PDA

View Full Version here: : 2" vs 1.25" EPs


brett
22-01-2007, 11:24 AM
hey i currently have an etx125 with the 1.25" focuser. over the next month or so i'm planning on getting the meade lightbridge 12" dob with the 2" focuser. my question is do the 1.25" EPs operate any differently to the 2" EPs or are they identical?

thanks :)

Starkler
22-01-2007, 11:54 AM
Your lightbridge scope will come with a 1.25" to 2" adapter so you can use your old 1.25" eyepieces without any issues.

OneOfOne
22-01-2007, 11:56 AM
You will find the 2" will have an adapter so you can plonk your existing eyepieces right in. Generally, my observations are that 2" tend to be of longer focal lengths and so less magnification. while you can find 2" of 20mm or longer, you won't generally be able to get anything much shorter. One of the problems you may find with the 2" is that they are much heavier which may cause some balance problems, my 2" XW-30 is a pretty big beast compared to its smaller bretheren of the 1 1/4 variety. The 2" will also be more expensive than a comparable 1 1/4 equivalent.

They say "once you have had 2" you won't look back" but you bank account may say otherwise. They may give a brighter image if the 1 1/4 does not let all of the light cone through, so that may be one difference. Hopefully someone who knows more about optics can answer this.

Essentially, just drop them in the adapter and away you go.

janoskiss
22-01-2007, 12:12 PM
2" EP will never be brighter on axis than an otherwise equivalent 1.25". 2" just allows a larger apparent field of view which is why you only need it in lower power wide FOV eyepieces. With 1.25" barrel the edge of the field would be cut off in these cases and you would not see the entire FOV.

brett
22-01-2007, 05:06 PM
thanks :)

allan gould
24-01-2007, 11:11 AM
Thought I would give you some feedback on the 2"15mm UWA eyepiece that I recently purchased as well as the 30MM UWA the same stable. I used them last weekend on a 2" diagonal and 8" SCT f10 scope. The views with these eyepieces were far, far above what I expected from this price range of equipment. The 30mm gave wide panoramic views of M1 and M42 that had excellent contast and detail at least 80-90% of the view. Some may say the edge performance drops off a little - it does but I generally recenter an object to get the best view without going to peripheral type viewing. On the Sunday night the 15mm was nothing but exceptional. With the 8" scope the Trapezium was 6 round points of light and with both eyepieces I was able to see an incredible anount of detail in M42.

Steady views with sharp, contrasty details. The view was better on that night than I can remember through my 10" with any other eyepiece. There are a lot of comments on the web about these eyepieces - for one, I am more than happy with them and they are exceptional value for money. They give very satisfying wide angle views such that objects you have seen time and time again appear fresh and in a different context. I found it hard to go back to a 1.25" eyepiece irrespective of its field of view.

Worth far more than I paid for them and I would recommend them without hesitation.
As far as their performance in a fast Dob - I would expect more seagulls at the edge but in an SCT or MAK they would be excellent. MyAsttroShop has the best price on these at the moment ~$125

janoskiss
24-01-2007, 10:11 PM
Allan, nice that those cheap ultrawides work well in your f/10 SCTs, but I do not think they would be suitable for an 12" f/5 Lightbridge, which is what Brett is asking about.

larry brockman
11-02-2007, 07:25 PM
Hi Bret,
I ave a 6" refractor that is equipped with a 2" focuser , I bought a 2" diagonal and 28mm 2 " ep. The result was great , this gave 42 x magnification and increased fov. Perfect for Moon, Planets and cruising the Milky Way. Great result at low magnfication.
Regards Larry Brockman