turning an old spy lense into a telescope?

[vlaiv]

2 minutes ago, winters solace said:

well im pretty sure its parabolic. it looks exactly the same as my dobs mirror snd that tiny one minus the gapping hole. why would it make lots of coma. becuase of the hole? also its 4am here ill be on tomrrow

I'm pretty sure that you can't tell if it's parabolic or spherical just by looking at it - you need an optical test to tell you which is it.

Coma is inherent property of parabolic mirror, and amount of coma is directly related to "speed" (or F/ratio) of mirror. At F/6 it is barely noticeable, at F/5 it's evident, at F/4 one needs coma corrector. It is quadratic function of F/ratio in angular units (cubic function if your units are length in focal plane) - so it rises very rapidly with faster optics.

Another thing worth noting is that F/2 parabolic mirror is going to be a nightmare to collimate (like coma, sensitivity to miscollimation rises with faster optics). For that reason I believe it is probably spherical mirror (and the fact that many designs with corrector use spherical mirrors).

[DaveS]

You won't be able to tell by eye if it's paraboloidal, hyperboloidal or ellipsoidal.

I very much doubt that you'll be able to use this for visual, especially if you want to use it as a dobsonian mounted newtonian 'scope.

Sorry to say you've got yourself into a pretty tough spot having dismantled it. Just looking at it it's a pretty extreme piece of highly specialised kit, and Isuspect the collimation will be a nightmare.

[winters solace]

well. there is no way to adjust the primary mirror within the housing it just gets bolted on. and it needed to be opened anyway it was a filty mess inside. dust from decades of sitting. 

who knows. this may just be an unusable lens from a different era. i dont have any kind of camera to test it on. so its probably just gonna sit and gather dust... again.

[henry b]

You have a very fast wide view lens package.  The primary  together with the correcting lens are fixed and non moving, the secondary lens are adjustable from the front allowing on site collimation. The only unknown is the back focus from the primary/corrector i suspect very short. The camera was fixed at the rear internally the whole unit was transportable.    do not let it gather dust again!    henry b

[winters solace]

ive looked at the back. the primary mirror is hard mounted to the back plate. 

[Stub Mandrel]

I'd love a play with that lens...

[R26 oldtimer]

Could use it for shaving...?

[DaveS]

Good if the primary and correcting lens system are fixed, and only the secondary needs adjusting.

However....

I hope that you marked / noted the position of each system before dismantling so they can go back with the same orientation.

I'll reiterate what others have said, this is a fast wide-field imaging system, probably totally unsuited to visual. I would try to get enough funds together for a basic cooled camera, could be an OSC CMOS for simplicity.

[Stub Mandrel]

2 hours ago, DaveS said:

I would try to get enough funds together for a basic cooled camera, could be an OSC CMOS for simplicity.

A cheap webcam, with its original lens removed, and aimed at the moon, will be plenty good enough for testing.

[winters solace]

im honestly close to just selling this thing. and just using my 8" dob since i cant even recycles this into something else.

[Apharov]

20 hours ago, winters solace said:

im honestly close to just selling this thing. and just using my 8" dob since i cant even recycles this into something else.

Selling the thing would indeed appear to be the best solution if you don't have the equipment to make use of the lens.

[winters solace]

yeah, i dont see myself being able to ever use this thing, any idea where i can sell this and how much i should ask for it?