3 replies to this topic

[Lucullus]

The Lunt 16mm Flat-Field Eyepiece says on it's circumference that it's "optimized at 656nm". Does this mean it's a disadvantage to use it for nighttime observing? How would such an optimization manifest itself in nighttime observing?

[SporadicGazer]

The Lunt 16mm Flat-Field Eyepiece says on it's circumference that it's "optimized at 656nm". Does this mean it's a disadvantage to use it for nighttime observing? How would such an optimization manifest itself in nighttime observing?

As I understand it they've tweaked the coatings slightly.  So, *IFF* everything else is perfect I guess it would be slightly worse than that same EP with equal quality conventional coatings.  (But when has everything else ever been perfect?  I'd just use it until I found something that worked better for me... or forever, whichever came first.)

[SeattleScott]

Ok so 656, seems like that’s in the red band? So higher transmission in red. Probably a warm tone to images. Subtle detail, but faint fuzzies might appear a little fainter, colorful stars might appear a little more colorful, and gas giants might look a touch better. That would be my guess.

But ultimately it will work fine for general purpose night viewing. Perhaps not quite as good as some eyepieces on certain targets, but nothing to sweat over.

[ChristianG]

Hello.

 

I have all 5 Lunt "Optimized at 656 nm" eyepieces. Got them for a very good price from Astronomers Without Borders a few years ago.

 

While I consider them excellent all-around eyepieces, with decent AFOV (especially the 19 mm) and good eye relief, I have always been suspicious of the so-called optimization for red light. To me the coatings looks quite typical. I have never detected any color tinge while using them. They are mechanically very similar to some "Flat Field" eyepieces once sold under a different name, but I was never able to compare the coatings.

 

That said, I have only used them for regular night astronomy and spotting-scope duty. That's because my 60 mm Lunt H-alpha (also bought from AWB) has a 7-21 mm zoom permanently in its case, and that works well. Cheers!

 

--Christian

 

Edited by ChristianG, 25 May 2025 - 07:52 PM.