My original question ask about setting circle coordinates for a Dob telescope by Glen C?

To futher clairify, The Dobs base will set level and its setting circle will be oriented to (0deg) true north at my geographical Long./Lat. home position. The elevation setting circle is set at 0 deg on level to 90 deg at straight up. My computer will know my current time and date.


I need to enter the known celestial coordinates of the sky object to be viewed into the (possibly the Excel) program and have it return to me the answer.


The answer I need is the azmuth in deg. from true north and the elevation in deg above the horizonal plane at my geogrphical point of viewing to the star in question.


I will then manually push my telescope into a position of these values. The scopes degree scale setting circles are a calibrated part of the scope and are used to position the scope in pointing to a position in the sky.


I'm a 72 year old amature astronomer in Woodland Wa excited with 16" appature fever. My math and programming skills are a bit rusty. Mabe a program exists. Thnx Glen C

My original question ask about setting circle coordinates for a Dob telescope by Glen C?
Well, first of all, there ARE programs that do this. There are a number of astronomical software programs including Sky Map Pro and Software Bisque; that does not exhaust the possibilities, some are inexpensive. There is one Carte du Ciel which is a free download utility but I damned if I ever could make it work.





What you really want though it to attach ENCODERS (typically US digital S2-2000) to your 16" dob and then hook them up to a computer. I have provided a link to what most folks consider the best computer: it is sold in the U.S. and is pricey, but it is excellent.





Now let me explain something. It is practically IMPOSSIBLE to use RA and Dec on a dobson mount. The reason is that when you move the scope you are always cutting cords which have peculiar effects on the readout, it's very difficult to move so that you get only one value changing. And then when you let go it all starts to change again because you are not tracking. You really DON'T want to be THINKING about angular conversions when you are in the field.





No matter. The Dob guys have figured this one out ten years ago. The solution is to do the conversion you are discussing, but keep it invisible to the user. You just punch in NGC 6888 and two arrows appear with values. Your object is to move each arrow until the value is zero. When the value is zero the object should be in the field of view.





If you want to note the RA and Dec you can get a readout while you have the object there. Argo Navis also has a utility that allows you to enter RA and Dec coordinates and then will convert it into the directional arrows. The Argo Navis database has many tens of thousands of objects.





There are cheaper digital setting circle units out there: an old Sky Commander will sell for maybe $200. These are respectable, not as good as the Argo Navis, but a good way to save money. In terms of overall capability Argo Navis defeats the competition, but judge for yourself. AN is made in Australia but sold in the U.S.





You can purchase these used items on ASTROMART which is the New York Stock Exchange of used equipment. You have to pay a one-time joining fee of $12. Your first purchase will compensate that fee (I bought $120 binoculars for $60). There are also a lot of active discussion group where people with advanced technical savvy will help you with your issues.





You also have Yahoo! groups. These are free. In your case you want Yahoo! Bigdob and Yahoo! argo_navis. So I'm giving you lnks to two groups, links to Argo Navis, and I'll let you ask about preferred skyware programs on BigDob.





All in all this is an issue where you don't need to re-invent the wheel. The math has been worked out and the technology implemented.





For the extreme budget minded there is a Yahoo group that specializes in retrofitting go-to systems from cheap sources, such as the $160 Meade ETX 60, to better telescopes. I'm afraid I've lost track of the name but if you ask on Bigdob someone will know. It may even be possible to buy a Meade paddle directly from Meade. implementing go-to however is signifcantly more complex than just having some dscs.





The other way to solve your problem is to implement what is called a wedge where you raise one side of the platform to the latitude of your area and point the altitude axis of rotation at the North pole. You would need a gun sight or tube to point it. You now have an equatorial mount and you can make your own setting circles and use standard RA and Dec coordinates.





Hope that helps,





GN
Reply:try this web page for teh equations http://www.ephemeris.com/space-time.html





yeah you can turn ra and dec to elevation and asimuth and point that way. you can let a computer do it for you. argo navis is really really expensive but really really good.
Reply:Look here for a formula and discussion:


http://www.asterism.org/clubact/calcfrm4...