Return to the Cloudy Nights Telescope Reviews home page


Observing >> Solar Observing and Imaging

Pages: 1 | 2 | (show all)
colinsk
Carpal Tunnel
*****

Reged: 01/17/08

Loc: CA
Re: Using a Nigh H-Alpha filter for Solar viewing? new [Re: Mark Strollo]
      #2431987 - 05/31/08 06:34 PM

I can think of two reasons that it may not be as good as a nighttime filter for nebula. One is the transmission of a h-alpha solar filter is theoretically between 5% and 85% of the H-alpha line. I have not measured any but I would be surprised if any were over 50%. Although if money were no object one could be designed.

Also, even fast moving solar materials are blue shifted out of the narrow passband so if there is any significant relative motion it could easily be blue or red shifted from view. A spec quoted for solar viewing is you will find h-alpha detail 2A from center in the blue and .5 from center in the red.

I could be totally wrong about this, but when I got my "nebula filter" from Lumicon, 15 years ago or so, the idea was it removed the lines caused by streetlights leaving some important emission lines. I think OIII and H-alpha were among them. And with my filter I have noticed no benefit when in a dark sky location however in my backyard in the middle of a small city I find a large benefit.

Now I have read of astronomers using monochromators to study important aspects of distant objects. Many of these monochromators are etalon based so it could be that there is a good use for a h-alpha filter if you had a very large amount of aperture.


Post Extras: Print Post   Remind Me!   Notify Moderator  
moron392
scholastic sledgehammer


Reged: 08/20/07

Loc: Charlotte, NC
Re: Using a Nigh H-Alpha filter for Solar viewing? new [Re: colinsk]
      #2522093 - 07/16/08 10:13 AM

what about 'tuning' the filters as well as using an energy rejection filter???

Post Extras: Print Post   Remind Me!   Notify Moderator  
colinsk
Carpal Tunnel
*****

Reged: 01/17/08

Loc: CA
Re: Using a Nigh H-Alpha filter for Solar viewing? new [Re: moron392]
      #2551646 - 07/31/08 12:11 AM

The red continuim can be a very good place to look for granulation on the photosphere. This is not h-alpha viewing which looks at the chromosphere! The set up is a normal whitelight filter with a 7nm or so H-alpha filter. See this thread:

http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/2547756/page/0/view/collapsed/sb/5/o/all/fpart/1

Very nice work!


Post Extras: Print Post   Remind Me!   Notify Moderator  
mischief
super member


Reged: 04/26/08

Loc: Northern California
Re: Using a Nightime H-Alpha filter for Solar view new [Re: Mark Strollo]
      #2591384 - 08/19/08 06:55 PM

As a prospective solar observer with a Lunt LSTB600 on order, I want to thank all of you for the terrific information on solar observing. I know a little about the electromagnetic spectrum but these posts really added to my knowledge and greatly needed by me and helpful to me. Thanks very much.

Post Extras: Print Post   Remind Me!   Notify Moderator  
nytecam
Postmaster


Reged: 08/20/05

Loc: London UK
Re: Using a Nightime H-Alpha filter for Solar viewing? new [Re: Mark Strollo]
      #3758143 - 04/21/10 04:29 AM

There's a lot of data in this thread but the unlaying principle is that narrow-band deepsky filters = very broad-band filters in solar terms and thus protentially dangerous for solar viewing. This point can't be overstressed - someone may loose their eyesight through confusion and ignorance

Post Extras: Print Post   Remind Me!   Notify Moderator  
ken hubal
Pooh-Bah
*****

Reged: 05/01/07

Re: Using a Nightime H-Alpha filter for Solar viewing? new [Re: nytecam]
      #4232701 - 12/06/10 06:24 PM

One simple word to sum this up...DON'T!!!

Post Extras: Print Post   Remind Me!   Notify Moderator  
Doc Willie
Pooh-Bah
*****

Reged: 03/31/10

Loc: Mid-Hudson Valley, NY, USA
Re: Using a Nightime H-Alpha filter for Solar viewing? new [Re: ken hubal]
      #4305045 - 01/10/11 03:20 PM

Well most of us are thinking of using the H filter WITH a white light filter. Your warning is, however, warranted.

Then the next question is, what about stacking an OIII filter with a UHC, and may even a SkyGlow filter behind the white filter?

