In summary, the broad band “light pollution” filter can be somewhat useful in compensating for some light pollution, but may not be the most impressive filter intended for deep-sky use. The broadband filter has an additional bonus, as it does work fairly well as a blue filter for observing Jupiter and for bringing out the white clouds and polar caps of Mars. Severe levels of light pollution may also be too much for the broad-band filters to handle effectively, so you still want to find as dark an observing site as you can and use averted vision. Look fainter from a dark sky site when using a broad-band filter than without one. Since some light is blocked by the filters, there can be times when a few objects may even In that case it may be better to use slightly higher power on some of the smaller objects to dilute the light pollution effect a bit. On star clusters, there is even less of an effect, since some of their emission falls in the portions of the spectrum blocked by these filters. I have found that using the filter on larger and more diffuse galaxies like M33, M81, M101, NGC 253 and NGC 2403 in my 10 inch when weak skyglow is present will help boost the visibility of the detail, but the effect is fairly mild. However, the improvement is not as noticeable on star clusters or galaxies. The broadband filters can offer a modest boost in contrast and visibility of the fainter outer detail in emission nebulae over non-filtered views for objects like the Orion Nebula (M42), the Lagoon Nebula (M8), the Merope Nebula, the Trifid (M20), and a number of others. Some available broad-band filters are the Lumicon Deep-Sky, the Astronomik CLS, the Celestron LPR, the Thousand Oaks Broadband LP-1, and the Orion SkyGlow. In addition, larger versions of these broadband filters which fit over camera lenses can be somewhat useful for photography of wide star fields when some skyglow is present. The greatest improvement in the overall view is often found with emission nebulae, but broadband filters can also give a slight contrast boost to some reflection nebulae and a few of the larger more diffuse galaxies under mild skyglow or dark-sky conditions. While these broad-band filters do not eliminate the effects of light pollution or make the objects brighter, in many cases, these filters can improve the visibility of some deep-sky objects to at least some degree. Since the eye is mainly a “contrast detector”, this selective screening out of some of the background skyglow increases the contrast and helps Deep-sky objects stand out more noticeably. The broad-band “Light-pollution Reduction (LPR) filters are designed to improve the visibility of a variety of Deep-Sky objects by blocking out the common Mercury vapor, Sodium, and some other emission lines from man-made or natural sources which contribute to light pollution, while letting through a broad range of other more useful wavelengths. Narrow-Band “Nebula” filters, and 3: Line filters. There are a number of different filters available on the market today for improving the views of various Deep-Sky objects, with most coming in one of three classes: 1. While many amateurs consider the term “skyglow” to mean man-made light pollution, there are actually several components that go into it (including some that are present even well away from man-made lighting). There are a number of popular misconceptions concerning what these filters can or cannot do, so here, we present the major ones and provide the truth about them: Since they were introduced in the late 1970’s, these filters have become a vital part of the amateur’s “observing arsenal”. Some filters even allow urban or suburban observers to view certain objects under less than pristinely dark skies by reducing the background glow of the night sky. Even those bright and easy “showpiece” nebulae often gain significant detail and contrast with proper filtration. With filters, objects which might ordinarily be difficult to impossible to see in most amateur telescopes even under dark sky conditions come within range of the experienced observer. One of the biggest breakthroughs in the past 40 years for deep-sky enthusiasts has been the introduction of effective multi-layer interference filters for certain classes of deep-sky objects. Useful Filters For Viewing Deep-Sky Objects
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |