Thank you John for the information on the ccd I will post a note on the qcuiag board asking for info.
You took a lot of time typing the reply to me thanks I will print it out and try to make sense of it all. Can you just check my calc on the 4mm and the 7.5mm please I got into a state over the final answer with the degrees and arcmins. Thank you Martin --- In [email protected], John Mahony <[EMAIL PROTECTED]> wrote: > --- Martin Farmer <[EMAIL PROTECTED]> wrote: > > > > I have a couple of questions that the group could possibly help me > > with these involve the Eyepiece menu and adding your own > > > > I have the following eyepiece selection :- > > > > Focal Length > > Field of View > > > > Vixen > > 13mm > > 65� > > > > Vixen > > 40mm > > 42� > > > > Vixen > > 4mm > > 45� > > > > TAL > > 40mm > > 45� > > > > TAL > > 25mm > > 52� > > > > TAL > > 7.5mm > > 52� > > > > I have a 1200mm focal length tube and I have put into the field of > > vision colum the following values:- > > > > 13mm = 42 > > > > 40mm = 84 > > > > 4mm =9 > > > > 40mm =90 > > > > 25mm = 65 > > > > 7.5mm=19 > > > > > > Are these the right figures to go into the Field of Vision box for > > these eyepieces, > > I checked the first two and they're correct, so assuming you used the same > method for all, they should all be correct. > > >Also I am confused on the CCD Field of what to put > > in there I have a Philips TouCam and the specification of the CCD is > > as follows:- > > > > � Image size: Diagonal 4.5mm (Type 1/4) > > > > � Number of effective pixels: 659 (H) � 494 (V) approx. 330K pixels > > > > � Total number of pixels: 692 (H) � 504 (V) approx. 350K pixels > > > > � Chip size: 4.60mm (H) � 3.97mm (V) > > > > � Unit cell size: 5.6�m (H) � 5.6�m (V) > > > > > > What do I put from this information into the CCD options please. > > You need to convert the chip size into arcminutes (at the focal plane). The > starting point for making sense of scope optics is that two stars 1� apart in > the sky will focus to points in the focal plane that are 1� apart, as measured > from the primary (ie, as seen from a distance of 1200mm). A full circle is > 360�, and a full circle of radius 1200mm would have a circumference of > 1200*2*pi ~= 7540mm, so the two star images would be 7540/360 ~= 21mm apart. > Thus the chip width of 4.6mm is 4.6/21 degrees at the focal plane, or about 13 > arcminutes. The height is (3.97/21)*60 ~= 11'. This assumes you're imaging at > prime focus (no barlow, etc). > > But you might want to check those numbers against images of actual star fields. > Multiplying the pixel size of 5.6� square by the 659X494 pixel numbers gives a > chip size of about 3.7mm X 2.8mm, smaller than the chip size listed above. So > either there are parts of the chip surface around the perimeter not used for > imaging (likely), or the pixels are larger than 5.6�, and 5.6 is only the size > of the light sensitive part of each pixel (also possible). A little > experimentation should show the true size of the field. Or ask on QCUIAG. > > BTW the chip is 659X494 pixels, but I believe the actual image output from a > Toucam is only 640X480 pixels. This gives an aspect ratio of 4:3, so the > actual used total light sensitive part of the chip surface (and the field of > view) should have a 4:3 ratio (that's what tipped me off that something was > wrong with the numbers). > > -John > > > > > > > > __________________________________________________ > Do You Yahoo!? > Tired of spam? Yahoo! Mail has the best spam protection around > http://mail.yahoo.com ------------------------ Yahoo! Groups Sponsor --------------------~--> $9.95 domain names from Yahoo!. Register anything. http://us.click.yahoo.com/J8kdrA/y20IAA/yQLSAA/1.XolB/TM --------------------------------------------------------------------~-> To Post a message, send it to: [email protected] To Unsubscribe, send a blank message to: [EMAIL PROTECTED] Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/skychart-discussion/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
