Solar observing from a large dob

I'm toying with the idea of getting a large dob and was wondering how
to do solar observing. Are 20" filters available? What about
Hydrogen Alpha? I don't want to stop down the aperture as I want
great resolution.

Thanks,

BigKhat

BigKhat wrote:

I'm toying with the idea of getting a large dob and was wondering how
to do solar observing. Are 20" filters available? What about
Hydrogen Alpha? I don't want to stop down the aperture as I want
great resolution.

Thanks,

BigKhat

My $.02:

Using 20" filter (apart from being impractical) will not help
much with the resolution. Usually during the day, the heat
of the Sun will deteriorate the seeing much below the theoretical
limits of the scope.

- Alex

"BigKhat" wrote in message
om...
I'm toying with the idea of getting a large dob and was wondering how
to do solar observing. Are 20" filters available? What about
Hydrogen Alpha? I don't want to stop down the aperture as I want
great resolution.

Thanks,

BigKhat
Seriously, in the heat of the day with the thermal movement in the sky,
and scope, you won't gain anything much from the larger aperture over
perhaps 6". You can build a white light solar filter close to you full
diameter from AstroSolar film (this is available in rolls, and I have seen
16" wide available, so 20" may exist). Hydrogen Alpha, you would be
talking perhaps $400,000...
To make an accurate Ha filter this diameter, is beyond allmost any company
in the world, and has a price tag to match.

Best Wishes

On 21 Oct 2004 12:29:33 -0700, (BigKhat) wrote:

I'm toying with the idea of getting a large dob and was wondering how
to do solar observing. Are 20" filters available? What about
Hydrogen Alpha? I don't want to stop down the aperture as I want
great resolution.

Thanks,

BigKhat

Doesn't Baader sell a 1 meter Solar Film?

Bill

(BigKhat) wrote:

I'm toying with the idea of getting a large dob and was wondering how
to do solar observing. Are 20" filters available? What about
Hydrogen Alpha?

If I rephrased that as "I want two surfaces with smoothness and
positioning to within 1/100 wavelength, 20" in diameter" would you
understand that Ha is either impractical or Bill Gates expensive?

Stop your 20" down to the size of whatever decent reflective
neutral-density filter you can find (Baader astro-solar film rocks!)
to see the sunspots, or buy a little dedicated solar 'scope with Ha to
see the funky patterns. You'll never get seeing worthy of a 20" in the
daytime anyway, and with the sun light gathering ability is generally
not a concern Perhaps you could wait till Meade works out how to
make dirt-cheap Fabry-Perot Etalons (a goal which just came a whole
lot close with their purchase of Coronado).


Tim
--
Copyright, patents and trademarks are government-granted,
time-limited monopolies. Intellectual property does not exist.

I have used my F8 8inch dob for solar viewing, I just turn the OTA so the EP
points down and I hold a white sheet of posterboard under it and catch the
suns image. Have only had one mistake happen, when I left a moon filter on
the EP, it didn't last more than 2 mins.


--


"And for the second time in four million years, the monolith awoke."
Arthur C.Clarke 2062dyssey three

SIAR
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"BigKhat" wrote in message
om...
I'm toying with the idea of getting a large dob and was wondering how
to do solar observing. Are 20" filters available? What about
Hydrogen Alpha? I don't want to stop down the aperture as I want
great resolution.

Thanks,

BigKhat


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Alexander Avtanski wrote in message ...
BigKhat wrote:

I'm toying with the idea of getting a large dob and was wondering how
to do solar observing. Are 20" filters available? What about
Hydrogen Alpha? I don't want to stop down the aperture as I want
great resolution.

Thanks,

BigKhat

My $.02:

Using 20" filter (apart from being impractical) will not help
much with the resolution. Usually during the day, the heat
of the Sun will deteriorate the seeing much below the theoretical
limits of the scope.

- Alex

Correct me if I'm wrong, but I thought that in good seeing or bad,
aperture always wins. That's why I was considering a big dob to begin
with.

Roger Hamlett says...

You can build a white light solar filter close to you full
diameter from AstroSolar film (this is available in rolls, and I have seen
16" wide available, so 20" may exist). Hydrogen Alpha, you would be
talking perhaps $400,000...

Would some sort of setup using a prism and a slit work?

Tim Auton says...

Stop your 20" down to the size of whatever decent reflective
neutral-density filter you can find (Baader astro-solar film rocks!)
to see the sunspots,

He could even make it off-axis...

Correct me if I'm wrong, but I thought that in good seeing or bad,
aperture always wins.

'Aperture always wins' has a few qualifiers.
Large scopes can be more susceptible to unsteady
seeing conditions than smaller scopes.

SSX