Hydrogen alpha filter

[Craig.a.c (Craig)]

I notice that alot of detailed images of the sun have been throuh a H-alpha or H-beta filter. If I was to use a H-alpha filter srewed in to an eyepiece alon with a Baadar solar film on the front of my telescope would I see any detail on the sun?

[monoxide]

no it doesn't quite work like that, from what i understand the baader film is a ND filter that blocks a high percentage of ALL wavelengths of light whereas the solar Ha filters are specialised narrowband filters that block all but a certain wavelength of light, thats why PST's etc cost so much.


someone else feel free to correct me if im wrong

[citivolus (Ric)]

The eyepiece filters also have a bandwidth of 15-30 times that of a good solar filter. As such, they let too much other light through and wouldn't be capable of showing any contrast. It would be like trying to use your laptop while 15 spot lights were pointed at the screen.

You can get filters that do what you describe, but they aren't cheap.

[Suzy_A]

There are basically two types of H-alpha filters:

Wide bandwidth for deep-sky photographic use. These have bandwidths around the H-alpha wave length of about 2 Angstroms (2 x 10-10 metres) or more - usually a lot more. Typical ones are the Baader ones such as the 35 nanometer (35 x 10-9 m or 350 Angstrom) H-alpha Passfilter 2" for 125 Euro or the 7 nm (7 x 10-9 m or 70 A) H-alpha Schmalbandfilter 2" for 195 Euro. Or the 2 A for 485 Euro. These are only for deep sky photographic use - if you use them on the sun, even with something to block out most of the light to get it to a brightness that won't fry your eyeballs or CCD, alll you see is a deep red circle.

Have a look at:

http://www.baader-planetarium.de/zub...ter.htm#hapass

Then there are the narrowband filters - less than about 1 A, and to reslly see any detail you need about less than 0.6 A. The really good ones are down to about 0.3 A.

have a look at http://www.baader-planetarium.de/zub...rotuberanz.htm

or

http://www.coronadofilters.com/

or

http://www.optcorp.com/ProductList.aspx?uid=471-306

As you can see, prices start at a few thousand and go up to 20,000 or so...

I have a Coronado PST which cost about $900 and I think it is barely adequate for only the most basic H-alpha solar observing. On a good day, and perhaps with a bit of imagination, you can see a few prominences and stuff.

[Merlin66 (Ken)]

Suzy_A is 100%. To really appreciate the detail on the sun, you need a really narrow Ha filter, hence the PST/ Solar Max etc. These work using a very sophisticated series of quartz filter plates and/ or multiple dichromatic filter elements ( hence the $$$). You'll definately need better than < 1 A to get good views.
This is why Karl and I are trying to maximise the detail/ dollar by modifying the PST ( taking the good bits!) and adding them to a larger telescope ( with a good energy rejection filter up front).
BTW... Suzy_A; don't be too critical of the PST, it's a great scope for its size and when the solar activity kicks back in I'm 100% sure there will be more whan enough Proms and faculae to satisfy you.
A good check, however, on the optics and tuning of the PST filter is to be able to see granulation structure on the surface...this normally requires a 10mm eyepiece on my unit. Do you see the same?

[Merlin66 (Ken)]

I attach a couple of photos taken on the 5th March with a 40mm aperture, Ha filter <0.8A ( not mine I should add! these are from Oldfield's blog; he's in Hong Kong and works through his apartment window 10 stories up!)
Not bad for a telescope less than 2" objective!!

[Suzy_A]

Originally Posted by Merlin66

BTW... Suzy_A; don't be too critical of the PST, it's a great scope for its size and when the solar activity kicks back in I'm 100% sure there will be more whan enough Proms and faculae to satisfy you.
A good check, however, on the optics and tuning of the PST filter is to be able to see granulation structure on the surface...this normally requires a 10mm eyepiece on my unit. Do you see the same?

My main issue with the PST is that the magnifation available with it is too low and the eyepiece that comes with it is... not the best. Also I had to do a few mods to it so that I could use it with a camera - the focal plane was nowhere near the film/sensor plane.

I've been intending on doing the mod to attach the good bits to my ED80 - I actually did it with rolls of stickytape and string to hold it together, and I asked someone to make up a few bits for me so that I can put it all together properly. Hopefully they'll get around to it soon...

[Merlin66 (Ken)]

Suzy_A,
The Kellner that comes with the PST, I agree is pretty basic! I'm sure you have a better 10mm in your box.
To get focus on a webcam I had to unscrew the eyepiece holder and remove the bottom spacer, then re-mount the eyepiece tube (it has the BF at the bottom).
If you are going to use the PST etalon on a 80mm scope, PLEASE make sure you also fit an effective ERF filter up front!!

[Suzy_A]

Originally Posted by Merlin66

Suzy_A,
The Kellner that comes with the PST, I agree is pretty basic! I'm sure you have a better 10mm in your box.
To get focus on a webcam I had to unscrew the eyepiece holder and remove the bottom spacer, then re-mount the eyepiece tube (it has the BF at the bottom).
If you are going to use the PST etalon on a 80mm scope, PLEASE make sure you also fit an effective ERF filter up front!!

I used my 16 mm Nagler with a good barlow....

As for the focus bit, yes, I removed the spacer and screwed the eyepiece tube back in, although there was a nasty crunchy sound as the metal ring scraped the glass prism..... Fortunatly there was no (visible) damage. I had to put a spacer (big washer) in to maintain a bit of separation.

And of course I used a ERF - I first tried a full aperture solar filter - a JMB? That was a bit dark so I tried a few other things that got the brightness about right.

I did try and get a full aperture (ie 105 mm[so I could also use it if I upgrade to a ED100 or similar]) photographic ND3 (or was it a 4?), but that was a no-go. B+W Schneider list such a beast, but getting hold of one was impossible. Even a 86 or 82 mm was unobtainable. Hoya also make a ND2.6 (NDx400) filter, which combined with something else like a red 25A should be OK, but I was unable to get the 82 mm ND2.6 either...

[Merlin66 (Ken)]

Suzy_A,
An ND filter isn't an ERF filter. All the ND will do, if you're lucky, will be to reduce some visible light getting through. The real problems are the UV and IR light that you can't "see" but your etalon ( and your eye) will feel the heat!
Normally you don't need an ND filter with the PST etalon; a Wratten #25 full aperture filter ( Surplus Shed sell them, 110mm diameter). This will filter out all the UV and visible light less than 600Nm (light red) add an IR filter to stop the heat above 700Nm and you have an effective ERF.
(As you probably already know so of the "lighter" ND filters are NOT suitable for visual work.)

[Suzy_A]

I forgot to mention the UV/IR blocking - I have those - a Baader 2" and also I had (until someone stole my camera gear) a 58 mm, 67 mm and 77 mm B+W Schneider 486 and 489 UV/IR blocking filters.