24 replies to this topic

[jim_s]

I've got a Meade Series 5000 20mm Ultra Wide Angle Eyepiece that I'm using on my Zhumell Z8. I LOVE this eyepiece! In order to be able to focus with it, however, I need to pull it back about 1/4" from fully inserted, otherwise I can't get it to focus. I generally just sort of do it by feel in the dark, and the clamping mechanism of the focuser assembly seems to do a pretty good job of keeping everything aligned.  I'd ideally like to purchase or make a spacer, however, that I could mount onto the eyepiece, so that I #1 didn't have to fiddle with it in the dark, and #2 it'd be firmly (ie, all lined up nicely in the focuser) and consistently positioned.  Is something like this made? Also, is this a normal type of problem that people face with an eyepiece like this?

 

I have a metal lathe, and can turn something appropriate fairly easily, but if something pre-made (probably of nicer quality than I'd make in my basement, LoL) is available, and is not ridiculously expensive, I'd definitely lean toward that.

 

Thanks for any help!

[GGK]

I've got a Meade Series 5000 20mm Ultra Wide Angle Eyepiece that I'm using on my Zhumell Z8. I LOVE this eyepiece! In order to be able to focus with it, however, I need to pull it back about 1/4" from fully inserted, otherwise I can't get it to focus. I generally just sort of do it by feel in the dark, and the clamping mechanism of the focuser assembly seems to do a pretty good job of keeping everything aligned.  I'd ideally like to purchase or make a spacer, however, that I could mount onto the eyepiece, so that I #1 didn't have to fiddle with it in the dark, and #2 it'd be firmly (ie, all lined up nicely in the focuser) and consistently positioned.  Is something like this made? Also, is this a normal type of problem that people face with an eyepiece like this?

 

I have a metal lathe, and can turn something appropriate fairly easily, but if something pre-made (probably of nicer quality than I'd make in my basement, LoL) is available, and is not ridiculously expensive, I'd definitely lean toward that.

 

Thanks for any help!

It sounds like you just need a 1-1/4 barrel extension that screws into the eyepiece barrel <filter> threads.  Like this one or any other brand:  https://farpointastr...AiABEgKwtfD_BwE

 

Sorry, just reread your title and saw you need a 2" extension.  I use the Tele Vue barrel extension.  It's very nice:  https://www.bhphotov...xtension_2.html

 

Gary

Edited by GGK, 15 June 2022 - 04:06 PM.

[jim_s]

It sounds like you just need a 1-1/4 barrel extension that screws into the eyepiece barrel <filter> threads.  Like this one or any other brand:  https://farpointastr...AiABEgKwtfD_BwE

 

Gary

Thanks, Gary - I saw those types of things, but it doesn't appear that something like that is going to help, as there is nothing inside the focuser that an extension on the 2" eyepiece barrel will bottom out against - the inside of the focuser is smooth the entire way through. Any extension is just going to sit farther down in the focuser barrel, but won't actually result in the eyepiece being positioned any further out of the focuser.  It is the shoulder of the larger diameter part of the eyepiece that bottoms out against the top surface of the focuser and that is resulting in the eyepiece being a bit too far down in there to focus properly. I think I need something that goes around the exterior of the eyepiece barrel, and effectively extends the shoulder of the eyepiece by about 1/4", so that the eyepiece sits a little higher in the focuser, and can thus focus properly. (LMK if I'm not understanding something basic, but I've felt around inside the focuser barrel, and can find nothing that an extension on the end of the eyepiece barrel would stop up against.)

 

Thanks Again!

[Ihtegla Sar]

Thanks, Gary - I saw those types of things, but it doesn't appear that something like that is going to help, as there is nothing inside the focuser that an extension on the 2" eyepiece barrel will bottom out against - the inside of the focuser is smooth the entire way through. Any extension is just going to sit farther down in the focuser barrel, but won't actually result in the eyepiece being positioned any further out of the focuser. It is the shoulder of the larger diameter part of the eyepiece that bottoms out against the top surface of the focuser and that is resulting in the eyepiece being a bit too far down in there to focus properly. I think I need something that goes around the exterior of the eyepiece barrel, and effectively extends the shoulder of the eyepiece by about 1/4", so that the eyepiece sits a little higher in the focuser, and can thus focus properly. (LMK if I'm not understanding something basic, but I've felt around inside the focuser barrel, and can find nothing that an extension on the end of the eyepiece barrel would stop up against.)

