[pacerr]

A tip re tripod adapters for this device: since the lens isn't attached to a camera, an after market tripod mount ring can be attached to the lens' focus ring and focusing may easily be accomplished twisting the aperture ring or the adapter itself.

I just picked up the Vivitar (Cosina?) version here in the Marketplace a few weeks ago.

H2

[pacerr]

A tip re the tripod mount issue: since the lens isn't mounted to a camera, an after market tripod ring adapter can be mounted to the focus ring while while focusing by twisting the aperture ring or the device itself. Seems backwards and strange at first but works well.

An Adaptall SP 35-80 Macro (01A) with a PK adapter and this device makes a wonderful nature walk accessory.

I've found that lenses longer than about 100mm begin to suffer the effects of motion blur, heat mirage and haze as do most terrestrial telescopes. Nevertheless I can't resist playing with it on a DA*300 once in a while.

H2

[ripit]

Just a bit of an update. I have been keeping an eye out for ones on ebay and I'm not finding much except a minolta one that seems a little more common. Looking at the bower one, it really looks like a a slightly modified telescope eye piece and a star diagonal. I have no idea about this one but other bower stuff I have had has been pretty budget quality. This seems to be a less common specialty item that goes for a premium (unless you get lucky on ebay which I'll still try to do ).

So I got a .965" eye piece for $3 shipped off ebay missing the tube just to play with. I had a vivitar 2x teleconverter that was kind of trashed (came with a lens I bought), not to mention I have the same vivitar telconverter in good shape. I had to loosen one lock ring, and the whole optical assembly screwed out of the teleconverter. I had to remove one more lock ring and all the elements came out. The lock ring that that held the elements push fit onto the first thread of the eye piece and seemed to hold it straight. I would glue it but this was just a trial run. I had to use a 12mm macro tube to push it out a little further and it worked fine. Quality was what I expected from a really cheap plastic element eye piece but it was plenty usable.

The eye piece was 12.5mm and seemed to give the view of about 2000mm with a 500mm lens. In other words, I put the 500mm lens on a tripod, and with a camera zoomed in 4x (the live view zoom for better focusing), a licencing plate on a car filled about the same amount of the frame as it did with the 500mm lens and the adapter. The image was up side down and reversed but a star diagonal should fix that.


So I'm going to keep looking for a premade one on ebay but I'm also thinking of building one with better optics and the star diagonal. Telescope optics are a lot more common including used compared these adapters so I'm thinking I could get decent optics for a lot less (unless I get lucky on ebay of course).

[wombat2go]

A star diagonal will give you an upright image but inverted side to side.

An Amici roof prism will give a corrected image, so you can read a roadsign etc correctly
These things appear to be plentiful and cheap, used by the telescopers when they want to view terrestrial objects, called "45 degree correct image prism diagonal "

[ripit]

Thanks a bunch of the info. I knew the 45 degree ones corrected the side to side but didn't know they were called something different. The correct term will certainly help searching for info on them. I really don't know much about telescope optics so I'll have to do a little reading up. Right now I wouldn't have a clue how to tell good optics from bad, other than I know plossi (if that's how you spell it) eye pieces are the best design. I'm in no rush though so I have plenty of time to do a little reading.

You wouldn't happen to know if the tubes screw off on all the eye pieces and or diagonals like the one I have does, do you? The one thing I read on doing this claimed .095" would be best as larger may have issued with not being close enough to the lens. 1.25" ones seem to be a lot more common. If the tube screws off, that might eliminate problems with length.

[ripit]

I'm continuing to look for a comercial one (I'm skeptical about the bower and its t mount so I cn only use it with my crappy 500mm, not my better lenses). I have a feling it will be a long wait but I'm sure I'll eventually run across something (maybe the vivitar or if I score a deal on price the pentax). I might even try an off brand one if the price is right. I really appreciate everyone input on some possibilities to keep an eye out for.

In the mean time, I have apparently decided to go full bore stupid with this one (wasting money and tons of time and work on a project that may just fail). In reality I enjoy hacking and modding so that may be why I take on stupid projects like this. Hopefully it will wind up better than when I tried to make a canon fd lens to pk mount adapter out of a teleconverter, on the presumption I might get better glass than the Chinese ones.

