Planetary Scopes

I've been thinking about getting a planetary scope for a while now but I don't know how much better planets will look through a longer focus refractor compared with a short focus reflector. I have a XT10 right now and I was considering getting some type of refractor. Scopes seem to be pretty pricey so I was thinking about just putting an aperature mask on my dob and using for planets. Do you think I would get good results with that or should I just buck up and buy a good refractor. Any experience/advice would be greatly appriciated. Thanks in advance.

Rick R.

A 4" unobstructed aperture mask will get you close to the view of 4" APO - some of the time. Tube currents and an aberration (I forget which one) from the mirror prevent it being as good.

It only takes 15 minutes to make a sturdy aperture mask using tape and plastic from an art folder.

My 4" APO's superior contrast results in it showing somewhat more detail on planets than does my C8. But my 14" dob's superior resolution has occasionally shown more detail on Jupiter than anything else I've got. And the best planetary scope I've ever seen is a 10 dob a colleague assembled himself, using the most expensive components.

A 4" APO is a fun toy which delivers sharp star images and Airy discs (it's enjoyable splitting Antares). But personally, unless you're really into Airy discs, I'd work on sharpening up your dob first, perhaps by installing a fan to blow across the mirror, as described in S&T some six months ago.

Renato

I've love to tell you to jump ;-) onto a refractor, but perhaps, Rick R., you may want to tell us first how the planets looked through your XT10 and what is it in the view you don't like. There may be a simple solution, saving you lots of $$$ or $$$$ (for an APO). (But we can take your
donations ;-). Being short focus, is your XT10 collimation dead on? How about the eyepieces? Are they good quality? Has the XT10 cooldwon?

Maurizo (who unfortunately has taken ill) used to sell a long focus Newtonian (imagine a 10" f/8). And the CCD image from that Newt of his, is like no other images I've ever seen! His sales pitch used to read something like "With Excelsior Optics who needs the space probe" ;-).

Ron B[ee]
PS You'll still need a small refractor to compliment your XT10 (maybe now, maybe someday).

The point I was trying to get at was just how much better would the planets be. They look great right now but I always wondered what it would be like using a long focus refractor on them. The first thing I really need is just a shorter focal length eyepiece with a wide field of view (probably a 4.8mm nagler). Thanks for the advice on all the little things I can do I've been meaning to fix up some of the little things and those sugguestion helped.