Advice on observing the sun using reflector & filter(s)

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Advice on observing the sun using reflector & filter(s)

Postby Peter_Iles-Smith » Sat Apr 16, 2016 5:13 pm

I've what might well be a bit of a daft question re observing the sun.

I've a Skywatcher 200 reflector & have successfully observed the sun using a Baader Astrosolar filter over the end (I know not to do it any other way & to check for pinholes etc).

My query is whether (& what type) of H-alpha filter could be used to complement this and let me see the sun in a different light so to speak. I've seen a number of expensive units & then much cheaper H-alpha eyepiece filters. I'm now slightly confused & finally wonder whether a Coronado or similar bespoke telescope would be a better complement? Though I think I need to have a quiet chat with the bank manager first though.

Any and all advice gratefully received.

Peter
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Re: Advice on observing the sun using reflector & filter(s)

Postby Gfamily2 » Sat Apr 16, 2016 10:28 pm

Peter_Iles-Smith wrote:I've what might well be a bit of a daft question re observing the sun.

I've a Skywatcher 200 reflector & have successfully observed the sun using a Baader Astrosolar filter over the end (I know not to do it any other way & to check for pinholes etc).

My query is whether (& what type) of H-alpha filter could be used to complement this and let me see the sun in a different light so to speak. I've seen a number of expensive units & then much cheaper H-alpha eyepiece filters. I'm now slightly confused & finally wonder whether a Coronado or similar bespoke telescope would be a better complement? Though I think I need to have a quiet chat with the bank manager first though.

Any and all advice gratefully received.

Peter


Hi Peter,

As far as I'm aware, the H-alpha filter has such a narrow bandwidth that you need to start with a bright source - so you can't use H-alpha on top of a Baader filter as there's not enough light left to see with.

And using a reflector with an open aperture and hoping to use a narrow band filter at the eyepiece is a no-no as well, as there's too much IR for the components between the objective and the eyepiece. You can get away with it with a reflector as the IR isn't absorbed in between (or so I've read)

A full aperture H-alpha filter is realistically the only way of using your existing scope, but that is mega-£££.
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Re: Advice on observing the sun using reflector & filter(s)

Postby Peter_Iles-Smith » Sun Apr 17, 2016 2:55 pm

Thanks very much for that. Much clearer now. Back to the piggy bank I guess
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Re: Advice on observing the sun using reflector & filter(s)

Postby The Man with the Corrugated Iron Roof » Mon Apr 18, 2016 7:39 pm

The eyepiece filters are usually broadband filters meant for night-time use. The exception is the Daystar Quark and similar filters that cost £700ish. You'll need an energy rejection filter at the objective to block some infrared energy. Use the Daystar ones or similar, as others may also block hydrogen alpha light, which is quite close to the infra red wavelength.

Depending on your piggy bank, the Coronado PST (which I have) and Lunt LS35 are worth considering.
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