Solar filter

[Kayaker72]

Hi Mike...

I know we've chatted about this. I do worry that the Ha filters you are talking about are for astro, not solar. Ha filters for astro fall into "narrow band" imaging as light for astro is typically coming from reactions involving oxygen, hydrogen (Ha), and sulfur. Thus, if you look for a "narrow" band around those emissions, you can pull out different and get more detail of nebula, etc.

But the real purpose of narrow band imaging is to avoid issues from light pollution. By focusing on wavelengths from space, you minimize the impacts of light emanating here on the planet (which is different wavelenghts) and bouncing around our atmosphere, interfering with the final image. So, the intent of narrowband imaging is to clean up the light hitting a sensor and to focus it on what is coming from Space.

But, "narrow band" for astro is typically 10-30 nm. When I've looked at Ha filters for solar imaging, they are trying to tightly focus on the peak of hydrogen alpha, 656.3 nm. Single stack are typically getting you a 0.7 nm range around the peak, and then double stack are usually less than 0.5 nm. So, solar imagers are really trying to be ~656.0 nm to ~656.5 nm, or tighter.

While I do not know this for sure, my concern is that 10-30 nm is not narrow enough and will let too much other light through, thus washing out Ha. So, it would be a red, detail-less image. I could be wrong. I know this as I was looking into the exact same thing but have so far opted to not go for it.

BTW, why Ha? This stuff facinates me, different light (and gravity for that matter) come from different layers of the sun. The different layers being at different temperatures, pressures, and even compositions support different reactions. At the very surface, the chromosphere which is hotter (~20,000C), is a reaction where the electron in hydrogen changes state with the temperature causing it to rise (to n=3), and as it falls (to n=2) it releases 656.3 nm light. Electron state change from n=3 to n=2 is called an "alpha"...as this is coming from a hydrogen atom, you get "hydrogen alpha" light.

White light mostly comes from the photosphere, which is just below the chromosphere. But the chromosphere being the surface, to see what is happening on the surface, you look for Ha bandwidth.

Getty back to my concern, if you do not get narrow enough around 656.3 nm, other light from the photosphere may still drown out the Ha light, thus the details of the chromosphere that we all want to see.

Like I mentioned, I've looked into it. I've decided to save my money at this point, but if I was to do it, I was leaning toward getting a Lunt 50 mm single stack dedicated solar telescope. The primary reason being, turns out, to get good photos of Ha, most solar photographers are using monochromatic cameras as our darn Bayer arrays actually are not tuned to Ha light. So, to do it well, you likely need both a dedicated telescope and a dedicated camera. That is a bridge too far for me.

So, for now, I am still thinking of just using white light filters with my camera lenses.

Thanks,
Brant

[Busted Knuckles]

I am going to at least double stack.

The 1st filter will be the solar film - 1st attempt - with the Ha after it. 2nd attempt will be the 10x nd filter with the HA after it. I will absolutely test the the 2nd attempt w/ a non camera rig - basically a large magnifying glass projecting to a board of some sort with temps being measured from ambient. Much of a step up in temp is a no go.

The higher reputation youtube folks pointed out that about 40% of the light from the sun - getting through the atmosphere/ozone layer - is IR we can't see, 50% visible and 10% UV. Excluding IR/Visible make UV exposure values drop.

I totally get that the visible/uv cut filters likley allow a very broad IR light stream in which might be too diffused in its origin to create any texture in the sun surface - we will find out when the filters arrive.