Finally created nebula filters for my binos. The setup is based on the initial thread about filters for Vixen SG 2.1x42:
- 2x Optolong 2" UHC Filter (eBay, $87.41 + free delivery from a very reputable seller in Taiwan)
- 2x Step Down Ring 58mm-48mm (eBay, $2.56 + free delivery from China)
- 2x Step Down Ring 72mm-58mm (eBay, $3.42 + free delivery from China)
- 2x 72mm Spacer / Adapter Ring, 36mm wide (eBay, $43.98 + $14.00 delivery from USA to Australia)
- 2x 50mm Push-On lens cap (eBay, $4.99 + $5.00 delivery from China to Australia)
- 2x Velcro 21cm/8.27in length ($7.0 for 25mm width 1m long with adhesive back)
All priced are in USD for a lot of 2 items and not per one item.
Initially I ordered 67mm-58mm step down rings and 67mm spacers, but unfortunately I couldn't use 67mm spacers as on the binocular's side of the spacers the inner diameter is just a couple of mm smaller than the outer diameter of the binoculars. I didn't count for that and to be fair it was difficult to predict. Step down rings have very thin outer thread which is great, but the spacers have very thick outer thread. If the spacers had the same thread thickness as step down rings, then there would be no issues at all. If you can cut about 3mm from the spacer that would work as well. Unfortunately it would be way too much effort for me so I ordered 72mm-58mm step down rings and 72mm spacers instead. There are plenty of options for 67mm spacers/adapter rings including noname filter adapter tubes for Panasonic Lumix DMC-FZ200 camera. Not much for 72mm, but they are still available.
Inner diameter of 2" filters is 46 - 48mm, a bit smaller than 50mm, so technically you will have 10x46 binoculars.
We've got a very rainy season right now in Sydney, so I couldn't do a proper and long test so I tested them in short periods between rains. Tested on M42 Orion Nebula, M8 Lagoon Nebula and M20 Trifid Nebula from my quite light polluted backyard with 10x50 mounted on a tripod and I'd say the results were amazing!
M42 Orion Nebula (diffuse nebula in Orion)
- Without filters: Small patch, but with decent visibility.
- With filters: Very good visibility, very good separation between light and dark areas. Distinctively larger than without the filter - much more outlying nebulosity is visible.
M8 Lagoon Nebula (diffuse nebula in Sagittarius)
- Without filters: Faint, but clearly visible.
- With filters: Same as for the Orion Nebula - Very good visibility, large boost in contrast, very good separation between light and dark areas. Distinctively larger than without the filter - much more outlying nebulosity is visible.
M20 Trifid Nebula (diffuse emission/reflection nebula in Sagittarius)
- Without filters: Couldn't see it at all. I just knew it had to be there.
- With filters: Small, faint, but clearly visible.
Conclusion: Definitely worth money and effort.