OAG?us usually?a real pain, even a pricy unit with?rotation, etc.
But the usual alternative, guide scope, can be even worse due flexure.
A saving grace of guide detectors is that the PSF (star shape) is largely unimportant so long as it can be roughly "focused".? An accurate enough centroid can be computed from almost any PSF?as long as there is sufficient brightness. But?it can be a problem finding a bright enough star in a small field.? So to increase the guider FOV get a cheap guider-reducer (0.5x) like is available from Orion (though that may mess-up the guider/scope focus distances).? And bin at least 2x2; 3x3 is probably better.
Also, determine the shortest acceptable exp time for your main camera (via "sky limited" concept).? It may be that camera is quiet enough to take short sub-exps that avoid guide-scope flexure, in which case you are probably better off with the guide scope.
If you are serious about long FL DS then an Adaptive Optic (AO) or Intensified Camera (EMCCD or ICCD or sCMOS) is almost mandatory.? Though if you have a top-notch (expensive) mount and really steady skies then you might be able to achieve high-res without such aids.? But I gave up on that a long time ago and used AO until?exploring?Intensified imaging.? You can see some results of AO and a few ICCD results at
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| | | | Stan Moore Astronomy Intensified Astronomical Imaging; Photon Counting; Deep Space Lucky Imaging Utah NightScapes 2008-07-23 | |
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(I am?remiss in updating that web site)
Stan
