GSO Plossl

[hszsky]

Hi guys,

Looking to get new plossl eyepieces. Just wondering how do GSO compares to the likes of Celestron Omni or Skywatcher super plossl series. Looking for 4, 6, and 9 mm focus range. Or any other suggestions for eyepieces under $40 each.

Thanks!

[Astro_Bot]

You should find the following useful.

The review:
http://www.brayebrookobservatory.org/BrayObsWebSite/HOMEPAGE/PageMill_Resources/Comparison%20test%20of%20TVPlossl%2 0vs%20Brandon.pdf

The review's CN discussion thread:
http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/3785488/page/0/view/collapsed/sb/5/o/all/fpart/1/vc/1

In short, and IMHO, the GSO Plossl appears to represent good value for money at most of the offered focal lengths.

[ZeroID]

I've got one GSO 10mm PLossl and it seems the best of my collection in that range but then again I don't have any expensive stuff to compare it with. But have to say I am more than happy with my GSO Superview 15mm and 20mm and if they are any indication of quality then I'd say it was a good bet.

[mental4astro]

Hi hszsky,

The Plossl eyepiece design was the bees knees of EPs 30 years ago. It offered better correction and reduced aberrations over other designs.

However, the plossl EPs made cheaply today all fall down with narrower fields of view and reduced eyerelief compared with more contenparary designs that also use superior glass materials and coatings. Eyerelief in particular is poor as the focal length of these plossls is shortened, with you needing to place your eyeball onto the eyelens, and you also need to look into a pinhole to see the image.

Plossls are a good way to start out with a new scope, but only if they come with the instrument. If you are going to start looking to cultivate a better eyepiece collection, or just increase the number of EPs you have, I suggest you look at other designs.

Note, I in no way advocate the need to spend big bucks on eyepieces. With a little research you can find some real gems within the modest end of $ for EPs! The TMB Planetary Type II is such an example. You can get these from eBay for around $60. They are a larger eyepiece than your 25mm plossl, and ALL of them have a larger eyelens than any of the plossls you mention, and the eyerelief with ALL of them is as good as the 25mm Plossl. They are smaller than more expensive eyepieces though, and have fewer and smaller elements, and the multicoating on the lenses is still excellent. I compared my 9mm TMB to a mate's 8mm Vixen LVW (a $300 eyepiece), and the image quality was superior in my $60 TMB, with an as comfortable observing quality. I actually saw MORE stars in my TMB than in my friends still impressive LVW.

Please consider a better alternative to the cheap plossls. These plossls do a job, but there are better eyepieces out there for only a few dollars more. The difference in performance is a quantum leap over these plossls.

Mental.

[mental4astro]

Here's a comparision photo between my GSO Super Plossl 9mm and my TMB Planetary Type II 9mm. Chalk and cheese really. You can see the difference in their eyelenes, and to look into the plossl you need to push hard onto the rubber eyeguard to look into the peep hole.

This TMB is twice the price of the Plossl (a $30 EP), but the observing quality makes it a world of difference.

The 9mm plossl came with a scope I bought new. I have never used it in a scope, and the only other time I took it out of its box (other than for this photo) was when I bought the scope to inspect it, and that was two years ago.

It is still better than some really terrible cheapie eyepieces out there, but if you know better, there are much better alternatives.

Mental.

[silv]

TMB Planetary Type II 9mm (http://www.astronomics.com/main/product.asp/catalog_name/Astronomics/category_name/4SXTTARRLMWX8H3UA5Q5HNAN82/product_id/TMBP09) - product description without malware warning. it says its good for planets and f/6 and above focal ratio.
:)

[Astro_Bot]

The OP was fairly specific about budget. I'm just saying. ;)

[mental4astro]

Silv, good article. But the article doesn't say it is for f/6 and slower scopes. It just states that it works with an 80mm f6 refractor, not that it is not suitable in a faster instrument.

I regularly use my 9mm in my 8" f/4 newtonian and find the image to be fantastic. Sure there is a small a punt of astigmatism right at the very edge, but an f/4 scope will test any eyepiece. You also need to make the effort to look for this too, otherwise you'd miss it too. Coma isn't a concern at this EP focal length.

In my 8" f/10 C8 it is tack sharp to the very edge, but that's to be expected in an f/10 scope.

The 6mm is the weakest model tough. It still tears strips off a 6mm plossl, with the same eye relief as the 9mm.

[mental4astro]

Yes, and that's why I didn't recommend Nagler or Ethos eyepieces, and phrased my words the way I did, ;) :thumbsup:

[loki78]

I am forced to agree with Alexander, I have a bunch of GSO plossls myselfs and am currently looking at pricier alternatives in the mid range, but I have read great things about the TMBs for their price.

For this small difference in price, I would absolutely recommend it as like Alexander said, looking through a pinhole can be really really annoying and I think takes away from the experience.

[silv]

Oohhhh! Marvellous! Bought :D

That's why I (noob) linked that product info. To hopefully get info out of this already very helpful thread. My 8" f/5 and I are very grateful.

(The eyepiece collection thread is not helpful at all in this regard.)

[hszsky]

Hi all,

Thank you for your replies and recommendations!

The scope I am using is Celestron Omni 5" SCT mounted on ioptron smartstar (tripod is quite unstable). Using mainly to observe planets, the TMB seems to be a good option. But the money seems to add up quickly if I buy a few focal length.

I do have a 2x barlow, so if I was going to buy one focal length, which should I go for?

And checking out local dealers website, I dont see TMB eyepieces. Do I need to purchase from oversea dealers?

Thanks again!

[mental4astro]

I had a C5 until recently, :(. Such a beautiful scope to use. Fantastic optics, compact and with enough grunt to keep me happy.

A 9mm TMB Type II would be perfect. It will give you 138X, which is right on the limit that the atmosphere will typically allow. With your 2X barlow you'll get 276X, again it is the upper limit when conditions are especially good, and just on the limit of the practical maximum for a C5.

Astronomics sells them for US$49.95 (http://www.astronomics.com/main/category.asp/catalog_name/astronomics/category_name/4SXTTARRLMWX8H3UA5Q5HNAN82/Page/1), and they ship to Oz.

There used to be a retailer here in Oz that sold them, but they closed down last year, :sadeyes: .

[MattT]

Only way to buy cheap is to buy 'pre loved' in the eyepiece classifieds, when you see one buy it quick, or get new from astronomics in the US which is more than you want to pay for now. I used the GSO 2.5 apo Barlow with a 20 and 15mm plossls which worked quite well, depends on what you have now in the eyepiece collection.
Matt

[hszsky]

Great thanks all, I will consider the TMB. Just need to save a bit more.

[hszsky]

What happened to your C5?