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8 inch dobsonian

Started by kalias, 11/04/2006 05:52AM
Posted 11/04/2006 05:52AM Opening Post
Hi! I am a complete newcomer to astronomy and, after looking at the stars for a year with binocs, I decided to take the plunge and purchase a scope. I was able to pickup a second hand 8 inch dobsonian from a friend at work. It came with a 26mm and 10 mm plossl and, after using it for the past couple of months, I would like to upgrade my eyepieces.

I have done a bunch of looking around and there appears to be alot of choices, only thing is, I am not sure which way to go. My requirements are as follows:
a) Find nebula, galaxies, etc. (still haven't seen M31)
b) Check out planets
c) Share with my two young sons. Oh, and no computers involved. I want to enjoy the journey of learning the stars.
d) Choose lenses that will do me for a few years.

Is a person better to go with an excellent set of plossls eps (televue?) or, should one stray into the world of wide angle lenses (orion stratus?)? For now I would like to pick up one or two lenses and stay under $250 Can.

thanks for your advice smile

kalias
Posted 11/04/2006 03:21PM #1
I suggest you might consider a 1rpd 30mm,80deg afov for a finder, it won't be in focus on the edge, but it is a great finder, and a poor mans wide field, a 9mm ortho and a 2x barlow will give you planetary observing, and somebody else's suggestion for an 18mm, or so. I use an ortho because out of focus stars bug me, but the field is narrow.
I sold my cheap plossls for pennies, but later regretted not having them for general use for others.
My $.02
Dan
Posted 11/05/2006 06:38AM | Edited 11/05/2006 06:38AM #2
I'd go with the Stratus (or Hyperion is basically the same or close) over the Plossl design. In addition to the wider apparent field of view (Plossl = 50-55deg, Stratus = 68deg), and you also get lots more eye relief from the Stratus making them easier to use - very important factor. Eye relief means you don't have to put your eye so close to the eyepiece.

Performance wise, even in a fast newtonian (F/5) they perform very well. Not as good as a Nagler, but close, especially considering the price differential.

I would get the 21mm and the 8mm, then a fairly good 1.5x barlow so you'd have 21, 14, 8, 5 when you add the barlow. If your scope accepts a 2" eyepiece, then later you can add a good longer focal length eyepiece for scanning the stars, something in the 30-40mm range.

FYI, I've personally compared the 13mm Hyperion to the Nagler 12mmT4 in my f/4.7 10" Dob and they perform closely, the Nagler having a much larger field of view of course, byt I find anything near 70deg extremely pleasing.

Good luck.
Posted 11/05/2006 06:48AM #3
Depending on your finances I'd recommend the following. First the wide angle finder eyepiece.

If you can afford it get the 35mm Stratus. It's 90% of a Pan at half the cost. Nothing will touch it for $200. A 35 Pan is still obviously better, but at a cost. Below the Stratus I'd look at the TV 32 plossl, the 30mm Celestron Ultima or Orion Ultrascopic. If those are still too expensive then try a 32mm GSO plossl. It's a heckuva bargain at Agena Astro.

For planetary use look at the B/TMB planetaries. Especially the 'garage sale' 6mm if you can find one. It's the best $50 eyepiece that ever sold. It gets tons of use in my 8" dob and in my refractors. I have the 'full-price' 4mm, 5mm, 7mm & 9mm B/TMBs but I still use the 6mm more than any of them. It's just the right focal length.