EP tech and specs

[Iddon]

G'day all.
Looking for a simple rundown on the various EP characteristics such as apparent FOV vs actual FoV.

And does anyone use 2" as standard for all aplications ? Or is it best to have a suite of 1.25" and 2"?

I have a range of basic 1.25 Meade EP, however am pondering if a suite of good quality 2" is a long term strategy to work towards ?

[asimov (John)]

After using 1.25" EPs for a long time, I only just recently purchased a 2"....Just to see what everyone was raving about. Dont get me wrong, I love using that 2" for nebula's & general low power wide-view, but I must say, I haven't said to myself.."Geez! I'm going to buy a whole fleet of these"....I just dont feel the need to own anymore 2" because I dont think it would be advantageous to me.

[ballaratdragons (Ken)]

Hi Grant.

I use both regularly.
I use my 2" 30mm SuperView barlowed and un-barlowed. That gives me two 2" EP's and that is probably enough as all my other viewing is done through 1.25" of various f/lengths barlowed and un-barlowed. I find I have a good range of EP's this way.

[asimov (John)]

Your a lucky boy Ken, to have a 2" barlow...I dont intend to get one yet (if at all) considering I have only one 2" EP.....In hind-sight, I should have bought one rather than the 1.25" barlow & just used the 1.25" adapter in it. Oh well, cant have everything!

[mch62 (Mark)]

Grant have a read of this page from TV.
Not saying go out and buy Televue eyepieces just a good articals which will explane every thing about eyepieces and scope FR's ect..

http://www.televue.com/engine/page.asp?ID=140
http://www.televue.com/engine/page.asp?ID=222
http://www.televue.com/engine/page.asp?ID=131
http://www.televue.com/engine/page.asp?ID=141
http://www.televue.com/engine/page.asp?ID=139

You have the 30mm 80deg 2" giving 66x .

You could go to a 55mm 2" 50deg plossel 36x with the f10 SCT for lower power and still be ok as far as exit pupil , but the actual field of view or true field( the area covered in the sky as seen through the ep) of the eyepiece will be about the same but at a lower power so the 30mm 80deg So there is nor need to go lower in power.



Mark

[stringscope (Ian)]

Grant,

In general the only advantage you get with a 2" eyepiece is the potential for a field stop larger than 27mm (this is the practical limit for 1.25" ep's) with the resultant increase in field of view. If you have a 32mm Plossl type eyepiece this will probably have a field stop of about 27mm diameter. This ep will beliver you the widest field of view in your scope using 1.25" ep's.

I notice you are using an 8" LX200 which I assume is F10. On this basis the the largest field of view you can get with this scope using 1.25" ep's is 0.8 of a degree or 48 arc min. I understand you can fit a 2" visual back to these scopes. However, I also understand some of the wider angle, longer focal length ep's can suffer vignetting due to the design of the scope. I have not operated this type of scope myself but there are other forum members here who could advise you further on this.

As you are using a LX200 I assume a "finder" eyepiece is not really required.

To respond to your question on long term strategy I would ask the following question:

What are you intending to observe?

If you are generally observing objects about 30 arc min or less in diameter then these will be nicely framed in eyepieces with a field stop of 27mm or less depending on what you are looking at. In this case the required FoV will be delivered by 1.25" ep's. If you are not happy with the quality of the Meade eyepieces I would suggest trying some alternative 1.25" eyepieces in the first instance.

If you want to frame IC2602 (Souther Pleiades) into a single field of view you will require a true FoV of 1 degree or more. To achieve this in the LX200 you will clearly have to use an eyepiece with a field stop in the 40mm + category. This will require a 2" ep.

Hope this is of some help.

Cheers,

[Iddon]

great advice guys - thx
FWIW - not overly impressed with the high mag Meade Series 4000 Super Plossl (9mm, 6mm) - however the 26mm and 15mm seem fine. I don't have much of a frame of reference or experience, however I can certainly see that at the higher mags any imperfections really come out.

[RAJAH235]

I like my Meade Super Plossl's. All 5 of them.(5,6.4,9.7,15 & 32mm). Not to mention the UWA 14 mm. They all give great results, with/w-out the #140 Barlow. L.

[beren]

For me the 22mm nagler is the ONE , for most nights its about the only eyepiece i use , perfect mid range power through my f/10 sct for general observing add a f/6.3 focal reducer for low power and barlowed for higher power ...excellent range of powers ,comfortable eye relief and WFOVs

[Iddon]

Hey beren,
what brand focal reducer are you using ? You happy with it ? Does it soak up the photons ?

[beren]

I have the meade , apparently the celestron FR so ive read rates more favourably but mine is the only one ive used and does well for me . When i was seeking advice for eyepieces i was told that eyepieces with focal lengths longer then 26mm would induce vignetting/feild curvature with a FR to{find that i can use a 32mm 62degree eyepiece with no real noticable problems}.

[iceman (Mike)]

not overly impressed with the high mag Meade Series 4000 Super Plossl (9mm, 6mm)

I'm not surprised though, with your focal length of 2000mm.. the 9mm and 6mm give HIGH magnification and will only be useful on the very best nights of seeing. Even your 9mm is giving you over 200x magnification, which you just won't be able to support on most nights.

In general, i'd be looking at a 12 or 11mm eyepiece as your smallest focal length and get a 2x barlow to use on those nights of magic seeing.

[Iddon]

happy to take advice here - is a 9mm by itself or a 15mm mit barlow going to soak up more photons for the faint DSO ? I was looking at 9P Temple the other night with the 9mm and I think I had better contrast and brightness than the 15+barlow? The seeing that night also seemed to support the 6mm - I just wasn't all that happy with the apparent FOV and critical eye position - though I don't have much to compare to, so I may be being overly critical.