25mm f1.6 lens, behind a scope...

Show and tell for your homebrew nv projects. DIY 'Stickies' here too.
Post Reply
sedstar
Posts: 1354
Joined: 21 Apr 2013, 23:13
Location: across the pond, PA, the states...

25mm f1.6 lens, behind a scope...

Post by sedstar » 19 Feb 2014, 08:56

this has been talked about before, but, i'm not sure if anyone TRIED it yet...

up till now, the "options" for a lens, when making a scope add-on? are traditionally 12 or 16mm, which one do you want?

i ordered my EJ230 with the 12, typical circular scope view with black around the edges... i am wsting pixels, wish I had got the 16, lol

someone once said "I wonder what a 25mm lens behind a scope would do" and i'm not sure it was tried or just THOUGHT and TALKed about... well, i have this "one inch" (25mm, i think, lol) projector lens now, and its a f1.6... hmmm...

my EJ230 is a little bit too long (even cut down) to try this except around the room close to me where it focuses up nicely and crisply. (beautiful picture, by the way)

I was inspired to wonder since i could do CLOSE focus, could i get this thing looking thru one of my scopes? working by HAND (which is maddening, lol) I was able to get an image, and then i saw it... blurry crosshairs!. not being able to focus this LENS as its already touching the EJ body with the lens cover off, and already machined down to the last bit of screws for the lens cover to catch on?

i taped the lens to the end of the EJ body. The lens has a fairly deep recess from the outside of the bezel to the first glass? *shrugs* after winding out the eyepiece to focus the crosshairs up decent?? I taped the bezel of the lens to the eyepiece body.

slightly tilted crosshairs, but, near enough the center it WORKED. taped up, i could now play with the side focus on the scope with free hands...it worked very well. Granted the moon is still big, and theres snow about making life easier, but still... never touched IR, all moonlight and snow. I could see a LOT.

it was nice to get some ZOOM into the middle of the scope view like that. the crosshairs did not get objectionably thick or big... i can see all of my "mil dots"... i left the scope (6-24x60mm, side focus) on 6x the whole trial, no IR illumination.

but...6x seemed like a little higher power, cos the screen view was LESS of the whole possibl scope view (remember, i was zoomed into the midle of the scope view)

every pixel is precious, and i was not only using all of them? i was getting more bang for my buck, pixel wise.

the effect was PLEASING ENOUGH, next time i might try to rig up my rolaids rail, as the back of the lens is .997" straight taper, heh heh... rolaids rail with scope mount should center it up about perfect. better than electrical tape on everything anyways, lol.

remember.. the SCOPE is on 6x... its lowest settng, where the exit pupil is at its biggest (most light) coming in... but my "zoomed in view" using a 25mm lens? kind of gave free magnification.

Humm... might have to try this on the 3-9x50mm scope? LMAO... 3x has good light gathering and the slight extra magnification (with ALL the light gathering of low pwoer...) seemed like a jolly good combination.

nothing proven yet, but... it might be possible to "scootch" a little more out of a scoped add on than we thought... this worked very well... I was using ALL of the screen pixels, so no resolution was wasted.
Well, I understand that, boys... but see, my CAT gets the silly idea you're making fun of HIM... then he gets, *really* mean...

sedstar
Posts: 1354
Joined: 21 Apr 2013, 23:13
Location: across the pond, PA, the states...

Re: 25mm f1.6 lens, behind a scope...

Post by sedstar » 19 Feb 2014, 08:58

makes me wonder what a "regular" lens in 25mm, f1.4 would do...
Well, I understand that, boys... but see, my CAT gets the silly idea you're making fun of HIM... then he gets, *really* mean...

User avatar
sunndog
ADMINISTRATOR
Posts: 6478
Joined: 10 Jun 2012, 17:51
Location: buxton, derbyshire

Re: 25mm f1.6 lens, behind a scope...

Post by sunndog » 19 Feb 2014, 09:01

25mm lens for an addon is/was quite popular sedders. bit of free magnification an all that
oslon black drivers
http://nightvisionforumuk.com/viewtopic.php?f=35&t=2333

when asking for advice, please include what n.v device and/or illumination you already have (if any) and what rifles you intend to use them on...cheers

sedstar
Posts: 1354
Joined: 21 Apr 2013, 23:13
Location: across the pond, PA, the states...

