Daft solar hydrogen alpha questions

[Dawson]

This stems from me realising that the blue filter in the diagonal of my Lunt Ha scope was very misty, and trying to clean it as stocks of replacements filters are depleted all over the world…

Questions:

1. I’ve always assumed the etalon lets through only 656nm, or a band 10nm around this wavelength, but nothing else. Is this correct?

2. When looking at an image of the Sun in Ha, I presume the whiter areas are emitting more Ha, and the darker areas, less, which has a corresponding effect on the pixels / wells of the sensor of the camera; see my image below.

3. What then is the purpose of the blue glass filter in the diagonal? Surely a blue filter restricts the amount of red light passing through.

Thanks for any clarification.

James Dawson
Nottingham

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[Kwong Man]

Hi,
I am not totally sure, but it could act like a blocking filter function (cut out UV light). I would check with the manufacturers, Lunt. I am not sure if you need to be cleaning that !

Kwong

[Peter Meadows]

Hi James,

I’ll try and answer your questions:

1. Yes a Ha telescope will only let light through centered on around 656nm with a bandwidth of < 10 nm (1 Angstrom). 2. Yes whiter areas are emitting more Ha and the darker areas less. So solar flares appear bright when they occur and filaments appear dark. Your image is very nice, showing plenty of detail in AR 3590 from last month. 3. Not sure what the blue filter is for but is likely to be a UV/IR blocking filter so care is required not to damage it (the visual colour of a filter does not necessary indicate what wavelengths it transmits or blocks).

[Dawson]

Peter,

Thank you very much.

I think that is my confusion. If only 656nm gets through the etalon, why is there a UV/IR blocking filter behind it, as the etalon will have filtered out those wavelengths already.

James

[Peter Meadows]

Hi James,

Good point – not sure not having a Lunt. I have a DayStar Quark where the UV/IR filter is before the etalon.

Peter

[Dawson]

Peter, I tested the 20mm glass filter and you are correct, it does block IR. I’ve lost my UV LED so can’t see if it blocking UV too or not.

But as you say, still seems odd for this to sit behind the etalons.

The glass filter is now at least clean so at least I can use it even if I can’t source a new one.

Thanks.

James

[David Basey]

Hi James,

This probably answers your questions https://luntsolarsystems.com/theres-more-to-the-eye-than-specifications/

David.

[Dawson]

David,

Thanks for the link, that does explain a lot. Appreciate your help.

James

[Patrick Francis Kavanagh]

Hello James:

I think your Sunspot image is outstanding.

Hello Peter:

Glad to meet you! I also have a DayStar Chromosome Quark, which I acquired 3 months ago, and which I have been using to image Sunspots for a lecture series I have been giving on Heliophysics.

Excuse me if I am out of protocol.

Regards to all,

Patrick Kavanagh,
CopernicusClub,
Mexico

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[Dawson]

Thank you Patrick. Your image is too very nice.

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