A cursory look at the explanations and tables above suggests that it won't work.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Don W
demi-god
*****

Reged: 05/19/03

Loc: Wisconsin, USA
Re: Using a Nightime H-Alpha filter for Solar viewing? new [Re: Doc Willie]
      #4305087 - 01/10/11 03:30 PM

The bottom line is this. If it were that easy we'd all be doing it already. But it's not. The mixing of other types of astronomical filters will NOT prevent the harmful radiation of the sun from entering your eyes. Period. Don't do it!!!

Post Extras: Print Post   Remind Me!   Notify Moderator  
Doc Willie
Pooh-Bah
*****

Reged: 03/31/10

Loc: Mid-Hudson Valley, NY, USA
Re: Using a Nightime H-Alpha filter for Solar viewing? new [Re: Don W]
      #4305747 - 01/10/11 08:01 PM

I SAID behind the white light filter. Not gonna consider otherwise.

If it worked 25% as well as dedicated solar scopes, it would still be worth me doing, and would still be worth your buying the good stuff.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Don W
demi-god
*****

Reged: 05/19/03

Loc: Wisconsin, USA
Re: Using a Nightime H-Alpha filter for Solar viewing? new [Re: Doc Willie]
      #4305775 - 01/10/11 08:15 PM

Putting some sort of filter behind the White Light Solar filter will not show you any H-Alpha features. What do you think it will do?

Post Extras: Print Post   Remind Me!   Notify Moderator  
brianb11213
Postmaster
*****

Reged: 02/25/09

Loc: 55.215N 6.554W
Re: Using a Nightime H-Alpha filter for Solar viewing? new [Re: Don W]
      #4306446 - 01/11/11 04:18 AM

Quote:

What do you think it will do?



I would expect a "broad band" Ha filter (used in conjunction with a "white light" filter of adequate density to provide protection) to give a view very similar to that which I enjoy using an ordinary deep red (Wratten #29) filter. A great "white light" view with significant steadying of the seeing compared with the usual green, but no Ha features at all - unless perhaps an unusually strong flare was in progress.

Edited by brianb11213 (01/11/11 04:20 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
David Knisely
Postmaster
*****

Reged: 04/19/04

Loc: southeastern Nebraska
Re: Using a Nightime H-Alpha filter for Solar viewing? new [Re: Doc Willie]
      #4307429 - 01/11/11 03:14 PM

Hi there. You posted:

Quote:

I SAID behind the white light filter. Not gonna consider otherwise.

If it worked 25% as well as dedicated solar scopes, it would still be worth me doing, and would still be worth your buying the good stuff.




Unfortunately, it won't work. The passband width of even imaging H-alpha filters (those used for emission nebulae) have a band width of between 30 and 100 angstroms (FWHM). This is much much too broad to see any solar H-alpha detail, as you need something around 1.5 angstroms or less just to pick up the prominences without an occulting disk being used. To get chromospheric disk detail requires a passband that is less than one angstrom wide, so again, adding the H-alpha "nebula" filter after a white light filter just won't work. The other factor which impacts things is brightness. H-alpha solar detail is quite faint, and when you run it through a typical white light solar filter, it will become too faint to see easily even if the second H-alpha filter was narrow enough. Basically, we are stuck with using the standard (and somewhat expensive) Fabry-Perot etalon-based H-alpha solar filters if we want to see something other than white light detail. Clear skies to you.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Doc Willie
Pooh-Bah
*****

Reged: 03/31/10

Loc: Mid-Hudson Valley, NY, USA
Re: Using a Nightime H-Alpha filter for Solar viewing? new [Re: David Knisely]
      #4308512 - 01/11/11 11:44 PM

Quote:


Unfortunately, it won't work. The passband width of even imaging H-alpha filters (those used for emission nebulae) have a band width of between 30 and 100 angstroms (FWHM). This is much much too broad to see any solar H-alpha detail, as you need something around 1.5 angstroms or less just to pick up the prominences without an occulting disk being used. To get chromospheric disk detail requires a passband that is less than one angstrom wide, so again, adding the H-alpha "nebula" filter after a white light filter just won't work.




I unnerstand now. Thanks for your patience in explaining this to a newbie.