Thanks Again!

Maybe a parfocal ring would help with that. https://www.amazon.c...1/dp/B00578MBN4

[jim_s]

Maybe a parfocal ring would help with that. https://www.amazon.c...1/dp/B00578MBN4

Ahh... Ok, that looks like what I need. Different diameter, but there's a 2" ring here: https://www.amazon.c...s/dp/B074FQZLTK and here https://www.amazon.c...s/dp/B073SNKZXX
 
I hate the idea of grub screws tightening directly against the eyepiece barrel (grub screws inevitably seem to eventually leave divots) - wonder if this one is a generic 2" ID? https://www.bhphotov...uning_stop.html
 
Thanks - That seems to be the path I need to follow!!

Edited by jim_s, 15 June 2022 - 04:44 PM.

[ButterFly]

Something like this is much cheaper that a parfocal ring, and can be used on other eyepieces if needed.  It is much, much cheaper than Televue's barrel extender.

 

There are M48 male threads at the top to screw onto the eyepiece like a filter would.  There is also a flange at the top to seat onto the focuser.  It effectively adds an extension equal to the eyepiece's barrel.  There are M48 female threads at the bottom to accept 2" filters like the eyepiece would.

 

 

 

Notice how the title is ridiculous, and thus incredibly hard to search for.

 

https://www.amazon.c.../dp/B07QV8RNB8/

[GGK]

Something like this is much cheaper that a parfocal ring, and can be used on other eyepieces if needed.  It is much, much cheaper than Televue's barrel extender.

 

There are M48 male threads at the top to screw onto the eyepiece like a filter would.  There is also a flange at the top to seat onto the focuser.  It effectively adds an extension equal to the eyepiece's barrel.  There are M48 female threads at the bottom to accept 2" filters like the eyepiece would.

 

 

 

Notice how the title is ridiculous, and thus incredibly hard to search for.

 

https://www.amazon.c.../dp/B07QV8RNB8/

Nice. I've not seen one of those before.

[ButterFly]

One came with my filter wheel. They also work to hide the 1.25" portion of Ethos', and I can use 2" filters with it.

[GGK]

One came with my filter wheel. They also work to hide the 1.25" portion of Ethos', and I can use 2" filters with it.

Do you know the total optical length (minus the male M48 threads)?  The TV barrel extender is high quality, but I wish it was shorter when I use it on the Ethos. 

[ButterFly]

Do you know the total optical length (minus the male M48 threads)?  The TV barrel extender is high quality, but I wish it was shorter when I use it on the Ethos. 

The two inch portion of the extended goes into the focuser.  It's total optical path length depends on the length of the eyepiece barrels.  It's path length is the size of the flange (~2mm), plus whatever the distance is to the bottom of your eyepiece barrel from its shoulder.  For the Ethos, it's the distance from the shoulder to the bottom of the 2" skirt, which has M48 threads.

[jim_s]

Something like this is much cheaper that a parfocal ring, and can be used on other eyepieces if needed.  It is much, much cheaper than Televue's barrel extender.
 ...

Huh, that's a kind of cool option!

In my case though, I have to wonder if it wouldn't move my problem to the other end of the scale? Instead of the eyepiece sitting too close to the focuser, I have to wonder if it wouldn't put the eyepiece too far from the focuser, as the barrel length of my 20mm eyepiece is a good 1.5"? Add to that what looks like about .25" for the shoulder on that adapter, and that'd move the eyepiece around 1.75" out. (I've never tried to see how far out it could sit, and still be focusable.) I also fear it might end up a bit unwieldy to have the bulk of the (very bulky) eyepiece hanging that far out. (It's what I think people refer to as a 'hand grenade' style eyepiece.)

