| Solar Equipment |
Choosing a Hydrogen-Alpha Filter
| | Greg Piepol | June 20, 2006 |
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| Coronado SolarMax Filters |
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There was a time when choosing a hydrogen alpha (H-alpha) solar filter was an easy operation. You either bought brand X or none at all. Now, getting exactly what you want can be a bit confusing at times. Taking a few moments to determine your needs can make the buying process easier and gets you a filter that satisfies your desires and budget.
Right off the bat, the cost of a H-alpha filter or telescope will be a determining factor. Because these precision instruments require insanely close tolerances and unusual manufacturing procedures, they are not cheap to purchase. Then there's the Angstrom (Å) rating. The lower a filters bandwidth (or angstrom rating) the more detail you will see on the disk and the greater the contrast will be between the lighter and darker solar phenomena. A .5Å filter will show richer details than a .7Å.
Bottom line: determine your maximum amount to spend and buy the largest aperture, lowest bandwidth filter you can afford.
To help you along, see where you fit into one of these categories: |
Sweet and Simple
At $499, the 1.0A Ha PST is hard to beat. All of the Chromospheric details are there: prominences, filaments and disk details. Lightweight and easily transportable, the PST can be mounted onto something as simple as a camera tripod. The SolarMax 40 gives similar views but drops the bandwidth to the sub-angstrom level of <.7A. This filter will continue to show good prominences but the disk detail will be greatly enhanced. |
Seriously Interested
Want to super charge your PST? Stack it! Adding a SolarMax 40 to the standard PST brings the bandwidth to .6A and really brings out the details (remember: lower A = more detail). The contrast between the lighter and darker phenomena improves significantly. Spicules cover the disk and active regions stand out.
Alternatively, the mid-priced SolarMax 60 filter is another sure winner in this category and makes it one of the best values in solar viewing. At 60mm, it is well suited for many of today’s 80mm, f/5 refractors. There’s enough aperture to allow for higher visual magnification and stunning results when imaging. |
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| SolarMax 90 Image |
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Both Feet
If Ha observing and imaging is your passion and you’re ready to jump in with both feet, then the SolarMax 90 is for you. Big enough for high resolution imaging or observing, the SM90 does everything well. Expect an excellent view of the structure within a prominence. Images can show individual spicules along the limb or around sunspots. Attach a CCD or video camera and you’re ready for NASA! |
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| Our Star in Ha Light |
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Looking before you leap
Try and look through the filter you’re interested in before buying. Some of the filters mentioned above can be seen at astronomy retail stores. Almost every star party now has a few Coronado filters on the observing field. This is an excellent way to get experience with the filter, ask questions of the owners and try different eyepieces. Also, in the United States, plan on attending the North East Astronomy Forum (NEAF) near NYC or the Riverside Telescope Makers Conference (RTMC) near Los Angeles. Both events will have several scopes and filters out under the sun.
Finally, attending the Coronado Hands on the Sun Conference (HOTS) in Tucson, Arizona is the ultimate way to get up close and personal with all of the equipment described here. |
Enjoy the sun!
Greg Piepol
www.sungazer.net |
| Classifications: Solar| 6/20/2006 - 6/20/2010 |
