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Re: [ATM] Cassegrain Secondary Magnification
Hi Rod,
I entered the Shaffer design into Oslo, but it has terrible color
aberration. But that is the basic design I am looking for. I will try
changing the design to use a meniscus made of BK7 and F2 to see if that
helps keep the color down.
Regards,
Alfredo
P.S. If you are interrested I will post you the oslo file.
> Hi Rod,
>
> Thank you for the offer to scan the article. You really got me
> interested in the Shafer design, if you do find a reference design or
> the articles would you please send them to me, like I mentioned to you
> getting this kind of literature here is quite a challenge. I hope I
> can design a system where the secondary obstruction is not that large
> by using a large secondary magnification factor.
>
> Regards,
>
> Alfredo
>
>
> -----Original Message-----
> From: Rod Brackenridge [mailto:rjbr@gawab.com]
> Sent: Tuesday, February 26, 2008 11:42 PM
> To: Alfredo Rainho Neves
> Subject: Re: Cassegrain Secondary Magnification
>
>
> Hi Alfredo,
>
> I agree, I once looked at these and then decided a Dall-Kirkham would
> be easier and probably perform at least as well. The article in ATM
> journal describes some better corrected (and
> shorter) designs with Mangin mirrors. The only problem I see is that
> the secondary obstruction then becomes quite large.
> Shafer's designs are better planetary instruments but the usable field
> is narrower.
>
> Regards,
>
> Rod.
>
> Alfredo Rainho Neves writes:
>
>> Hi Rod,
>>
>> I actually used oslo to analyse this design, it has a lot of of-axis
>> coma; but since I want a planetary scope that should not be a big
>> problem. The design differs from the Klevzov, in that it uses a
>> plain secondary
> mirror
>> after the meniscus, while the Klevzov uses mangin mirror. I would
>> like to compare the two designes before building one. But since I
>> cannot find any data on the Klevzov, I guess I will try the
"field-makutov".
>>
>> Thanks,
>>
>> Alfredo
>>
>>
>>
>> -----Original Message-----
>> From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net] On
>> Behalf
> Of
>> Rod Brackenridge
>> Sent: Tuesday, February 26, 2008 9:28 PM
>> To: atm@atmlist.net
>> Subject: Re: [ATM] Cassegrain Secondary Magnification
>>
>>
>> Hi Alfredo,
>>
>> Not sure if this helps:
>>
>> http://www.telescopes.ru/articles/article5.phtml
>>
>> The same author also later describes several more developed designs
>> for 8 inch scopes with F2.5 primaries and F ratios between 7 and 10.
>> The design specifications are in ATM Journal issue 2. Shafer also
>> describes similar designs using sub-aperture Maksutov correctors in
>> the old Telescope Making magazine.
>>
>> Good Luck,
>>
>> Rod Brackenridge.
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>
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