Achromatics "alpha" There is? (1 Viewer)

[Granpoli]

Hello,

I was wondering if all spotting scopes with achromatic lenses provide similar images, I know that the models with ED lenses don't, but with the achromatic ones...???
Has anyone been able to compare "alpha" achromatics with non-alpha achromatics?
cheers
Gpoli.

 

[wllmspd]

The trouble with achromats is that they generate chromatic aberration especially for short focal ratios and high powers that blurs the view. That’s why many scopes use ED glass to correct it to some degree. If you can fit filters you could use one that blocks some of the blue, which will lessen the visual impact, but add a slight colour cast to the image. An alpha achromat would likely be a very long focal ratio to minimise the effect, but would not be very practical. Alphas are nearly universally apochromatic (ie have ED glass in).

Peter

 

[Tringa45]

Prior to the reintroduction of the Swarovski ATS/STS scopes about 2012 there were non-HD versions of the old ATS/STS and ATM/STM scopes.
The 65 mm versions (f/7) were allegedly quite good up to about 30x.

John

 

[Hermann]

The forum knows almost everything. Check this old thread about the Nikon EDIII vs. the Nikon III, especially the posts by Alexis Powell and Henry Link: Fieldscope III ED vs Fieldscope III

Hermann

 

[Hermann]

Prior to the reintroduction of the Swarovski ATS/STS scopes about 2012 there were non-HD versions of the old ATS/STS and ATM/STM scopes.
The 65 mm versions (f/7) were allegedly quite good up to about 30x.

You can go back even further: When Leica introduced their first scopes (the 77mm scopes), they offered an Apo-Televid 77 and a (cheaper Televid) 77. The Televid was OK, but not brilliant, especially not over 30x. The Apo was a lot better at higher magnifications but some difference was visible at 20x already.

Hermann

 

[Hermann]

Had a chance to compare a Nikon Fieldscope EDII with a Nikon Fieldscope II. My mother has both. At magnifications below 30x the Fieldscope II is OK, even though there's some difference in contrast. At higher magnifications the EDII pulls ahead, and the differences are not subtle. I think the Fieldscope II works best with the 20x and the 24x WA eyepieces. At those magnifications the Fieldscope II is perfectly useable.

Edit: The Fieldscope II is an f7 achromat. In other words: It's fairly slow for a birding scope.

Hermann