Bahtinov Mask achieving focus was time consuming. Now alignment and focus is done quickly making the most of the clear sky. Super service as always, delivered next day with no fuss   (18/08/2017) Neil L - Bridgend, South Wales


  Essential even with f/12 refractor  Delayed purchase of this essential piece of kit until I obtained an EOS (Canon) adapter for photographic work. However, this Bahtinov mask is equally important for visual work on the large gas planets, even when seeing is poor. Highly recommended, even when used with a 5 inch f/12 refractor.   (17/06/2017) Alan - Hampshire, UK


  Quick delivery!  Fast turnaround from order to delivery. I bought it to fit my William Optics ZS 71 to find it also fit my DSO Lens Zhongyi Mitakon 135mm lens!! Works like a charm, sharp images & adjustable fitting.   (16/06/2017) Neil - Eastbourne


Our standard delivery charge for most of the UK is £2.95. All orders are shipped promptly, lower value items are sent Royal Mail 1st class and higher value or larger goods are shipped via reputable courier. All goods are shipped fully insured with FEDEX, UPS, DPD and Royal Mail, we do not use budget courier services, please note we can only ship to UK mainland addresses. We are not able to ship to forwarding agents or PO boxes.

Our Order Lookup system (see very top of each page for the icon and link) updates the order status in real time for you - simply by entering your order number and postcode..

We hold stock, dozens of telescopes and literally thousands of accessories that we ship out each business day, normally orders received before lunch are shipped that business day. We also direct ship from our UK suppliers, this means we have access to thousands of products that can ship fast to our customers.

Deliveries to UK mainland addresses are all shipped with fully insured premium services for £2.95, *some exceptions apply including many AB, FK, HS, IV, KA, KW, PA, PH, ZE postcodes. We will quote delivery charges to these areas where applicable prior to shipping (this does not normally affect lower value items shipped by Royal Mail).

You must inform us within one working day if the goods are lost or damaged in transit so that we can make a prompt claim against the delivery company and correct the problem. Please ensure all address details are accurate, we cannot be responsible for failed deliveries or losses arising from incorrect delivery addresses.

You agree that proof of delivery supplied by our delivery company is sufficient evidence to establish that goods have been received.

If your product is sent by Courier they will attempt delivery twice and a signature will be required. If they are unable to deliver because you are not available and after 5 days you have not contacted them to re-arrange. the goods will be returned to us and the return delivery costs may be charged to you

Altair Starwave Bahtinov Focusing Masks

MPN: SWBM





Total Price: 10.50

Select Tube Size OD (mm)


Whether you’re doing planetary visual observing, planetary imaging, or deep sky imaging, the Bahtinov Mask is a great accessory to get the best focus for your telescope quickly and easily. Credit goes to Russian amateur astronomer Pavel Bahtinov for making his idea available to the astronomy community.

Starwave TM Bahtinov masks are adjustable to fit a wide range of optical tubes, unlike masks which are only able to fit one telescope. They have an adjustment lattitude of about 50mm in aperture making them very versatile.

Remember to measure your tube or dewshield diameter not the optics size! Please choose a size that sits as close to the centre of the span as possible for best results, for example if your tube diameter is 150mm do not choose the 105-150mm, the better choice would be the 125-160mm.



Recently Viewed