"Why" are Hydrogen Alpha filters so expensive?

Roland, I can remember back some years when I was out at the A-fest and
we were viewing through one of your personal Ha filters. I think the
one you had at that time was a "bit" more expensive than the T-Scanner
model? (The University Model perhaps if I can remember correctly?)

Then later, we both went over, and was checking out Jack Mosevich's
set-up with his .7A T-Scanner. Gordon Garcia was with us too I
remember, as were a few other buddies.

I gotta tell you that I never forgot those enjoyable moments with you
fellas, as I learned alot that day from you all. Gordon surely has
great enthusiasm, and knowledge too.

Before that day, I never really personally realized how satisfying doing
observation during daylight was! All I kept thinking after that was,
"Guess I'm gonna have to save some money up for one of these babies!"
Ha Solar veiwing is really something to behold!
Really gave me the goosebumps!
Thank you again Roland, Gordon, and Jack for that most memorable day!
Mark

I have a Del Woods T-scanner that cost about $1800.

Hi Roland, thanks. David K. posted that he has a similar filter and it sounds
like this could be a real viable alternative.

For each aperture size you have to change the focal length to maintain around
F30 with this type of filter.

So can I do this with barlows, masking, both?

How the heck did you get the 8" refractor to F30?

rat
~( );

email: remove 'et' from .com(et) in above email address

How the heck did you get the 8" refractor to F30?

rat
~( );

Nevermind that, it's too easy. I can get the Traveler to F29 at full aperture
with just a 5x powermate. Cool.

Hmmm, the wheels are turning.
rat
~( );

email: remove 'et' from .com(et) in above email address

[snip]
The Chinese are making these lenses because they were able to get
financing
from the World Bank to purchase all the equipment needed to completely
outfit a
modern factory. That is not an option for us US manufacturers because we
are
not a "developing country".

Roland Christen

Do you have any more details on this story? I'm curious.

Regards, Michael

Roland,

Would you have a link handy by any chance to the T-scanner you
describe below? I feel MUCH more comfortable dishing out $1800 than
$6000 .... a link, if available, to Wolfgang Lille would also be
appreciated.

Off I go to Google trying to find them directly .... thanks for
the heads up!!

Anthony.

Chris1011 wrote:

$5300 for a 90 mm...

Now I know why I don't observe the Sun in H-Alpha.



I have a Del Woods T-scanner that cost about $1800. It is used after the scope,
so has no aperture limit. I have used it with an 8" refractor stopped down to
3" on poor seeing days and up to 8" full aperture on days when the seeing was
really good. At that aperture, the prominences take on a whole new character.

For each aperture size you have to change the focal length to maintain around
F30 with this type of filter. Wolfgang Lille in Germany has taken images with
his Dell Woods filter and a 13" chromat lens that exceed anything I have ever
seen, amateur or professional.

If you are just playing around, then a 60mm Coronado is probably fine. If you
want to do professional work, then the Dell Woods would be the way to go.

Roland Christen

In message , Tom Hole
writes

"Chris1011" wrote in message

Yes, the equipment is at the cutting edge of technology. No, I don't think
they
will ever come down in price when more manufaturers jump in. The level of
accuracy required to make etalon plates makes them very expensive.

I'd be willing to bet the same conversations that apply to "high tech"
astronomy gear now were seen in magazines and such back then. I hope that H
alpha filters will follow the same trend and become less expensive as
technology allows the cheaper manufacture of such devices.

In a sense these modern etalon filters are the new cheaper technology.
But they won't get that much cheaper unless there is a sudden mass
market fad for seeing the sun in H-alpha. Narrow bandpass etalon filters
are high precision and intrinsically expensive to make.

The older (1930's) Lyot method of stacked perfect calcite crystals was
much more expensive. And ISTR needed a thermostatic oven to keep it
tuned. I guess a very keen amateur could make a Lyot filter from scratch
using infinite patience and some very expensive raw materials.

It would be cheaper and much much faster to buy an etalon though.

Regards,
--
Martin Brown

Actually, when we made our first 5" triplet refractors back then they cost
around that price. Glass hasn't gotten any cheaper, unfortunately.

Roland Christen

I am curious as to what APO refractors were available in 1970. Not too many if
I am not mistaken.

jon

a link, if available, to Wolfgang Lille would also beappreciated.

http://mitglied.lycos.de/LilleSonne/

There are only a few images taken by Lille on this site. He has taken thousands
of very high resolution photos of the sun both in Ha and white light. I have
seen some spectacular ones displayed at several astro-gatherings in Germany.

Roland Christen

Enyo wrote:
Another size myth. Bigger is better for solar as much as it is for night
viewing.

Which is to say, not always. Although the best view through the larger
filter will be better than the best view through the smaller filter, it
will be much longer between best views through the larger than through
the smaller.

I'd say it depends on the Fried parameter. If the Fried parameter is
large enough, the seeing slow enough, and you have the cash, definitely
go with the bigger one. But I think the question was asked in the
context of trying to find a point of diminishing returns, both in terms
of observing time and cost of the filter.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

Fabrication of a quartz etalon h-alpha filter was described in one of the
origional ATM books. It was daunting and required an oven to tune it to the
passband, as I recall.
As for narrow passbands, Mossbauer spectroscopy gives some the narrowest at
1 part in 10 to the 14th. But the cesium fountain atomic clocks take the cake
for the narrowest pass band, about 15 minutes in 14 billion years
Bill Bambrick
41 N, 73 W, 95 ASL