Baader solar continuum vs OIII filter

[sgazer]

I've just made up a white light solar filter with the Baader solar film for my C80-ED scope and I've been reading the threads regarding use of a green filter vs the Baader solar continuum filter in conjunction with the solar film. There are some suggestions that the continuum filter doesn't give a massive improvement over a green filter.

Not wishing to buy a 2" continuum filter (for use with my DSLR) I remembered I had a 2" OIII filter. Now the continuum filter has a bandwidth of about 20nm at 540nm and the OIII is about 20nm at 500nm. I think a normal green filter would be about 100nm bandwith at around 500nm. Thefore, if a wideband green filter helps, would the OIII filter help a bit more due to its narrower bandwidth (similar bw to the continuum filter and fairly close in frequency)?

Thanks

[russ]

I have no idea but will be equally interested to know.

[Merlin66]

Certainly well worth trying! I'm assuming the transmission efficiencies are similar.

I've tried various filters, but to be honest I didn't have an OIII / Hb at the time, so even for completeness would be an interesting trial.

Ken

[russ]

I have an OIII, i'll compare the view with the #56 green filter. Just need to get home and have some clear sunny skies. Hopefully i'll be able to try when i get home at 5pm.

[brianb]

Let us know what you find.

I think the choice of 540nm for the solar continuum filter is to do with the maximum output of the solar surface being at that wavelength, also the eye is pretty sensitive to that wavelength so you can have the filter pretty dense without it appearing to be so. 500nm is not that far off so I would expect similar results but do not have an OIII filter to try myself. The "green" is also friendly to badly colour corrected scopes, I would expect "blue-green" to be a bit less so.

[sgazer]

I'll try and give it a go today if it's still sunny enough when I get home, although I'm new to solar imaging and all its unforseen problems and there only appears to be one small sunspot at the moment, so I can't guaranty any useful results today!

[sgazer]

well, I suppose a bank holiday weekend isn't the best time for imaging the sun! By the time I got home, it was starting to cloud over ready for the weekend's rain. However, there were a few fleeting gaps in the clouds and I managed to get 3 frames with the Baader solar film and Skywatcher OIII filter fitted to my Canon 1000d, although these still have some cloud passing in front. I wasn't able to try it without the OIII filter as it had totally clouded over by then. I must say though, that the liveview made focusing on the sun very easy, there was a small sun spot visible in the liveview image, so I adjusted the focus until this was as clear as possible. Attached is one of the frames, cropped and stretched and the hue adjusted to make it orange, instead of green.

There's a sunspot on the bottom left and a smaller one towards the top right. I don't know how much the OIII helped, but if it's sunny again this year, then I will try it with and without the filter.