Merlin66

Probably does..... Any element corrector/ reducer etc. has a design spacing to the CCD chip to give optimum performance. When the filter is introduced between the element and the CCD then the change to the optical length needs to be considered. Andrew's answer above gives the solution, taking into account the effect of the filter.

Andrew, You are 100% correct! I apologise for muddying the water... I'll take my pills now and lie down.....

Andrew, The reason I didn't use the "optical" path for the corrector was that the corrector "doesn't" see the filter, and, as far as it's concerned it's still functioning as if it were at a 55mm spacing. The filter just takes the focus from the corrector (at 55mm) and moves it by 1mm to reach the CCD. Think through the set-up if the filter were 18mm thick! The 6mm change in the focal position would not change the design of the corrector.....it would be (55+6=61mm) from the CCD. Yes No??

Guys, Stop. Think about it slowly and clearly.... The two "issues" are - mechanical "fixed" distance and "optical" path distance. The difference is +/- the filter "correction" depending on your frame of reference. I'm thinking with a corrector ( as distinct from a reducer) - the optics of the corrector are designed such that when placed in the optical path (somewhere) that the design distance from the corrector to the focus, and hence the CCD is a fixed distance. If we then place a filter element (say 3mm) between the corrector (say requiring 55mm spacing) and the CCD; looking at the optical path the design distance for the corrector remains unchanged but the "optical" path increases by 1mm. To me this says that with a filter the 55mm spacing would actually be 56mm - the corrector still functioning at it's 55mm plus the, added 1mm. If we maintained the "physical" spacing of 55mm, the corrector would have to be placed (55-1=54mm) from the CCD, which is not it's design position.

Terminology..... If you want a fixed distance between the reducer/ corrector and the CCD chip say 50mm. When you add a 3mm filter element, the physical distance would need to be 49mm and the "extra" 1mm coming from the filter change of focus position...

CdC is a star mapping program - independent of the type of telescope... If you're looking for the addition functionality of GOTO with a specific mount, then look for the ASCOM drivers for that mount.

+1 from me!

Alan, Simple as.... When you set up CdC with your longitude and latitude in the Setup menu, move to the "Solar System", click the "Comet" Tab and then the "Load MPC file" That's it!

Themos, If you really want to get southern hemisphere user feedback you should cross post in IceInSpace http://www.iceinspace.com.au/forum/

Russell, See message #29 above. Just the rotation of the mount RA axis until the 2nd image is a horizontal landscape image.....

Themos, I'll see what I have. The electronic finder set-up I have is a Zuiko 200mm f4 lens with an ATiK16ic camera. FOV = 63 x 84 arc Min The fits header info: AVISUMIN= 280.0 AVISUMAX= 426.0 AVISUTYP= 0.0 APOLY0 = 0.43113530426640000 APOLY1 = -1.01591339168100000 APOLY2 = 1.109754879585E-005 APOLY3 = -3.508152104379E-005 APOLY4 = 0.00500787253995900 APOLY5 = -3.507013049586E-005 APOLY6 = -1.102732033609E-005 APOLY7 = 0.01427973577929000 EQUINOX = 2000.0 CTYPE1 = 'RA---TAN' CTYPE2 = 'DEC--TAN' CRVAL1 = 24.7022333335500000 CRVAL2 = -58.2075496941600000 CRPIX1 = 330.514907382500000 CRPIX2 = 247.987018971600000 CD1_1 = 6.358427089425E-004 CD1_2 = -0.00201002309470900 CD2_1 = -0.00200937046438600 CD2_2 = -6.318189145967E-004 CDELT1 = -0.00210757339460800 CDELT2 = 0.00210698552014600 CROTA1 = 0.0 CROTA2 = -72.4954476428000000 END It would be much easier to supply the plate solved fits file....drop me an email.

AstroArtV5 supports the WCS fits header: The WCS (World Coordinate Systems) is a standard composed by FITS keywords which permit to share the astrometric calibration on many different platforms. These keywords are written to the FITS header by Astroart when the image is saved after an astrometric calibration, for future use by any other FITS reader which supports WCS. Here is a brief description of some of the most important WCS keywords: ▪ CTYPE1 and CTYPE2 indicate the coordinate type and projection. The first four characters are RA-- and DEC- in case of equatorial coordinates (other coordinate types like galactic or ecliptic coordinates are not managed by Astroart). The second four characters contain a four-character code for the projection type (-TAN). ▪ CRPIX1 and CRPIX2 are the pixel coordinates of the reference point to which the projection and the rotation refer. ▪ CRVAL1 and CRVAL2 give the center coordinate as right ascension and declination or longitude and latitude in decimal degrees. There are three options for the scale and rotation: ▪ Historically, CDELT1 and CDELT2 have been used to indicate the plate scale in degrees per pixel and CROTA2 has been used to indicate the rotation of the horizontal and vertical axes in decimal degrees. ▪ The FITS WCS standard uses a rotation matrix, CD1_1, CD1_2, CD2_1, and CD2_2 to indicate both rotation and scale, allowing a more intuitive computation if the axes are skewed. This model has been used by HST and IRAF for several years. ▪ The 1996 proposed FITS WCS standard used PC001001, PC001002, PC002001, and PC002002 to represent the rotation matrix but retained CDELT1 and CDELT2 for the scale. It is also read by this software, but should not be used for new WCS's. Astroart supports both the approximate standard based on keywords CDELT and CROTA and the more precise system based on keywords CDx_y.

Themos, I use AstroArtV5 which has built-in plate solving....could this be used with your proposed method?

I use one on my NEQ6pro which is fully loaded with a C11, three cameras, Spectroscope etc. Needs 5 x 5 kg counterweights! It works very well - you just need to make sure ALL the bolts are tight..... Recommended. (They only come in Henry Ford Black - I had to repaint mine white to match the mount ;-) )

The "polar" axis, the RA axis, is aligned to the pole using the altitude and azimuth screws on the base of the mount. If it's aligned, then in theory (!?) the axis can rotate 360 degrees and still be aligned with the pole. This movement allows you to track a celestial object just by driving the RA axis..... Hope this helps.