You will find a lot on this in a radio astronomy textbook. Also off axis parabolic mirrors are common components of optical systems where an uninterrupted light path is required https://wp.optics.arizona.edu/optomech/wp-content/uploads/sites/53/2016/10/= 521_Tutorial_Newman_Kevin.pdf __________________________________________ David C Brown 43 Bings Road Whaley Bridge High Peak Phone: 01663 733236 Derbyshire eMail: dcb.home@gmail.com SK23 7ND web: www.bings-knowle.co.uk/dcb *Sent from my etch-a-sketch* On Fri, 10 May 2019 at 09:21, AB Pearce - UKRI STFC < alan.b.pearce@stfc.ac.uk> wrote: > Another option may be to search for details of using a satellite dish off > axis to mount multiple LNAs to access multiple satellites. > > > -----Original Message----- > From: piclist-bounces@mit.edu On Behalf Of Mike > Sent: 10 May 2019 08:33 > To: piclist@mit.edu > Subject: Re: [OT]:: Parabolic off focus focus > > Russell, > > Light entering a parabolic reflector at an angle causes a optical > distortion called "coma", since the shape of the focused spot becomes > elongated in the shape of a coma. Searching for this term might yield a > way to determine the extent for a given reflector size etc. > > Regards > > Mike > > On 10/05/2019 08:00, RussellMc wrote: > > I wish to establish what happens to parallel light entering a > > parabolic reflector from off axis angles. > > The intention is to work out where the light is focused from a solar > > parabolic reflector that is statically pointed as the sun moves away > > from the on-axis correct-focus position. > > What I wish to investigate is how effectively one or a few vacuum > > solar tubes located horizontally in parallel above the dish at right > > angles to the main axis will collect energy as the sun moves 'off axis'= .. > > Such tubes will cause shadowing, but blocked light will fall on the > > upper sides of the tubes. > > > > - I could easily do some practical experiments and observe focus spot > > alterations (and will) but a numerical solution is 'a good idea'. > > - I can "easily enough" sit down and work out the geometry (odds are > > that it will take a few false starts to get it right but 'not too too > > hard') but, > > - It seems that others will have considered this before now and there > > may be a ready built 'calculator' avaiable somewhere. > > > > Garglabet divulges many many parabola focus pages, but none seem > > interested in off axis illumination of a dish designed for on axis > focusing. > > (There are designs where the illumination axis and focus axis differ - > > but these too are always used with illumination along a single intended > axis. > > > > Any leads? > > > > I expect that the focus spot will broaden both along the sun-track > > axis and also at 90 degrees to it. Broadening along the solar path > > axis can be accommodated by a thin longish collector. Broadening in > focus "width" > > requires additional collector tubes as it gets wider. > > > > > > Russell > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .