How to describe a flawed eyepiece?

[DaBozUK]

I bought some GSO revelation astro eyepieces and 2 of them are flawed. I'm using Saturn as my target, and with 6 eyepieces now, it's easy to see which don't work properly.

The two faulty eyepieces will not focus correctly and have streaks and double images. But how do I describe or diagnose these flaws sufficiently to the retailer?

Is there a website that shows example images with flaws so I can point to the closest match?

Finally, I need to collimate properly before making complete diagnosis, but presumably if the collimation was that far off, then all eyepiece would show the same problems?

Cheers

Boz

[Ad Astra]

Hi Boz,

You can check collimation, but you might also try these in a refractor (eliminating the collimation issue) to show that it isn't just a problem with your particular scope.

One thing you can do is note the shape of the star images across the field with a sketch. Generally, the stars will be distorted in a particular manner. Look up the terms "coma", "barrel distortion" and "pincushion distortion" on wiki - these may help you describe the star field and its distortion in more professional terms.

Double images - note if they are on all stars in a field, or just particularly bright ones. Streaks, ditto.

Still, I've got to say, that if you are having all these problems, your retailer should take them back or exchange them without you having to go into all that detail. A good retailer will have a satisfaction guaranteed policy.... you did go with a source highly recommended by your pals on SGL.... didn't you?????

Let us know how the seller handles things and post a review of the process here. If needed, you may even let them know you are an SGL member and that you WILL be posting a review of the transaction - GOOD OR BAD!

The bottom line is that no retailer can personally test every EP and accessory that they sell - but they can, and must stand behind what they sell.

Let us know how you get on. If nothing else, we all need to know who to shop with ---- and who to avoid.

Sorry your having such trouble,

Dan

[glowjet]

I am sure under the Sale of Goods Act you will have the right to return the EP`s if you are not satisfied with the performance and ask for a refund or replacement oculars, there should be no trouble from the retailer as the Law is on your side.

[NGC 1502]

Finally, I need to collimate properly before making complete diagnosis, but presumably if the collimation was that far off, then all eyepiece would show the same problems?

Boz

I think that the first step is to make sure collimation is ok.

A second check is to use the EPs with another (well collimated !)

scope. If you are a member of an astronomy club (or can contact

one) that would help too. Perhaps someone could try the EPs in

their scope ?

Also, collimation issues tend to show up more at higher power,

are the problem EPs high power ones ?

Maybe contact the supplier, say you have issues with the EPs,

and that you are trying to sort it, to find out what the problem is.

That way they will know you are not blaming the product without good cause.

Hope you sort the problems, Ed.

[Tyr]

Boz,

Re finding someone knowledgeable who can physically have a look at them. I believe the Reading Astronomy Society has a meeting tomorrow evening.

Reading Astronomical Society Amateur Astronomy in Berkshire, UK

Perhaps you could see if someone there can have a look at them for you.

Hopefully they'll be meeting on a night I don't have family plans some time when I can go along myself.

I got a chance to try my new GSO 32mm last night and thankfully it was very good indeed. Sorry to hear your having problems with yours.

Good luck, be interested to hear how you get on.

Tyr

[DaBozUK]

Also, collimation issues tend to show up more at higher power, are the problem EPs high power ones ?

That's a good point, I know the tube isn't collimated well (I accidently moved some of the primary mirror thumbscrews) and the worst problem occurs with the 9mm. The effect is double images, which gets as you go off focus, so in focus the double images are on top of each other but slightly offset horizontally, but change focus and the double images separate. Go off focus the other way and the double images separate the other way.

[DaBozUK]

Boz,

Re finding someone knowledgeable who can physically have a look at them. I believe the Reading Astronomy Society has a meeting tomorrow evening.

Reading Astronomical Society Amateur Astronomy in Berkshire, UK

Perhaps you could see if someone there can have a look at them for you.

Hopefully they'll be meeting on a night I don't have family plans some time when I can go along myself.

I got a chance to try my new GSO 32mm last night and thankfully it was very good indeed. Sorry to hear your having problems with yours.

Good luck, be interested to hear how you get on.

Tyr

Yes, I got the email for the RSA meet this weekend, and this is probably my best chance to get this sorted properly.

Hopefully, it's just poor collimation and high power that's the problem!

Thanks all, and I'll update you next week.

Boz

[DaBozUK]

So I went to the Reading Astro Soc last night and although no one else brought scopes, I did get confirmation that the scope is collimated well enough and a consensus of opinion that if all the other eyepieces work fine, then the double image of the 9mm must be a flaw.

I need to double check the 40mm EP again, but I'll be sending the 9mm back.

Boz

[DaBozUK]

All credit to Scope n Skies, a new 9mm was returned next day and works a charm.

Boz

[spaceboy]

Glad to hear you got the EP sorted. And more so that you didn't have to wait too long for a replacement.