Conventional narrowband filters (12nm or smaller bandwidth) do not work with the Hyperstar III system due to its very low f#.  The cone angle of the rays passing through the filter are so far from normal incidence that the actual operating wavelength of the filter (at the incident light angle) is no longer at H-alpha wavelengths.  One possible solution to this problem is to use a filter with a very large passband.  I have just purchased a 35nm bandwidth H-alpha filter from Ian King Imaging and can’t wait to see if the Hyperstar III will work with it.  My first target for testing the new combination will be CTBI, the supernova remnant in Cassiopeia that I have had trouble imaging before as it is so faint.  It will be very interesting to see if the new filter allows me to get a decent image of this difficult object.  If it does, I might just give Simeis 147 a go – I have always left this one well alone as it is so large and faint.

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4 Responses to “New H-alpha filter ordered – broadband 35nm bandwidth”
  1. Daniel says:

    Hi Greg, just a quick message to say I recently bought a Baader 45nm Ha filter and have been using it with my Hyperstar setup.

    Im no longer getting the bloating stars that I had, using the 12nm filter and early tests have been pretty positive. I took this image under pretty awful conditions, full moon, windy and hazy with a DSLR. but still achieved ok results.

    http://farm4.static.flickr.com/3449/3825529691_d431637861_o.jpg

    Im looking forward to trying it out some more over the coming weeks.

    Daniel
    :O)

  2. Greg Parker says:

    Well that result with a 45nm bandwidth filter looks pretty good. Is that a Hyperstar III that you are using? On which ‘scope?
    Greg

  3. Daniel S says:

    Hi Greg, yes, that’s the Hyperstar III on a C14, I’ve only this last week nailed how to collimate the hyperstar properly and this was taken before I’d got to grips with the hardware, so i’d expect MUCH better things from the Ha filter.

    Daniel
    :O)

  4. Greg Parker says:

    Great stuff! Another Hyperstar user 🙂 On a C14 you have a great piece of kit there!! I use the software CCDInspector to occasionally collimate the Hyperstar – it’s quite an expensive piece of software, but it is totally invaluable for collimating the HIII (and it’s quick too 🙂

    Greg

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