 

I appreciate the tip on that extender - it'd definitely keep it from going too far in!  I'll keep the existence of that type of thing in mind for future conundrums. (And you're right, that product name seems like it's specifically intended to limit sales, LoL! :-)  I ended up ordering a pair of inexpensive 5mm parfocal rings ($14 total), which look like they'll be about the perfect thickness to get it about to where I normally leave it hanging out a little bit.

 

Thanks for everyone's help!!

[Kunama]

I recently modified my TV Nagler 12mm T4 to be parfocal with my Nagler 22mmT4 and almost parfocal with the N31T5.

I asked a friend to make a barrel extender 25mm long and a parfocalising ring 30mm wide......

 

 

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[Waynosworld]

I've got a Meade Series 5000 20mm Ultra Wide Angle Eyepiece that I'm using on my Zhumell Z8. I LOVE this eyepiece! In order to be able to focus with it, however, I need to pull it back about 1/4" from fully inserted, otherwise I can't get it to focus. I generally just sort of do it by feel in the dark, and the clamping mechanism of the focuser assembly seems to do a pretty good job of keeping everything aligned.  I'd ideally like to purchase or make a spacer, however, that I could mount onto the eyepiece, so that I #1 didn't have to fiddle with it in the dark, and #2 it'd be firmly (ie, all lined up nicely in the focuser) and consistently positioned.  Is something like this made? Also, is this a normal type of problem that people face with an eyepiece like this?

 

I have a metal lathe, and can turn something appropriate fairly easily, but if something pre-made (probably of nicer quality than I'd make in my basement, LoL) is available, and is not ridiculously expensive, I'd definitely lean toward that.

 

Thanks for any help!

Your Zhumell Z8 should have come with an extension, I have to use an extension on my large dobs when I do not use a Coma Corrector, this is something that I have got used to, I thought all Zhumell dobs came with extensions, maybe you bought it used?

 

I would just buy a 20mm to 35mm extension and be done with this issue as you will likely have issues with other eyepieces also.

[jim_s]

Your Zhumell Z8 should have come with an extension, I have to use an extension on my large dobs when I do not use a Coma Corrector, this is something that I have got used to, I thought all Zhumell dobs came with extensions, maybe you bought it used?

 

I would just buy a 20mm to 35mm extension and be done with this issue as you will likely have issues with other eyepieces also.

Hmm... Yes, I bought the Z8 as a parts/incomplete deal off eBay years ago - it had no base, and no finder, but I thought everything else was there - sounds like maybe the extender you mention was also missing, though.

 

So far, it's only the 2" eyepiece that's had this focusing problem (the other eyepieces I have are all 1.25", BUT there is a little adapter that those fit into, which fits into the 2" focuser, and it just so happens to lift those smaller eyepieces about 1/2" up from the edge of the focuser, so I bet that's why I'm not having the problem w/ the 1.25" eyepieces!

 

At present, I have just the one 2" eyepiece, so the parfocal ring should get things set right on that one, but if I end up with more 2" eyepieces, I'll definitely need to get one of the extenders.

 

Thanks for solving this mystery!!

[MadHungarian]

Agena Astro used to have a bunch of random misc stuff like this.  Maybe they have/had spacers as well.

[havasman]

https://www.astronom...nsion-tube.html

 

That's made for your problem and yes it is common for Zhumell Dobs to need one. And you can get nylon screws to replace the ones that might scratch your eyepiece barrels at a good hardware store or McMaster-Carr's website.

[Chad7531]

Your Zhumell Z8 should have come with an extension, I have to use an extension on my large dobs when I do not use a Coma Corrector, this is something that I have got used to, I thought all Zhumell dobs came with extensions, maybe you bought it used?

I would just buy a 20mm to 35mm extension and be done with this issue as you will likely have issues with other eyepieces also.

I thought all the GSO reflectors needed 35mm extensions too, so when I got my older z10 used I bought one because it didn’t come with one. I couldn’t reach focus with it, took it off and turned out it didn’t need any extensions at all. Weird.

