Can eyepieces be mis-colimated?

taxman (Matt) · #1 11-09-2008, 07:44 PM

I have been playing with my new Megrez 90 and have noticed considerable side-flaring (a red "tail") on Jupiter and Uranus with the supplied 2" 25mm SWA.

However, when I switch to my 2" 27mm GSO superview, there is none. No false color either.

The WO 1.25" 6mm SP doesn't seen to have any of these issues either.

I am a little underwhelmed with my supplier, Astronomy Alive, too with issues like "super low price on OTA" that didn't come with the case which was not mentioned until it arrived (the website says it comes with a case), the 9mm SWA coming without original packaging and having to drill holes in a dovetail he assured me would fit perfectly.

The case I bought for extra was also obviously used (tear in the foam) and the supplied keys don't fit the lock.

Seriously, I think I was done, and when I contact the guy, it's as though he has done me a favour by letting me spend over 2K on crappy gear.

I do have a close working relationship through my job with the Office of Fair Trading in QLD, and if the eyepice is truly junk, it would be the straw that breaks the camels back and I think I'm going to have to make a complaint.

Or is not the supplier at all and Williams Optics stuff always this bad?

taxman (Matt) · #2 13-09-2008, 06:48 AM

So yes or no - can eyepieces be miscollimated or not?

Thanks, guys & girls...

CoombellKid · #3 13-09-2008, 07:41 AM

To tell you the truth... I've been buying and researching astro gear from
time to time for 6+ years and I have never heard of Astronomy Alive.

I usually stick with the major or known retailers. On another note I couldn't
tell you about your Q... only because I've never heard of it in an EP. And
not ever having tried the SWA ... both are not IMO high quailty in any case.
So you maybe just seeing the imperfections of low quality.

regards,CS

dannat (Daniel) · #4 13-09-2008, 08:48 AM

the SWA ep's can have a few problems in fast scopes - i have the 9mm swa & the er is crap, its ok in slower scopes - the spl line is a better bet. In the 2" range the 32mm in the one to choose, both the 25 & 40mm can have a few problems - there have been a few reports on CN. I would send the gear back & get them to check everything - or advise you will take the matter further. Buying something that looks used is totally unacceptable.

I have heard of astronomy alive & looked at their site but never bought anything from them

Wavytone · #5 13-09-2008, 11:01 AM

It appears there are quality issues with all the gear coming from China and if something is wrong yes do something about it. As for eyepieces... yes they can have problems, either due to poor manufacturing, poor assembly, and abuse in the hands of owners who think disassembling them is a good idea. In addition I'm fairly certain a lot of inferior elements that are "seconds" that cannot be assembled as premium eyepieces are flogged off in cheap Chinese no-name-brand eyepieces, when more reputable makers would have scrapped the elements. If you're lucky you get one that works well enough, if unlucky you have a glass brick.

Possible:
- wedge in one or more elements, causing a constant chromatic aberration visible across the field, like looking through a thin prism. The giveaway is that this aberration rotates with the eyepiece if you turn it in the drawtube.

- decentering errors - if one element was manufactured slightly off-axis the effect is grotesquely serious and an eyepiece with this should be detected and failed before it ever gets out.

- misalignment - during assembly of most good eyepieces there is a test where the elements are rotated to find the orientation where they give the best performance in the eyepiece. This requires sophisticated test gear and is well beyond what you can do at home. If this is poorly done, or has been disturbed, the view through the eyepiece will be impaired. Once upon a time an alignment mark was then made on the edge of each element so that if ever disassembled there was some chance of reassembling it properly.

For the latter reason it is ill-advised to disassemble eyepieces, especially short focal lengths (under 15 mm) - if you do, they will never work as well as when they were new.

It's possible the one you have has been messed with but you'll never be able to prove anything.

GrahamL · #6 13-09-2008, 08:58 PM

I beleive the owner of that buisness (astromelb) visits here regularly
(yesterday ) by the sites log ...perhaps you could drop him a pm and try and sort out any problems .