Is GSO 9mm Plossl Really that Bad?

[Renato1 (Renato)]

Hi to All,
I bought a few cheap second hand GSO Plossls from a member here a while back. And some time later saw a member here totally lambasting his GSO 9mm Plossl, and I thought - "Hey. I've got one of those, I wonder what it's like?"

So last week, I compared it to my 9mm TMB and 9mm Orthoscopic eyepieces by looking at the moon's terminator and Saturn, using my 5" Skywatcher MAK ( I forgot I also had a 9mm Nagler).

Anyhow, I quickly saw a problem with the 9mm GSO plossl - it needed cleaning. After cleaning, I tried it on two nights, and I can't honestly say I saw much by way of difference in detail between it and either the TMB and the Orthoscopic.

The main problem with the GSO that I did see was very shallow eye-relief. It is much easier to gunk up its front lens than with my Orthoscopic (no chance of doing it with my TMB), and I can see length of one's eyelashes becoming a factor.

I haven't done the comparison in a short focal length telescope yet (it's raining all the time), so my opinion may yet change, but so far, I don't see the GSO 9mm plossl as a dud eyepiece.

What do you think?
Regards,
Renato

[koputai (Jason)]

I reckon there are not many 'dud' eyepieces around.

I've had GSO Plossl's and they were quite good, better in fact than a few bigger name, bigger dollar eyepieces. The only reason I don't still have them is that I had a serious cull and kept only the very best (and a few quirky ones).

Before i disposed of the GSO's, I got rid of most of the others, including several TMB's (very average) and a Seibert (total rubbish).

For the money they are hard to beat.

Cheers,
Jason.

[dannat (Daniel)]

Plossl and Ortho are amongst the sharpest ep's, it just try have small fov compared to tr latest designs

[jjz (Joe)]

Sorry if it's a little off topic can you explain how you cleaned them? I have a10 inch Dob and some GSO eyepieces and I can see some crud it at least one of them.

Thanks Joe

[brian nordstrom (As avatar)]

Renato I have one in a kit of cheap eyepieces that live in my UTE full time , so I always have some on hand and I find the 9mm GSO to be a very good eyepiece in my Takahashi sky90 , a little tight as you say but it handles the f5.5 light cone very well and is very sharp .
Nothing wrong with mine as well .

Brian.

[Renato1 (Renato)]

Originally Posted by koputai

I reckon there are not many 'dud' eyepieces around.

I've had GSO Plossl's and they were quite good, better in fact than a few bigger name, bigger dollar eyepieces. The only reason I don't still have them is that I had a serious cull and kept only the very best (and a few quirky ones).

Before i disposed of the GSO's, I got rid of most of the others, including several TMB's (very average) and a Seibert (total rubbish).

For the money they are hard to beat.

Cheers,
Jason.

Hi Jason,
Leaving aside the obvious, like the cheap SR eyepieces that come with cheap telescopes (though some Huygens aren't too bad), I have to agree with you that there aren't that many duds I've come across. I do actually have a semi-dud eyepiece - my 16mm 1.25" Widescan - a total dud in my dob and in my C8, but brilliant in my 80mm refractor.
Cheers,
Renato

[Renato1 (Renato)]

Originally Posted by dannat

Plossl and Ortho are amongst the sharpest ep's, it just try have small fov compared to tr latest designs

I agree. Though my Orthos are slightly sharper than my Plossls, but I can only really tell that is the case when I push them to really high power with Barlows- like 200X in my 80mm refractor - where they hold definition a bit better. I have an extremely hard time telling them apart at lower power.
Regards,
Renato

[Renato1 (Renato)]

Originally Posted by jjz

Sorry if it's a little off topic can you explain how you cleaned them? I have a10 inch Dob and some GSO eyepieces and I can see some crud it at least one of them.

Thanks Joe

Hi Joe,

The way I clean them is that I buy a lens cleaning kit from cameras stores. The kit typically come with a packet of papers, lens fluid and a little blower. The blower is inadequate, and I use a much bigger blower.

So, I blow anything off the front of the eyepiece with the big blower.