I have kind of strayed in a different direction. Any time I say it should do something, I really don't know but I think (going to have to try). I ripped the mirror box with prism and lens mount attached out of a pentax p3 (it wasn't in working condition). It works fine like it did in the camera. If I remove the focusing screen, it seems to lose heavy magnification? It goes from a full image to a smaller circle in the center. The image seems to be clear though so perhaps some magnification behind the cameras original eye piece? I also have a Minolta mirror box ripped out of a camera stripped down a little further. It behaves the same. With the original eye piece and the prism removed (just the mirror), it works with a telescope eye piece. The image is right side up but mirror image. The prism should correct mirror image and the telescope eye piece should work (the prism shouldn't be changing the image) but it doesn't. I have a strong feeling the path of light going through the prism is to long (basically exceeded the flange focal distance so to speak). That just got me thinking I can try it and see if it does macro which would confirm this. A Barlow lens is supposed to find this an d I have one on the way.

I also have another eye piece with tube on the way. also a 1.5x eyepiece with image correction (corrects mirror image and upside down). I assume this is just a magnifier (barlow?) with image correction and you put your own eye piece in it but I guess I'll find out. I also have a set of 3 roof prisms on the way gutted from mead binoculars and seller says

"These turn the image upside down and backwards. If you use these with a telescope that has an uncorrected image, this will correct it. You can use these to make correct image eyepieces, finderscopes and binoculars. These are about 7/8" in diameter by 7/8" long. They come out of Meade binoculars. Fun to experiment with and useful items."

Could be all I need is this and the eye piece along with my stripped teleconverter, but like I said, I like experimenting (and apparently wasting money). I'm only into it about $30 (which could have gone towards buying one premade, lol) and two broken cameras that were collecting dust. Even if that works I may play with the mirror boxes from the cameras as I suspect the optics are better than the cheap stuff I bought.

[ripit]

On a side note, the reason I haven't tried a 45 degree diagonal yet is they are a bit more expensive so I am proceeding with more caution in that direction. I would have to drop 30-40$ on a diagonal that is 1.25 inch just to find out it will not work. There are of course cheaper ones, and I'm looking around (maybe something cheap/used).

Of course if I find a way that works well, better parts with better optics are an option but I'm trying to stay very cheap for experimenting.

[wombat2go]

Hey Ripit
Those photos are reminiscent of the Alien movie when Ash, the Hyperdyne Systems 120-A/2 robot, got pulled apart and could still talk.

[ripit]

Yea, I didn't really bother to strip them down, lol. If I wind up using either in the end, I'll tear off the unnecessary parts, maybe cut back the metal some and make some sort of a housing.

I was thinking a little more like borg by the way.

[wildman]

From a practical standpoint why not something like this?:

Amazon.com: Bushnell Bear Grylls Monocular 9 x 32mm Roof Prism Waterproof/Fogproof Spotting Scope, Black: Sports & Outdoors

[ripit]

From a practical standpoint why not something like this?:

Amazon.com: Bushnell Bear Grylls Monocular 9 x 32mm Roof Prism Waterproof/Fogproof Spotting Scope, Black: Sports & Outdoors

My calculations may be way off but this is more the direction I want to go.

I'm thinking more along the lines of a telescope. There is no telling what will work, but in theory, compared to what you would see in a camera , it could go as far as 57,600mm f16 (theoretical maximum with that parts I have or will have and you could go further). Yes that reads 57,600mm. The only unknown is if a barlow lens as I have no idea if they cause light loss. Of course I do not need anywhere near that magnification, even for looking at stars and faster might be better. From what I gather (mentioned in a forum anyway) f7 and faster is considered a fast telescope (the range they can use is a bit higher that a camera).

Here is where that is coming form. I noticed that the 500mm lens I have with a 12.5mm eye piece, and no other parts was right about the same magnification as the 500mm on my camera in live view, zoomed in 4x, or about 2000mm equivalent on a camera. I was rather shocked, but this is where I think its coming form (again, I could be way off, I'm half guessing). and apsc sensor is what, 24mm diagonal? The most the human eye can get is 9mm? I'm not sure if its a crop factor thing or if the image is being compressed down to a smaller area, or both, but just a 4mm eye piece and the 500mm lens and nothing else should give the same as a 6000mm lens on a camera. Put a 1.6x telconverter in front of the 500mm lens and that is now the same as 9600mm on a camera. Ad a 3x barlow lens (made for use with telscopes) and you have 28,000.

