I ordered Astronomik Hydrogen Alpha Filter from Perseu company.
Although Teleskop-Service company (where I use to buy astronomy accessories) is in Germany they charge for shipment of the single filter 18,-Euro. Then I noticed that Perseu (Portugal) also offers the filter for the same price (119,-Euro), but shipping charge are as low as 3,-Euro (at first I thought that it was some typo error). Although filter travelled from Germany (from manufacturer - Astronomik) to Portugal and then to Slovakia I saved 15,-Euro!
And the most surprising was that I ordered filter on Friday and I had it at home on Wednesday - such express shipment only for 3,-Euro!
Here is the link to Perseu for ordering the filter:
Perseu - Astronomik Hydrogen Alpha Filter

The filter's transimission characteristics is:

Filter tests

As soon as I tested the filter's performance I forgot about it's high price. That's the difference!

Although the tests were not done during the same night, the results are definitely clear:

NGC7000 without any filter Camera: SAC8 + 0.6x Mogg focal reducer Telescope: 80mm F5 Skywatcher refractor Result focal ratio: F3	NGC7000 with H-alpha filter Camera: SAC8 + 0.6x Mogg focal reducer + H-alpha filter Telescope: 80mm F5 Skywatcher refractor Result focal ratio: F3
Cropped part of raw frame Exposure: 2s (gain 100%, binned, Amp Off)	Cropped part of raw frame Exposure: 14s (gain 100%, Hi-Res, Amp Off) Note: Hi-Res mode is less sensitive than binned mode, so the filter transmission cannot be compared by simple comparison of exposure times
Cropped part of processed frame Exposure: 30x2s (gain 100%, binned, Amp Off)	Cropped part of processed frame Exposure: 72x14s (gain 100%, Hi-Res, Amp Off)

Here is blinking comparison of the two above pictures:

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Last Update: 06.10.2004