I haven’t tried my 2” EP but it’s parfocal with my 1.25 EPs in their 2”-1.25 reducer, which is pretty cool.

[Chad7531]

Your Zhumell Z8 should have come with an extension, I have to use an extension on my large dobs when I do not use a Coma Corrector, this is something that I have got used to, I thought all Zhumell dobs came with extensions, maybe you bought it used?

I would just buy a 20mm to 35mm extension and be done with this issue as you will likely have issues with other eyepieces also.

I thought all the GSO reflectors needed 35mm extensions too, so when I got my older z10 used I bought one because it didn’t come with one. I couldn’t reach focus with it, took it off and turned out it didn’t need any extensions at all. Weird.

I haven’t tried my 2” EP in it yet but it’s parfocal with my 1.25 EPs in their 2”-1.25 reducer, which is pretty cool.

[Noto]

Your Zhumell Z8 should have come with an extension, I have to use an extension on my large dobs when I do not use a Coma Corrector, this is something that I have got used to, I thought all Zhumell dobs came with extensions, maybe you bought it used?

 

I would just buy a 20mm to 35mm extension and be done with this issue as you will likely have issues with other eyepieces also.

I have an extension that came with my Orion XT8+. However, I only need it for one, 2-inch EP in my line up. It's more of a pain in the butt to use the extension, and I found myself not using a very nice EP.

 

Hmm... Yes, I bought the Z8 as a parts/incomplete deal off eBay years ago - it had no base, and no finder, but I thought everything else was there - sounds like maybe the extender you mention was also missing, though.

 

So far, it's only the 2" eyepiece that's had this focusing problem (the other eyepieces I have are all 1.25", BUT there is a little adapter that those fit into, which fits into the 2" focuser, and it just so happens to lift those smaller eyepieces about 1/2" up from the edge of the focuser, so I bet that's why I'm not having the problem w/ the 1.25" eyepieces!

 

At present, I have just the one 2" eyepiece, so the parfocal ring should get things set right on that one, but if I end up with more 2" eyepieces, I'll definitely need to get one of the extenders.

 

Thanks for solving this mystery!!

However, I went to ACE Hardware and purchased a few rubber O-rings for about $1. I stack 3 (about 3/8-1/2"), and it works just fine (and I leave them on the EP when stored).

 

I also thought about cutting down different pipe fittings, but the materials, time, and tools required were way beyond slipping on a few O-rings.

 

Hope this helps.

 

Edited by Noto, 16 June 2022 - 12:17 PM.

[Neanderthal]

Mirror position can have an impact on reaching focus. I took a photo of the Focuser position when reaching the Focal Plane on my AD8, as I was having difficulty reaching focus in a couple situations. It's really easy to see where yours is at with a piece of scotch tape and the moon. 

 

This thread documents my battle of the focus, lol.   https://www.cloudyni...ession-tonight/

[Waynosworld]

Hmm... Yes, I bought the Z8 as a parts/incomplete deal off eBay years ago - it had no base, and no finder, but I thought everything else was there - sounds like maybe the extender you mention was also missing, though.

 

So far, it's only the 2" eyepiece that's had this focusing problem (the other eyepieces I have are all 1.25", BUT there is a little adapter that those fit into, which fits into the 2" focuser, and it just so happens to lift those smaller eyepieces about 1/2" up from the edge of the focuser, so I bet that's why I'm not having the problem w/ the 1.25" eyepieces!

 

At present, I have just the one 2" eyepiece, so the parfocal ring should get things set right on that one, but if I end up with more 2" eyepieces, I'll definitely need to get one of the extenders.

 

Thanks for solving this mystery!!

 

When I said you will likely have issues with other eyepieces I was thinking about 2" eyepieces.

