I need a better eyepiece.

Pinwheel (Doug) · #1 09-02-2013, 02:36 PM

Hi all, awhile back when I started out I bought a set of 1.25" eyepieces for my 8" reflector. Anyway after sorting out collimation issues etc I never really was 100% happy with the image as I always had triangle like distortion on bright stars. Now that I've started playing around with digital astrophotography it dawned on me that the distortion was not present on my images. Last night I did some more photos & then swapped back to eyepieces & the old problems is back. I have now released my eyepieces from ebay are just too cheap & nasty! I have 40mm, 30mm, 20mm, 10mm, 6.5mm & 4mm 1.25" plossi & I mostly use the 40mm & the 20mm eyepieces.

What I wish to ask is can someone recommend a better quality eyepiece at a reasonable price & where to get them from.

Cheers.

barx1963 (Malcolm) · #2 09-02-2013, 02:49 PM

Hi Doug
Triangle shaped distotion can often be caused by pinching of the primary mirror. If the clips holding the mirror in place have been tightened so they are actually pressing down on the surface of the mirror it will cause this. However I would suspect it would also show up in images. Do you see the effect if you defocus slightly, ie the blurred star image is slightly triangular?
With eyepieces do you notice this effect more or less with different EPs? I would suspect that it is more prominent in the shorter ones. With the longer lengths (especially the 40mm) cheaper EPs often exagerrate the coma that is natural in newtonion scopes. Stars towards the edge of the field start to look like little seagulls and as you move the scope while looking through the EP the stars appear to follow a curve path.

As you may gather from my sig, I like the high end Televues, but they are pricey. Personally I think the best value EP out there is a 24mm Panoptic (http://www.bintel.com.au/Eyepieces-a...oductview.aspx) which is getting pricey but not too bad. Look out for a second hand one, they do come up from time to time, but move quick!

Malcolm

Pinwheel (Doug) · #3 09-02-2013, 03:24 PM

Hi Malcolm, too much pressure on primary was one of the first things I checked out. The truth of the matter is I bought cheap, too cheap! the whole set cost about $100 including postage. They look professional but there cheap. $339 for a single eyepiece is out of my price range but I'm happy to pay a fair price for a pre loved eyepiece if it falls in my lap. My problem is I don't know what I'm buying..the techno-bull doesn't mean a thing. Maybe one-day I could send you my set for you to compare? Sadly I'm along way from the main populous to setup next someone to compare optics.

Lee · #4 10-02-2013, 09:03 PM

I bought two Televue Plossl's several years ago (20mm/32mm) - the difference from the stock standard stuff that I'd got with scopes (even the 'premium' no-branders) was unbelievable - well worth the expense, and not *too* expensive....

ZeroID (Brent) · #5 11-02-2013, 09:32 AM

Worth looking at the GSO Superview 15 & 20 mm EPs'. Not sure what the Aust price is on them but the are about $60-$70 NZ and are my most used. Probably only $50 is Aust,

mental4astro (Alexander) · #6 11-02-2013, 10:24 AM

Hi Doug,

I too can recommend the GSO Superveiws if you are on a tight budget. I have the 15mm & 30mm and both are excellent for their price. I haven't used the 42mm, but from what I've read it is also a good performer for the price. Excellent eye relief, and 68deg AFOV with the 15mm, 20mm and 30mm. The 42mm and 50mm are a little narrower in AFOV, but still good.

They are not of the same quality as the Panoptics, but you can also do a whole lot worse for even more money than these Superviews. I've tried many other EPs around the 30 - 40mm mark, and the Superviews are definately NOT amoungst the worst performers. You won't be disappointed with these.

You can find these at their best price at Andrews Communications. Look under the GSO banner:

http://andrewscom.com.au/site-section-10.htm

There are other cheaper GSO eyepieces there too, but the Superviews are the better ones.

Note also that the 50, 42 & 30mm Superviews are also 2" eyepieces.

Mental.

dannat (Daniel) · #7 11-02-2013, 12:57 PM

imo if you want better than superviews look for astrotech paradigm, good eye relief & reasonable fov, they are sold my matt from telescopesandastronomy in SA as BST explorer.
which focal lengths are you after?? the 40mm & 20mm -also suggested the 32mm/25/20 Televue possl are good, below these focal lengths the eye relief decreases where i dont find them comfortable to sue

AstralTraveller (David) · #8 11-02-2013, 01:26 PM

If you rotate the eyepiece do the triangles also rotate? If yes, it's the ep. If no, look elsewhere.

