Re: Disassembling Rubinar 10/1000

On Mar 28, 4:34 pm, Bhogi <bh...@xxxxxxxx> wrote:
On 27 mar., 23:54, Winstone <winstonewar...@xxxxxxxxx> wrote:





On Mar 28, 5:50 am, Bhogi <bh...@xxxxxxxx> wrote:

On 27 mar., 13:17, Pia <pia_...@xxxxxxxxx> wrote:

On Mar 27, 4:04 pm, Bhogi <bh...@xxxxxxxx> wrote:

On 27 mar., 01:29, Winstone <winstonewar...@xxxxxxxxx> wrote:

On Mar 27, 7:47 am, Bhogi <bh...@xxxxxxxx> wrote:
http://www.rugift.com/photocameras/tourist-fl-eyepiece-attachment.htm
It's strange you don't get clear image. I got nice diffraction rings
even with 2x teleconverter. This may be the reason, contrast might be
realy low at close distances.

You mean you can get nice diffraction rings even with
2X teleconverter at a target distance of 1 meter? what
tiny source of light can do that? What I meant to say was.
My image is not sharp at 1 meter target but using other
objects at infinity or several meters away, it is very sharp.

Well then, you made it! Happy clear nights.
I have a lamp with "matte" aluminium reflector that gives nice
pinpoints of light when the light is on.

Thanks again for the help. Without you, I may not be able
to remove it because there is nowhere in the internet
that mentions that the shoe and mounting ring has to
be removed. Maybe you ought to write up a web
site about it. :)

Happy to help.
Good idea, I might just do that.

I wonder if you have seen thru an MTO1000. Can
you compare the images between it and the
Rubinar?

I can't I only have the rubinar but there are 2 things:
1) rubinar is SAID to be opticaly slightly superior - diffraction
limited
2) mto has fewer lenses which is a good thing, with rubinar I get a
large purple donut shaped flare on photos with VERY bright light
source in the frame.

Did you get a 1/4 wave or diffraction limited certificate when
you purchased your Rubinar? Some got it but I don't. I wonder
why they no longer issue it maybe because of quality changes
in the newer version? What do you  think?

If I recall corectly I did get it. Why you didn't get it is pure
speculation.

Maybe the quality changed and it's no longer 1/4 wave
or maybe they just want to save paper (trees could
be getting scare in Russia). There is not even a manual in
my Rubinar bag. The manufacturer just file attached the
manual.


Another thing. Which surprised me. I reread the cloudynights
review of the Rubinar. See:

http://www.cloudynights.com/item.php?item_id=643

The author can focus at infinity using 5 eyepieces and an
uncut celetron 90 degree mirror diagonal without modifying
the aluminum infinity stop. He only removed it when he
took out the rear field flattener & found out he couldn't focus
with some eyepieces. With the rear field flattener installed,
he can focus using any eyepieces and diagonal. How about you.
What's the reason why you removed the infiniity stop?

Because I bought it for use with canon EOS camera with built in flash
that need an extension ring to mount the lens. That's beyond infinity
so infinity stop had to go.

What exactly is your canon EOS model? And where did you
buy the adapter? I had planned to use camera too. Are you
satisifed with the image? They say a NIkon can produce more
colorful images.


Is it
because you want your eyepieces to focus at infinity?

That's how we use telescopes, I'm sure you won't use it for ant
watching either.

Unfortunately, I wasn't able to view the scope at the stars
prior to taking off the aluminum stop because of cloudy
skies so I don't know if the original unmodified Rubinar
can focus at infinity using a normal diagonal and any
eyepieces (which the cloudynight reviewer above can).
I'm asking this because if it can focus there is no need
to remove the infiniity stop unless you want to focus
close, right?

I was realy surprised at a few articles about rubinar. They made no
sense for my rubinar, but as you discovered, there are obviously two
versions of the lens. For use with my diagonal, I have to focus beyond
the infinity almost to the phisical limits of the lens, where the
front cell hits the mirror cell (not mirror).
So I realy can't imagine, how cloudynight revier could do it with my
lens.
He couldn't.

Last things I want to know. If you use a full fledge 1.25" TV
Everbright with longer tube (not cut). Would the image
really degrade in quality significantly? Next time you
are free, please test whether it's significant. The reason I
can't test it myself is because my diagonal tube is not
cut or shortened. According to the reviewer above, his
system becomes 1600mm (F/15) with a diagonal with
normal tube. What if the diagonal tube is shortened like yours,
would the focal length becomes like 1200mm (f/12) or so?
I need to know the figure so I can calculate the degradation
in spherical abberration of a full diagonal and shortened
diagonal.

Thanks.

Win




Win

If it's a "relay" diagonal you can't just calculate magnification the
normal way. Maybe it introduces some additional magnification..

No. It reduces the magnification to half. With a 30mm eyepiece,
I can do 50X using a televue diagonal (I assume the focal
length of the scope becomes 1500/30=50X. But with the
included straight thru, i get only 22X. Somehow the relay
can reduce the magnfication from 50X for a normal
diagonal to just 22X. Know what optical path is involved?
Can't figure this out.

Like I said, IF it has a relay lens, it projects reduced image from
the 44mm flange distance to the eyepiece. I guess it also inverts the
image for normal viewing.

Whatever it is (after reviewing about relay lens, it is
possible it is that). It is very effective when viewing target one
meter away. Without it. You have to use 1600/30= 54X
which can get the target a bit dimmer esp since any
close focusing introduces spherical aberrations and
moving the focal point backward also produce more
aberrations. So viewing target one meter away can
produce something like 1/2 wavefront error. By getting
lesser magnification in the relay (actually it is a zoom
with variable 22X-44X mag), the image is better.
When you use 22X magnification at closeup
you can see great contrast

BTW.. with typical 8" SCT. What's the equivalent
flange distance to the eyepiece? 100mm?? They
take into account the diagonal when designing
8" SCTs?

I don't know but I'm sure with all SCTs you have enough space for any
diagonal and focuser. Rubinar is a camera lens and has just enough
space for the camera.

Win- Hide quoted text -

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