29 replies to this topic

[symbiosis]

I've been asked by my local makerspace to run a class on building a basic Dobsonian -- a parent/child sort of project. I'm sourcing material for 4.5" f/8 kit, but need an inexpensive, but serviceable eyepiece(s) for hopefully no more than $30. I'm trying to keep the total cost for each person to $200 for the build, so it may be a case of sending them home with a single, compromise e.p. -- I'm thinking a 10mm.

 

Obviously, 4.5" is a beginner project, and if anyone walks away from the class with a serious interest, they'll be upgrading and can get a better quality e.p. then.

 

TIA.

Edited by symbiosis, 05 April 2025 - 04:48 PM.

[Jim Waters]

FYI

https://agenaastro.c...anufacturer=GSO

[kwyjibo]

https://www.amazon.c...9kZXRhaWwy&th=1

[EsaT]

I'm thinking a 10mm.

About 10mm would be good start for the Moon and planets.

But for outside solar system objects it would be limited and good for only very compact fuzzies or small asterisms/clusters.

Showpiece objects like Orion Nebula or Pleiades would need lower magnification for balanced view between brightness and image size, or far lower magnification and wider view.

[Mike W]

25mm would be MUCH better!

[Tony Cifani]

I've been asked by my local makerspace to run a class on building a basic Dobsonian -- a parent/child sort of project. I'm sourcing material for 4.5" f/8 kit, but need an inexpensive, but serviceable eyepiece(s) for hopefully no more than $30. I'm trying to keep the total cost for each person to $200 for the build, so it may be a case of sending them home with a single, compromise e.p. -- I'm thinking a 10mm.

 

Obviously, 4.5" is a beginner project, and if anyone walks away from the class with a serious interest, they'll be upgrading and can get a better quality e.p. then.

 

TIA.

How soon is the class and how many students are you expecting (...how many eyepieces do you have to purchase)?

 

I think a 10mm eyepiece at 91x will be difficult for beginners as they will be using this to locate objects in the night sky.

 

If you can swing two of these - a 20mm and a 9mm (66 degree) - great. If just one eyepiece, I'd go with the 15mm.

 

https://www.svbony.c...epieces/#F9157C

[T1R2]

How soon is the class and how many students are you expecting (...how many eyepieces do you have to purchase)?

 

I think a 10mm eyepiece at 91x will be difficult for beginners as they will be using this to locate objects in the night sky.

 

If you can swing two of these - a 20mm and a 9mm (66 degree) - great. If just one eyepiece, I'd go with the 15mm.

 

https://www.svbony.c...epieces/#F9157C

Unfortunately the 9mm 66* suffers from Edge of Field Brightening and Kidney Beaning pretty badly. I think its the worst of the set,  The 20mm has about the same tfov as a 32mm plossl, so that's good, I thought the 15mm was ok also.  

[Tony Cifani]

Unfortunately the 9mm 66* suffers from Edge of Field Brightening and Kidney Beaning pretty badly. I think its the worst of the set,  The 20mm has about the same tfov as a 32mm plossl, so that's good, I thought the 15mm was ok also.  

I know. I've heard, but the criteria is for under $30. There's not a lot of choices available unfortunately. I was thinking maybe a couple of Svbony Plossl eyepieces, but even those would exceed $30 for two and availability was questionable from what I could find online (looking at 25mm and 10mm).

[EsaT]

I know. I've heard, but the criteria is for under $30. There's not a lot of choices available unfortunately. I was thinking maybe a couple of Svbony Plossl eyepieces, but even those would exceed $30 for two and availability was questionable from what I could find online (looking at 25mm and 10mm).

That budget limit is definitely challenge.

 

Maybe 25mm Plössl eyepiece and 3x Barlow would give the most for such budget...

Assuming Barlow has detachable lens cell giving ~1.5x multiplier that would give ~17mm, which would have very good balance between brightness and image size for say Orion Nebula.

And full Barlowing would give ~8mm, which is very good start for the Moon and planets and without short eye relief issues of most cheap short focal length eyepieces.

[symbiosis]

How soon is the class and how many students are you expecting (...how many eyepieces do you have to purchase)?

 

I think a 10mm eyepiece at 91x will be difficult for beginners as they will be using this to locate objects in the night sky.

 

If you can swing two of these - a 20mm and a 9mm (66 degree) - great. If just one eyepiece, I'd go with the 15mm.

 

https://www.svbony.c...epieces/#F9157C

I'm just putting together a synopsis/syllabus now -- so have no idea yet how many students. I'm expecting no more than a handful. I'm seeing the challenge on eyepieces and thinking it might be an item that I kick in a bit of my own money for, if necessary. I would really like to see the folks walk away from the class with something that could potentially get them into the hobby, and I know a crappy eyepiece is just that. I'm also looking online for used copies of "Turn Left at Orion", which I think is a book that ought to be packaged with every beginner telescope!

Edited by symbiosis, 06 April 2025 - 09:57 AM.

[Mike W]

I'm just putting together a synopsis/syllabus now -- so have no idea yet how many students. I'm expecting no more than a handful. I'm seeing the challenge on eyepieces and thinking it might be an item that I kick in a bit of my own money for, if necessary. I would really like to see the folks walk away from the class with something that could potentially get them into the hobby, and I know a crappy eyepiece is just that. I'm also looking online for used copies of "Turn Left at Orion", which I think is a book that ought to be packaged with every beginner telescope!

