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HK and Baader film question


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Hi I'm going to get one of those ready made baader filters for my SW200p for visual use and maybe photos later.

It seems the sun is out more than the stars. Boo!

I was wondering can you use an HK filter with baader film?

There are lots of ads for HK ccd filters.

Advice and thoughts would be appreciated. Thanks

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In a word No.  An conventional Ha filter is absolutely not for use on the Sun.  A Hydrogen Alpha (Ha) solar telescope is an entirely different thing and is constructed especially to view the Sun in Ha light.  The prices reflect the very specialised nature of the filters in those scopes!!

The Baader film will give you good white light (ie full spectrum) views of the Sun and is also suitable for Solar photography.  You will see the sunspots, faculae (bright streaks and crazing) and the surface granulation quite easily.

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I have not tried it, but I think the H-a filter might have some benefit for imaging combined witih a white light filter, especially if used with a sensitive mono webcam. I wouldn't expect it to show anything that you can't already see in white light, though. It won't be like a hydrogen-alpha telescope.

For visual, I think it will just make your view very dark and red and you'd be better off without it. :sad:

For imaging, making sure that the solar film is always on first (never add any filters without the solar film already on!), it might help steady the view and pick out more detail of what can be seen in white light compared to using no filter. Here's a daytime moon shot I took using a Baader 7nm H-a filter. I am fairly sure the H-a filter steadied the view and helped to pick out more detail than with no filter (I did not test this though...). The video frames were clear and punchy, a little bit like H-a imaging of DSO's seems punchy:

9644160764_191de01d5d.jpg

Click on image for higher res.

The Baader solar continuum filter would overall be a better option as a filter to use with white light. It would help both visual and imaging. It will steady and sharpen up the view. I would chose that over the H-a, though I may experiment with the H-a at some point with white light.

For the moon, I've since bought a red filter for use with my refractors. The red filter lets much more light through than the 7nm H-a filter, letting me use a shorter exposure time and to use Barlows (the H-a was too faint on the moon for me to use a Barlow), and seems to do a good job. Red is less affected than green and blue by the seeing conditions, being a longer wavelength, hence it helps steady the view. :laugh:

Hope that helps.

Luke

Edited by Luke
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Im not entirely sure that a 7nm would work effectively. The baader Ha filter has a bandpass of 7nm, the etalon (filter) you get with a solar telescope is 0.7 angstrom (0.07nm) - quite a big difference.

1 Angstrom = 0.1nm

Edited by Uranium235
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I have to disagree with you Pat.

The Baader film is perfectly good (usual disclaimer).  It is safe and can be used for both visual and photographic observing of the Sun.  You can buy it either as a pre-mounted film in a holder that simply attaches over the end of your scope or as a sheet for you to make your own holder.  With care and simple DIY skills and tools (scissors and cardboard) you can make a perfectly safe and servicable filter.

I have not used the Thousand Oaks product myself but all reports suggest that it too is perfectly good and safe to use.

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I have tried both ND5.0 Baader film and Thousand Oaks glass filters. I much prefer the clean high contrast 'white' white light view you get with the Baader film. I don't like the yellow/orange tint you get with the thousand oaks filters.

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I have used an Orion and Thousand Oaks glass filters and Baader film (commercial product) - still have all three. In my 4" APO frac I believe that the Baader film provides a sharper image and better contrast. As stated above whatever solar filter is used it must be in place over the objective before any filter is added to the eyepiece.

Whether an imaging Ha filter helps visually  I don't know - I have only used a Baader continuum filter which gives an improved result. I know that other solar observers rate a green filter as good as a Continuum.

Although more expensive I now use a Lunt Herschel Wedge + Baader Continuum Filter + Binoviewers - all I can say once used you will never go back and use a front filter again. However, that comes at a cost.

Mark

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