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Orpington Astronomical Society

Astronomy => Astrophotography => Topic started by: Simon E on Oct 16, 2009, 16:02:35

Poll
Question: OAG as opposed to Piggy back
Option 1: Good votes: 0
Option 2: Bad votes: 0
Option 3: don't bother votes: 0
Option 4: ok votes: 0
Title: OAG on a SCT
Post by: Simon E on Oct 16, 2009, 16:02:35
Anyone using one, are they good.

simon
Title: Re: OAG on a SCT
Post by: Mac on Oct 16, 2009, 17:16:22
all my guiding is via piggy back,
so i cant really help with off axis guiding.

Mac.
Title: Re: OAG on a SCT
Post by: RobertM on Oct 16, 2009, 19:11:17
Si, off axis is good but you may well have difficulty finding a bright enough guide star especially with a small chipped guide camera.  That is the main reason most use a piggy backed guide arrangement.  Also a good off axis guider could cost you more.

Robert
Title: Re: OAG on a SCT
Post by: MarkS on Oct 18, 2009, 17:34:35

OAG also affects your image composition - it becomes necessary to adjust your view to ensure a bright enough star falls on the guider.

In theory, for SCTs, an advantage that OAG has over piggy backing is that it will also correct for slight shifts in the primary mirror as the scope changes position during tracking.

Mark
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