Ealing data

1
Ealing data

• Observatory location for planetarium software
• Latitude 403840 N 40.644 N
• Longitude - 112188 W 112.3022 W
• Altitude 4252 feet 1296 meters
• Objective diameter 16 400mm
• Obstructed diameter 152.4 mm 38
• Contrast effective aperature ( D_eff D_obj
  d_obstructed) - 248 mm
• Light grasp effective aperatrue ( D_lg sqrt (
  D_obj2 d_obstructed2 ) ) - 313 mm
• Focal length 200 5080mm
• F ratio 12.7
• Prime focus distance
• Back of focuser tube housing to prime focus
  34cm, including 2 right angle (2/27/2005)
• Back of focuser tube housing to back of right
  angle 26cm (2/27/2005)
• TFOV 1/3 (1200) 168x with standard eyepiece
  odd of reflections.

• Fully (100) illuminated circle
• Linear diameter _____ mm
• TFOV angular diameter _______ arcmin
• Diffraction free image size per Sinnotts
  equation
• 36mm or 72 of a 2 barrel
• (Sky Telescope May, 1991528-531 at 531. W
  0.0007 F3 )
• Maksutov 5 finder - FOV 1 with 40mm lens
  even reflections
• 70mm refractor finder - FOV 3.3 - odd
  reflections - similar to a binocular view in
  scale
• Telrad finder - three circles - ½?, 2 and 4.
• Digital setting circles Orion Skywizard
• Obtain manual at
• http//www.telescope.com/text/content/pdf/inst_078
  03.pdf

2
Best seeing is the 30 diameter circle
surrounding the zenith
Zenith
Meridian
08 00 LST
02 00 RA
14 00 RA
Looking south
3
A typical three hour observing session covers two
these 30 diameter circles
Eastern 30 zone and its stars drift into
zenithal good seeing position later in the
evening.
West-most star in good seeing zone observed at
start of session.
Zenith
Meridian
08 00 LST
West 02 00 RA
East 14 00 RA
Looking south
4
Observation planning can help minimize meridian
swaps

• Working west to east within a nights drift zone
  minimizes scope travel and meridian swaps.

5
Relationship of meridian swap, local sidereal
time and target right ascension (RA)

• Local sidereal time measures the position of the
  meridian on your star charts.
• On the observing night, keep an extra watch set
  to local sidereal time (LST). Obtain LST from -
• ltlt http//tycho.usno.navy.mil/sidereal.html gtgt
• A meridian swap will be needed if
• RA current target gt Local sidereal time gt RA
  Desired target - or
• RA current target lt Local sidereal time lt RA
  Desired target
• A meridian swap is not needed if
• RA current target RA Desired target gt Local
  sidereal time - or
• RA current target RA Desired target lt Local
  sidereal time

Zenith
Meridian
10 00 RA
08 00 LST
03 30 RA
13 00 RA
14 00 RA
02 00 RA
Looking south
6
Right angle slewing Initial rough RA slew to
target vicinity

• Minimize meridian swaps and potential off
  turning tube to lower than horizontal by only
  using the RA rough slew
• Slew in right ascension to bright star on same
  RA as target.
• Slew in declination to vicinity of target.

Do not use the declination rough slew route
5h
6h
M37
30
Aldebaran
10
Do use the RA rough slew route

• Avoid using the Declination rough slew route.
  Declination rough slew route can turn tube to
  lower than horizontal where subsequent RA slew
  crosses the meridian.

Estimate declination slew at right angles to
declination lines and not along angled right
ascension lines.
7
RA rough slewing grab points RA and Dec clutches
Right ascension clutch
Grab points for right ascension slewing
Declination clutch
Meridian looking south
8
Declination rough slewing grab points
Slewing arm
Meridian looking south
9
The declination clutch housing can be used as a
pointer during the initial rough slew
When slewing in right ascension, use declination
clutch housing as pointer sight to rough align
target in right ascension.
Then use the Telrad mounted on the housing to
navigate the scope to your waypoint bright star.
A Telrad finder has three circles - ½?, 2 and
4.
Meridian looking south
10
Right angle slewing Medium slews to target

• Medium slews are 2-8 in either RA or
  declination. On chart, measure travel to target
  in eyepiece True Field of Views (TFOVs)
• The slew controller speed is too slow to use for
  medium slewing.

