Sky and Telescope - February 2017 - 70

Astronomer's Workbench by Jerry Oltion

The Craig Daniels
Dogson Telescope

º Learn more about the Dogson on Craig's
website at http://tinyurl.com/gmsm87k

And now for something completely different.

the scope simple, Craig eliminated the
traditional focuser. Instead, he focuses
by moving the primary mirror up and
down the "tube" on a sled. (Sound
familiar? Schmidt-Cassegrains and
Maksutovs do this.)
Since Craig lives near the coast,
he doesn't leave his primary mirror
exposed to the salt-laden air. It's easily
removed through a trap door in the
side of the scope for storage in a sealed,
desiccated plastic container.
All this would simply make an oddlooking Dobsonian if it were mounted
on a traditional alt-azimuth rocker
and ground board, but Craig opted for
simple and direct here, too. Inspired
by the stability of classic mounts like
Hadley's, Herschel's, and Lord Rosse's
telescopes, and especially F. J. Sellers's
1920s design, Craig decided to set the
back end of his scope on the ground
and prop the front end on a stick. An

S Above: Craig Daniels with his Dogson telescope. Right: The top end of the Dogson holds the
eyepiece, setting circles, split-pupil finder, and swing-out camera mount.

70

F E B R U A R Y 2 0 1 7 * SK Y & TELESCOPE

S The inside of the Dogson, showing the
primary mirror sled.

early articulated "dog-leg" prop lent the
Dogson its name.
To use the scope, Craig simply sets
the back end on the ground, aims the
front end at his target, and adjusts slowmotion altitude via coarse threads at
the top of the foreleg. Gentle sideways
tugs adjust for azimuth.
Says Craig, "The Dogsonian design
eliminates bearings, counterweights, and
weight. It's also easier for an amateur
astronomer to build, since weight distribution and eyepiece hole location aren't
critical. Adding accessory items to flat
surfaces is fairly easy. For considerations
of operation, transport, and storage, this
is a one-piece, one-handle design."
For aiming, Craig uses several
options, starting with open sights
near the top of the scope, which he
says "eliminates that time-honored
tradition of groveling on the ground
to sight up the OTA." From there he
uses a split-pupil finder. Indeed, Craig's
split-pupil finder was the inspiration for
mine, featured in this space (S&T: June
2013, p. 66). Craig is kind of a gadget

CR AIG DA NIELS (3)

WHAT WOULD YOU GET if you took
practically every convention in telescope making and stood it on its ear?
Something that looks and functions
remarkably like the "Dogson" created
by Oregon ATM Craig Daniels.
Craig didn't set out to make the antiDob. His goal was to produce a simpleto-build, easy-to-use, modest-aperture
scope that would break neither the bank
nor the back of the person carrying it
out the door for an evening's observing.
He started with a 6-inch f/8.3 mirror.
Why f/8? Because at long focal lengths a
6" mirror can remain spherical and still
be well within ¼-wave accuracy. Spherical mirrors are way easier to produce
than parabolic mirrors, so that gives a
first-timer a leg up right away.
The "tube" is a wooden box. Boxes
are easier to build than tubes or trusses.
In order to keep the secondary mirror small and keep the upper end of


