Celestron NexStar 8i Manuale Utente
37
and not touching it. It is easier if you use two people for this process; one to release the camera shutter and
one to hold the card. Here's the process for making the exposure.
one to hold the card. Here's the process for making the exposure.
7. Find and center the desired target in the viewfinder of your camera.
8. Turn the focus knob until the image is as sharp as possible.
9. Place the black card over the front of the telescope.
10. Release the shutter using a cable release.
11. Wait for the vibration caused by releasing the shutter to diminish. Also, wait for a moment of good
seeing.
12. Remove the black card from in front of the telescope for the duration of the exposure (see
accompanying table).
13. Replace the black card over the front of the telescope.
14. Close the camera's shutter.
Advance the film and you are ready for your next exposure. Don't forget to take photos of varying duration
and keep accurate records of what you have done. Record the date, telescope, exposure duration,
eyepiece, f/ratio, film, and some comments on the seeing conditions.
and keep accurate records of what you have done. Record the date, telescope, exposure duration,
eyepiece, f/ratio, film, and some comments on the seeing conditions.
The following table lists exposures for eyepiece projection with a 10mm eyepiece. All exposure times are
listed in seconds or fractions of a second.
listed in seconds or fractions of a second.
Planet
ISO 50
ISO 100
ISO 200
ISO 400
Moon
4 2 1 1/2
Mercury
16 8 4 2
Venus
1/2 1/4 1/8 1/15
Mars
16 8 4 2
Jupiter
8 4 2 1
Saturn
16 8 4 2
The exposure times listed here should be used as a starting point. Always make exposures that are longer
and shorter than the recommended time. Also, take a few photos at each shutter speed. This will ensure
that you get a good photo. It is not uncommon to go through an entire roll of 36 exposures and have only
one good shot.
and shorter than the recommended time. Also, take a few photos at each shutter speed. This will ensure
that you get a good photo. It is not uncommon to go through an entire roll of 36 exposures and have only
one good shot.
NOTE: Don't expect to record more detail than you can see visually in the eyepiece at the time you are
photographing.
photographing.
Once you have mastered the technique, experiment with different films, different focal length eyepieces, and
even different filters.
even different filters.
L
L
o
o
n
n
g
g
E
E
x
x
p
p
o
o
s
s
u
u
r
r
e
e
P
P
r
r
i
i
m
m
e
e
F
F
o
o
c
c
u
u
s
s
P
P
h
h
o
o
t
t
o
o
g
g
r
r
a
a
p
p
h
h
y
y
This is the last form of celestial photography to be attempted after others have been mastered. It is intended
primarily for deep sky objects, that is objects outside our solar system which includes star clusters, nebulae,
and galaxies. While it may seem that high magnification is required for these objects, just the opposite is
true. Most of these objects cover large angular areas and fit nicely into the prime focus field of your
telescope. The brightness of these objects, however, requires long exposure times and, as a result, are
rather difficult.
primarily for deep sky objects, that is objects outside our solar system which includes star clusters, nebulae,
and galaxies. While it may seem that high magnification is required for these objects, just the opposite is
true. Most of these objects cover large angular areas and fit nicely into the prime focus field of your
telescope. The brightness of these objects, however, requires long exposure times and, as a result, are
rather difficult.
Table 6-2
Recommended exposure time for photographing planets.