H-Alpha Filter

[Dazzyd]

Hi all

I was wondering if there's a way to create a H-Alpha filter to go onto the front of a scope like you can create a white light one with the Baader solar film? OR, which I'm suspecting, is the H-Alpha world jsut in the realms of the dedicated solar scopes?

I like the white-light photos I've been taking especially when I apply the warming filter in photoshop but the h-alpha shots are just something else, stunning!

Thanks

[umadog]

You are correct, I'm afraid. Halpha requries a dedicated telescope. The reason is that the filter bandwidth needs to be super-narrow and there's no simple way of doing that. These scopes have multple filters, one of which is tunable. It has to be tunable because the bandwidth is so narrow that the red and blue shift of the Halpha line can cause it to be thrown outside of the filter's pass band. So tuning the filter will maximse contrast for features that may be moving either towards or away from the observer.

[Dazzyd]

I thought so but it was worth asking. Thanks for the reply umadog

[ollypenrice]

Whoa, this is not correct. You can indeed buy front fitting H alpha filters. This is the 60mm Lunt, for instance. http://luntsolarsystems.com/blog/the-new-ls60f-unobstructed

The bad news is that they are expensive and also need the rear blocking filter (which looks like a star diagonal.)

Why would you buy a front filter like this rather than a complete solar scope? You won't save much money and the solar scopes can use singlet lenses because, obviously, there is no need for colour correction.

Well, if you want to do full disc imaging you can put one of these front filters on, say, a ZS66 and have a short enough FL to fit the disc onto a DMK41. My Lunt LS60 has too long a FL for this to be possible.

These front filters can also be 'double stacked' onto existing Ha scopes to reduce further the bandpass and enhance disc detail.

Olly

[umadog]

You're right, Olly, it's wrong of me to say one needs a dedicated solar scope, but those add-on filters aren't economical for most people. They're significantly more expensive than a dedicated solar scope because the etalon has to be full aperture (or close to it). In a dedicated solar scope the etalon can be placed further down the light path and so can be substantially smaller in diameter, which makes it cheaper. For example, that 60mm aperture filter with a 6mm blocking filter is $1850. The equivilent (dedicated) tilt-tunable solar scope is $1300. You could upgrade to pressure tuning and still be paying $350 less than the front-mounted filter.

[LukeSkywatcher]

I believe (because it says so on the tin) that this filter when used in conjunction with the Baader solar film improves the view:

http://www.firstlightoptics.com/solar-filters/baader-solar-continuum-filter.html

How good is it? i have no idea.

I might invest in one.

[hunterknox]

I believe (because it says so on the tin) that this filter when used in conjunction with the Baader solar film improves the view:

http://www.firstligh...uum-filter.html

How good is it? i have no idea.

I might invest in one.

It's better than just using the standard view with Baader film, but not that much better than using Baader film with a generic dark green filter (wratten 58). It shows you a bit more detail in white light but that's about it.

[umadog]

Sounds like it may help a bit:

I don't believe the claim about atmospheric turbuelence.

[LukeSkywatcher]

It's better than just using the standard view with Baader film, but not that much better than using Baader film with a generic dark green filter (wratten 58). It shows you a bit more detail in white light but that's about it.

Good to know. I gave away most of my colour filters a couple of yrs ago, but i just checked and i still have a dark green (wratten 56).

Must have been a reason i kept it.

[Stu]

I think Moonshane is actually quite happy with the improvement the Continuum filter gives, there's another thread around somewhere with this in.

Stu

[x6gas]

OK so I used my home brew Baader Solar Film solar filter for the first time today. I was quite amazed (but shouldn't have been) that I could see absolutely nothing unless the sun was fullonunobstructedbycloud.

But, I was wondering what the view (or indeed the imaging) would be like through an Ha filter on the EP end - is the image just too dim by then?

[malc-c]

OK time for a blond question here, if you use a Baader Ha filter in front of the eyepice / camera, and have a Baader solar film filter on the front of the scope, would you still capture any provenances, or do you need additional filters ?

[hunterknox]

OK time for a blond question here, if you use a Baader Ha filter in front of the eyepice / camera, and have a Baader solar film filter on the front of the scope, would you still capture any provenances, or do you need additional filters ?

Short answer, no (what Umadog said above).

The very best standard Ha filters have a bandpass of ~3 nm whilst even the most basic Ha solar scopes these days have a bandpass of ~0.1 nm. A "night time" Ha filter would probably give a similar view to the continuum but would not show prominences, filaments etc.

[Moonshane]

link to my short review

after my initial goof with the Baader film, I am now much much happier with the Continuum filter. I can only say what I see and this is a much improved image with excellent detail, granulation and reduced wobble/steadier visual images. never used a green filter so cannot say what the differences are but I'd buy this filter again. if you enjoy solar observing and want a little extra detail, you'll get it.

[umadog]

So it does produce steadier images? Why is that?

[Moonshane]

It certainly seems to in my experience. I am not sure why but presume it is due to the reduction of wavelengths like when a red filter is used on the moon to reduce shimmer?

[ollypenrice]

Another option for white light viewing in a refractor only is the Herschel Wedge, eg from Lunt of Baader. This give excellent white light views and a hint of granulation.

I agree that front Ha filters are not a great idea unless you want to tailor the FL to the chip size. They are certainly expensive, too.

Olly