Then I put a drop of lens cleaning fluid on a paper sheet I've torn off, and gently dab it on the glass, and gently try move anything still there off with strokes of the wet paper.

Then I clean the glass with the dry part of the paper, where necessary folding the paper over a few times and using its edge to get into the corner edges of the glass.

While I've never had any problem with that fluid, I did buy a few bottles of Orion's eyepiece cleaning fluid, which worked just as well, but made me feel better.

A warning - I have written the above on some US forums, and some people expressed horror, claiming that I was removing the coatings. They insist they just use the weight of the paper to clean the glass - but I couldn't for the life of me see how they cleaned the edges.
Regards,
Renato

[Renato1 (Renato)]

Originally Posted by brian nordstrom

Renato I have one in a kit of cheap eyepieces that live in my UTE full time , so I always have some on hand and I find the 9mm GSO to be a very good eyepiece in my Takahashi sky90 , a little tight as you say but it handles the f5.5 light cone very well and is very sharp .
Nothing wrong with mine as well .

Brian.

Hi Brian,
Thanks for that - you are getting good performance with the 9mm GSO in your Tak, and I am happy with it in my Mak. They must have something going for them.

I remember when S&T did their evaluation of the then available Plossls years ago, and they rated them against four or five criteria. Televue were the best against each criterion, but most of the others scored reasonably well too - there weren't any they rated as poor.

Regards,
Renato

[brian nordstrom (As avatar)]

So they work well at f13-15 and also well at f5.5 ,, not many eyepieces can lay claim to that , even some of the big dollar ones have trouble sometimes with this ,, food for thought aye, Renato ?
On the other hand I have a 6mm no name Ortho in .965 size and it lives in a .965-1.25 inch adaptor made from a plastic 3x barlow ( YUCK !!) anyway this eyepiece shows the planets like no other eyepiece I own , true it is spectacular , even tho its like looking down a straw , .
But no its an excellent planetary eyepiece , very jewel like in feel .

Brian.

Originally Posted by Renato1

Hi Brian,
Thanks for that - you are getting good performance with the 9mm GSO in your Tak, and I am happy with it in my Mak. They must have something going for them.

I remember when S&T did their evaluation of the then available Plossls years ago, and they rated them against four or five criteria. Televue were the best against each criterion, but most of the others scored reasonably well too - there weren't any they rated as poor.

Regards,
Renato

[jjjnettie (Jeanette)]

Love my GSO ep's.

[Renato1 (Renato)]

Originally Posted by brian nordstrom

So they work well at f13-15 and also well at f5.5 ,, not many eyepieces can lay claim to that , even some of the big dollar ones have trouble sometimes with this ,, food for thought aye, Renato ?
On the other hand I have a 6mm no name Ortho in .965 size and it lives in a .965-1.25 inch adaptor made from a plastic 3x barlow ( YUCK !!) anyway this eyepiece shows the planets like no other eyepiece I own , true it is spectacular , even tho its like looking down a straw , .
But no its an excellent planetary eyepiece , very jewel like in feel .

Brian.

Hi Brian,
The little eyepiece that could!
Perhaps you should invest in a commercial .965 to 1.25 adapter. I don't think the field of view in a 6mm Ortho should be any different in the two barrel sizes. I have a 5mm 0.965 Ortho and its FOV looks standard to me.
Regards,
Renato

[Renato1 (Renato)]

Originally Posted by jjjnettie

Love my GSO ep's.

Another satisfied customer.
Cheers,
Renato

[Tropo-Bob (Bob)]

I had some GSO EPs about 5-6 years ago. I thought that the 9mm was by far the best performer in the range and was of a good standard. The other GSO Plossls gave too much false colour for my liking.

[Renato1 (Renato)]

Originally Posted by Tropo-Bob

I had some GSO EPs about 5-6 years ago. I thought that the 9mm was by far the best performer in the range and was of a good standard. The other GSO Plossls gave too much false colour for my liking.

Thanks, another positive for the 9mm, and an interesting perspective on the others.
Regards,
Renato