 

When I first bought my 14.5" Starsplitter I had the exact opposite issue, I did not have enough in focus/travel for my Meade 14mm UWA 4000 series eyepiece, but I was wanting to look at the planets, specifically Mars at the time so I really had no other 2" eyepieces. but as time passed Mars went away and I bought the book "Turn Left at Orion" and started searching for DSOs which was a new thing for me, searching for DSOs with a Meade 14mm or 8.8mm UWA 4000 series eyepieces is a challenge so I bought a 35mm Panoptic, well that was the best eyepiece for me as it actually gave me a FOV to use compared to all my other high power eyepieces, it is the eyepiece I use the most now although Mars is returning this year.

 

You are better off just buying an extension and having it when you start buying more eyepieces, it is not an expensive item and it is better to have it when you need it rather than to not have it and being upset with yourself for not getting one.

 

I fixed mt Starsplitter by putting in much taller heavier duty springs, but your not going to fix your issue with shorter springs on a  Zhumell Z8, you can put a spacer under your focuser like my Z12 has, but that possibly could start causing issues with your 1.25" eyepieces depending if any of them are close to having the focuser racked all the way in when using them.

[CowTipton]

Ahh... Ok, that looks like what I need. Different diameter, but there's a 2" ring here: https://www.amazon.c...s/dp/B074FQZLTK and here https://www.amazon.c...s/dp/B073SNKZXX
 
I hate the idea of grub screws tightening directly against the eyepiece barrel (grub screws inevitably seem to eventually leave divots) - wonder if this one is a generic 2" ID? https://www.bhphotov...uning_stop.html
 
Thanks - That seems to be the path I need to follow!!

I have that Hyperion 2" ring.  It's right around 1/4" wide if I recall correctly.  Maybe perfect for you.

Mine sits permanently on my Paracorr 2 exactly 48mm behind the shoulder as a replacement for my focuser's extension tube.

I haven't noticed any scratches but then I haven't removed it either.  All I do is measure every now and then with a caliper to make sure it hasn't moved (it hasn't.)

[n2dpsky]

I hate the idea of grub screws tightening directly against the eyepiece barrel (grub screws inevitably seem to eventually leave divots) - wonder if this one is a generic 2" ID? https://www.bhphotov...uning_stop.html
 

I use this Baader ring on my Coma Corrector.  It's excellent.

[jim_s]

I have that Hyperion 2" ring.  It's right around 1/4" wide if I recall correctly.  Maybe perfect for you.

Mine sits permanently on my Paracorr 2 exactly 48mm behind the shoulder as a replacement for my focuser's extension tube.

I haven't noticed any scratches but then I haven't removed it either.  All I do is measure every now and then with a caliper to make sure it hasn't moved (it hasn't.)

Yes, that Hyperion ring looks really nice, in that it appears to have an internal fastening collar, so the grub screws seem to bear on that inner ring, and not directly on the eyepiece. I like @havasman's suggestion of getting nylon set screws for the parfocal rings. While I agree that having a 'universal' solution would be ideal, until such time as I end up with more than two 2" eyepieces (at present, I have only one 2" EP, but ordered a pair of parfocal rings), the parfocal rings should be sufficient.

Edited by jim_s, 16 June 2022 - 03:05 PM.

[Starman1]

I've got a Meade Series 5000 20mm Ultra Wide Angle Eyepiece that I'm using on my Zhumell Z8. I LOVE this eyepiece! In order to be able to focus with it, however, I need to pull it back about 1/4" from fully inserted, otherwise I can't get it to focus. I generally just sort of do it by feel in the dark, and the clamping mechanism of the focuser assembly seems to do a pretty good job of keeping everything aligned.  I'd ideally like to purchase or make a spacer, however, that I could mount onto the eyepiece, so that I #1 didn't have to fiddle with it in the dark, and #2 it'd be firmly (ie, all lined up nicely in the focuser) and consistently positioned.  Is something like this made? Also, is this a normal type of problem that people face with an eyepiece like this?

 

I have a metal lathe, and can turn something appropriate fairly easily, but if something pre-made (probably of nicer quality than I'd make in my basement, LoL) is available, and is not ridiculously expensive, I'd definitely lean toward that.

 

Thanks for any help!

For that little space, a parfocalizing ring would do it:

https://www.amazon.c...s/dp/B073SNKZXX