H-Alpha filter recommendations?

[Leveye]

Any recommendations anyone can make for a filter for mostly imaging the sun?  I'd be buying a 2" filter but not sure which exact wavelength to get. Much appreciated.

[DrRobin]

Hi,

You can't use a 2" Ha filter for imaging the sun, it has to be either a White light filter/wedge or if you want to go down the Ha route it has to be an Etalon based Ha scope or front mounted Etalon.

Ha scopes come from Lunt, Coronado to name a couple.  Baader film is what everyone starts with for white light solar.

Robin

[Leveye]

You can surely image with a solar filter on the front and an H-Alpha in between that and the camera sensor i have read about doing so or am i mistaken? I am not looking for visual just imaging purposes but of course worry about heat.

[brantuk]

You need to be totally sure of what you're doing with the sun Leveye. If not then you run the risk of damaging your scope, or camera, or eyes, and it all happens pretty quickly too.

You need to describe your set up fully in order to get good advice - so the make/model of filters used, scope used, and any other relevant items in the imaging train. And a link to the article that describes what you are trying to do. Otherwise no one will give advice if they think you're not taking it seriously.

[DrRobin]

Hi,

Yes you could do that but you wouldn't gain anything.  If you put a white light solar filter on the front and then a 7nm Ha filter, it will show you the Ha band with a bandwidth of 7nm, but don't expect to see any surface details other than sunspots (which are visible without the 7nm Ha filter).

An Etalon (Solar Ha filter) has a bandwidth of 1A (Angstrom) or less and there are 10 Angstroms in a nano-metre, so your filter will be 70 times too wide to see the prominances, filaments and other surface details.

Most people using a white light filter use a Solar continuum filter to improve contrast in the sunspots.

Sorry to be the bearer of bad news.

Robin

[Merlin66]

+1 from me.

[Zakalwe]

You can surely image with a solar filter on the front and an H-Alpha in between that and the camera sensor i have read about doing so or am i mistaken? I am not looking for visual just imaging purposes but of course worry about heat.

Absolutely not.

As others have said, unless you know what you are doing with solar, pointing a scope at the Sun is an excellent way of destroying a camera or damaging your eyesight. I've seen people posting on the Solarchat forum that have damaged their eyes through making mistakes with solar. It's not worth messing with.

[lensman57]

Any recommendations anyone can make for a filter for mostly imaging the sun?  I'd be buying a 2" filter but not sure which exact wavelength to get. Much appreciated.

Unless you know what u r doing or your equipment is specifically designed for solar work I would be very careful with solar work. The risk of permanent damage to your eyes are very real if there is any failure in the equipment.

Regards,

A.G

[Merlin66]

Guys,

Let's give Leveye a chance.

As Dr Robin correctly states above, if you have a proper white light filter securely fitted up front ( i.e Baader Solar Film), you can in theory use any additional filter you want to try.

The Continuum, light green, LPR etc have all be used at one time or another to try to "enhance" the image.

The basic point is the view/ image is still only a white light image and no Ha features will be visible.

[Leveye]

I have some experience imaging the sun.  I'm using a Celestron C8 SCT with a thousand Oaks series 2 solar filter and a Canon DSLR. What H-Alpha filter does anyone recommend for the most details of the surface of the sun and solar spots? Again i'm unsure when i see them rated between 6-12 in the wavelength? Much appreciated.

[Leveye]

Anyone? I'm looking at Baader and also Astronomik filters.

[Steve Ward]

Have you not read any of the replies ... ?

No Ha filter designed for nighttime Ha enhancement will be of any use in Whitelight solar enhancement , the filter you would find gives the best contrast and detail is the Baader Continuum , closely followed by either a #56 Green or an OIII (my personal preference)

[Leveye]

None of the filters i'm looking at say strictly for nighttime use they say not for solar observation which as i stated above is not my intention.The Astronomik ones are even in the Photography section on the website. I simply wanted opinions based on anyone's past experience and results actually using these filters no need to be so rude sir.

[Zakalwe]

 Again i'm unsure when i see them rated between 6-12 in the wavelength? Much appreciated.

