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  1. #1
    never2dark's Avatar
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    Cool Newbie question: Solar filter + hydrogen alpha for transit?



    I have an Orion 180mm Mak that I'd like to use during the Venus transit, then for subsequent observations of prominences and sunspots as well as arcs and granularity later. It looks like the Coronado Solar Telescopes have an energy rejection filter and some sort of tuneable Ha filter assembly.
    I have two dumb questions: First, having only ever used a Mylar solar filter before on a 4" Mak, the sun was featureless except for the sunspots (and Mercury, as this was during the last Mercury transit). Would adding a standard EP-threaded hydrogen alpha filter make the view too dark? Or would the dimmer image let me see the prominences, granularity, etc.?
    Second, what would be the best energy rejection filter for this application: glass, black poly, or Mylar?
    Thanks in advance for any wisdom you can impart!!

  2. #2
    CalanRoupe's Avatar
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    Unfortunately, adding the HA EP filter will not work. That filter is designed for viewing nebula. And NEVER! EVER! try and use an EP filter (of any kind) without a full aperture solar filter to view the sun. You'll burn your eye out in a heartbeat.

    Only buying either the full-aperture HA filter (designed for solar viewing) or a solar viewing telescope like the PST will get us the prominences.......

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  4. #3
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    Actually, you can get some prominences with a white light solar filter and Ha filter combination if you are patient and don't mind a LOT of work to see the minimal amount of them. Do keep in mind however that this setup will never approach the level of a dedicated Ha solar scope.

    Allan

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  6. #4
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    Solar filter at the front and HA filter at the back should work pretty well.
    HA filter at the back only works poorly for those that value their eye sight.

    Two layers of properly coated aluminized mylar (aluminum inside to inside to avoid scratches) is the prefered way to make a solar filter. Any scratch or pin prick hole will allow WAY TOO MUCH sunlight through.

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    It is not aluminized mylar. Do not use that term as some unknowing people will try to make solar filters out of space emergency blankets and injure their eyes as a result. It is Baader AstroSolar Safety Film, not aluminized mylar.
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  10. #6
    never2dark's Avatar
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    Ok, given a glimmer (sic.) of hope, I have procured an Astrozap holder with Baader film for my scope and TWO Orion extra narrowband Ha filters to stack at the EP. Hopefully the quick rolloff at +/-3.5nM x 2 will give me only 25% light at +/-3.5nM and cut me back to only 80% at Ha (minus 99.99% due to the film) and I can still see something. Total cost is just over $350. All filters are rushing to me from around the country now, so expect a first light report sometime early next week! Thanks for the help everyone!

 

 

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