Eyepiece recommendations

[Reesa]

I'm sure this has been asked over and over, but I couldn't find it in the search, so sorry about that. Anyway, i want to get some good eyepieces and I was wondering if there are certain brands to get. I'm looking for a good brand at a good cost(I know they can get very expensive).

Would these be good?

http://http://cgi.ebay.com/Meade-1-25-Plossl-Eyepiece-Moon-Filter-Telescope-Set_W0QQitemZ200235890113QQihZ010QQcategoryZ29954Q QssPageNameZWDVWQQrdZ1QQcmdZViewItem

[RickJ]

Need more info. What's the scope's f ratio? What's a low power eyepiece in one scope may be medium power in another. Do you wear glasses? A 6mm plossl would be difficult for an eyeglass user to to use due to the limited eye relief it has.

These appear to be a very basic plossl design which isn't bad. They do indicate reasonable coatings and the plossl is a good basic design for general viewing. Main problem is cheaper ones often aren't so great toward the edge of the field in fast scopes.

While many see no problem with short focal length eyepieces I wear glasses and once you get shorter than 12mm I can't see the full FOV in a plossl with my glasses on. I much prefer to use a barlow to get high power. Gives eye relief I need and no eyelashes hitting the lenses leaving oily lines behind. The sweet spot is larger as well.

For general low power viewing an eyepiece of 5mm exit pupil is a good starting point. For maximum field, if your eye is young, 7mm can be used to get the widest possible FOV for a particular eyepiece design. But contrast will be lower than at 4 to 5mm. Medium power would be about 2mm and nigh power 1mm to .75mm. Highest power for double stars would be .5mm

To calculate this divide the eyepiece focal length by the f ratio of your scope. So assuming an f/10 SCT the 32mm would barely make the cut as a low power eyepiece. For that you'd want a 2" 50mm eyepiece. the 6.4 would be almost too high for high power. At f/6 things change and the 32 is in the correct range for low power, the 12mm for medium power and the 6.4 for higher power though again a barlow might help more in that department.

If the scope is f/4 then the 32mm is too low of power wasting light that doesn't go in your eye's pupil. Still it will give the best image at that power any scope can -- if you are using a refractor. In a reflector the secondary shadow will make for a black hole in your viewing experience. When the exit pupil is larger than your eye's pupil the secondary's shadow becomes a major problem. The 12.4mm would be a medium low power. Higher than most would want but usable. The 6.4 would be a good medium medium high power. Sort of like driving an old two speed automatic I had on my first car, a 1955 DeSoto. Low wasn't low enough and high wasn't high enough.

Hope this helps.

Rick

[Siguy]

First of all, they're charging too much for that particular set. They were either $30 or $40 before.

Well, Rick's advice is really good. But you need to state the specs of your scope before we can suggest EPs for you.

[redshifter]

I personally am not a fan of standard plossl eyepieces below about 12mm focal length or so due to the shorter eye relief for the reasons Rick mentioned.

[Reesa]

Well, I'm not done with the scope yet, but I should be by this weekend. It's a 6" f/8 Dobsonian. I do wear glasses most of the time. I was thinking plossl because it seems like I can get ok quality for the cost. I know there are better types, but then it's gets too expensive. I was thinking a 12-15 and a 25-30. Are there other sizes that would be better? Also, what about good brands (less well known brands)?

[Siguy]

Alright, if you have an f/8, your highest useful magnification would be in a 4mm eyepiece. Your lowest magnification would be a 56mm, but I'm guessing you only have a 1.25'' focuser. So a 56mm 1.25'' eyepiece will really have the same field as a 32mm Plossl, just smaller. The optimum planetary eyepiece has an exit pupil of ~0.8mm, so a 6mm is a nice planetary for your scope with a magnification of 200x and an exit pupil of 0.75mm. Optimum wide-field eyepieces have an exit pupil of 5 to 7mm, so there is more flexibility.

This comes in handy:
http://www.klhess.com/telecalc.html

Personally I think you should just get one of each of these:
http://www.agenaastro.com/Agena-Enhanced-Wide-Angle-Eyepiece-s/139.htm
These eyepieces are really good for "bang-for-the-buck". A lot of people don't like the field curvature, but in an f/8 it's practically nonexistant. My main eyepieces are all Orion Expanse eyepieces, exactly the same as what I linked above.

[redshifter]

Well, I'm not done with the scope yet, but I should be by this weekend. It's a 6" f/8 Dobsonian. I do wear glasses most of the time. I was thinking plossl because it seems like I can get ok quality for the cost. I know there are better types, but then it's gets too expensive. I was thinking a 12-15 and a 25-30. Are there other sizes that would be better? Also, what about good brands (less well known brands)?


I use this in lower focal lengths: http://www.telescope.com/control/product/~category_id=eyepieces/~pcategory=accessories/~product_id=E0010

Not much more $ than a decent plossl, but much more comfortable to use. They have a longer eye relief as well as a nice big lens to look through as opposed to a small peephole that lower focal length plossls can have. I have the 9.5mm as well as another 7.5mm of an Orion line that has been discontinued (the Lanthanum line). The ED2 eyepieces should do well for you.

[Siguy]

I should add that, unless you have astigmatism, you can take off your glasses and refocus to look through eyepieces with short eye relief.

As for the ED eyepieces, a lot of people find them difficult to look through, as you need to have your eye right over a "sweet spot". I suggest Vixen Lanthanums, which virtually have the same specs, but are higher quality.

[redshifter]

Hmmm...no issues with my 9.5mm ED2. Dunno about the other focal lengths however.

[Reesa]

I finished the scope last night!! It seems to work really well, but I only have an 8mm & a 12.5mm (both with really small FOV) and a binocular eyepiece that give me a huge field of view. I think I'm going to Starizona today to get a good eyepiece. Thank you for all the information.

[Siguy]

Great work, that's a beautiful scope!

[Reesa]

Great work, that's a beautiful scope!


Thank you. I bought a Celestron Omni 25mm eyepiece yesterday and am excited to try it. Unfortunately, we're in the middle of monsoon season, so it's raining most nights. I was lucky the night I finished my telescope because the sky cleared for a few hours, it was really dark, and full of stars. Now I just have to wait for another one like that.

oh, the anticipation!!