One angstom passband. That is about as astounding as the scale of interstellar and intergalactic distances.


Post Extras: Print Post   Remind Me!   Notify Moderator  
BYoesle
Post Laureate
*****

Reged: 06/12/04

Loc: Goldendale, Washington USA
Re: Using a Nightime H-Alpha filter for Solar viewing? new [Re: Doc Willie]
      #4308966 - 01/12/11 08:42 AM

As noted above, beyond the passband issues of the night-time nebula filter, the reason you really can’t use a white light filter in conjunction with such a broad-band nebula filter is that the white light filter will render the chromosphere and prominences completely invisible.

Under “normal” conditions, it takes a total eclipse by the moon to block out the hundreds of thousands as times brighter photosphere to view the prominences around the edge of the sun. If you use a standard white light filter as required to reduce the photosphere’s brightness to a safe level, then you’re also reducing the brightness of the chromosphere by the same amount. Even if you used and occulting disc to simulate an eclipse, and had a proper narrow band filter to view the prominences (or the disc itself), this wavelength of light will have been reduced in brightness by the same amount as the photosphere, and therefore the chromosphere will be totally invisible.

Solar H alpha filters are indeed expensive. But the technology required to render the photosphere invisible and allow only the light from the chromosphere safely through is incredibly complicated and requires unbelievable tolerances. On the other hand, nothing else you can observe with a telescope is as awesome and inspiring to witness as a solar flare, eruptive prominence, or the beautifully mesmerizing clouds of glowing hydrogen that are constantly changing…


Post Extras: Print Post   Remind Me!   Notify Moderator  
attckbvr
Carpal Tunnel


Reged: 11/11/08

Loc: British Columbia, Canada
Re: Using a Nightime H-Alpha filter for Solar viewing? new [Re: BYoesle]
      #4309320 - 01/12/11 11:54 AM

Amen Bob! well said!

Post Extras: Print Post   Remind Me!   Notify Moderator  
Doc Willie
Pooh-Bah
*****

Reged: 03/31/10

Loc: Mid-Hudson Valley, NY, USA
Re: Using a Nightime H-Alpha filter for Solar viewing? new [Re: attckbvr]
      #4309689 - 01/12/11 03:13 PM

As I said, you need eight telescopes.

Post Extras: Print Post   Remind Me!   Notify Moderator  
RodgerHouTex
Pooh-Bah
*****

Reged: 06/02/09

Loc: Houston, Texas, USA
Re: Using a Nightime H-Alpha filter for Solar viewing? new [Re: Doc Willie]
      #4401656 - 02/21/11 01:53 PM

There are alternatives to etalons though right. I seem to recall seeing prominence photos etc. long before etalons existed as far as I recall. Didn't folks back then use a spectrohelioscope? I believe the principal was to gather light with an objective, focus it on a slit, and then tune another slit to the frequency you wanted and then reexpand it to a disk using another lens. Or something like that?

Post Extras: Print Post   Remind Me!   Notify Moderator  
colinsk
Carpal Tunnel
*****

Reged: 01/17/08

Loc: CA
Re: Using a Nightime H-Alpha filter for Solar viewing? new [Re: RodgerHouTex]
      #4402915 - 02/22/11 12:10 AM

Spectrohelioscopes are great as you can tune them to any frequency. However that are quite complicated. Look up Fred Vieo's book that is online for free to learn about the technology.

http://www.spectrohelioscope.org/

Then there are Lyott filters that can have a much narrower bandwidth than an etalon that use the birefringence of quartz or calcite. There are even tunable Lyott filters that consist af many crystals and polarization elements.

http://en.wikipedia.org/wiki/Lyot_filter


Post Extras: Print Post   Remind Me!   Notify Moderator  
Don W
demi-god
*****

Reged: 05/19/03

Loc: Wisconsin, USA
Re: Using a Nightime H-Alpha filter for Solar viewing? new [Re: colinsk]
      #4403226 - 02/22/11 07:21 AM

Ok, this has nothing to do with the subject or purpose of this thread. Please start another one.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1 | 2 | (show all)


Extra information
3 registered and 11 anonymous users are browsing this forum.

Moderator:  Scott in NC, Phillip Creed 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled


Thread views: 28472

Jump to

CN Forums Home




Cloudy Nights Sponsor: Astronomics