Whats the lowest usable f/stop ratio I can use on my Maksutov-Newtonian scope?
In my experience, Newtonians with such low f/stop ratios typically produce significant coma. In addition, they also require super-precise collimation of the entire optical train, which is very difficult to achieve without some professional laser collimators. My advice for you is to get a Meade .67 focal reducer. They are the best. Here are some places you can look at various Meade products, due to time constraints I didnt see if they carried the 67 or not…but I highly recommend Meade products for any telescope needs. http://www.thescienceshop.ca/meade_accessories/meade_eyepieces/meade_eyepieces_splash.htm http://www.optcorp.com/ProductList.aspx?uid=347-469 http://www2.arnes.si/~gljsentvid10/accs.html and here are j
