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Main
Date: 03 Sep 2007 22:06:13
From: John Nichols
Subject: Meade DS 16 Reflector Question
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Does anyone here know the focal length for a Meade DS 16 reflector?
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Date: 05 Sep 2007 01:42:01
From: William Hamblen
Subject: Re: Meade DS 16 Reflector Question
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On Mon, 03 Sep 2007 22:06:13 GMT, "John Nichols"
<bejay@worldnet.att.net > wrote:
>Does anyone here know the focal length for a Meade DS 16 reflector?
72"
Bud
--
The night is just the shadow of the Earth.
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Date: 05 Sep 2007 20:11:50
From: John Nichols
Subject: Re: Meade DS 16 Reflector Question
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"William Hamblen" <wrhamblen@comcast.net > wrote in message
news:atjsd3hh9c3iuh4m57l4p73ncv4sbleg8h@4ax.com...
> On Mon, 03 Sep 2007 22:06:13 GMT, "John Nichols"
> <bejay@worldnet.att.net> wrote:
>
>>Does anyone here know the focal length for a Meade DS 16 reflector?
>
> 72"
>
Uh huh.
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Date: 06 Sep 2007 11:13:37
From: Steve Paul
Subject: Re: Meade DS 16 Reflector Question
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"John Nichols" <bejay@worldnet.att.net > wrote in message
news:a4EDi.69542$ax1.36581@bgtnsc05-news.ops.worldnet.att.net...
>
> "William Hamblen" <wrhamblen@comcast.net> wrote in message
> news:atjsd3hh9c3iuh4m57l4p73ncv4sbleg8h@4ax.com...
>> On Mon, 03 Sep 2007 22:06:13 GMT, "John Nichols"
>> <bejay@worldnet.att.net> wrote:
>>
>>>Does anyone here know the focal length for a Meade DS 16 reflector?
>>
>> 72"
>>
> Uh huh.
Okay, so here's the whole enchilada in one post... ;-)
Aperture * Focal Ratio = Focal Length
Meade DS-16 is given as 16" aperture and F4.5 focal ratio, so...
16" * F4.5 = 72"
There are 25.4mm in one inch, so...
72" * 25.4mm/1" = 1828.8mm
And there it is, complete. :-)
--
Posted via a free Usenet account from http://www.teranews.com
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Date: 06 Sep 2007 19:24:24
From: John Nichols
Subject: Re: Meade DS 16 Reflector Question
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"Steve Paul" <smarshallpaul@gmail.com > wrote in message
news:46e00d19$0$24191$88260bb3@free.teranews.com...
>
> "John Nichols" <bejay@worldnet.att.net> wrote in message
> news:a4EDi.69542$ax1.36581@bgtnsc05-news.ops.worldnet.att.net...
>>
>> "William Hamblen" <wrhamblen@comcast.net> wrote in message
>> news:atjsd3hh9c3iuh4m57l4p73ncv4sbleg8h@4ax.com...
>>> On Mon, 03 Sep 2007 22:06:13 GMT, "John Nichols"
>>> <bejay@worldnet.att.net> wrote:
>>>
>>>>Does anyone here know the focal length for a Meade DS 16 reflector?
>>>
>>> 72"
>>>
>> Uh huh.
>
> Okay, so here's the whole enchilada in one post... ;-)
> Aperture * Focal Ratio = Focal Length
>
> Meade DS-16 is given as 16" aperture and F4.5 focal ratio, so...
> 16" * F4.5 = 72"
>
> There are 25.4mm in one inch, so...
> 72" * 25.4mm/1" = 1828.8mm
>
> And there it is, complete. :-)
>
Thanks, Steve, for your very helpful replies.
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Date: 03 Sep 2007 18:27:07
From: Steve Paul
Subject: Re: Meade DS 16 Reflector Question
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"John Nichols" <bejay@worldnet.att.net > wrote in message
news:pz%Ci.488098$p47.236541@bgtnsc04-news.ops.worldnet.att.net...
> Does anyone here know the focal length for a Meade DS 16 reflector?
Google will give you an answer as fast as you can type "Meade DS-16" and hit
the enter key.
Since you made me curious to know if it was the same as the Dob, I got this
one covered.
6" F4.5
-Steve
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Date: 04 Sep 2007 01:37:52
From: John Nichols
Subject: Re: Meade DS 16 Reflector Question
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"Steve Paul" <smarshallpaul@gmail.com > wrote in message
news:5PidneZ8NvutF0HbnZ2dnUVZ_uygnZ2d@comcast.com...
> "John Nichols" <bejay@worldnet.att.net> wrote in message
> news:pz%Ci.488098$p47.236541@bgtnsc04-news.ops.worldnet.att.net...
>> Does anyone here know the focal length for a Meade DS 16 reflector?
>
> Google will give you an answer as fast as you can type "Meade DS-16" and
> hit the enter key.
>
I wouldn't bet on that, Steve, as it happens I already tried that before
posting my query here. :)
> Since you made me curious to know if it was the same as the Dob, I got
> this one covered.
>
> 6" F4.5
>
Now, if it's 16" at F4.5, a bit of arithmetic here will give me the focal
length?
