New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1874-11-14
THE TRANSIT OF VENUS.
PRACTICAL SUGGESTION FOR OBsEIvAroRIEs AND
AMATEUR ASTRONOMERS

ppACTICA SUCCESSION FOR OBSERNATORlES AND
AMATEUR ASTRONOMERS.
70 the Edilor OF The Trt6Hne.
SIR: When the observations OF the APP
preaching Transit OF Venus shall have been made in the
homisphere where alone will be visible, there will be
reat variety of causes o, error the influence OF which
ust no eliminated before the correction Of the sumed
nar,ax can be determined Among these are the errors
OF the tables OF Venus Its right ascension at the mo-
ent OF conjunction may be either greater OF less than
was predicted and ITS decuaton may be either greater
or less Further. its motion In right ascension ana In
dceuaton may be either greater or less than Is shown
I'm the tables and the observations cannot be taken
simultaneously in different parts OF the eafth ths may
have an important bearing.
The determination OF these need not be entirely
confined TO the observations OF Venus in its transit
have seen VEINS without diff Guilty at the time OF Its in
erior conjunction, without ever protecting the object
glass from the direct rays OF the and have seen
II within e3 Of the suns conter by protecting the OBJ
iect glass aperture inches power 9j As clouds then
arose which lasted for several days. IL Is impossible for
me to say how much nearer might have seen It, But
tina - sufficient 10 bring the Observations III the
meridian circle within less tnan twelty!Onr hours
OF the actual time OF conjunction. u the weather
shall permit believe that Venus may DC seen IN the
telescope the meridian circle, with proper protection
at any Observatory IN the country on every clear DAY
within week OF the transit. The oD'erVatons before
and after being upon opposite limbs, VIII give the error
of ascension, and, affected by the error OF equa-
toral semidiameter OF the motion IN rlSht ascension
and the observations or the upper anu lower lnOs Will
give the error OF deehna0n ana OF the motion III de-
cluatlon subject correction for parnN and refrac
ton IL that there VIII be Liabilities 10 peculiar
errors these observations but perhaps they Will o.
no greater than he causes vi error In the ooserya
lions OF the transit itself.
The protection OF the object glass from the direct rays
of the sun will difficult. large screen, painted
black with hole IN the center OF the size OF the object
elass or somewhat less 20 be erected at distance OF
not less THIS should be capable OF
being moved up from day To day as Venus rises IN
deelinatiOn Pointing the telescope each day TO the
right declnatOn the eye should De drawn back from Tue
eye-pcco until the hole IN the screen s distinctly seen
ana then II can bo easily adjusted In position by
attendant or BY the AID OF temporarily attached scale,
by the observer himself.
When saw Venus tho nearest to the sun the cusps
were extepded through an OF about 27Oo In conse
quence OF tho atmosphere OF Venus / would suggest
that tue measurement of the ousps each day may
Also aid In the determination OF The amount
and density OF OF Venus, and OF It'd in
nuence III the observations or the transit
Hsv ! etR, Noy. ~, ISJL HEAEI ~. PARkuURsr.