I have no idea if the Barlow causes light loss but the 1.6x front mount telconverter won't (it has a huge 105mm objective lens and I have done the math, it will not lose any light on the 500mm lens). Honestly all I need are a few thousand mm or less which should be quite easy (I think, I'm new to telescopes which is what I'm basically trying to do, for the kids to look at stars or whatever). Just the 500mm lens, the 1.6x, and a 12mm eye piece gives about the same view as a 3200mm lens on a camera. I'm actually thinking of trying/using some of my 300mm lenses as I don think I'll need all that magnification and they are much better quality than the cheapo 500mm.

Fyi, I know you lose image quality with a front mount teleconverter but not as much as you might think in this case. The telconverter I have is a century optics which is top of the line (the exact one I have is currently $649.00 at adorama).

Just the 500mm lens as pictured in post 18, last picture which is finished and working (with an upsidown image which might not matter for stars) is compatible to 2000mm on a camera, could go to 3200mm f8 with the 1.6x converter. Comparing it to a under 100$ telescope from walmart with plastic lenses, I think it will be better.

I'm only waiting on 1 step ring and I can use the 1.6x lens.

This hopefully will also be very versatile (I may wind up in the end having built a couple of different adapters and have many different lenses I could use it with).

On a side note, this can all be done with some simple telescope parts, using them in the manner and configuration they were intended to be used (and I'll have those parts soon). The only reason for experimenting with the mirror boxes from the cameras I I figured they may have better optics (as in the mirror and prism), and I enjoy modding/hacking mechanical things. I have read up a little more since I first posted, and I am far from the first to do this (the most common way is to just drill a hole in a lens cap and glue an eye piece in, its that simple but I like over complicating things). Also from what I gather, camera lenses work very, very well from a collimation perspective (alignment of the elements).


Sorry for the long disorganized ramble but that is about how organized my thoughts and ideas on this are right now, lol. Things will be a little more clear when I get a few parts and tinker a little more. I also have more time than money.

[ripit]

Can anyone tell me aprox what the magnification on theirs is? Does a lens have about the same magnification (viewed image size) as it would on a camera or is it magnified more?

[momchilatanasoff]

Hi, i was reading this thread with big interest , i am looking for the cheapest and most portable way to view stars ,check mountain routes when i trek ,check for climbing tours ,etc... I anyway need to buy a telephoto lens ,due to the fact that my only two lenses are 28mm 2.8 miranda prime and 35-80 4-5.6 pentax zoom,both of witch i really love but are just ...short... Anyway , as i don't yet have the telephoto , i can buy any of the pentax compatible types - m42 , tamron adaptall , K bayonet,So i am searching for the cheapest ,yet sufficient way to do it...
All the best
Momchil

[momchilatanasoff]

Not really an active thread , huh ?
Anyway ,the question still stays for me , and any help would be greatly appreciated ...
So far looks like i am going to buy Tamron Adaptall-2 80-210mm f/3.8-4 (103A) with a PK adapter and will hope to find the Tamron Wide field tele view adapter....
All the best

[ripit]

kind of a strange coincidence this thread popping up now (it was started almost a year ago).. I bought a vivitar pk mount adapter a couple of days ago. In hind site, its probably not worth trying to build one unless you really like tinkering. ts quite problematic getting everything together within a short enough distance to work, especially without things protruding where it hits the lens. I tried with some decent 1 1|4 inch parts but never got it working. I wound up spending as much as a really good one would cost or more. If you were to try, I would recommend a 20mm eye piece. The 10mm I used just jacked the magnification up too much and gave too small of an image to view comfortably. I kind of gather 20mm is about what the commercial ones are. I'm guessing the tamron one you are looking for would be better, but if for whatever reason, if you have a hard time finding on, the vivitar one seems common enough. I won the one I got used on ebay for about 44$. I actually have the m42 version already and while it seems a little cheap and plasticy, it works well enough I suppose (for the money). Ther was a store in canada that was selling them new for $50 but I couldn't find them again. of course there is always the pentax one but I'm guessing thwy are going to tend to be quite expensive if you find one.

Good luck with whatever you find.