<s>
In	O
astrophotography	O
,	O
the	O
Wright	B-Algorithm
camera	I-Algorithm
design	O
,	O
presented	O
by	O
Franklin	O
Wright	O
(	O
Berkeley	O
,	O
California	O
)	O
in	O
1935	O
,	O
just	O
a	O
few	O
years	O
after	O
the	O
introduction	O
of	O
the	O
Schmidt	O
camera	O
,	O
was	O
his	O
"	O
short	O
"	O
alternative	O
to	O
the	O
original	O
arrangement	O
.	O
</s>
<s>
Wright	O
placed	O
the	O
Schmidt	O
corrector	O
at	O
the	O
focal	O
plane	O
,	O
and	O
had	O
the	O
mirror	O
aspherised	O
to	O
cancel	O
coma	O
resulting	O
from	O
the	O
altered	O
aperture	B-General_Concept
stop	O
position	O
(	O
the	O
aperture	B-General_Concept
stop	O
effectively	O
coinciding	O
with	O
the	O
corrector	O
)	O
.	O
</s>
<s>
While	O
astigmatism	O
remains	O
present	O
in	O
the	O
Wright	B-Algorithm
camera	I-Algorithm
,	O
it	O
combines	O
with	O
the	O
mirror	O
's	O
Petzval	O
field	O
curvature	O
to	O
result	O
in	O
a	O
flat	O
best	O
image	O
surface	O
.	O
</s>
<s>
In	O
effect	O
,	O
the	O
only	O
monochromatic	O
fourth	O
order	O
(	O
wavefront	O
)	O
aberration	O
of	O
the	O
Wright	B-Algorithm
camera	I-Algorithm
is	O
relatively	O
strong	O
astigmatism	O
.	O
</s>
<s>
In	O
terms	O
of	O
the	O
wavefront	O
error	O
,	O
the	O
flat-field	O
P	O
–	O
V	O
errors	O
are	O
identical	O
in	O
both	O
,	O
Schmidt	O
and	O
Wright	B-Algorithm
camera	I-Algorithm
,	O
given	O
by	O
W	O
=	O
h2/16DF3	O
(	O
h	O
being	O
the	O
height	O
in	O
the	O
image	O
plane	O
,	O
D	O
the	O
aperture	B-General_Concept
diameter	O
and	O
F	O
the	O
focal	O
ratio	O
number	O
)	O
.	O
</s>
<s>
However	O
,	O
while	O
the	O
off-axis	O
error	O
in	O
the	O
flat-field	O
Schmidt	O
results	O
from	O
defocus	O
,	O
in	O
the	O
Wright	B-Algorithm
camera	I-Algorithm
it	O
is	O
caused	O
by	O
astigmatism	O
.	O
</s>
<s>
On	O
the	O
other	O
hand	O
,	O
the	O
best	O
(	O
curved	O
)	O
image	O
surface	O
of	O
the	O
Schmidt	O
is	O
practically	O
free	O
from	O
off-axis	O
aberrations	O
,	O
hence	O
clearly	O
superior	O
in	O
quality	O
to	O
a	O
best	O
(	O
flat	O
)	O
field	O
in	O
the	O
Wright	B-Algorithm
camera	I-Algorithm
.	O
</s>
<s>
Also	O
,	O
since	O
the	O
Wright	B-Algorithm
camera	I-Algorithm
requires	O
twice	O
as	O
strong	O
corrector	O
to	O
cancel	O
spherical	O
aberration	O
of	O
the	O
mirror	O
,	O
its	O
chromatic	O
error	O
is	O
double	O
that	O
in	O
a	O
comparable	O
Schmidt	O
camera	O
.	O
</s>
<s>
On	O
the	O
plus	O
side	O
,	O
the	O
Wright	B-Algorithm
camera	I-Algorithm
is	O
only	O
about	O
half	O
as	O
long	O
as	O
an	O
equivalent	O
diameter	O
Schmidt	O
.	O
</s>
