PDA

View Full Version : Telescopic sights see through plane's cowling



Lurch1962
05-10-2007, 04:19 PM
Planes such as the Val, Ki-27, etc. which have telescopic sights allow one to effectively see through the cowling. The zoom factor with these sights is the same as for the 30 degree wide FOV. But have you noticed just how well you can see below the boresight axis?

Even though the objective lens of the sight is positioned rather well forward, it's not so far forward as to allow such an unobstructed view.

It's a little like the "Wonder Woman" cheat, methinks.

I wonder what the magnifications and fields of view actually were for these kinds of sight?

--Lurch--

Lurch1962
05-10-2007, 04:19 PM
Planes such as the Val, Ki-27, etc. which have telescopic sights allow one to effectively see through the cowling. The zoom factor with these sights is the same as for the 30 degree wide FOV. But have you noticed just how well you can see below the boresight axis?

Even though the objective lens of the sight is positioned rather well forward, it's not so far forward as to allow such an unobstructed view.

It's a little like the "Wonder Woman" cheat, methinks.

I wonder what the magnifications and fields of view actually were for these kinds of sight?

--Lurch--

striker-85
05-10-2007, 08:30 PM
Ya I noticed that too. The sites are very helpful though for the Val and SBD when on carriers in multiiplayer servers. It helps to reduce spawn kills if you check through the gunsight before starting your roll.

leitmotiv
05-10-2007, 09:16 PM
Er---heh, heh---gents, the tele sights are mounted above the cowlings of the said aircraft, as a quick gander at their profiles will show. The magnification isn't allowing the user to see through the cowling, but to see wayyyy beyond the cowling.

Lurch1962
05-11-2007, 04:54 PM
leitmotiv,
Yes, you're correct about the sight placement. But the point of view as modeled would be (or should be) at the location of the sight's objective lens (at the front of the tube). If the front of the cowling is not sufficiently well below the sight line, the pilot would see an out-of-focus portion of the cowling's top surface at the bottom of the field of view.

In Il-2, the image circle produced by the sight is roughly 20 degrees in diameter. Therefore if the cowling is less than about 10 degrees below the optical axis, it should be seen.

Your comment about seeing "...wayyyy beyond the cowling" leads me to suspect that you believe the point of view of the telescopic sight to be actually located some distance out in front of the aircraft (??). This can't be so, as the prop is visible when looking through it.

Another quirk... When leaning back in the normal position in the seat (i.e., NOT when looking through the magnified telescopic sight view) the tiny bit of the image seen through the eyepiece should be magnified as compared to the rest of the view. Just because one is some distance back from the eyepiece does not mean the magnification gets smaller. The only thing that changes is the amount of the field visible through the eyepiece. If you have a pair of binoculars (or telescope, or microscope) you can try this out for yourself.

I'm sure some of you have played Microprose's Pacific Air War 1942. The planes in that sim which had telescopic sights did indeed properly magnify the view even when you were in the 'normal' flying position. BUT, there was an error... the little magnified view was inverted (upside down). This cannot happen in real life--the view will always remain upright, no matter how far from the eyepiece you are.

--Lurch--

leitmotiv
05-11-2007, 05:04 PM
Obviously you have never used a telescopic rifle. You do not see your barrel through the telescope. You are using intuition.

Lurch1962
05-11-2007, 05:38 PM
Actually, I have used rifle telescopes. Their fields of view are rather small; depending on magnification, of order 5 degrees. Given the height they're typically mounted on the gun, they can't pick up the front sight/barrel (or if they do, the closeness and narrowness of the barrel end would render it so defocused and hence blurry it would be somewhat difficult to make out).

One could do a screen grab of the planes in question and "measure" the size of the cone extending from the front of the sight which would not allow the cowling to be visible.

As regards optics, by way of bona fides I'll add that I work for an optical firm, and fabricate laser line generator lenses and high precision astronomical optics up to 17 inches aperture. Over the years I've made complete telescopes and binoculars for astronomical observing, as well as gunsight-like finders. So I do have a modicum of knowledge in this area... Sorry for the brag-fest! http://forums.ubi.com/images/smilies/blush.gif

Xiolablu3
05-11-2007, 09:53 PM
Hehe, I have been strugglingwith these sights for about ayear now online, and I never realised you could zoom into them.

I always thought what a stupid idea it was to have a big black ring around the sight! http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif http://forums.ubi.com/images/smilies/35.gif

No wonder I could never hit anything with them.

Must remember to bind a key when I reinstall!

tigertalon
05-12-2007, 04:52 AM
Lurch, you are absolutely correct. I played a bit with FMB.I sat a Ki-27 down on tarmac ready for takeoff:

http://i155.photobucket.com/albums/s307/TigerTalon/2.jpg

Then I looked through the sight. This is what I saw:

http://i155.photobucket.com/albums/s307/TigerTalon/1.jpg

Now in order to be able to see what I saw (the roof and the tower), I must have been able to see through a large part of the nose:

http://i155.photobucket.com/albums/s307/TigerTalon/3.jpg

BTW, anyone noticed how A5M4 has a bit of cowling bited of to allow better down visibility from the sight?

http://i155.photobucket.com/albums/s307/TigerTalon/A5M4_sight.jpg

leitmotiv
05-12-2007, 05:09 AM
WHOOPS. I stand hugely corrected! I remember a LIFE magazine article from ca. 1941 which was about the use of the U.S. Navy telescopic sight in dive bombing. It had a number of views ostensibly through the sight. I suspect they were "idealized" in the light of what is being demonstrated here---that A5M4 cowling "divot" is fascinating! That should have aroused my curiosity years ago! A big tip of the hat to you, Lurch, for scientific curiosity and expertise!

Lurch1962
05-14-2007, 12:58 PM
Xiolablu3,
http://forums.ubi.com/images/smilies/16x16_smiley-very-happy.gif (in commiseration with your long-standing "problem").

leitmotiv,
Thanks for your gentlemanly admission, and of course your kind comments!

tigertalon,
Thanks for going through the effort of making those shots! If I had an easy way to link to some images (I'll have to try image shack or rapidshare, I guess) I'd have supplied some similar images for the Ki-43 to buttress my point. As the old saying goes, a picture's worth a thousand (million?) words.

In general, among the player-flyables with telescopic sights, it seems that the upper surface of the cowling (blurred out of focus) should extend upward into the lower part of the sight to perhaps as far as the bottom edge of the outermost (segmented, or "dashed") reticle circle.

--Lurch--

leitmotiv
05-14-2007, 11:36 PM
I think you ought to PM Oleg with all your evidence so he can file it so that, hopefully, these errors will not be repeated in the future on airplanes like the Fokker D.XXI, etc. Again. fascinating work. Can't escape from the tyranny of the cowl with a telescope any more than you can with a reflector sight!