http://www.tinyurl.com/gmsm87k

Sky and Telescope - February 2017

Table of Contents for the Digital Edition of Sky and Telescope - February 2017

Contents
Sky and Telescope - February 2017 - Cover1
Sky and Telescope - February 2017 - Cover2
Sky and Telescope - February 2017 - 1
Sky and Telescope - February 2017 - Contents
Sky and Telescope - February 2017 - 3
Sky and Telescope - February 2017 - 4
Sky and Telescope - February 2017 - 5
Sky and Telescope - February 2017 - 6
Sky and Telescope - February 2017 - 7
Sky and Telescope - February 2017 - 8
Sky and Telescope - February 2017 - 9
Sky and Telescope - February 2017 - 10
Sky and Telescope - February 2017 - 11
Sky and Telescope - February 2017 - 12
Sky and Telescope - February 2017 - 13
Sky and Telescope - February 2017 - 14
Sky and Telescope - February 2017 - 15
Sky and Telescope - February 2017 - 16
Sky and Telescope - February 2017 - 17
Sky and Telescope - February 2017 - 18
Sky and Telescope - February 2017 - 19
Sky and Telescope - February 2017 - 20
Sky and Telescope - February 2017 - 21
Sky and Telescope - February 2017 - 22
Sky and Telescope - February 2017 - 23
Sky and Telescope - February 2017 - 24
Sky and Telescope - February 2017 - 25
Sky and Telescope - February 2017 - 26
Sky and Telescope - February 2017 - 27
Sky and Telescope - February 2017 - 28
Sky and Telescope - February 2017 - 29
Sky and Telescope - February 2017 - 30
Sky and Telescope - February 2017 - 31
Sky and Telescope - February 2017 - 32
Sky and Telescope - February 2017 - 33
Sky and Telescope - February 2017 - 34
Sky and Telescope - February 2017 - 35
Sky and Telescope - February 2017 - 36
Sky and Telescope - February 2017 - 37
Sky and Telescope - February 2017 - 38
Sky and Telescope - February 2017 - 39
Sky and Telescope - February 2017 - 40
Sky and Telescope - February 2017 - 41
Sky and Telescope - February 2017 - 42
Sky and Telescope - February 2017 - 43
Sky and Telescope - February 2017 - 44
Sky and Telescope - February 2017 - 45
Sky and Telescope - February 2017 - 46
Sky and Telescope - February 2017 - 47
Sky and Telescope - February 2017 - 48
Sky and Telescope - February 2017 - 49
Sky and Telescope - February 2017 - 50
Sky and Telescope - February 2017 - 51
Sky and Telescope - February 2017 - 52
Sky and Telescope - February 2017 - 53
Sky and Telescope - February 2017 - 54
Sky and Telescope - February 2017 - 55
Sky and Telescope - February 2017 - 56
Sky and Telescope - February 2017 - 57
Sky and Telescope - February 2017 - 58
Sky and Telescope - February 2017 - 59
Sky and Telescope - February 2017 - 60
Sky and Telescope - February 2017 - 61
Sky and Telescope - February 2017 - 62
Sky and Telescope - February 2017 - 63
Sky and Telescope - February 2017 - 64
Sky and Telescope - February 2017 - 65
Sky and Telescope - February 2017 - 66
Sky and Telescope - February 2017 - 67
Sky and Telescope - February 2017 - 68
Sky and Telescope - February 2017 - 69
Sky and Telescope - February 2017 - 70
Sky and Telescope - February 2017 - 71
Sky and Telescope - February 2017 - 72
Sky and Telescope - February 2017 - 73
Sky and Telescope - February 2017 - 74
Sky and Telescope - February 2017 - 75
Sky and Telescope - February 2017 - 76
Sky and Telescope - February 2017 - 77
Sky and Telescope - February 2017 - 78
Sky and Telescope - February 2017 - 79
Sky and Telescope - February 2017 - 80
Sky and Telescope - February 2017 - 81
Sky and Telescope - February 2017 - 82
Sky and Telescope - February 2017 - 83
Sky and Telescope - February 2017 - 84
Sky and Telescope - February 2017 - Cover3
Sky and Telescope - February 2017 - Cover4
https://www.nxtbook.com/nxtbooks/aas/st_202012
https://www.nxtbook.com/nxtbooks/aas/st_202011
https://www.nxtbook.com/nxtbooks/aas/st_202010
https://www.nxtbook.com/nxtbooks/aas/st_202009
https://www.nxtbook.com/nxtbooks/aas/st_202008
https://www.nxtbook.com/nxtbooks/aas/st_202007
https://www.nxtbook.com/nxtbooks/aas/st_202006
https://www.nxtbook.com/nxtbooks/aas/st_202005
https://www.nxtbook.com/nxtbooks/aas/st_202004
https://www.nxtbook.com/nxtbooks/aas/st_202003
https://www.nxtbook.com/nxtbooks/aas/st_202002
https://www.nxtbook.com/nxtbooks/aas/st_202001
https://www.nxtbook.com/nxtbooks/aas/st_201912
https://www.nxtbook.com/nxtbooks/aas/st_201911
https://www.nxtbook.com/nxtbooks/aas/st_201910
https://www.nxtbook.com/nxtbooks/aas/st_201909
