Rifle Scopes Sunshade w/ARD vs non-ARD Sunshade

[AEROMechanic]

Which would be better at keeping stray light rays from entering the objective lens; a 2" sunshade w/ARD or a 4" sunshade with no ARD, or is it a push between the two?

What are the disadvantages of using a longer sunshade, if any?

Thanks
LarryA

 

[Sportin Wood]

Re: Sunshade w/ARD vs non-ARD Sunshade

Either will work fine. Get the 4" w/out the ARD

 

[AEROMechanic]

Re: Sunshade w/ARD vs non-ARD Sunshade

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: StanwoodSpartan</div><div class="ubbcode-body">Either will work fine.</div></div>

Good to know

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: StanwoodSpartan</div><div class="ubbcode-body">Get the 4" w/out the ARD.</div></div>
Out of curiosity, have there been issues with ARDs that make you want to choose a plain sunshade or is it that you've always used a regular shade and it's worked just fine?

 

[rickey]

Re: Sunshade w/ARD vs non-ARD Sunshade

Curious as well...?

 

[Cesiumsponge]

Re: Sunshade w/ARD vs non-ARD Sunshade

The ARD theoretically works better by blocking more direct light at lower angles (the Sun with respect to the horizon) and offers a more compact package. However the cross sectional area of the honeycomb walls are also solid, effectively reducing the actual objective diameter. That is, the ARD will also reduce the light gathered by the objective simply because there is material in the way of the objective lens.

This is how I rationalize it. If you had a sunshade 4" long for a 56mm objective, a light ray would have to be just under 29 degrees from horizontal to enter from the top edge of the sunshade to hit the bottom of the objective lens. It's the angle calculated as a right triangle based on the length of the sunshade (in reality, the length of the sunshade plus the recessed depth of the actual objective lens nestled in the scope body) and the height of the shade. With an ARD, it would be the length of the ARD unit and the width if the cells, so a 2" USO ARD which has large cells might offer protection down to about 5 degrees. Smaller cells would offer a lower angle, better protection but also nerf your contrast and light gathering from reducing the effective light gathering area of the lens.

The answer is "it depends" and will vary depending on what you require.

 

[AEROMechanic]

Re: Sunshade w/ARD vs non-ARD Sunshade

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Cesiumsponge</div><div class="ubbcode-body">The ARD theoretically works better by blocking more direct light at lower angles (the Sun with respect to the horizon) and offers a more compact package. However the cross sectional area of the honeycomb walls are also solid, effectively reducing the actual objective diameter. That is, the ARD will also reduce the light gathered by the objective simply because there is material in the way of the objective lens.

This is how I rationalize it. If you had a sunshade 4" long for a 56mm objective, a light ray would have to be just under 29 degrees from horizontal to enter from the top edge of the sunshade to hit the bottom of the objective lens. It's the angle calculated as a right triangle based on the length of the sunshade (in reality, the length of the sunshade plus the recessed depth of the actual objective lens nestled in the scope body) and the height of the shade. With an ARD, it would be the length of the ARD unit and the width if the cells, so a 2" USO ARD which has large cells might offer protection down to about 5 degrees. Smaller cells would offer a lower angle, better protection but also nerf your contrast and light gathering from reducing the effective light gathering area of the lens.

The answer is "it depends" and will vary depending on what you require. </div></div>

This is great insight, thanks

LarryA