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Date: 23 Jul 2007 08:02:52
From: Margo Schulter
Subject: Using variable polarizing filter?
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Hello, everyone, and I'm posting to seek advice from
experience that people might have on the mechanics of
using a variable polarizing filter for the first time
to try my first viewing of Luna with a 20cm f/6 Dob.
The instruction sheet looks helpful, and my main concern
is simply to be sure that I move at each step so as to
protect the filter and avoid things that could cause
scratches, etc.
This is an Orion 1.25" filter which I'm planning to use
likely with a 7.5mm EP (160X).
Thanks for any advice that you might be able to lend.
Most appreciatively,
Margo Schulter
mschulter@calweb.com
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Date: 23 Jul 2007 20:29:26
From: thad@thadlabs.com
Subject: Re: Using variable polarizing filter?
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On Jul 23, 5:43 pm, j...@optcorp.com wrote:
> If it is the type of filter that completely fits down the barrel than
> the two halves of the filter can be seperated and make excellent
> single filters for Mars, Jupiter, moon and general viewing.
In fact, the Orion variable polarizing filters can be separated into
two halves. The 1-1/4" is shipped as two halves that simply
screw together; the 2" version comes preassembled.
Thus, a half could be used by itself.
Interesting tidbit: similar filters just became available for
photographic use, too:
<http://www.singh-ray.com/varind.html >
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Date: 23 Jul 2007 17:43:17
From:
Subject: Re: Using variable polarizing filter?
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If it is the type of filter that completely fits down the barrel than
the two halves of the filter can be seperated and make excellent
single filters for Mars, Jupiter, moon and general viewing.
OPTwebman
On Jul 23, 1:02 am, Margo Schulter <mschul...@web1.calweb.com > wrote:
> Hello, everyone, and I'm posting to seek advice from
> experience that people might have on the mechanics of
> using a variable polarizing filter for the first time
> to try my first viewing of Luna with a 20cm f/6 Dob.
> The instruction sheet looks helpful, and my main concern
> is simply to be sure that I move at each step so as to
> protect the filter and avoid things that could cause
> scratches, etc.
>
> This is an Orion 1.25" filter which I'm planning to use
> likely with a 7.5mm EP (160X).
>
> Thanks for any advice that you might be able to lend.
>
> Most appreciatively,
>
> Margo Schulter
> mschul...@calweb.com
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Date: 26 Jul 2007 08:34:35
From: Margo Schulter
Subject: Re: Using variable polarizing filter?
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john@optcorp.com wrote:
> If it is the type of filter that completely fits down the barrel than
> the two halves of the filter can be seperated and make excellent
> single filters for Mars, Jupiter, moon and general viewing.
>
> OPTwebman
Hi, there, John, and thank you and others at OPT for excellent service
and customer support.
Upon the opening the package, I can confirm that this is an Orion
Variable Polarizing Filter #5560, 1%-40%, which indeed comes in two
halves; there's a nice photograph showing how they assemble. The
documentation says that using either half alone will not reduce
overall brightness, but can be very helpful in controlling reflected
light or glare. Maybe the best test would be to try either half for
planetary use; I'm not sure if this is the same type that you are
discussing, although it likewise has two halves.
The main thing I'm wondering at this point is whether the filter should
be separated into its two halves for storage in the nice padded case
provided, or can fit assembled into its case. Anyway, it looks really
fine, and I'm much looking forward to using it.
Most appreciatively,
Margo Schulter
mschulter@calweb.com
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Date: 26 Jul 2007 07:56:44
From: Marty
Subject: Re: Using variable polarizing filter?
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I store mine assembled in it's little plastic box with no problems.
Usually, using it on the moon, I wind up cranking it up to it's darkest
possible adjustment. The moon is BRIGHT.
Marty
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Date: 26 Jul 2007 20:11:09
From: Margo Schulter
Subject: Re: Using variable polarizing filter?
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Marty <movac5@webtv.net > wrote:
> I store mine assembled in it's little plastic box with no problems.
> Usually, using it on the moon, I wind up cranking it up to it's darkest
> possible adjustment. The moon is BRIGHT.
> Marty
>
Hi, there, Marty, and it looks like you've nicely answered my remaining
question about storing the filter assembled -- and I like the box.
Intuitively I'd definitely follow your approach with the Moon. Some days
ago I took a quick look without a filter at Jupiter at 48X in my 20cm Dob,
and rapidly decided that it would be wise to wait until I had a filter in
place!
Possibly that was a sign that my eyes had achieved some degree of dark
adaptation, despite urban skyglow and some local light trespass to boot
(although a towel over my head and the focuser helped with the latter).
I guess this because for the telescope's actual first light test, a
friend and I moved it out onto a balcony (not really a good location
with the railing and all), and viewed Venus at 48X and 120X without
any discomfort. However, this was going right outside from my lighted
apartment without any towel on my head to minimize the effect on my
eyes of the usual apartment lighting. I've read that Venus and Jupiter
can have comparable apparent magnitudes, with Venus usually but not
always brighter, and suspect that dark aptation (or the lack thereof)
may have been a relevant factor affecting my comfort.
Anyway, starting on the Moon with the darkest setting sounds to me also
like the way to go.
With many thanks,
Most appreciatively,
Margo Schulter
mschulter@calweb.com
Lat. 38.566 Long. -121.430
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Date: 23 Jul 2007 06:43:51
From: Ben
Subject: Re: Using variable polarizing filter?
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Margo,
To protect it from scratches obtain a large pill bottle
from the pharmacist, insert a few cotton balls and keep
the cap fixed tight. Works fine when keeping it with
my EP's.
When using the thing I hold it up to a streetlight
and rotate it to the appropriate brightness for Moon,
planet or whatever. It takes a little practice and
you still have to "tune" it but it's no great hassle >
Ben
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Date: 26 Jul 2007 08:16:11
From: Margo Schulter
Subject: Re: Using variable polarizing filter?
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Ben <bet71743@netzero.com > wrote:
> Margo,
>
> To protect it from scratches obtain a large pill bottle
> from the pharmacist, insert a few cotton balls and keep
> the cap fixed tight. Works fine when keeping it with
> my EP's.
Thanks for sharing this solution.
> When using the thing I hold it up to a streetlight
> and rotate it to the appropriate brightness for Moon,
> planet or whatever. It takes a little practice and
> you still have to "tune" it but it's no great hassle>
I'll try this idea or something similar; if in doubt, at
least with a full or gibbous Moon, I might start at 1% and
adjust up from there to minimize the "surprise" for my eyes
(and with a 20cm Dob, I suspect that even 1% of the brightness
of a full Moon might not be so obscure, although I'll have to
try this). However, I really like your idea of getting the
filter in the general ballpark by testing it first with the
naked eye on some bright local source.
Most appreciatively,
Margo Schulter
mschulter@calweb.com
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