Compromise eyepiece for f/5 ( 30mm, >=70°)

[Schorhr]

Sorry...

I know there have been so many threads about entry level eyepieces, but I really tried reading into the subject.

The problem is, that both the number of eyepieces & clones as well as the number of different opinions regarding the use in fast scopes is just overwhelming to comprehend. Also, many reviews address the usual entry type telescopes with f/6 or slower.

What I am looking for is a inexpensive 2" eyepiece for my ordered 254/1200 (f/5) with 6-7mm exit pupil.

I can tolerate coma and blurriness - to some degree - as long as it's better (and has more apparent field) then the Kelner, Plössl and such that I have now.

I have a 40mm/40° as stated in another thread, but on the f/5 the exit pupil would be 8mm and I'dd favor higher magnification with a larger view.

I want to spend <€100, and I know I will have to compromise.

Initially I wanted to go with the Hyperions, but the larger focal-length ones are not cheap, thus I'dd rather save up for a real good one later.

So far I have narrowed it down to these;

Sorry if I mixed up brands/clones/specifications, please correct me.

30mm/70° Revelation ~€42 wo/shipping

No clue about this one, just read about it on here.

I read both type of comments, that they are "OK" at f/5, and "terrible even at f/9", so not sure about it.

30mm/80° Astrobuffet/1rpd ~€50 w/shipping+tax for a "blem" (minor non-optical flaws)

(Clone of the Widescan, similar to BW?)

As far as I have read similar to owl and others, even less sharp at the edges on f/5 then the TS-WA32, but compansated a little by the larger apparent field (so I read in a review of both). At the low price, I'dd live with it.

32mm/70° TS-WA €60-80

(lots of similar ones here?)

Seems to be recomended a lot on german message boards, but usualy for f/6.

LET 28mm/55° 27€ wo/shipping

Could be a discount solution untill I save up for a better one.

Specified for "f/5 or slower", so it probably won't be too great.

In addition, I would buy a cheap overview eye-piece and one cheap one for for 200x/250x magnification, as I do only have some for the region of 10-25mm... The 4mm from my fleamarket-telescope is not usable at all IMHO. I've seen some decent planetary and similar for 66°, but not sure how well they perform on f/5... I do not wear glasses, but it would be great if I could let my fiancé look through them as well, which does wear glasses.

I'd also get a used one or others recomended... I am Thankful for any suggestions, offers and comments :-)

-Marcus

[John]

I'd avoid the 30mm 80 degree eyepieces at F/5 - the outer 50% of the field of view will look very messy !.

Of the ones you list I reckon the TS-WA 32mm would be the best bet although there will still be some astigmatism at the edges of the field. If you can find one, maybe used, the Skywatcher Aero ED 30mm would be a step up again.

[Schorhr]

Thank you for your reply! Good point.

Yes, I read that they will have a lot of blur outside ~50%, though according to SvenWienstein.de it's basically comparable to the TSWA, and just adds another 10° messy field where the TSWA has ended? The chart on 30mm2zOkulartest (sorry, all german) sort of states similar observations, though it seems to vary from observer to observer of course.

As it's cheaper (under 50€) and the outer area could still be used to spot objects that where roughly in the FOV with the finder but would not be with a 60° or 70° EP.

Also, I was hoping that with a barlow it might be a bit more usable? Would be nice to view the moon as well.

But I suppose a big plus for the TSWA would be that it is lighter, thus causling less balancing troubles when using with the travel scope.

Are the Aero 30MM/68° that much better?

As they cost €149 that's not too much of a step up... IF they really have a better performance.

I stumbled across them the other day and thought that they might be just another clone of the other 70° eye-pieces, as I was unable to find (german) reviews of it. All I could really find on SGL was your comment on them in another thread :-)

A nice thing is that they are relatively light as well.

Just as side note, any experience on the LET eyepieces?

[John]

I used to own the Japanese version of the 30mm 80 degree eyepieces - a Kokusai Kohki 30mm Widescan III, which was slightly better optical quality than the chinese clones but even that suffered considerably in scopes faster than F/7. I found the astigmatism was really distracting at F/5.

I found the Aero 30mm a bit better corrected than the 32mm SWA's like the TS-WA's - whether it's worth the extra cost only you can decide.

As you said in your 1st post, in the <£100 (or even <£200) price range there will always be some compromises in wide angle eyepiece performance in fast scopes though and that generally shows itself as outer field of view astigmatism.

