Re: [APML] H-alpha solar photography nightmare

["Bert Katzung" <katzung1@attbi.com>]

Hi Emmanuele:
I think the Lumicon H-alpha has a pretty broad bandwidth (around 10 nM or
greater?) for sun work unless it's a special filter that I don't know about.
The Lumicon H-alpha filter that I have is a standard non-solar filter for
imaging H-alpha nebulas and it has a pretty wide bandpass. As you know, the
DayStar and Coronado solar filters work down around 0.3 to 0.8 nM bandwidth.
I believe the non-solar H-alpha filters that have been mentioned recently on
the CCD lists for solar prominence imaging were Custom Scientific's 3 or 4
nM bandwidth filters.

I'm a little unclear on how you positioned your filter(s). If I understood
the recent CCD posts correctly, you should use a regular solar filter (eg,
Baader film) over the objective (just like solar visual observing). Is that
what you mean by the "IR prefilter"? The H-alpha filter should go at the
camera end. Add neutral density filters of any type as needed to get the
exposure up to something you can achieve with the camera you're using. (I
haven't tried solar imaging with an H-alpha filter of any kind, so I'm
speculating here. I am interested in trying my CCD camera on it, though.)

I hope this all makes sense.... my apologies if I misunderstood your post.

Bert

Bert Katzung
katzung1@attbi.com
www.astronomy-images.com

----- Original Message -----
From: "Emmanuele Sordini" <vega@ulisse.it>
To: <astro-photo@seds.org>
Sent: Sunday, October 06, 2002 2:33 PM
Subject: [APML] H-alpha solar photography nightmare


> Hi everybody,
> here comes a report of my troubles with a Lumicon H-alpha filter (which,
by
> the way, has nothing to do with Lumicon going down the tubes). Some days
> ago, I met with a friend of mine in an attempt to use his Lumicon filter
> for observation and photography of solar prominences and the like.
> We used a 102-mm Vixen achromat refractor, for which an adapter was made
to
> fit the IR prefilter on the objective lens, which is conceived for a 8"
> SCT. Here are my first use impressions:
>
> 1) The Sun looks like a very bright red fireball, too bright for anybody
to
> tell such elusive features as prominences. Probably the filter is made for
> photographic use, not visual.
> 2) Focusing is, as usual, a pain in the butt, even with my Nikon F3
> equipped with D red-dot focusing screen and DW-4 magnifier.
> 3) Needless to say, we didn't notice any prominence whatsoever, even
> adjusting the filter tilt. I saw breathtaking pictures of the solar
> chromosphere but I've actually seen no hint of anything through that
> filter. Perhaps should the bandpass be even narrower?
>
> So here come my questions:
>
> A) Are any structures supposedly visible with an H-alpha filter so
> difficult to find? I have a hunch we should have used a high magnification
> (i.e. 100x at least) and should have carefully scanned all the Sun border
> for something. Am I correct?
> B) Is focusing the same as deep-sky of regular solar photography?
> C) Are there any special tricks that I am not aware of, or is the filter
> out of order (which I strongly doubt)?
> D) What can be seen/shot through those filters?
> D) How does the Lumicon compare with other competing products (Daystar,
> Coronado,...) as to usability and performance?
>
> I apologize for my long post but I am in dire need of answers. Any help
> will be greatly appreciated.
> Thanks in advance and clear skies,
>
> Emmanuele Sordini
>
>
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