Anyone? I'm looking at Baader and also Astronomik filters.

That refers to nanometres. To see H-a details you need filters that have a bandpass in the Angstrom range (typically 5 Angstroms). 5 Angstroms = 0.5 nanometres

If all it took to see H-a detail was a white-light filter and a night-time H-a filter then no-one would bother spending $thousands on an Etalon.

[Leveye]

Thank you for an answer in that regard about the ratings of wavelength. It get a bit confusing. You keep using the "nighttime" description in terms but i've yet to read that they are only good at night. I will look again sir.

[Zakalwe]

No problems.

There's a wealth of info about H-a solarscopes on Stephen Ramsden's site:

http://www.solarscopereviews.com/

Here's another site that I found that will be of interest to you:

http://dailysolar.weebly.com/white-light-imaging-with-narrowband-filters.html

HTH

[DrRobin]

Leveye,

Perhaps it would help if you posted a link to article you are reading about using Ha filters with white light filters as it has got all of us stumped as to what it would do. We wouldn't want you to waste your money on something that might not work, whereas a solar continuum filter will give enhanced views.

Robin

[Steve Ward]

There's a very well informed , well written piece on this subject on Cloudy Nights , when they are back on line after another reshuffle I will post a link to it.

[JamesF]

I'd assume (though I am not certain) that the problem is along these lines...

The H-alpha band is one wavelength only.  From remote targets such as nebulae and galaxies as there's not a great deal of light anyhow you can cut out everything but, say, a 3nm band centred on the H-alpha and because there's little to compete with the "signal" on the H-a line in that 3nm range of wavelengths, the H-a is what you see.,

Our Sun however is throwing out huge amounts of light in all sorts of visible wavelengths.  Even with a white light filter, if you add an H-a filter to the optical train, even 3nm wide, there's still a large amount of light coming through in all those wavelengths compared to the "pure" H-a which is swamped by it and you see no H-a details.

As Robin said, the etalon in a PST for example allows only a tiny fraction of light either side of the H-a wavelength to pass through -- it's perhaps 50 times "narrower" than a 3nm filter.  That allows the H-a signal to dominate once again.

James

[Leveye]

Thanks for all the educating comments finally guys i'm learning a lot from all this and i really appreciate it. Look up! -C-

[glowingturnip]

intrigued by those continuum filters...

now predicting a race where we all try to outbid each other for one on ebay

[frugal]

The H-alpha band is one wavelength only.  From remote targets such as nebulae and galaxies as there's not a great deal of light anyhow you can cut out everything but, say, a 3nm band centred on the H-alpha and because there's little to compete with the "signal" on the H-a line in that 3nm range of wavelengths, the H-a is what you see.,

Also, the DSO targets we are looking at are all red-shifted to some degree or another. So if you use a 5 Angstrom filter then you are likely to cut off anything with a significant red-shift.

[JamesF]

Also, the DSO targets we are looking at are all red-shifted to some degree or another. So if you use a 5 Angstrom filter then you are likely to cut off anything with a significant red-shift.

Ah, yes, good point.  That had not occurred to me.

James

[Macavity]

Just to add a (possibly spurious!) point: I read somewhere that really FAST scopes have problems with very narrow band filters. Something to do with the incident angle of the rays on the filter I guess? Aside: I notice Baader make double-stacked CaK filters... Two non-parallel, standard, CaK filters perhaps? 

To be honest... (if you're not going the PST etc. route) I rather *like* (almost prefer?) CaK images. They show both surface details and the stuff going on just above? START out with an (obligatory!!) objective white light filter, add CaK filter(s) etc. Certainly a route I am considering - Now the price of dedicated solar scopes has escalated somewhat...

[JamesF]

I think there can be a problem with some filters in very fast scopes, yes.  I'd guess that filters generally do refract different wavelengths to different degrees but that generally the filter is so thin that it isn't noticeable.  At steep incident angles perhaps that is no longer true.

I'm also a fan of CaK.  Sadly not too many people post CaK images here, but it's always a pleasure to see the ones that Alexandra does.

James