Re: What eyepieces/filter for 10" dob

Something that has not been mentioned is exit pupil size. Your pupil probably dilates to somewhere between 5 and 7 mm in diameter, depending on your age. To gain the maximum field of view that 2" eyepieces can give would require something like a 31mm Nagler. Your telescope has an f/5 focal ratio, so the exit pupil would be about 6mm. Can your eyes handle a 6mm exit pupil and can your pocketbook handle a 31mm Nagler?

The telescope maker's choice of 25mm and 10mm eyepieces for this telescope is a good one: a 10mm eyepiece gives a 2mm exit pupil for maximum visibility of faint objects and a 25mm eyepiece gives a 5mm exit pupil for wide-field views which viewers of all ages are likely able to take in.

What did the telescope maker leave out? In order of importance and in my opinion:

1) A high power eyepiece or barlow for planetary viewing. You have been observing planets at 125x magnification which is pretty low for planetary viewing. Small details would be easier to see at 250x using a 5mm eyepiece or a 2x barlow and your 10mm eyepiece. The caveats are: is the atmosphere above you steady enough to support 250x magnification and do you mind moving your scope every 30 seconds or so. A good barlow is less expensive than a good 5mm eyepiece because eye relief is expensive at that focal length.

2) Filters. I think the filter set you linked to is more for aesthetic enhancements than dramatic changes such as a nebula filter make, but I do not have personal experience with such a set.

3) More expensive 25 and 10mm eyepieces. Generic Plossls are very good for the price, so upgrading would probably only be worthwhile if you go to wide-angle eyepieces of high quality and, therefore, high price.

4) An expensive 2" wide-field eyepiece for young people with large pupils to give extra-wide views of a few large objects. If you know your pupil dilates to at least 6mm and you like using super-wide true fields of view, I think a 31mm Nagler would be fun.

The reason I put them in this order is the first is an inexpensive ADDITION to the capability of your scope, the second is an inexpensive ENHANCEMENT to its capability, the third is an expensive enhancement, and the fourth is an expensive addition of questionable value.

--

Jim

My eMail is not SPAMLESS. :)
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