Re: Disassembling Rubinar 10/1000

On 26 mar., 10:12, Winstone <winstonewar...@xxxxxxxxx> wrote:
On Mar 26, 4:22 pm, Bhogi <bh...@xxxxxxxx> wrote:



On 26 mar., 01:50, Winstone <winstonewar...@xxxxxxxxx> wrote:

On Mar 26, 8:28 am, Bhogi <bh...@xxxxxxxx> wrote:
On 26 mar., 00:35, Winstone <winstonewar...@xxxxxxxxx> wrote:

On Mar 26, 5:40 am, Bhogi <bh...@xxxxxxxx> wrote:
http://ejarm.com/m42to125diagonal.jpg
I made it from black delrin plastic. Your adapter is thinner I think,
I left 10mm of space to use the m6 screws. I use the inexpensive 1.25"
diagonal from surplusshed. I shortened the tube on the diagonal as
much as possible, because I wanted to use the lens with the field
flattener lens, otherwise I'm not sure I could focus to infinity. The
1000 rubinar is ok with all my eyepieces (surplusshed), but the 500 f/
5.6 can't focus to infinity with one eyepiece.

What 500 f/5.6 are you talking about?

http://www.rugift.com/photocameras/rubinar_500_lens.htm

I also ordered a lumicon 1" eyepiece extension (not yet received)
so that I can put any diagonal and it won't hit the rear field
flattener. Why did you cut your diagonal. You can just secure
the front 10mm of any diagonal without getting it all the way
inside that can hit the field flattener. Unless you want shorter
diagonal to avoid aberrations? Why have you compared
using normal diagonal and shortened diagonal? Is the
aberration of the normal diagonal significant? What other
issues or pro/con between using each of them?

You obviously haven't tested the lens with the diagonal yet. The lens
is designed for use with cameras that have 44mm flange distance.
That's not enough distance to mount any 1.25" diagonal. Without the
infinity stop you can focus past the infinity - increase the "flange
distance" - but not by very much. That's one reason to keep the
diagonal as close as possible.

For optimum quality. Why don't you use a diagonal that has the
same 44mm flange distance. Not possible? The reason I'm
using a 1" eyepiece extension is because I'm using a Televue
Everbright diagonal and i can't just cut the tube to focus it
closer.

A 1.25" diagonal needs some space + the eyepiece needs somespace, I'd
guess all in all a minimum of 60mm. Now if you have a long diagonal
tube this increases.
I think your diagonal tube is not very long so I think you won't have
any problems.

With your inexpensive surplusshed diagonal that
you can cut shorter. What is the estimated equivalent
flange distance closest you can get? If close to 44mm.
Then it means I don't even have to adjust the infinity stop
(except perhaps if I want closer focus)?

My guess about 60mm, maybe more. You definitely need to remove the
infinity stop.
Why don't you just try it with the unmodified lens? Just be careful
not to touch the field flattener.

Also to focus at closer like 1 meter and beyond infinity,
the adjustment of the screws of the aluminum ring is
the same, right. Or is there a separate adjustment if
one wants to focus closer and beyond infinity?

The adjustments you are talking about are just about the distance
scale, how the focusing collar is oriented. With the changed flange
distance I don't think the distance scale is acurate enough. I actualy
never use the distance scale.
All the lens does is move the front group of lenses relative to the
primary mirror. Other than that there is no optical adjustment
possible.

But there is a big difference. I mean normally one can't
adjust the front all the way to focus at 1 meter and less until
the  front lens cell comes off. So is there something inside the
aluminum tube that stops it. So you mean by simply loosening
the 3 screws, the front cell itself can be unscrew all the way
from the second half or rear part? Also the two front lens are
contained in one cell?)?

This is last detail I need to know before I start disassembling
it and in the point of no return.

Win

Infinity stop is a piece of aluminium that stops the front cell from
turning the whole 360 degrees in both directions. When you open the
lens you'll see how trivial that is. You don't just loosen the screws
you have to remove the stop.

How much you can focus beyond infinity (increase flange distance)
depends on how far the cell can be moved towards the primary, and near
focus depends on when you totaly unscrew the front cell. You can't
accidentaly unscrew the front cell, it takes a few full 360 degree
turns to do that.
The front cell is one piece yes, exactly like in this drawing:
http://ejarm.com/rubinar.jpg

Follow my directions from the first post, take pictures, and let us
know.
.

Relevant Pages

  • Re: Disassembling Rubinar 10/1000
    ... I left 10mm of space to use the m6 screws. ... flattener lens, otherwise I'm not sure I could focus to infinity. ... That's not enough distance to mount any 1.25" diagonal. ...
    (sci.astro.amateur)
  • Re: Disassembling Rubinar 10/1000
    ... I left 10mm of space to use the m6 screws. ... flattener lens, otherwise I'm not sure I could focus to infinity. ... That's not enough distance to mount any 1.25" diagonal. ...
    (sci.astro.amateur)
  • Re: Disassembling Rubinar 10/1000
    ... I left 10mm of space to use the m6 screws. ... flattener lens, otherwise I'm not sure I could focus to infinity. ... That's not enough distance to mount any 1.25" diagonal. ...
    (sci.astro.amateur)
  • Re: The length of the focal length?
    ... a lens system's physical length may be short than its focal length. ... that F effective equals F when u is at infinity. ... Object distance has no bearing. ...
    (rec.photo.digital.slr-systems)
  • Re: close focus formula
    ... the lens and reverse it and put it back to the cell.. ... so when the target is focus closer, ... a russian 4" maksutov at distance of 1 meter. ... This means the exit pupil coming from the ...
    (sci.astro.amateur)