Question for the expert optics members? (1 Viewer)

G

giosblue

Well-known member

• Dec 20, 2015

• #1

If you have a scope with a focal lengths of say 450mm with a fixed 30x
and lets say if has 100% resolution.

If you increase the focal length of the scope the magnification goes up, lets say in this case to 40x. Does it still retain it 100% resolution?

The reason I'm asking is this. On the Opticron ER80 with the SDLv2 EP, the zoom range is 20x60, but on the HR80 it's 24x72.
If we say the zoom is just usable at 60x on the ES, does this mean at 60x on the HR80 its better than the ES, because you still have some zoom left?
I suppose what I'm really asking is, do you get more out of your optics by increasing the focal length of the scope?

Ron

 

FrankD

Well-known member

• Dec 20, 2015

• #2

It isn't that simple. The two scopes you are comparing have two different optical systems. It isn't just a longer focal length but also a different optical system. Not quite apples to apples.

 

G

giosblue

Well-known member

• Dec 20, 2015

• #3

FrankD said:

It isn't that simple. The two scopes you are comparing have two different optical systems. It isn't just a longer focal length but also a different optical system. Not quite apples to apples.

Click to expand...

Thanks Frank, yes I know, that was just an example, supposing everything was the same. except the focal length.

 

J

JerryLogan

Well-known member

• Dec 20, 2015

• #4

giosblue said:

Thanks Frank, yes I know, that was just an example, supposing everything was the same. except the focal length.

Click to expand...

In general, shorter focal length scopes present more of an optical challenge to eyepieces than longer focal length refractors because of the acute light path angles at the edge of the image. You can get near apo performance from an achromatic scope if you're willing to go 900-1200 focal length but there's always the convenience/image trade off.

Part of what makes high end spotters expensive is the cost of correcting a 480mm f/5 to overcome the challenges in the short and steep light path. The reward is that the scope will be vastly easier to carry and mount.

Best,
Jerry

 

mooreorless

Well-known member

• Dec 21, 2015

• #5

If my information is right about Opticron the 2 scopes you are talking about take a different eyepiece. They do not list the focal length of the spotters that I can find so far. Some people that have the Nikon 82 ED spotting scope with the MCII zoom eyepiece 25X-75X have said that the scope was ok at 75X. Maybe Pete Gamby [sales etc. Manager for Opticron ] might be able to answer your question on this. There are some dealers in the USA and I would like to try the Opticron HR 80 ED esp. with Nikon completely closed out the 82ED , but there is not much info and back feed of these Opticron spotters. I don't want to buy one for$1700 and find I don't like it etc.

 

FrankD

Well-known member

• Dec 21, 2015

• #6

Steve,

The eyepieces (the HDF and SDL V2) are interchangeable on all of Opticron's scopes from the MM3 series upwards (price and performance). You can put the same HDF zoom on the MM3 50 mm, the ES 80 and the HR 66...as one example.

As for the image quality, I don't think you would find any fault with either the ES or the HR series. Their only drawback, in my experience, is that their physical length is longer than many of their competitors.

 

mooreorless

Well-known member

• Dec 21, 2015

• #7

Hi Frank,

It sounds like focal length is longer in these spotters, so that could be a good thing for image QC. I have no way of checking these scopes out. Thanks for your reply! I thought you needed an adapter for some of the scopes to use the "big" zoom on the 70mm spotter etc.

 

J

jring

Well-known member

• Dec 21, 2015

• #8

Hi,

if you need an adapter to use an EP with a specific body, the Opticron page will state so as with SDLv2 and IS series scopes.
For the record, the SDLv2 has a focal length of 24-8mm so you can easily calculate the focal length of the bodies and other EPs from the magnifications given.

Regards,

Joachim

 

mooreorless

Well-known member

• Dec 26, 2015

• #9

http://opticscamp.com/opticron-spot...692-opticron-sdl-spotting-scope-eyepiece.html