M-M wrote:
>
> I really was not expecting it but there it was in my viewfinder and I
> got it!
>
> This is a real-time photo, not faked at all.
>
> http://www.mhmyers.com/d80/DSC_11664w.jpg
>
> I used a home-made rig to attach the D80 to view through the eyepiece of
> the Fieldscope (instead of replacing the eyepiece with a camera
> adapter). Approx f.l.= ~2100mm
>
> --
> m-m
I always thought they were a fly by night operator :O)
On Thu, 17 Jul 2008 00:10:11 -0400, M-M <nospam.m-m@ny.more> wrote:
: I really was not expecting it but there it was in my viewfinder and I
: got it!
:
: This is a real-time photo, not faked at all.
:
: http://www.mhmyers.com/d80/DSC_11664w.jpg
:
: I used a home-made rig to attach the D80 to view through the eyepiece of
: the Fieldscope (instead of replacing the eyepiece with a camera
: adapter). Approx f.l.= ~2100mm
I have to confess I thought you might be bluffing a little, but I was wrong.
That is one **** nice picture.
> On Thu, 17 Jul 2008 00:10:11 -0400, M-M <nospam.m-m@ny.more> wrote:
> : I really was not expecting it but there it was in my viewfinder and I
> : got it!
> :
> : This is a real-time photo, not faked at all.
> :
> : http://www.mhmyers.com/d80/DSC_11664w.jpg
> :
> : I used a home-made rig to attach the D80 to view through the eyepiece of
> : the Fieldscope (instead of replacing the eyepiece with a camera
> : adapter). Approx f.l.= ~2100mm
>
> I have to confess I thought you might be bluffing a little, but I was wrong.
> That is one **** nice picture.
>
> Bob
I was thinking the same thing - until I looked closely at the moon's surface
behind the wings. The heat of the engines distorts the details of the
surface much in the shape of contrails. IF it is a fake, M-M is an expert
artist, but I doubt it. Congrats, Mike!
On Thu, 17 Jul 2008 19:02:12 -0500, George Kerby <ghost_topper@hotmail.com>
wrote:
:
:
:
: On 7/17/08 6:19 PM, in article 5kkv7490luaacvvu5g84lf9i4l2s4u7che@4ax.com,
: "Robert Coe" <bob@1776.COM> wrote:
:
: > On Thu, 17 Jul 2008 00:10:11 -0400, M-M <nospam.m-m@ny.more> wrote:
: > : I really was not expecting it but there it was in my viewfinder and I
: > : got it!
: > :
: > : This is a real-time photo, not faked at all.
: > :
: > : http://www.mhmyers.com/d80/DSC_11664w.jpg
: > :
: > : I used a home-made rig to attach the D80 to view through the eyepiece of
: > : the Fieldscope (instead of replacing the eyepiece with a camera
: > : adapter). Approx f.l.= ~2100mm
: >
: > I have to confess I thought you might be bluffing a little, but I was wrong.
: > That is one **** nice picture.
: >
: > Bob
: I was thinking the same thing - until I looked closely at the moon's surface
: behind the wings. The heat of the engines distorts the details of the
: surface much in the shape of contrails. IF it is a fake, M-M is an expert
: artist, but I doubt it. Congrats, Mike!
I meant that before I looked at the picture, I suspected that it might not
quite measure up to the hype. I never had any doubt that it was real.
On Thu, 17 Jul 2008 19:03:25 -0400, M-M <nospam.m-m@ny.more> wrote:
>In article <g5odbm$ocb$1@aioe.org>, "Maurice Blanchard" <momo@momo.qc>
>wrote:
>
>> >
>> > The aperture was probably about f/16 or smaller (no choice),
>>
>> probably about ? You dont know ? lol
>
>
>I really don't know. It's not a camera lens but a telescope. Wiki "exit
>pupil"
Since it's a simple telescope, you know the focal ratio, or f-number.
It's just the focal length divided by the objective lens diameter
(entrance pupil). So for my telescope, the focal length is 50" and
the entrance pupil is 6", which makes it an f/8.3 scope. Telescopes
are generally of a fixed focal length and a fixed entrance pupil, so
the f-number is constant.
If you were just using that scope to form an image on the sensor, that
would be your answer. But it's a little more complicated by your setup
because I think you're using a lens on the camera rather than doing
what a lot of people do, i.e., just mount a DSLR body or astronomical
imager to the scope.
