SkyWatcher Evostar 100 / 900 ED...
All filters are parfocal Astrodon: b>
most frustration nell'astrofotografia with CCD is that of having to find the correct firing position with the H-alpha filter: the narrow band filters keep out much light so you must use a very bright star for perfect focus. All filters Astrodon Tru-Balance L, C, R, G, B, H-Alfa, OIII and SII are parfocal on optics with focal ratio less than f / 4. Login This means you can adjust the focus by using a filter C or G, install a filter H-Alpha and immediately proceed with the acquisition. This is one of the key advantages of the Tru-Balance filters Astrodon that made them so popular in a short time.
The thickness of the filter determines how it can be parafocality: Tru-Balance filters are dichroic filters with very resistant treatments deposited on a single glass substrate of high quality. The reduced thickness (3mm) of this substrate is controlled accurately with error +/- 0.05mm. The change from lot to lot is less than 0.1mm, measuring slightly less than the critical areas of focus of a system f / 5. On request it is possible to select within various batches filters with less variation and then get a set of filters that have the exact same thickness (prices on request).
balance corrected blue-green OIII: < / b>
when applying the same weight to the three colors (1: 1: 1) for the point of the white balance, the next step is to obtain a correct blue-green color corresponding to the issuance OIII in the region Central of planetary nebulae. Login This it requires that the emission line OIII has a component equal both in the green channel than in the blue, AFTER you apply the weights G2V for correct color balance of the stars and therefore white. < br> This is what is meant by "" œParadosso RGB color "": when applied weights G2V-color to your camera and filters, the proper balancing of the emission line OIII for the final images in the blue and green it is impossible. There is little to do but slightly alter the weight-color G2V. This is the problem in "" œmescolare "" in astrophotography emissions in narrow bands (eg. OIII) with colors in wide stripes (RGB). This problem does not affect the emission lines H-Alpha and SII because both fall in the curve of the red filter. The problem is characteristic of the emission line dell'OIII close to 500nm which falls between the curve of the blue filter and that of the green filter. The problem is even more evident when using photometric filters UVBRI as the blue photometric filter has a very low transmission nell'OIII.
Note however high and similar transmission filters green and blue Astrodon level of emission line OIII : from the time that the weights applied are 1: 1: 1, the transmission nell'OIII must be the same for both the green filter for the blue one. This not only allows to obtain a correct blue-green color for the OIII but does so with a high efficiency. The speech is valid for both the series and that for that I. In other words you will eventually get such a M27 with the right color. B> The Astrodon Tru-Balance filters provide color nebulae OIII requiring a balance by up to 10%, no other filter on the market has such efficiency.
The figure shows will follow what you mean by image "" œtroppo green "" or "" œtroppo blue "" in comparison with well-balanced image.
The last image shows the planetary nebula M27 taken with a CCD sensor and a KAF3200ME C14: color combination 1: 1: 1, exposure of 10min for R, G and B using the filters Astrodon Tru -BALANCE series E. Note the details that have emerged despite a total exposure time of 30 min reduced and how the color of the nebula is well balanced, neither too green or too blue. "
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