Eyepiece Selection

[ausmensan]

Hi,

I want to buy one eyepiece which will act as my workhorse E.P for a Nexstar 8i (2032mm). Given a budget of around 300-350 AU$ what would you select?

I have a Celestron Ultima Barlow (1-1/4) to use with it, and have been considering the Meade 14mm UWA which is currently $299 at Star Optics. If you would like to help with this process, I would appreciate your views!

Cheers

Simon :)

[Miaplacidus]

Mmmmmm....

Well, of course there are a thousand different possible answers...

But isn't 14 mm just too short for a 2 metre FL scope? And you've already got the barlow (which I assume you intend to use).

I reckon I would maybe scrimp and save for the 24 Panoptic (I already have one) — maybe even wait and try to score one second hand. (Even this might not be long enough. 30mm might be better...)

[astro744]

If you have only 1.25" diagonal and intend on staying with that configuration then you want an eyepiece that will give you the maximum true field of view (TFOV) for the 1.25" size. There are three in the Tele Vue series to chose from, (all have 27mm field stop and will give 0.76 deg TFOV):

24mm Panoptic has 68 deg AFOV, and will give 2.4mm exit pupil at 85x, but is a little above your budget.

32mm Plossl has 50 deg AFOV and will give 3.2mm exit pupil at 64x and is well under budget, enough to buy a bandpass filter (UHC or O-III).

40mm Plossl has 43 deg AFOV and will give 4mm exit pupil at 51x and is well under budget, enough to buy a bandpass filter (UHC or O-III).

Note the AFOV of the 40mm will look narrow compared to the 68 AFOV of the Panoptic but may be more suitable on some objects when used with a bandpass filter. You may be disappointed in the narrow AFOV though.

The 32mm plus O-III is a very good combination and will Barlow well, but a Powermate may be better to avoide increasing the eye relief. (2.5x or 5x Powermate only availabe in 1.25" and the 2.5x would be an excellent choice just get the latest version since it is threaded for filters).

If if you really want 68 degrees go for the Pan. It works well in all telescopes down to f4 should you ever get a short Newtonian.

If you want 82 degrees you will have to fork out more money but the 16mm T5 Nagler with 22.1mm field stop will give you 0.62 deg TFOV at 127x. It just fits the full Moon at 127x. Another alternative to the 16mm T5 Nagler is a 19mm Panoptic (68 deg AFOV) which has only slightly less TFOV.

I would go with the 24mm Pan since it will give you maximum TFOV for your 'scope plus a magification high enough to give you a good sized planet when combined with your 2x Barlow. (170x). Add a 2.5x Powermate (or Barlow if you can source) and you get 212x and about the limit for a C8 with above average but not exceptional seeing).

If the Pan is really stretching your budget then get the 32mm Plossl since it is a very nice eyepiece too and you'll have money left over for a bandpass filter of your choice should you want one.

Whatever you choose, enjoy!

[Miaplacidus]

Yeah, that's what I meant to say. I'm just too lazy...

[andrew2008]

Keep in mind a Vixen LVW 22mm with 65deg FOV, 0.79deg TFOV at 92x would be nice. And $70 cheaper than the 24mm Panoptic.

There was one in the classifieds section that may still be up for grabs. Had been eyeing it off for myself.

http://www.iceinspace.com.au/forum/showthread.php?t=46248

[Waxing_Gibbous]

What andrew2008 said or TMB 40mm Paragon or Takahashi 50mm plossel.

[GrahamL]

some good ones up for grabs in buy and sell

the t4 is close to your budget
http://www.iceinspace.com.au/forum/showthread.php?t=48369

:)

[CoombellKid]

Graham,

That Pentax XL28mm in the same thread wouldn't be too bad a buy either.

Cheers,CS

[GrahamL]

yeah lotso tempting stuff there Rob , You only want one for now simon ?:lol:. workhorse ? .. my most used is around the 110x, The 17
at 119 x is a pretty handy magnification you would likely get a lot of use from.


For some further info Simon
http://www.excelsis.com/1.0/entryvotes.php?sectionid=22&entryid=263&page=2
bit of hay amoungst the chaff there sometimes but a great resource

[Astrobserver99]

I reckon a 24mm Baader Hyperion would be ideal. Decent prices too.

[ausmensan]

@ Nighthorse, ha ha, yes only one workhorse e.p. Isn't it pathetic? I try to kid myself that it will only be one, but buying astro equipment is a bit addictive. I must stop..

[Wavytone]

Well... no one eyepiece will do it all, even with a Barlow or zoom. You need to look at what focal lengths you want in your eyepiece set, aiming for steps between them around 1.5X (a set of 4-5 ep's) or 2X (set of 3 - low, medium, high).

Your scope can usefully span a range of eyepiece focal lengths from about 40mm (I'm thinking of my 2" TMB) down to about 8 or 9mm, a span of 4X from high to low.

If you want to build around the Meade 14mm, a simple set would be one eyepiece around 28-30mm for low power and another at 8-9mm for high power.

My pick for the low end would be the 30mm TMB (find one secondhand on Astromart) or Vixen NLVW 30mm. At the short end, a mid range eyepiece around 8-9mm would do fine, my pick would be a Vixen LVW8mm or a Panoptic.

If cost is a consideration, I'd choose a 9mm ortho - not a plossl. If cost is no limit then go for a Radian, Nagler or Ethos.