Sprial Solving

Spiral Solving

Here's another way to do spiral solving. This is a further adaptation of Bob Denny's spiral solve code from the Visual PinPoint source. We're not limited in size of checkerboard here, and this code fragment is meant to do spiral solving of a pointing exposure to re-sync a very confused telescope.

Function Arbitrary

' real code goes here, does whatever this ' function is supposed to do ' ok, now we're at the point where we need to ' solve an image, so we do so (however you ' want; this just happens to be from a script ' of mine): Logtext "Plate-solving image." plate.AttachFITS fn ' Attach the image plate.RightAscension = ovec.RightAscension ' Set approx coordinates plate.Declination = ovec.Declination plate.ArcsecPerPixelHoriz = PointSolveScale ' Set scale factors plate.ArcsecPerPixelVert = PointSolveScale plate.UpdateFITS() ' Write this to headers spiral = false On Error Resume Next ' Failure here should not be fatal If Not plate.Solve Then ' Get the real position spiral = True ' set a flag! plate.DetachFITS ' Clean up Log Err.Description Else Log "ok! " & plate.MatchedStars.Count & " stars matched." End If 'if not plate.solve On Error Goto 0 ' ok, here we check whether the straight ' solve worked. If not, we go to a spiral solution: If spiral then plate.AttachFITS fn ' Attach the image If Not SpiralSolve(ovec.RightAscension, ovec.Declination, 5) Then Log "SpiralSolve failed to solve the pointing exposure." plate.DetachFITS AimCamera = False Exit Function End If End If ' real code goes here, whatever ' else this function is supposed to do.

End Function Function SpiralSolve (ra, dec, gridlimit) ' careful - don't make 'gridlimit' too high a number. If you ' use ten here, then 440 possible fields will be searched. It ' can get out of hand pretty quickly. Log "Doing a spiral search to solve this pointing exposure." dim RAstep dim Decstep dim top dim x dim y ' Here we calculate the size of the squares in ' the checkerboard we are going to search: RAstep = ((PointSolveScale * plate.Columns) / (3600 * 15)) / Cos(dec * PI / 180) Decstep = (PointSolveScale * plate.Rows) / 3600 plate.ArcsecPerPixelHoriz = PointSolveScale ' Set scale factors plate.ArcsecPerPixelVert = PointSolveScale ' we assume plate is the PinPoint Plate object, and ' that you have already attached an image. plate.FindImageStars ' Scan the image only once ' counts rows/columns outward from middle For top = 1 to gridlimit ' counts out the x,y positions of a box of "radius" equal to top For x = -top to top For y = -top to top If abs(x) = top Or abs(y) = top then plate.RightAscension = ra + (RAstep * x) plate.Declination = dec + (Decstep * y) plate.FindCatalogStars On Error Resume Next If Not plate.Solve Then Logtext "Solution failed at " & x & "," & y On Error Goto 0 Else Log "Plate solved at " & x & "," & y plate.UpdateFITS SpiralSolve = True ' if we solve the image, we bail out On Error Goto 0 Exit Function End If On Error Goto 0 End If ' abs(x) = top Or abs(y) = top next 'y next 'x next 'top SpiralSolve = false End Function