I thought I would just add a point about hydrogen alpha (Ha) filters.
If you're contemplating a glass DSO Ha filter that costs about £100-400 for solar observing then don't. These are for night time astronomy use not for solar and here's why:
1. The Ha filter is not designed for solar heat. It will crack quickly followed by the smell of burning - either eyeball or your equipment. You MUST have a blocking filter (normally called an Energy Rejection Filter, ERF for short) - that's what the white light foil does.. solar scope blocking filters used for Ha normally retail for about £3-400 then you have the cost of the actual tunable Ha filter.. so you can see.. there's no cheap short cut..
2. Ha filters for DSOs are anything from the range of 35nm bandwidth to 3nm bandwidth - the width of light passed around the magic 656.3nm light wavelength spectral line. This will not return any Ha images other than a round blob. They are not narrow enough to show prominences - for that you need 0.9-0.1 angstroms bandwidth (i.e. 10 angstroms to 1 nm).
3. A DSO broad or narrow band filter behind a white light blocking filter may help make the image more contrasty or show some surface granulation.
Just incase people think they can get cheap solar prom and eclipse shots
My experience, other than white light - I built my own spectrograph - it's performance was measured by others at R6000 and 0.9Angstroms bandwidth.. a couple of mods over summer will see that bandwidth fall to 0.3-0.4A. This is not only good enough to show proms as the solar scopes do.. it can also differentiate the speed of the matter in the proms on the suns surface (± about 200,000Km/hour) measured by redshift in the spectra..
Once finished ... it should be pretty good as I get to image in multiple colours at the same time.
If you're contemplating a glass DSO Ha filter that costs about £100-400 for solar observing then don't. These are for night time astronomy use not for solar and here's why:
1. The Ha filter is not designed for solar heat. It will crack quickly followed by the smell of burning - either eyeball or your equipment. You MUST have a blocking filter (normally called an Energy Rejection Filter, ERF for short) - that's what the white light foil does.. solar scope blocking filters used for Ha normally retail for about £3-400 then you have the cost of the actual tunable Ha filter.. so you can see.. there's no cheap short cut..
2. Ha filters for DSOs are anything from the range of 35nm bandwidth to 3nm bandwidth - the width of light passed around the magic 656.3nm light wavelength spectral line. This will not return any Ha images other than a round blob. They are not narrow enough to show prominences - for that you need 0.9-0.1 angstroms bandwidth (i.e. 10 angstroms to 1 nm).
3. A DSO broad or narrow band filter behind a white light blocking filter may help make the image more contrasty or show some surface granulation.
Just incase people think they can get cheap solar prom and eclipse shots
My experience, other than white light - I built my own spectrograph - it's performance was measured by others at R6000 and 0.9Angstroms bandwidth.. a couple of mods over summer will see that bandwidth fall to 0.3-0.4A. This is not only good enough to show proms as the solar scopes do.. it can also differentiate the speed of the matter in the proms on the suns surface (± about 200,000Km/hour) measured by redshift in the spectra..
Once finished ... it should be pretty good as I get to image in multiple colours at the same time.
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) so the images will be short and the DSLR shutter taking the focus of the heat.
