DIY 10mm Eyepiece and Performance Comparison

[Rocket_the_Raccoon]

The Ingredients :
1. eyepiece scavenged from a pair of 10x25mm compact binoculars
2. 1.25" eyepiece barrel scavenged from a low quality Huygens 8mm
3. PVC SCH-40 3/4"x1/2" adapter as the "inner barrel" of the eyepiece
4. baffle from a 5x24mm finder as the "top cap" of the eyepiece (not used)
5. chalkboard stickers for fitting of (1), (2), and (3) above
6. E6000 crafting glue
7. Tamiya XF-1 flat-black model paint for blackening (2) and (3)

 VS 

 

The Performance Comparison :
- the DIY 10mm is a 1-2 König, coated at least on air-glass surfaces
- my veteran Omcon Plossl 10mm is a Celestron silver-top equivalent, edges darkened, but fully coated only
- tested on a f/5.7 refractor using the moon (sharpness, field of view, brightness), Jupiter (contrast, brightness), and Vega (edge distortion) 

1. TFOV - the DIY EP is obviously wider
2. Centre Sharpness - about the same, the DIY EP might be very slightly sharper
3. Edge Sharpness - Omcon Plossl is better
3. Edge Distortion - Omcon Plossl is better
4. Image Brightness - the DIY EP gives slightly brighter images
5. Contrast - Omcon Plossl is better

 

[timwetherell]

Great to see someone experimenting with optics! It's a lot of fun and can yield some surprisingly good results  

I have an old Erfle 20mm scavenged from something like a gun sight? Back when I had my little 60mm refractor with it's nasty eyepieces I'd always wanted an Erfle because Patrick Moore raved about them. I guess back in the long long ago before things like Naglers were common, that was about the best one could do. My Erfle isn't particularly brilliant optically compared to modern offerings but it has a high nostalgia value!

 

[John]

Good stuff Rocket !

Way back when I had my 1960's Tasco 60mm refractor I realised that the stock hygens 1 inch eyepieces were pretty limited and I wanted a wider field so I nicked the eyepiece from our family pair of 8x30 binoculars. A bit of tape around the barrell to make it fit the diagonal socket and I had a Kellner or Achromatic Ramsden (never sure which it was) of around 17mm focal length but with no field stop fitted so an apparent field of around 60 degrees I guess. At last I could see clusters, the Orion Nebula etc in a decently wide field. The Tasco was F/13.3 so the edges of the FoV were not too bad and the view felt like a proper "picture window" into space

Got me hooked on wide fields of view, that venture, and thats cost me a fair bit over the intervening years !

[Rocket_the_Raccoon]

8 hours ago, timwetherell said:

Great to see someone experimenting with optics! It's a lot of fun and can yield some surprisingly good results  

Thanks and yes, I was surprised how well the eyepiece performs given its cost. I have also made a DIY 33mm but instead of scavanged from binoculars eyepiece, it was built from scratch with binoculars objective lenses. I am in the process of some final performance testing and will write up a post once it is done.

8 hours ago, timwetherell said:

I have an old Erfle 20mm scavenged from something like a gun sight? Back when I had my little 60mm refractor...

I think some of the wide -field binculars use Erfle eyepieces too.

8 hours ago, timwetherell said:

My Erfle isn't particularly brilliant optically compared to modern offerings but it has a high nostalgia value!

Indeed! I treasure my DIY eyepieces despite their costs, it is the efforts and accomplishments that matter.

[Rocket_the_Raccoon]

7 hours ago, John said:

Good stuff Rocket

Thank you!

7 hours ago, John said:

Way back when I had my 1960's Tasco 60mm refractor I realised that the stock hygens 1 inch eyepieces were pretty limited and I wanted a wider field so I nicked the eyepiece from our family pair of 8x30 binoculars. A bit of tape around the barrell to make it fit the diagonal socket and I had a Kellner or Achromatic Ramsden (never sure which it was) of around 17mm focal length but with no field stop fitted so an apparent field of around 60 degrees I guess. At last I could see clusters, the Orion Nebula etc in a decently wide field. The Tasco was F/13.3 so the edges of the FoV were not too bad...

Almost all long 60mm refractors have above average objective lenses. I used to own a f/15 and I still remembered the view of the Trapezium at the heart of M42 at 150x with a 6mm Ortho.

Also, I have a similar DIY ~18mm eyepiece like yours, scavanged from an old 10x50mm binoculars but mine is not wide field, possibly a Kellner. It actually has better edge sharpness than my Celestron 3-element 20mm (1-2 modified König) on my f/5.7 refractor.