I would include a cheap planisphere

[GrassLakeRon]

As Mr. Waters said a GSO Plossl from Agena Astro. Best ep, my opinion, for less then $30.

[star acres]

My 2 cents: My 9 MM SvBony is the favorite of the batch.  I probably use it more than any eyepiece. 68 degrees and 18 MM eye relief. It's comfortable. 

[Tony Cifani]

Unfortunately the 9mm 66* suffers from Edge of Field Brightening and Kidney Beaning pretty badly. I think its the worst of the set,  The 20mm has about the same tfov as a 32mm plossl, so that's good, I thought the 15mm was ok also.  

Edge of field brightening aside, would the kidney bean blackout effect be less pronounced in a slower F/8 reflector like OP is talking about making? What kind of telescope did you experience this problem with the 9mm 66º EP?

[T1R2]

Edge of field brightening aside, would the kidney bean blackout effect be less pronounced in a slower F/8 reflector like OP is talking about making? What kind of telescope did you experience this problem with the 9mm 66º EP?

This was in my 60mm f13.3 refractor, so it didn't seem to make a difference. IIRC it was about the same in my f6.5 AR127

[pregulla]

For a single eyepiece a zoom would probably be a best choice. Svbony 7-21mm seems to fit your budget

[jrmacl]

For a single eyepiece a zoom would probably be a best choice. Svbony 7-21mm seems to fit your budget

yup $29.99

 

https://www.svbony.c...v-52-36-degree/

 

edit: oh I didn't know above was a link even cheaper, well here's another source and also they are $50 on amazon but were $34 last week

Edited by jrmacl, 08 April 2025 - 03:48 PM.

[jrmacl]

symbiosis, on 05 Apr 2025 - 2:48 PM, said:

I've been asked by my local makerspace to run a class on building a basic Dobsonian -- a parent/child sort of project. I'm sourcing material for 4.5" f/8 kit, but need an inexpensive, but serviceable eyepiece(s) for hopefully no more than $30. I'm trying to keep the total cost for each person to $200 for the build, so it may be a case of sending them home with a single, compromise e.p. -- I'm thinking a 10mm.

Obviously, 4.5" is a beginner project, and if anyone walks away from the class with a serious interest, they'll be upgrading and can get a better quality e.p. then.

TIA.

Also check out the links in the "cheap 32mm Plossl" thread, it really blew my mind- $4 for SV131's and $6.50 for celestron omni's. You could buy a whole set of ep's for $30

Posted Yesterday, 10:05 PM
https://www.aliexpre...rch|query_from:
or

https://www.aliexpre...rch|query_from:
 

Edited by jrmacl, 08 April 2025 - 04:22 PM.

[SporadicGazer]

  ... and also they are $50 on amazon but were $34 last week

I see a coupon, so $42.50 on Amazon right now, but honestly that's not much of a deal compared to prices even a few months ago.

 

Plus no quick Prime delivery so it's probably out at the warehouse, with more stock expected.

[EsaT]

For a single eyepiece a zoom would probably be a best choice. Svbony 7-21mm seems to fit your budget

Except it fails badly in single eyepiece idea, because of being super narrow zoomed out and needs 25mm or 32mm Plössl to get wide view to fit in for example Pleiades and to get views of Milky Way's star rich areas.

25mm Plössl would be toward 80% wider and 32mm Plössl over 100% wider...

Edited by EsaT, 11 April 2025 - 06:28 AM.

[Jon Isaacs]

Edge of field brightening aside, would the kidney bean blackout effect be less pronounced in a slower F/8 reflector like OP is talking about making? What kind of telescope did you experience this problem with the 9mm 66º EP?

 

I had the generic 9 mm version, I bought it more than 20 years ago and I literally wore the paint off it. I never had difficulty finding the exit pupil nor with blackouts... 

 

It's an inexpensive eyepiece, what are the positives? It offers a wide, well corrected field with a reasonable amount of eye relief.. 

 

 

I would see what Bill Vorce at the Telescope-Warehouse.com has to offer. I would contact him via Email 

 

He has supplies of entry level equipment including 4.5 inch F/8 mirror sets. He has 32 mm Plossls that are fully coated for about $23

 

https://telescope-wa...ses-great-value

 

He's a good guy.

 

Jon

Edited by Jon Isaacs, 11 April 2025 - 08:32 AM.

[ryanr256]

High Point has the Meade 26mm super plossl for $19.95:

https://www.highpoin...plossl-eyepiece

The 9.7, 15 and 20 are $19.95 also.

[symbiosis]

So, on advice here, I ordered the SVBony 7-21mm zoom. I haven't had a chance to try it, but immediately out of the package, there is something really wrong. Don't know if this is silicone or what. it's not on the outside surfaces of the glass, but internal. Bizarre.

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[jrmacl]

So, on advice here, I ordered the SVBony 7-21mm zoom. I haven't had a chance to try it, but immediately out of the package, there is something really wrong. Don't know if this is silicone or what. it's not on the outside surfaces of the glass, but internal. Bizarre.

yeah, return that one. did you get it on amazon or the svbony store?

[symbiosis]

yeah, return that one. did you get it on amazon or the svbony store?

yes, from Svbony.