Herschel Wedge

I viewed the sun through an antique Brashear Herschel wedge at this
year's NEAF solar party and was very impressed with the view. I can
find two models currently available, one by Intes and another by Baader,
at about 2x the price. Any experienced users out there who can comment
on either or both of these, perhaps make a comparison?

Evan Miller

On Tue, 03 May 2005 03:21:09 GMT, Evan Miller
wrote:

I viewed the sun through an antique Brashear Herschel wedge at this
year's NEAF solar party and was very impressed with the view. I can
find two models currently available, one by Intes and another by Baader,
at about 2x the price. Any experienced users out there who can comment
on either or both of these, perhaps make a comparison?

Evan Miller

What is the benefit of using one over a full-aperture solar filter?
-Rich

Hi Rich/Evan/All,

There's probably some advantages, and disadvantages to using a Herschel
Wedge.

Some advantages may be that you'd never have to worry about a filter
blowing, or falling off the front of a scope, or being unknowningly, or
accidently removed. Perhaps a risk of an eye injury accident is less. I
myself always worry about the accidental removal of a front mounted
filter

High quality Herschel Wedges do provide incomparable views versus
cheaper full aperture solar filters. The Baader AstroSolar film, or a
high quality Zeiss Glass filter do give very similar-comparable views to
the Wedge.

Disadvantages I see with the Wedge, would be perhaps using it with Oil
Contacted Lenses, that there may be a possibility after much use, of the
contacting oil drying-evaporating. Also due to the heat that may
accumilate within an Optical Tube, it may cause glues that are holding
Tube Baffles to become compromised. Also, the heat may have an effect on
lubricants withing an OTA (Baffle lubes on SCTs/MCTs)
With a front mounted Solar Filter, no heat buildup within the OTA can
possibly happen.

Another characteristic of Herschel Wedges, is that the bottom of these
are open. 99% of the light, and heat exit the Wedge in this manner, and
this light can generate a whole lot of heat, possibly burning Legs of
Tripods, observer's clothing, etc. Mark D.

On Tue, 3 May 2005 10:02:27 -0600, (Mark D) wrote:

Another characteristic of Herschel Wedges, is that the bottom of these
are open. 99% of the light, and heat exit the Wedge in this manner, and
this light can generate a whole lot of heat, possibly burning Legs of
Tripods, observer's clothing, etc. Mark D.

It is certainly possible to set your shirt on fire.

This sounds like personal experience. Did this happen to you?

--- Dave
--
----------------------------------------------------------------------
Pinprick holes in a colorless sky
Let inspired figures of light pass by
The Mighty Light of ten thousand suns
Challenges infinity, and is soon gone




"William Hamblen" wrote in message
...
On Tue, 3 May 2005 10:02:27 -0600, (Mark D) wrote:

Another characteristic of Herschel Wedges, is that the bottom of these
are open. 99% of the light, and heat exit the Wedge in this manner, and
this light can generate a whole lot of heat, possibly burning Legs of
Tripods, observer's clothing, etc. Mark D.

It is certainly possible to set your shirt on fire.

On Tue, 03 May 2005 03:21:09 +0000, Evan Miller wrote:

I viewed the sun through an antique Brashear Herschel wedge at this
year's NEAF solar party and was very impressed with the view. I can
find two models currently available, one by Intes and another by Baader,
at about 2x the price. Any experienced users out there who can comment
on either or both of these, perhaps make a comparison?

Evan Miller

Have used the Intes one with my TMB115 for the last year or so, and found
it to produce better images than with my Baader filter. See my posts on
alt.binaries.pictures.astro. I would not want to go back to an objective
filter now.
There can be a problem with excess heat directed out the bottom, and I
would not use it with anything larger than a 5" or so, nor would I want to
put it on anything other than a refractor.
Some would question the safety aspect, and it is probably not quite as
safe as a well secured undamaged objective filter, but used with care you
should be ok.
Phil Bishop

On Tue, 03 May 2005 18:11:45 GMT, "David Nakamoto"
wrote:

This sounds like personal experience. Did this happen to you?

