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Old 08-11-2012, 08:27 PM
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rcheshire (Rowland)
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Join Date: Apr 2010
Location: Geelong
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Borg Canon Takahashi glass.

Hi. Delving into equipment decisions again???

Are there any Borg users out there willing to share their experience.

In mind is widefield, 71FL f3.9 Astrograph, 5 elements including triplet focal reducer - Cost around 2k. Will atttach an SBIG ST-8300C.

The Tak 4 element Petzval's are superb and in another thread I understand that there was disappointment with the FSQ-85ED @ 3.8k. I'm not sure that the 106 (5.6k), as beautiful as it is, suits my needs - essentially wide field.

Perhaps I should stick with my Canon 200mm for now, which is stopped down with an aperture disk - aka inverted reducer rings - stack thereof.

I would consider a Ritchey Cretien for narrow field if I ever got around to it - happy with wide field right now.

Second question - I understand that the SBIG crop factor is 1.95; that is, 18 x 13.5mm, relating it to full frame - because I am using a camera lens with it - effective focal length is 390mm which is close to the Borg in any case.

For wide field, am I gaining anything by purchasing what is essentially an achromat Fluorite doublet, in the Borg. I don't know if the triplet focal reducer is also a field flattener.

Questions, questions

Last edited by rcheshire; 09-11-2012 at 04:52 AM.
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