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Advantages to Autoguiding with APO over Achro?

Started by SJJindra, 03/02/2005 09:00AM
Posted 03/02/2005 09:00AM | Edited 03/02/2005 09:04AM Opening Post
I have a CI700 Mount with a Celestron 9.25" OTA (used at F6.3), Tak FS78 OTA (used at F8.1 or F6), and currently an 80mm ST (400mm focal length F5 achro) that I use as a guide scope for my SXV-H9. I use MaximDL V4 as my aquisition/guiding software. I also have a Borg 76ED (500mm focal length F6.6) for quick looks.

My question: Would there be a significant advantage to guiding with the 76ED. Is there a significant advantage to guiding with an ED/APO as opposed to an achromat (less bloated guide stars, better snap to focus, etc.) or would this be a waste of good glass? Of course, going to the 80 ST as my visual quick look scope will definitely be a downgrade.

Thanks for your thoughts.
Steven Jindra
Posted 03/02/2005 09:09AM | Edited 03/02/2005 11:07AM #1
Hi Steve,
I have used different guidescopes with my STV. More important is matching the focal length of a guidescope to your guiding needs than apo/achro. I have seen no differences in guide quality with either scopes. Other considerations are the adjustability of the guiding scope and a nice helical graduated focurser is a big plus.

The eFinder on my STV is a teeny tiny non-APO fl 100mm "telescope" and 3cm aperture and it guides perfectly.

Posted 03/02/2005 12:53PM | Edited 03/02/2005 01:02PM #2
For now, the ST80 stays. Overall I have been happy with the guiding of the 80ST. Just trying to stack as many of the cards in my favor as possible and wanted to make sure my guide scope was not a weakness.

There has been a bit of discrepancy of quality of guiding dependant on which area of the sky I am imaging. Part of this may well have been a balance issue. In the past my East/West balance was good (slightly favoring the East), but my North/South balance was a little off when aiming nearer the zenith. I have since remounted everything, testing for balance on all axis,in all directions, I just haven't had an opportunity to do any imaging since.

Thanks for the feedback.
Steven Jindra
Posted 03/02/2005 02:43PM #3
Hi Steve,

While i cant comment on achro to apo, i can tell you there is a differenece from one achro to another. My ST-4 autoguider guides much more consistently since i switched from a Synta 80mm f/11 to a Stellarvue SV80/9D. The 80/9d is a mechanically and optically superior scope.

John Krawczyk
Crownsville, MD