Baader AstroSolar Film
Updated 7 May 2002
Click here for instructions to build a solar filter for your binoculars.
Imagine safely observing the Sun in natural white light color for less than $40. Stop imagining and do it! Baader AstroSolar Film makes it happen. AstroSolar Film is available in sheets which allow you to make your own filter cell or you can purchase in a pre-made filter. I used the sheet and made this filter in just under an hour. As you can see, you can make a professional-looking filter that won't embarrass you at star parties!
The A4 size sheet is large enough to make three filters for an 80mm scope. And larger scopes might not benefit from much larger aperture. To decide if you would prefer making the filter yourself, here are instructions from Baader for making your own filter. This stuff is just great, you can make filters for just about anything - binoculars, camera lens, your finder scope - and it is ideal for making solar eclipse glasses as well. There is no need to worry about making the film tight when creating the filter, in fact stretching the material will harm it's optical quality.
I mounted the filter on my NexStar 80GT and using a compass for North, performed an auto-align. When the NexStar pointed at each of the alignment stars, I simply accepted the location. I then chose Sun from the Planet menu and after pressing Enter, the hand controller scrolled a warning about viewing the Sun with a safe and suitable filter. Pressing Enter a second time interrupts the warning and the scope slews towards its target. Since the alignment is only as accurate as your leveling of the tripod and pointing towards true North (not necessarily magnetic North) don't be too surprised if your scope doesn't put the Sun in the field of view. Occasionally I have gotten a good enough alignment to have the NexStar put the Sun in the FOV of a 10mm eyepiece. When it misses, use the shadow cast by your scope to point the way. Once I get the Sun in the eyepiece, I have found tracking has been good enough that the Sun doesn't drift too quickly to spoil the enjoyment.
The image is just spectacular. Sunspots are easily viewable and magnification can be taken fairly high (better than 100x) without the image suffering. The image is very natural looking, the sun is white, not blue or amber as seen with most solar filters. The background sky is jet black. The Sun's disk is not as bright as an unfiltered full moon, so it is not overpowering. The contrast between the sunspots and the Sun's disk is very good. In short, this is great stuff.
When not in use, I store my filter in a plastic storage container from the kitchen section of the department store.
So, if you've never tried daylight astronomy, stop waiting, Baader AstroSolar Film makes solar astronomy affordable with no loss of premium performance.
You can purchase sheets of film from Astro-Physics (www.astro-physics.com) or you can buy pre-made filters specially made for NexStar scopes (by Celestron) from the SightsandSoundShop (www.sightandsoundshop.com). Kendrick, of dew removal fame, also sells a variety of pre-made filters (www.kendrick-ai.com). In Europe, you can purchase filters and film directly directly from Baader (www.baader-planetarium.de).
Join the Baader Planetarium discussion group on Yahoo