High Power Eyepieces for Celestron 9.25

I am fairly new to astronomy and I now own a C9.25 that I am currently buying eyepieces for. Could any of you C9.25 owners or otherwise experienced astronomers advise me on how short of a focal length the C9.25 will tolerate (7mm, 4mm, etc.???) and what types of lenses work best at higher powers in this scope? I know I want lenses with good eye relief so that makes Pentax SMC XLs and Radians attractive to me but I thought I would ask other observers what their experinces were to guide my shopping (and spending).
Thanks,
Lynn

Obviously, that's a very big question you will get many opinions about. If you apply the "50x per inch of aperture" guideline, you'd get 462.5X as maximum,which you'd achieve with a 5mm eyepiece (470X). Is your C9.25 up to that optically? They do have a very good reputation, but have you star tested to determine if your's is a good performer? Then, often as not, local seeing conditions and the state of your scope's cooling will limit magnification more than optics. My advice would be to see how things go for you with eyepieces of not much less than 10mm and buy a good quality Barlow before investing much in really short focal length eyepieces, regardless of design.

I pretty much agree with what others have already said. I can't offer you advice based on specific experience with the C9.25, but I've had an 8" f/10 SCT and now use a 10" Newt, so this is in the ballpark aperture range that I use. In general I think how high you can go is less interesting than how high you SHOULD go, i.e. what is going to be the best choice most of the time. In time you can fill out your eyepiece set as seems appropriate to you, but to get started I would think of something like a 10mm Radian, 10.5mm Pentax XL, 9mm UO ortho, or 9mm Nagler Type 6. It's true you don't need the extra field of the Nagler or Pentax, but the Pentax and Nagler are superb eyepieces, and the extra field can be fun with lunar observing. A good Barlow can be an economical way to experiment with higher magnifications before making a significant investment. You could try 7mm on for size if you had a 14mm eyepiece and a 2x Barlow--that sort of thing. Quite generally, if your 9.25" scope is well-collimated I would think that your high magnification "cruising speed" would usually be higher than 200x and lower than 300x for atmospheric reasons.
--
Mike

Lyn, I'd suggest something that would give you about a 1mm exit pupil. At f/10 this would be a 10mm eyepiece. I'd suggest an 11mm TV plossl or a 10.5mm Pentax XL (which is more versatile). Anything from 9mm to 11mm will be useable many nights. The 9mm Nagler T6 would be very tempting but is expensive. The 10mm Orion ultrascopic is a very comfortable eyepiece. Below 9mm seeing is going to be a problem on a lot of nites. Clear skies!

Well done! You've covered this thoroughly. Your idea about mentoring is a good one, but it's not all that hard to do by yourself if you do some reading beforehand and take it in very small increments. I'm trying to get my old Meade 2120 tuned up for Mars as well, so I'm going through some of the ame kinds of things but with optics that are probably not as good as yours.

Lots of good thoughts here. I find that my 13mm Nagler (at 180x and .45 deg true field) gives the most pleasing views all around and when I want a boost for planetary detail the 8mm Radian (294x @ .20 deg true field) is about as high as is needed. Frankly, I use the Radian more than my 7mm Nagler (335x @ .24 TF) -- (why I'm not sure, but the Radian just seems to fit better) -- and have not yet had good enough seeing to be able to use my 4.8mm Nagler (490x @ .16 deg TF). I suspect that you'll use your 12mm most often but if you want a higher power non-barlow magnification, I suggest the 8mm Radian. It is a very fine (IMHO) eyepiece.