MiniSHG and Ha 7nm filter

[Merlin66]

The attached screen shot shows a few things:
1. The Baader 7nm Ha filter actually has peak transmission at 6580A.
2. The movements in the solar surface are clearly seen as "wiggles" in all the absorption lines.


The measured resolution R=33529 and the dispersion 0.0635 A/pixel match up pretty well with the SimSpec for the MiniSHG.

[multiweb]

Pretty cool. :thumbsup: Very interesting.

[Rob_K]

Fascinating, thanks Ken!

Cheers -

[Merlin66]

OK,
I think what has happened is the "light sharpening" has caused some artefacts which exaggerate the wiggles.
In an un-sharpened version the wiggles are obvious in the Ha etc. and not in the tellurics.

[JA]

Hi Ken,

The peak transmission is an interesting result.:thumbsup: I wonder if the bandwidth is to spec. In trying to deduce this from the graph, I'd be curious to know the vertical scale and starting point/zero. Thanks for sharing your work - very interesting Ken:thumbsup:

Best
JA

[Merlin66]

JA,
Looking at the peak @ 6580A and assessing the FWHM (based on the visible curve in the blue wing) the 50% line seems to be at 6545A.
This would give a FWHM of 2 x 35A = 70A which is the Baader spec.

[JA]

Thx Ken. So if the 50% transmission line passes through 6545A and knowing that the max transmission for this filter is probably around ~88-90% (from Baader literature for the 7nm CCD) that makes the Ha transmission not that great, around 65-70% very roughly.... Yes? If so, as an aside, that's quite a revelation, since when you look at the data when comparing filters, the graphs do not have such fine resolution and clearly could lead to the wrong impression of what represents a good filter for a particular application/ budget.

Best
JA

[Merlin66]

JA,
Yes, that sounds about right.
You could probably tilt the filter to get better transmission.....