I'm not saying you shouldn't upgrade the eps but if the problem is in the scope better eps won't help.

mental4astro (Alexander) · #9 11-02-2013, 01:49 PM

Quote:

Originally Posted by AstralTraveller

If you rotate the eyepiece do the triangles also rotate? If yes, it's the ep. If no, look elsewhere.

Very good advise to start with! Blooming obvious too, but I was only too quick to recommend stuff first rather than chase the problem first.

AstralTraveller (David) · #10 11-02-2013, 02:52 PM

Quote:

Originally Posted by mental4astro

Very good advise to start with! Blooming obvious too, but I was only too quick to recommend stuff first rather than chase the problem first.

Do you think I haven't spent hours inside a mass spec looking for an exotic problem when the real issue has been staring me in the face? Did something similar just last week - though nothing was disassembled. You learn after a while to check the obvious and simple.

Rob_K · #11 11-02-2013, 02:54 PM

Quote:

Originally Posted by AstralTraveller

If you rotate the eyepiece do the triangles also rotate? If yes, it's the ep. If no, look elsewhere.

I'm not saying you shouldn't upgrade the eps but if the problem is in the scope better eps won't help.

Spot on David. I have some GSO Plossls all of which give perfectly good views and I find it hard to believe that all of your range of eyepieces have exactly the same fault with them, producing big triangle-like distortions. Check the scope first. Maybe the weight of the camera drags things back into some sort of alignment, who knows.

Good luck!

Cheers -

Peter.M · #12 11-02-2013, 08:04 PM

Quote:

Originally Posted by AstralTraveller

Do you think I haven't spent hours inside a mass spec looking for an exotic problem when the real issue has been staring me in the face? Did something similar just last week - though nothing was disassembled. You learn after a while to check the obvious and simple.

Checks quadrupole before changing cones?

OzEclipse (Joe Cali) · #13 11-02-2013, 09:25 PM

I agree with a lot of the advice about looking at the optics, defocussing the image and rotating the eyepiece before blaming the eyepieces.

Another thing to check is whether too much force being applied to the secondary. Depends on the design. This could be from side clamps or it could be from too much pressure from back packing behind the spider if it's a tube type spider.

Some might disagree with me but I think that a high power eyepiece, even a medium power eyepiece is a more critical examination of optical defects than photographs are. It seems highly unlikely that a set of six eyepieces of different focal lengths will all be identically made with the same triangular distortion.

Finally, if you do find you have to buy new eyepieces, don't buy so many. You really don't need that many. A long focal length instrument builds up magnification quickly and possibly needs more eyepieces so as not to jump big steps in magnification but with an 8" newt you can make do with a lot less. You've already noted that you mainly use two focal lengths. Spend a little more on those two focal lengths and forego the rest. Another strategy is to buy a good quality barlow or Televue powermate. Then buy eyepieces that are not focal length multiples same as the barlow. For example, a 2X televue powermate and a 40mm and 13mm eyepieces give you 40, 20, 13, and 6.5mm equivalent focal lengths. Note that switching in a barlow or powermate is less convenient than having parfocalized eyepieces.

Good luck

Joe

skytry (Peter) · #14 13-02-2013, 07:52 PM

hi Doug,
you have opened up a very good topic, one which I have
enjoyed reading,
if you wear glasses like I do, I try and get the best results I can
till I can find / stumble across better eyepieces,
I have many different brands, some cheap and not so cheap,
some better than others, haven't quite reached my ideal eyepiece
yet
I have a choice between Refractor & Reflector scopes too use,
and between them both I have not hit on the truely good eyepiece yet,
yet I haven't given up,

I am enjoying the very informative comments given by other learned
IIS'ers here, which I enjoy the read & learn as I go,

I enjoying the experience,
regards,
Peter.

GraemeT (Graeme) · #15 13-02-2013, 08:15 PM

Getting back to the original question. I, too, have an 8" dob, felt the need for better eyepieces than the plossls I'd been using. My first try was a TMB planetary, but I found it a bit fiddly and with the dob's original focusser.
I've since upgraded to a Moonlite and am really enjoying my 82 deg. Explore Scientific 2" series. Much better than your usual GSOs and cheaper than Televues.
At present, they are on special in the good ole hew hes hay.
My 2 bob's worth.