Ealing data

1. Fully (100%) illuminated circle • Linear diameter _____ mm • TFOV angular diameter _______ arcmin • Diffraction free image size per Sinnott’s equation • 36mm or 72% of a 2” barrel • (Sky & Telescope May, 1991:528-531 at 531. W = 0.0007 * F^3 ) • 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_07803.pdf • Observatory location for planetarium software • Latitude – 40°38’40” N | 40.644° N • Longitude - 112°18’8” 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_obj^2 – d_obstructed^2 ) ) - 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. Ealing data

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. Eastern 30° zone and its stars drift into zenithal good seeing position later in the evening. A typical three hour observing session covers two these 30° diameter circles 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. Working west to east within a night’s drift zone minimizes scope travel and meridian swaps. Observation planning can help minimize meridian swaps

5. 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 - • << http://tycho.usno.navy.mil/sidereal.html >> • A meridian swap will be needed if: • RA current target > Local sidereal time > RA Desired target - or • RA current target < Local sidereal time < RA Desired target • A meridian swap is not needed if: • RA current target & RA Desired target > Local sidereal time - or • RA current target & RA Desired target < Local sidereal time Relationship of meridian swap, local sidereal time and target right ascension (RA) Zenith Meridian 10 00 RA 08 00 LST 03 30 RA 13 00 RA 14 00 RA 02 00 RA Looking south

6. 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. Right angle slewing – Initial rough RA slew to target vicinity 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. 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. Right angle slewing – Medium slews to target 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. 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. • Don’t 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. Right angle slewing – Finding during the medium slew Position of the main finders mounted on the telescope. Meridian looking south

12. 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 Right angle slewing – Fine tune slews to target 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. 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 camera’s weight are removed, otherwise the scope will be unbalanced and will fall when the declination clutch is loosened. Other use notes • 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. 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. Other use notes -2

17. 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 ______________: A naked-eye limited magnitude chart for the SPOC site 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 << http://obs.nineplanets.org/lm/rjm.html >> and << http://www.imo.net/visual/major01.html#table2 >>.