Re: 25mm f1.6 lens, behind a scope...

Post by sedstar » 19 Feb 2014, 09:43

i didnt know anyone had tried it... why isnt it done more often then?

we always tell newbies to pick between 12 and 16mm lenses for the EJ230 and 700 box cam version...

i know really FINE crosshairs arent real popular these days, but, i had an old weaver scope that came on a 308 my brother gave me, that thing had real thin crosshairs and a small dot in the middle...

this makes me wonder if the system couldnt be tweaked a little more. I HAVE made my own lens out of various lenses laying around before, my MAIN problem doing it, is that i get too much glare and washout, but i was always trying to use them scopeless... used behind a day scope, with a tube around it sealing out all exraneous light? this might not be a problem, maybe.

i'm just thinking... if 25mm was "really cool", what would 30mm do? LMAO...

with a THIN enough crosshairs? this might be something to push the envelope a bit.

my generic tasco 3-9x50? thats a 16 to 17mm exit pupil... my 6-4x60 only has a 10mm exit pupil at its lowest power setting.

if i could "push" the focal length up a bit, i gain all the way around. free magnification, free resolution, in a sealed environment like that? i *might* be able to make a f1.0 lens home made work, if it didnt have to "deal with" off axis light and washout...

I just need really thin crosshairs on a reasonably priced scope to play with...
Well, I understand that, boys... but see, my CAT gets the silly idea you're making fun of HIM... then he gets, *really* mean...

User avatar
sunndog
ADMINISTRATOR
Posts: 6478
Joined: 10 Jun 2012, 17:51
Location: buxton, derbyshire

Re: 25mm f1.6 lens, behind a scope...

Post by sunndog » 19 Feb 2014, 09:51

when watecs were the camera to have we did used reccomend 12,16, or 25mm lenses.....i think its just that the KT&C cams come with either 12 or 16mm that 25mm has fallen by the wayside
i tried a 25mm once, and while it did work well i found it really screwed up my range finding and made the crosshairs too thick on my favoured scopes

others swear by them though. in fact some have nearly gone to war over 12mm vs 25mm lol
oslon black drivers
http://nightvisionforumuk.com/viewtopic.php?f=35&t=2333

when asking for advice, please include what n.v device and/or illumination you already have (if any) and what rifles you intend to use them on...cheers

poppy mae
Posts: 1234
Joined: 19 Aug 2012, 21:21
Location: Wirral Chesire

Re: 25mm f1.6 lens, behind a scope...

Post by poppy mae » 19 Feb 2014, 10:01

25mm all the way.....

m_pragnell
Posts: 315
Joined: 22 Nov 2012, 23:11
Location: Torquay

Re: 25mm f1.6 lens, behind a scope...

Post by m_pragnell » 19 Feb 2014, 10:38

Well that's poppy starting the war again :D

Radagast
junior librarian
Posts: 2617
Joined: 04 Apr 2013, 10:51
Location: Sydney Australia

Re: 25mm f1.6 lens, behind a scope...

Post by Radagast » 19 Feb 2014, 10:45

Now that's just size exaggeration. If this was a US board it would be 9mm vs .45. Of course the only answer to that is 9mm! :P

phoenix
BRUCE ALMIGHTY
Posts: 4749
Joined: 09 May 2012, 14:40
Location: Aberdeen

Re: 25mm f1.6 lens, behind a scope...

Post by phoenix » 19 Feb 2014, 12:23

All my Watec builds use 1/2" 25mm, f1.2, C mount IR coated lenses off E bay.
Keep the scope magnification down and use the "free" magnification from the lens to bring it back up again. No wasted screen pixels showing useless black areas around the edge of the screen.

Cheers

Bruce
LAND ROVER - THE WORLD'S WORST 4X4 BY FAR

User avatar
some bloke
TRADER MEMBER
Posts: 7492
Joined: 27 Jan 2012, 16:14
Location: Cornwall or Leicester

Re: 25mm f1.6 lens, behind a scope...

Post by some bloke » 20 Feb 2014, 04:48

I have just bought an M12 25mm for an old Sony HAD bullet cam I'm bringing back into play now I'm more aware of IR block filters etc. :thumbup:
Image

Post Reply