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Date: 04 Sep 2007 01:43:39
From: John Nichols
Subject: Re: Meade DS 16 Reflector Question
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"John Nichols" <bejay@worldnet.att.net > wrote in message
news:QF2Di.66688$ax1.64047@bgtnsc05-news.ops.worldnet.att.net...
>
> "Steve Paul" <smarshallpaul@gmail.com> wrote in message
> news:5PidneZ8NvutF0HbnZ2dnUVZ_uygnZ2d@comcast.com...
>> "John Nichols" <bejay@worldnet.att.net> wrote in message
>> news:pz%Ci.488098$p47.236541@bgtnsc04-news.ops.worldnet.att.net...
>>> Does anyone here know the focal length for a Meade DS 16 reflector?
>>
>> Google will give you an answer as fast as you can type "Meade DS-16" and
>> hit the enter key.
>>
>
> I wouldn't bet on that, Steve, as it happens I already tried that before
> posting my query here. :)
>
>> Since you made me curious to know if it was the same as the Dob, I got
>> this one covered.
>>
>> 6" F4.5
>>
> Now, if it's 16" at F4.5, a bit of arithmetic here will give me the focal
> length?
>
So I make 1890mm in focal length. Is that right?
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Date: 03 Sep 2007 23:42:15
From: Steve Paul
Subject: Re: Meade DS 16 Reflector Question
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"John Nichols" <bejay@worldnet.att.net > wrote in message
news:fL2Di.66694$ax1.49974@bgtnsc05-news.ops.worldnet.att.net...
>> Now, if it's 16" at F4.5, a bit of arithmetic here will give me the focal
>> length?
>>
>
> So I make 1890mm in focal length. Is that right?
Right enough. :-)
-Steve
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Date: 04 Sep 2007 07:33:15
From: Margo Schulter
Subject: Re: Meade DS 16 Reflector Question
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Steve Paul <smarshallpaul@gmail.com > wrote:
>
> "John Nichols" <bejay@worldnet.att.net> wrote in message
> news:fL2Di.66694$ax1.49974@bgtnsc05-news.ops.worldnet.att.net...
>
>>> Now, if it's 16" at F4.5, a bit of arithmetic here will give me the focal
>>> length?
>>>
>>
>> So I make 1890mm in focal length. Is that right?
>
> Right enough. :-)
> -Steve
>
Let's see. A 16" aperture would be twice 8" or 203mm, or 406mm.
That times 4 would be about 1624mm, and adding 203mm (the .5 in f/4.5)
would make 1827mm or so.
My calculator shows 1828.8mm, since 16" is more precisely 406.4mm.
Interestingly, the focal length is precisely 72" or six feet (if we
take the specs as exact), with the metric conversion adding a bit
of computation.
The current official definition is 25.4mm=1", and that's a key to
the "bit of arithmetic" involved here. The basic idea is to take
the aperture, multiply by the f-ratio number, and at some point
in the process convert to millimeters.
Of course, for a scope with an aperture having a metric size like
400mm, say, it would be easy: just multiply by 4.5 and get a focal
length of 1800mm. That would mean a scope with a bit less aperture
than 16", but tidier metric calculations for things like eyepiece
magnification or true field of view. <grin >.
Most appreciatively,
Margo Schulter
mschulter@calweb.com
Lat. 38.566 Long. -121.430
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Date: 04 Sep 2007 19:31:37
From: John Nichols
Subject: Re: Meade DS 16 Reflector Question
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"Margo Schulter" <mschulter@web1.calweb.com > wrote in message
news:46dd0a3b$0$33702$d368eab@news.calweb.com...
> Steve Paul <smarshallpaul@gmail.com> wrote:
>>
>> "John Nichols" <bejay@worldnet.att.net> wrote in message
>> news:fL2Di.66694$ax1.49974@bgtnsc05-news.ops.worldnet.att.net...
>>
>>>> Now, if it's 16" at F4.5, a bit of arithmetic here will give me the
>>>> focal
>>>> length?
>>>>
>>>
>>> So I make 1890mm in focal length. Is that right?
>>
>> Right enough. :-)
>> -Steve
>>
>
> Let's see. A 16" aperture would be twice 8" or 203mm, or 406mm.
>
> That times 4 would be about 1624mm, and adding 203mm (the .5 in f/4.5)
> would make 1827mm or so.
>
Thanks, Margo and Steve!
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Date: 03 Sep 2007 20:45:53
From: Steve Paul
Subject: Re: Meade DS 16 Reflector Question
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"Steve Paul" <smarshallpaul@gmail.com > wrote in message
news:5PidneZ8NvutF0HbnZ2dnUVZ_uygnZ2d@comcast.com...
> "John Nichols" <bejay@worldnet.att.net> wrote in message
> news:pz%Ci.488098$p47.236541@bgtnsc04-news.ops.worldnet.att.net...
>> Does anyone here know the focal length for a Meade DS 16 reflector?
>
> Google will give you an answer as fast as you can type "Meade DS-16" and
> hit the enter key.
>
> Since you made me curious to know if it was the same as the Dob, I got
> this one covered.
>
> 6" F4.5
>
HEY!, Who snipped the '1' off that 16" . ;-)
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