Baader 889nm Methane Filter

[DeepSolar64]

Here is a very informative link on the Company Seven website on the Baader 889nm methane filter. The article mentions using the Baader film or an ERF ahead of the methane filter and camera. Would not a Herschel wedge work as well?

The current SPOD image by Sergio Alessandrelli has an included methane 889nm image included among the others. The Sun imaged well at this seldom used wavelength.

I bet an SHG could do it too!

James


http://www.company7.com/baader/options/methane125.html

[Montana]

James, like the Baader CaK filter it will never be narrow enough to look directly in an absorption line (if there is one there). I expect as it is in infra red it will calm the seeing right down. I expect it is similar to a TiO filter which I think (no idea really) is around 700nm? It will give a white light view with calmer seeing. No good for visuals.

Alexandra

[JochenM]

A friend of mine has one of those Baader CH4 (Methane) filters. It's fun for messing around with Jupiter and Saturn (with sufficiently large apertures).

But as Alexandra mentioned, it has a pretty wide bandpass (8nm if I'm not mistaken), so it'll have limited use in solar work. It probably compares better to using a red filter behind some solar film rather than a proper narrowband of its own.

[DeepSolar64]

I don’t think it could be labeled as a methane filter if they weren’t a CH4 line there but I agree that it is too wide a bandpass to isolate the line. In this way it reminds me of the Baader K-Line filter.

It certainly is an imaging only filter since it’s well outside the visual range on the IR side. And should give a steadier view than Baader 540nm continuum.

JP

[Bob Yoesle]

I jumped on the G-band and TiO filter bandwagon, but in reality these have sat in their boxes after getting an initial use... All the detail I need is already covered by three primary filter bands: the narrow-band chromosphere with CaK @ 394 nm and H alpha @ 656 nm, and photosphere with a wide-band Continuum @540 nm (e).

If my seeing is bad enough not to allow use of these three filter systems, I simply forego imaging, I don't see the point of all these miscellaneous photosphere and/or chromosphere filters which show essentially the same features as the three primary ones I already have. And depending of the telescope optics, shorter and longer wide-band wavelengths may not offer much of an advantage - if any - due to spherochromatic aberration issues:

Spherochromatic Aberration.jpg (483.28 KiB) Viewed 1427 times

telescope-optics.net

[DeepSolar64]

I certainly see your point Bob. CaK or CaH, Ha and 540nm continuum are certainly tops. On CaK though I can see use for a more broadband filter for photosphere as well as an ultra-narrowband one for CaK features. A wider band K-line filter like the Antlia wedge/filter would be better at imaging faculae across the disc than the 540nm filter would be and is significantly cheaper than a true narrow bandpass CaK filter like a Lunt module would be.

JP

[Sergio Alessandrelli]

Hi

I used the Baader Methane filter with a Baader cool-ceramic and a 0.9 ND filter. It works for me with an APO FLT132. It reduced a lot the turbolence, my local seeing is never good, but with less resolution and a more noisy image. I want to repeat the the test with a larger aperture telescope in the future.

Bye

Sergio

[marktownley]

Hi

I used the Baader Methane filter with a Baader cool-ceramic and a 0.9 ND filter. It works for me with an APO FLT132. It reduced a lot the turbolence, my local seeing is never good, but with less resolution and a more noisy image. I want to repeat the the test with a larger aperture telescope in the future.

Bye

Sergio

For the reasons Bob has stated above regards spherical aberration, you will probably get a better result stopping the 132 to a much smaller aperture and using a 540nm continuum filter.