Making Pre-Point ChartsAnd Using Them In The Field

Ted BlankIOTA Annual Conference

Las Vegas, NVOctober, 2015

Ask (Ernie) And Ye Shall Receive!• IOTA member Ernie Iverson has a standing offer to create custom pre-

point charts for you for any event for your location

• If you want to try pre-pointing,I encourage you to take him up on his offer! However:

• He needs sufficient lead time – it’s a volunteer operation• He will ask you for basic information about your location and equipment• Asking him to print 8 hours of Level 6 charts (33 charts) is probably not a good

idea without a specific reason

• However you can learn a lot by trying to create your own pre-point charts too.

• More understanding of what’s going on “up there” is always useful.

• More time spent with charts at home will increase your chances of success in the field when “stuff happens”

The sky must be dark to find pre-point stars, so no need to print charts for times before Astronomical Twilight

AstronomicalTwilight

2:28 UTC(7:28 PDT)

Should I Print Charts In Equatorial mode or Alt-Az Mode?

EQ mode (North Up) Alt-Az mode (Zenith Up)

If you have an EQ mount, generate EQ charts. Alt-Az charts are more difficultto generate. This topic probably needs it’s own presentation to do it justice.

Ready To Print!• You could just take your laptop out into the field with you,

but that has drawbacks…– Battery life in cold weather, dirt, night vision…

• Better to print charts• Use laser printer for water resistance or • Put them in a 3-ring binder in plastic pages for dew

resistance• Print charts at several levels of detail, with overlap

• Level 3 (45⁰) for coarse navigation, stars to m6.5• Level 4 (20⁰) for many areas of the sky, stars to m8.5• Level 5 (10⁰) for more detail, stars to m10.5• Level 6 (5⁰) for finest detail, stars to m11.5

• Print additional charts to help you star-hop to your selected pre-point stars if in star-poor areas

Charts I Printed for The Oenone Event(Because I Need All The Help I Can Get Finding Pre-Point Stars)

You want the number of stars on your charts to roughly match what you see on your TV screen, so set your Guide9 “Star display limiting

magnitude” appropriately for each level chart you print.

(Ernie Iverson’s Recommendations)

Guide9DisplayLevel

Guide9 “Star Display”

Limiting Magnitude

Scope Step for printing Comment

3 6.0 or 6.5 Overview 2 hrs

4 8.5 Mini (50mm) 1 hr (finder scopes)

5 10.5 Midi (80mm) 30 min. 70 and 80 mm scopes

6 11.5 Maxi (125mm) 15 min. Also C8 and larger

7 or 8 12.5 End Event

Adjust these values up or down so your charts match your LCD screen views.(This will change if you change cameras, add or remove focal reducers, etc.)

Make sure your watch has a backlight and can be set (T2) to UT and 24-hr mode.

Timex Expedition, about $30, has “IndiGlo” backlight and T1/T2 for UTC

How will you be sure your scope is pointing at the star you think it is (to start your star-hop)?

A green laser pointer in a removable holder

with a stay-on button that fits into the finder

scope bracket is a lifesaver. Take it from site to site with you.

What you’ll seein the sky

What you’ll seeon your LCD screen

I use EQ-1 mounts for Midi and Maxi both I Cannot Star-Hop While Watching An LCD TV Screen And Moving A Sticky Alt-Az Tripod!

• Might succeed with a “Mighty Mini”, but…– Directions may be backwards or upside down– Tripod head will exhibit “stiction”– Legs of tripod may dig in and tilt entire rig

• My approach: always use EQ-1 mounts even for smaller Midi (80mm) scopes– Do a rough polar alignment at each mobile site– Now slow-motion controls will take you back and

forth along the same line of declination, just like your charts

– Tougher to get lost in the sky, saves time at each site– Drawbacks – heavier, bigger, harder to pack for

airline travel

Scotty Degenhardt’sSears Sprinkler Tripod

Remember, in the east, the stars will appear to rise, in the west they will appear to set

Only in the south will they appear to move almost horizontally.If you want your stars to drift horizontally or diagonally across your

LCD screen, you’ll have to rotate your camera in the drawtube.

Graphic: StellariumGraphic: Stellarium

Print extra chartsto get you from

hereto

here

Sometimes you need a “helper” star to get you to your pre-point star!

Pre-point star, m7

Helper starm2.4, easy to find

If you are early or late for a particular pre-point star, just go to it and then traversethe line of declination with the RA axis knob until you reach “now”.

Turn DEC knobto follow this axis(stays at same valueof RA)

Turn RA knobto follow this axis(stays on same lineof declination)

I bring either a portable LCD TV or a S.C.O.R.E.* box to each site

*Self Contained Occultation REcorder, designedand built for me by Bruce Berger.

You can also pre-point the night before – add 4 minutes to chart times

You can also extend your animation trail back in time to include the previous night

Demo