But here's how you can figure it out. Plug in your values to the
following:
Ft = telescope focal length
D = telescope entrance pupil
ft = Ft/D = telescope focal ratio
Fep = eyepiece focal length
Fc = camera focal length
fc = camera focal ratio (f-number)
Mp = Fc/Fep = Projection magnification
Fe = Ft*Mp = Effective focal length of the camera/telescope system
fe = ft*Mp = Effective focal ratio, or f-number of the
camera/telescope system
So, plugging the values in for my telescope and a camera lens I might
use, I get:
Ft = 1270mm
D = 152.4mm
ft = 1270/152.4 = 8.3 which is the telescope f-number
Fep = 25mm (as an example, I have many)
Fc = 50mm
fc = 1.8
Mp = 50mm/25mm = 2
Fe = 2*1270mm = 2540mm, which is the effective focal length
fe = 2*8.3 = 16.6, which is the effective f-number
The exit pupil of my telescope with the 25mm eyepiece is Fep/ft, or
3mm. The entrance pupil of the camera is Fc/fc, or 28mm. This tells
me that I have a bad setup since ideally, for best light transmission
from the telescope to the camera, the exit pupil of telescope should
match the entrance pupil of the camera. I should choose a different
lens. Fortunately, I have others that are a better match with a much
shorter focal length. Or I could change the eyepiece on the
telescope, or both the eyepiece and the camera lens. What I want is a
selection of eyepiece and camera lens that gives me the effective
system magnification I'm looking for while keeping the exit pupil of
the scope as close as possible to the entrance pupil of the camera.
This matchup of the exit pupil of the scope with the entrance pupil of
the camera is the main reason that for afocal astronomical
photography, a small P&S camera or a webcam generally work better than
a large DSLR. Not to cross thread topics, but afocal astronomical
photography is once of the few cases I can think of where a smaller
sensor with higher pixel density would work better than a larger
sensor with lower pixel density.
Where the DSLR really shines is if you mount the body to the telescope
without a lens and use the sensor to image the output of the telescope
directly. This would work much better than even a properly matched
small sensor high pixel density P&S camera.
In article <ud5084hbp2j4ji5d28mvcmtoo90ch17vl9@4ax.com>,
Steve <steve@example.com> wrote:
> it's a little more complicated by your setup
> because I think you're using a lens on the camera rather than doing
> what a lot of people do, i.e., just mount a DSLR body or astronomical
> imager to the scope.
Hold it there. I am not using the camera lens. I mounted the DSLR body
to the telescope zoom eyepiece.
The problem is I don't know how much I zoomed. It was probably about
35X, making the exit pupil 82/35= 2.3mm.
The f.l. is not given for this spotting scope, but I think there is a
way to determine aperture from diameter of exit pupil. Like I said
before, it is probably about f/28.
> Where the DSLR really shines is if you mount the body to the telescope
> without a lens and use the sensor to image the output of the telescope
> directly. This would work much better than even a properly matched
> small sensor high pixel density P&S camera.
That is what I was doing. I got very good results previously using my
Coolpix- it even auto-focused- but I wanted the larger sensor image.
On Fri, 18 Jul 2008 04:03:16 -0400, M-M <nospam.m-m@ny.more> wrote:
>In article <ud5084hbp2j4ji5d28mvcmtoo90ch17vl9@4ax.com>,
> Steve <steve@example.com> wrote:
>
>> it's a little more complicated by your setup
>> because I think you're using a lens on the camera rather than doing
>> what a lot of people do, i.e., just mount a DSLR body or astronomical
>> imager to the scope.
>
>
>Hold it there. I am not using the camera lens. I mounted the DSLR body
>to the telescope zoom eyepiece.
>
>The problem is I don't know how much I zoomed. It was probably about
>35X, making the exit pupil 82/35= 2.3mm.
>
>The f.l. is not given for this spotting scope, but I think there is a
>way to determine aperture from diameter of exit pupil. Like I said
>before, it is probably about f/28.
>
>> Where the DSLR really shines is if you mount the body to the telescope
>> without a lens and use the sensor to image the output of the telescope
>> directly. This would work much better than even a properly matched
>> small sensor high pixel density P&S camera.
>
>That is what I was doing. I got very good results previously using my
>Coolpix- it even auto-focused- but I wanted the larger sensor image.
>
>See http://www.netaxs.com/~mhmyers/camera.html#FS
Oh, ok. I didn't realize you weren't doing the same thing with the
DSLR that you were doing with the Coolpix. Also didn't know it's a
zoom scope where you have a little less ability to determine the exact
current magnification as you do with fixed focal length eyepieces.
I like the shot though, and that's all that matters. Soon I'm going
to have to get around to posting shots taken with my 6" newtonian.
It's a Criterion Dynascope RV-6 and the optics are excellent. I'm
surprised by how good it looks for a 6 incher. I've used my Canon
S400 P&S to image it and it's not bad. Eventually I'll get a camera
mount and try the D200.
Re: FINALLY! The shot I've been waiting for! 
Linear Mode