Eyepiece TFOV
Medium slew distance
Either route is okay for fine slewing
Slewing arm

• Medium slewing is best done by ignoring the
  reversed eyepiece view for a moment. Look over
  the top of the scope frame with the naked eye,
  and holding the slew arm, practice which motion
  in RA or declination will take you to the target.
  
• Then look in the eyepiece and ignoring the
  direction of travel of the TFOV, move your arm in
  the proper direction, counting off the eyepiece
  TFOVs. Visualize the direct view movement of the
  scope as you get closer to the target.

11
Right angle slewing Finding during the medium
slew

• Two finders suitable for medium slewing are the
  
• Maksutov 5 FOV 1 with 40mm lens even
  reflections similar to a small refractor view,
• 70mm refractor FOV 3.3 - odd reflections
  similar to a binocular view.
• Dont discount the 70mm finder. It is similar
  to a binocular view. Familiarizing yourself with
  the asterisms in the 2-3 star field leading to
  your target with binoculars prior to your Ealing
  session can translate into a quick find during
  the session using the 3 70mm finder.

Position of the main finders mounted on the
telescope.
Meridian looking south
12
Right angle slewing Fine tune slews to target

• Reserve final fine tune slew for last 1. The
  slew controller speed is too slow to use for
  medium slewing 2-4.
• Fine slew using either the RA route or
  declination route

Final fine slew distance
Eyepiece TFOV
Either route is okay for fine slewing

• Use slew controller for slow travel
• Wide buttons Declination
• Narrow buttons Right ascension

13
Park position
But tube remains above horizontal on the east
side of the bay.
Only time when weight rises above horizontal
RA park position marker
Dec park position marker
Meridian looking north
Meridian looking south
14
Park position check the declination park
markings from a distance
When moving to declination park and looking up at
the marks from below, the perspective effect
can make the parking marks appear to be aligned,
when if fact they are not. Step back two or
three feet from the scope and recheck that the
declination parking marks are aligned.
15
Other use notes

• When exiting building, set combination lock to
  555.
• Safe position of the rolling ladder during
  telescope slewing is by the north east corner of
  the room, short-ladder side next to the north
  east door.
• Rolling ladder is unlocked with a foot pedal/bar
  below the first step. Standing on the first step
  triggers the anti-roll lock.
• Red wall lights should be kept at ½ power to
  prevent the lights from overheating the red glass
  covers. If overheated, the glass covers will
  fracture.
• An astrophotography camera holder is available.
  The square weights can be removed to keep the
  telescope balanced. Square weights equal to the
  cameras weight are removed, otherwise the scope
  will be unbalanced and will fall when the
  declination clutch is loosened.

• An aperature mask is stored behind the drive
  power console.
• Aligning finders
• The Maksutov finder can be aligned to scope by
  strong-arming it into position. This finder is
  mounted on friction disks.
• The other finder scopes have three screw rings
  for finder aligning.

16
Other use notes -2

• Open rolling roof after Sun is low enough that
  direct rays do not strike the scope or
  observatory.
• Chock for rolling roof is stored behind roller.
  
• Tie-down for rolling roof is stored by leaving
  it dangle vertically in the corner.
• The tie-down is released by pushing the tab
  button in the center of tie-down lock mechanism.
  
• The Skywizard moves between modes with the up
  and down arrow keys.

17
A naked-eye limited magnitude chart for the SPOC
site

• Due to light pollution in the eastern sky of the
  site, an light pollution reduction (LPR)
  broadband filter is recommended for east and
  south deep sky object viewing.
• A limiting magnitude chart for the SPOC site
  made ______________

N
NE
NW
W
E
SE
SW
S
NELM values determined using some of the 26 IMO
limiting magnitude fields for the northern sky.
See ltlt http//obs.nineplanets.org/lm/rjm.html gtgt
and ltlt http//www.imo.net/visual/major01.htmltab
le2 gtgt.