Post on 27-May-2020
DIY:DIY:
field of viewfield of view
templatestemplates
Blake NancarrowBlake Nancarrow
why?why?
�� sense of scalesense of scale
�� eyepiece selectioneyepiece selection
�� star hoppingstar hopping
inspirationinspiration
�� wire rings wire rings
Sky & TelescopeSky & Telescope
�� acetate template acetate template
with with TirionTirion
what you needwhat you need
�� telescope & eyepiece datatelescope & eyepiece data
�� star chartstar chart
�� rulerruler
�� calculator or spreadsheetcalculator or spreadsheet
�� drawing or presentation softwaredrawing or presentation software
�� printer (ideally laser)printer (ideally laser)
�� acetate film or transparency sheetsacetate film or transparency sheets
processprocess
1.1. gather telescope data (finder too)gather telescope data (finder too)
2.2. gather eyepiece data (gather eyepiece data (binosbinos too)too)
3.3. calculate TFOV sizescalculate TFOV sizes
4.4. get scale of star chartget scale of star chart
5.5. draw scaled TFOV ringsdraw scaled TFOV rings
6.6. test printtest print
7.7. final printfinal print
telescope datatelescope data
�� focal lengthfocal length
telescope data telescope data –– exampleexample
�� focal length (in mm)focal length (in mm)
–– CelestronCelestron SPSP--C8: 2000C8: 2000
–– Edmund SSC 6": 1220Edmund SSC 6": 1220
eyepiece dataeyepiece data
�� focal lengthfocal length
�� apparent field of view (AFOV)apparent field of view (AFOV)
–– manufacturer literaturemanufacturer literature
–– fine folks on internetfine folks on internet
–– drift testsdrift tests
eyepiece data eyepiece data –– exampleexample
72723636baaderbaader
hyperionhyperion--asphericaspheric
40401818MeadeMeade
orthoscopicorthoscopic
52522626CelestronCelestron
plplöösslssl
AFOV (AFOV (°°))fl (mm)fl (mm)
calculatecalculate
�� TFOV = TFOV = AFOVAFOVepep / ( / ( flfltt / / flflepep ))
�� where:where:
–– TFOV = true (real) field of viewTFOV = true (real) field of view
–– AFOVAFOVepep = apparent field of view eyepiece= apparent field of view eyepiece
–– flfltt = focal length telescope= focal length telescope
–– flflepep = focal length eyepiece= focal length eyepiece
calculate calculate –– exampleexample
eyepiece flep AFOVep flt TFOV (°)
baader 36 72 2000 1.296
Celeston 26 52 2000 0.676
Meade 18 40 2000 0.360
baader 36 72 1220 2.125
Celeston 26 52 1220 1.108
Meade 18 40 1220 0.590
binos 376' at 1000 yards 7.162
chart scalechart scale
�� measure with accurate rulermeasure with accurate ruler
�� watchoutwatchout
–– scales may varyscales may vary
chart scale chart scale –– exampleexample
�� Pocket Sky AtlasPocket Sky Atlas
18.3 cm = 3518.3 cm = 35°°
7.15 cm = 157.15 cm = 15°°
�� average ratio ofaverage ratio of
°° per cm:per cm:
0.49910.4991
make ringsmake rings
�� use a presentation appuse a presentation app
–– PowerPoint (Window$)PowerPoint (Window$)
–– Impress (Linux)Impress (Linux)
–– Keynote (Mac)Keynote (Mac)
�� use a drawing appuse a drawing app
–– Illustrator or FireworksIllustrator or Fireworks
–– (OO) Draw(OO) Draw
�� calculate scaled ring sizescalculate scaled ring sizes
make rings make rings –– exampleexample
eyepiece scope TFOV (°) ring (cm)
baader SP-C8 1.296 0.647
Celeston SP-C8 0.676 0.337
Meade SP-C8 0.360 0.180
baader SSC 6" 2.125 1.060
Celeston SSC 6" 1.108 0.553
Meade SSC 6" 0.590 0.295
binos 7.162 3.575
make rings make rings –– live demolive demo
36mm in SP-C8
26mm in SP-C8
18mm in SP-C8
36mm in SSC 6”
26mm in SSC 6”
18mm in SSC 6”
binos Telrad
make rings make rings –– exampleexample
36mm in SP-C8
26mm in SP-C8
18mm in SP-C8
36mm in SSC 6”
26mm in SSC 6”
18mm in SSC 6”
binos Telrad
PowerPoint tipsPowerPoint tips
�� use Shift key to use Shift key to
draw perfect circlesdraw perfect circles
�� check oncheck on
Lock Aspect RatioLock Aspect Ratio
�� enter size with enter size with
two or three digitstwo or three digits
�� follow size figure follow size figure
with units (" or cm)with units (" or cm)
printprint
�� turn off scaling, i.e. turn off scaling, i.e.
print at 100%print at 100%
�� test on paper sheetstest on paper sheets
�� verify scale with chartverify scale with chart
�� final print on final print on
clear acetate filmclear acetate film
other tipsother tips
�� label printout for particular chartlabel printout for particular chart
�� beside circles show mm, TFOV in beside circles show mm, TFOV in °°, x, x
�� include other scaled objectsinclude other scaled objects
–– Moon Moon ½½°°
–– Andromeda 2Andromeda 2½½°°
–– Big Dipper 25Big Dipper 25°°
samplesample
finfin
�� thanksthanks
�� questions?questions?