[Moonshane]

Personally, as you say that you have the f5 scope on order, I'd wait until you get it to see what it's like in use before you spend on further eyepieces.

For your budget, I would personally compromise on apparent field and go for a Televue 32mm Plossl.

This would give you a sharp view across the field and an exit pupil within your range. The field of view would be around 1.3 degrees which is quite respectable and usable. Even a 26mm Nagler would 'only' give 1.7 degrees.

With a TV 32mm Plossl there would be no compromise in image quality at all.

Even a much cheaper GSO 32mm would be pretty good but the TV would give better views in scopes down to f4.

[Schorhr]

Thanks for the detailed response, Moonshane!

Yeah, unless I get a real good offer for a used eyepiece, I'd wait for my telescope probably.

Before I spend 120€ for a 50° Plössl, I'dd probably go with the €27 LET... What I have read about the 32mm Plössl is not too good either, at least on f/4.

As I am thinking about an EQ platform, apparent field is probably not as importaint, at least when using the platform... Still, a "space view" ep would be nice later.

jahmanson: Thanks for the review of the 80° eyepieces... Seem only few enjoy the view on a fast telescope. So unless I can get it really cheap I'll probably go for the TSWA or Aero later, perhaps when I can get hold of a used one.

Yeah, "you get what you pay for"... :-)

[Merlin66]

I can assure you the TV 32mm plossl works very well on scopes at f4.

(I use(d) one for many years on various scopes from 12" f5 to a 28" f4.5)

[Schorhr]

Thanks for the info :-)

How do ERFLE-type eyepieces perform by the way?

I saw that TS offers them now for €59 (GS SuperView 30mm 2" Wide Angle Erfle Eyepiece - 68 Degrees).

Though the €159 MER30 erfle variant seems to have a "built-in" coma corrector (lens?).

All confusing. Also stumbled across the William Optics SWAN (similar to tswa according to one forum, better according to another one?), I guess I'll try to find some more reviews.

[mdstuart]

What about getting one of those coma correctors...

[Schorhr]

Later, perhaps. From what I read, some can tollerate it at f/5, some can't even at f/6.

As I have a €20 76/300 clone (f/4), I think I can tolerate it.

Even with those cheap entry-level eyepieces it should be much better on f/5. But perhaps I just have very low expectations anyway ;-)

[John]

What about getting one of those coma correctors...

Unfortunately that won't correct the astigmatism that lower cost wide angle eyepieces produce

You would need to buy a well corrected wide angle eyepiece like a Panoptic or a Nagler to see if your coma corrector is working

On Erfle eyepieces, the 70 degree eyepieces you have listed, like the TS-WA are based on the Erfle design with similar strengths and weaknesses.

[Schorhr]

Easy solution :-)

[Moonshane]

I can certainly vouch for coma correctors (specifically the Televue Paracorr) when using a f4 newt.

the difference is really staggering when using Televue eyepieces and also excellent with Baader Genuine Orthos which is all I have.

but as John says, it is only good quality eyepieces that reveal coma as otherwise the coma is effectively masked by faults in the eyepiece. at f5 you don't generally need a coma corrector though unless it really bothers you.

[Schorhr]

Yeah, I think the coma corrector is something for a possible future purchase of nagler eyepieces then :-)

I wonder how well the 40mm/40°+ performs on the f/5, is there any downside other then "wasting aperture" with the larger exit pupil?

[Moonshane]

apart from light sky background it may perform OK as the field is narrow. it will seem a little restricted in view though possibly.

[John]

I wonder how well the 40mm/40°+ performs on the f/5, is there any downside other then "wasting aperture" with the larger exit pupil?

The downside is that you are wasting aperture of course

Another is that a 32mm 52 degree eyepiece (ie: a plossl) will show you just as much sky without the excessive exit pupil / aperture wastage.

[Schorhr]

Yeah... same view but less apparent field... though compared to most cheap eyepieces I have the 40mm isn't too bad at all.

Maybee I'll focus on a planetary then and change the 40mm after a while... Or get the LET...

Looking at Jupiter yesturday with the narrow field 10 & 4 mm EP (haven't had a chance to use the TS Zoom yet) really increased the wish to get a better planetary eyepiece where planet's stay in view just a bit longer...

[Schorhr]

Just read that the LET are the Apex eye-pieces, which seem to be reverse kellner and are not good at all at f/5.

I wonder why even (otherwise) trust-worthy companies describe them as suitable for f/5 and faster systems.

Plössl then or TSWA... Depending on how much the EQ platform will cost.