Svbony Lens issue.

[martin77]

Anyone else had an issue with Svbony red range eyepiece barrels being machined marginally too large? I bought from Amazon a 15mm 1.25" wide angle and it is sticking in the barrel of my Nexstar 4SE. I think it's going back because I am worried about debris dropping into the mirror assembly  - the eyepiece tube on a 4SE is plastic and it is shaving away tiny fragments that could end up God knows where.

[Ricochet]

I don't recall anyone reporting such an issue but there will be be a bit of variation in sizes and at the cheaper end of the market the tolerances are probably not quite so stringent so it isn't a massive surprise that this could happen. If you opt for a replacement you might find that it fits perfectly or you could put the refund money towards a different 15mm if that is a focal length you want to stick with. A 15mm Starguider would be the obvious choice, but there is a nice 15mm Panoptic in the classifieds if it is within your budget and you don't mind the tight eye relief. 

[martin77]

On 21/02/2021 at 19:57, Ricochet said:

I don't recall anyone reporting such an issue but there will be be a bit of variation in sizes and at the cheaper end of the market the tolerances are probably not quite so stringent so it isn't a massive surprise that this could happen. If you opt for a replacement you might find that it fits perfectly or you could put the refund money towards a different 15mm if that is a focal length you want to stick with. A 15mm Starguider would be the obvious choice, but there is a nice 15mm Panoptic in the classifieds if it is within your budget and you don't mind the tight eye relief. 

Thanks Ricochet - I tend as a rule to steer clear of second hand unless I can actually see it but thanks anyway. I may attempt to de-burr it with a dremel as on very close inspection there is just the merest hint of an irregularity on the leading edge of the cloak. The Lens itself is worth perseverance I think.

[Ricochet]

I think of you are going to buy anything second hand online this forum is probably the best place to do so, providing you take precautions. 

With regards to taking a dremmel to the nose piece of your eyepiece, you should find that it unscrews from the main body of the eyepiece. This will allow you to do any modifications safely away from the optical elements inside. 

[fozzybear]

9 minutes ago, Ricochet said:

I think of you are going to buy anything second hand online this forum is probably the best place to do so, providing you take precautions. 

+1

[Louis D]

First, I would go slowly by hand with fine emory cloth if the amount to be removed is localized and of a small amount.  Dremel tools can be very aggressive and will remove a lot of material before you know what happened.  I would use one only as a last resort.

[SiriusB]

Some Variation in ep barrel size & focusser/diagonal bore seems fairly common, least @ the lower end of the market.

 

By way of reference i have an old vixen barlow,(actually an extension tube now as i can't seem to find the lens element!) 😳

Putting a circle T ep into this there's an air cushion effect~ both neither too big or too small.

I'd offer to machine the barrel down to size for you for free, but with the postage both ways, you'd probably find it cheaper to locate a replacement barrel. But the offers there.

Take the barrel off to see what fitment it is & scour the interweb~ only if you really like this ep though.

[SiriusB]

....or if you can take the barrel off & take a picture of both ends maybe some kind soul will take pity & find a replacement in their parts bin.

If it's got female filter thread both ends, that's easiest to find a replacement.

[martin77]

22 hours ago, Louis D said:

First, I would go slowly by hand with fine emory cloth if the amount to be removed is localized and of a small amount.  Dremel tools can be very aggressive and will remove a lot of material before you know what happened.  I would use one only as a last resort.

Agree 100% -  it is a last resort to be honest. The burr is tiny but is enough to just cause particularly extraction to be a bit iffy - I may just live with it but I'm a bit pedantic about such things. 👍

[martin77]

12 minutes ago, SiriusB said:

Some Variation in ep barrel size & focusser/diagonal bore seems fairly common, least @ the lower end of the market.

 

By way of reference i have an old vixen barlow,(actually an extension tube now as i can't seem to find the lens element!) 😳

Putting a circle T ep into this there's an air cushion effect~ both neither too big or too small.

I'd offer to machine the barrel down to size for you for free, but with the postage both ways, you'd probably find it cheaper to locate a replacement barrel. But the offers there.

Take the barrel off to see what fitment it is & scour the interweb~ only if you really like this ep though.

That's brilliant of you and I thank you for your kind and very appreciated offer. Its marginal and I'll probably live with it - it's just the tiny amount of (and it is tiny) of debris that I worry that it may drop onto the mirror.

Thanks once again 🙌

[SiriusB]

You're welcome.

My advice would be to solve the issue one way or another though.