Seems like someone has beaten me to it ;-)
Anyway: with a bit of explanation...
the Hydrogen-Alpha solar filter is a Fabry-Pérot-Etalon, followed by a blocking filter to restrict the range of wavelenths.
The Etalon consists of two extremely well-figured and highly refelective plane mirrors facing each other.
Normally, hardly any light would through (except maybe a millionth of the incident light - just thing of stacking up two mirrors and looking through).
Now, when the two mirror surfaces are exactly parallel, light bounces between them so often, with a tiny bit getting through each time, that they suddently become transparent again.
But (and this is the clever bit) they only do this for a wavelength that inferferes constructively between a ray that has just arrived at the second mirror and ones that have bounced back and forth between the mirrors several times.
This means the separation has to be an integer multiple of half the wavelength you want to transmit, which makes for a highly selective filter.
For this to work, however, the plates have to be very parallel, indeed. Think of fractions of a second of arc.
If they are not, you get some sort of infinity-mirror-effect of fainter and fainter solar images fading to the side where the mirrors are separated a bit more than at the others.
I am sorry to be the bearer of bad news:
This does look like a faulty etalon.
Most likely, the plates of the main filter are not parallel, which means that the etalon needs re-adjustment. For a cemented etalon, most likely, the etalon is in need of repair.
My conjecture would be twofold, depending on the kind of adjustment possible:
- First of all, it is likely that the etalon has come apart very slightly on the side where the image trail points to (Has the instrument received any bad bumps recently?)
- Secondly, if the etalon is a cemented one, then it needs repair. If the etalon, however, has a screw that presses down on each spacer, then the one where the images trail to might need some minute tightening.
If you have never done this before or have not passed, say, a lab class in experimental physics on university level (or are not an avid amateur optician), I would recommend that you seek assistance from the manufacturer.
Hope this can be fixed easily.
All the Best,
Edited by Eikonal, 27 May 2019 - 10:51 AM.