Saw it done.

This sounds like personal experience. Did this happen to you?
=A0=A0=A0=A0=A0=A0--- Dave
-------------------------------------------------------------
Hi Dave/All, no, this never happened to me personally, but did happen to
a good friend of mine, reknown solar observer, and solar photgrapher
Gordon Garcia.

And Gordon said that it was during the winter months also, that he set
fire to a heavy winter coat! ("Hey, I smell something burning!") hee
hee

As far as Baader Astro-Solar Film versus the Herschel Wedge, I'd have to
say that both do an outstanding job of showing good Sunspot Detail, and
also surface granulation of the Sun's surface. Something that wasn't
readily apparent to me with past Solar Filters I had, like the Mylar
Tuthill Solar Skreen.

While I've never personally owned one, it has been said to me that the
the Zeiss Full Aperture Glass Filters were the best Glass Filters ever
produced. Not easy to come by though. Mark

"William Hamblen" wrote in message
...
On Tue, 03 May 2005 18:11:45 GMT, "David Nakamoto"
wrote:

This sounds like personal experience. Did this happen to you?

Saw it done.

Ouch ! ! !

Hi Mark,

I once burned a "Sunspot" on my garage wall from the sun. Not from a
Herschel, but from having my 25" Primary out of the scope during
cleaning and sitting near the garage entrance. Ole Sol came out from
behind a cloud and the mirror focused a spot on the underside of my
open garage door... Why is getting smoky in here? I heard of a
similar story that happened to a fellow's car (burned the headliner).

Back on topic... Last year, Baader innovated a nifty new solution to
the output heat. The 2" Baader Zeiss Herschel Wedges now have a metal
light trap in place of the usual output mirror of other Herschels. It
diffuses the light energy so that you no longer have a concentrated
output. This makes it cool and diffuse so that you no longer have to
be concerned with burning anything or someone carelessly looking into
the output. Even after hours of use, the trap doesn't get hot. Its an
elegant new solution that takes care of the one herschel aspect that
has chased some folks off.

As for oiled lenses, there is no issue from even long-term exposure of
an oiled objective to the sun (keep in mind that the objective does not
see concentrated energy). Internal heating of the tube is also not
problem. I've used the herschel for hours at a time with no heating or
notable tube currents. The only situation where you could get some
tube heating is if you position the sun well off-axis and allow the
image to continually fall on a baffle in the focuser near the focus.
A herschel should only be used in a refractor (never with a
newt/mak/sct).

In terms of comparison to objective white light filters, I've never
seen an objective filter that could match a Baader Herschel. I can't
speak to the Russian Intes, the Baader uses a superb Zeiss wedge prism
and incorporates some internal features that reduce light scatter. The
field around the sun is jet black, like observing the Moon at night.
The Baader AstroSolar mylar is darned good and a heck of a value, but
the Herschel is notably better in contrast and resolution. Granulation
is easy and visible on most days (all but the very worst seeing).
Sunspots frequently display fine details and shading that I never saw
with any objective filter (and I have used Zeiss objective glass
filters, which are superb and as good as the Baader film). I've
shocked quite a few experienced observers with the views through my
Herschel. The Herschel views have really kept me fascinated with white
light viewing - in spite of now owning a very good narrow-band H-alpha
setup.

Herschels also have the advantage of transmitting a true white-light
spectrum. All coated objective filters end up passing only a portion
of the spectrum. Of all the objective filters, the Baader film comes
closest to reproducing white light, but still filters some wavelengths.
This also means if you are trying to post-filter the image to select
out specific wavelengths for study, you have to consider the effects of
the objective filter (not so for the Herschel).



Regards,
Bob Luffel

Alpine Astronomical
www.alpineastro.com