https://www.nxtbook.com/nxtbooks/aas/st_201908
https://www.nxtbook.com/nxtbooks/aas/st_201907
https://www.nxtbook.com/nxtbooks/aas/st_201906
https://www.nxtbook.com/nxtbooks/aas/st_201905
https://www.nxtbook.com/nxtbooks/aas/st_201904
https://www.nxtbook.com/nxtbooks/aas/st_201903
https://www.nxtbook.com/nxtbooks/aas/st_201902
https://www.nxtbook.com/nxtbooks/aas/st_201901
https://www.nxtbook.com/nxtbooks/aas/st_201812
https://www.nxtbook.com/nxtbooks/aas/st_201811
https://www.nxtbook.com/nxtbooks/aas/st_201810
https://www.nxtbook.com/nxtbooks/aas/st_201809
https://www.nxtbook.com/nxtbooks/aas/st_201808
https://www.nxtbook.com/nxtbooks/aas/st_201807
https://www.nxtbook.com/nxtbooks/aas/st_201806
https://www.nxtbook.com/nxtbooks/aas/st_201805
https://www.nxtbook.com/nxtbooks/aas/st_201804
https://www.nxtbook.com/nxtbooks/aas/st_201803
https://www.nxtbook.com/nxtbooks/aas/st_201802
https://www.nxtbook.com/nxtbooks/aas/st_201801
https://www.nxtbook.com/nxtbooks/aas/st_201712
https://www.nxtbook.com/nxtbooks/aas/st_201711
https://www.nxtbook.com/nxtbooks/aas/st_201710
https://www.nxtbook.com/nxtbooks/aas/st_201709
https://www.nxtbook.com/nxtbooks/aas/st_201708
https://www.nxtbook.com/nxtbooks/aas/st_201707
https://www.nxtbook.com/nxtbooks/aas/st_201706
https://www.nxtbook.com/nxtbooks/aas/st_201705
https://www.nxtbook.com/nxtbooks/aas/st_201704
https://www.nxtbook.com/nxtbooks/aas/st_201703
https://www.nxtbook.com/nxtbooks/aas/st_201702
https://www.nxtbook.com/nxtbooks/aas/st_201701
https://www.nxtbook.com/nxtbooks/aas/st_201612
https://www.nxtbook.com/nxtbooks/aas/st_201611
https://www.nxtbook.com/nxtbooks/newtrack/st_201612
https://www.nxtbook.com/nxtbooks/aas/st_201610
https://www.nxtbook.com/nxtbooks/aas/st_201609
https://www.nxtbook.com/nxtbooks/aas/st_201608
https://www.nxtbook.com/nxtbooks/aas/st_201607
https://www.nxtbook.com/nxtbooks/aas/st_201606
https://www.nxtbook.com/nxtbooks/aas/st_201605
https://www.nxtbook.com/nxtbooks/aas/st_201604
https://www.nxtbook.com/nxtbooks/aas/st_201603
https://www.nxtbook.com/nxtbooks/aas/st_201602
https://www.nxtbook.com/nxtbooks/aas/st_201601
https://www.nxtbook.com/nxtbooks/aas/st_201512
https://www.nxtbook.com/nxtbooks/aas/st_201511
https://www.nxtbook.com/nxtbooks/aas/st_201510
https://www.nxtbook.com/nxtbooks/aas/st_201509
https://www.nxtbook.com/nxtbooks/aas/st_201508
https://www.nxtbook.com/nxtbooks/aas/st_201507
https://www.nxtbook.com/nxtbooks/aas/st_201506
https://www.nxtbook.com/nxtbooks/aas/st_201505
https://www.nxtbook.com/nxtbooks/aas/st_201504
https://www.nxtbook.com/nxtbooks/aas/st_201503
https://www.nxtbook.com/nxtbooks/aas/st_201502
https://www.nxtbook.com/nxtbooks/aas/st_201501
https://www.nxtbook.com/nxtbooks/aas/st_201412
https://www.nxtbook.com/nxtbooks/aas/st_201411
https://www.nxtbook.com/nxtbooks/aas/st_201410
https://www.nxtbook.com/nxtbooks/aas/st_201409
https://www.nxtbook.com/nxtbooks/aas/st_201408
https://www.nxtbook.com/nxtbooks/aas/st_201407
https://www.nxtbook.com/nxtbooks/aas/st_201406
https://www.nxtbook.com/nxtbooks/aas/st_mars
https://www.nxtbook.com/nxtbooks/aas/st_201405
https://www.nxtbook.com/nxtbooks/aas/st_201404
https://www.nxtbook.com/nxtbooks/aas/st_201403
https://www.nxtbook.com/nxtbooks/aas/st_201402
https://www.nxtbook.com/nxtbooks/aas/st_201401
https://www.nxtbook.com/nxtbooks/aas/st_201312
https://www.nxtbook.com/nxtbooks/aas/st_201311
https://www.nxtbook.com/nxtbooks/aas/st_201310
https://www.nxtbook.com/nxtbooks/aas/st_201309
https://www.nxtbook.com/nxtbooks/aas/st_201308
https://www.nxtbook.com/nxtbooks/aas/st_201307
https://www.nxtbook.com/nxtbooks/aas/st_201306
https://www.nxtbook.com/nxtbooks/aas/st_201305
https://www.nxtbook.com/nxtbooks/aas/st_201304
https://www.nxtbook.com/nxtbooks/aas/st_201303
https://www.nxtbook.com/nxtbooks/aas/st_201302
https://www.nxtbook.com/nxtbooks/aas/st_201301
https://www.nxtbook.com/nxtbooks/aas/st_201212
https://www.nxtbook.com/nxtbooks/aas/st_201211
https://www.nxtbook.com/nxtbooks/aas/st_201210
https://www.nxtbook.com/nxtbooks/aas/st_201209
https://www.nxtbook.com/nxtbooks/aas/st_201208
https://www.nxtbook.com/nxtbooks/aas/st_201207
https://www.nxtbook.com/nxtbooks/aas/st_201206
https://www.nxtbook.com/nxtbooks/aas/st_201205
https://www.nxtbook.com/nxtbooks/aas/st_201204
https://www.nxtbook.com/nxtbooks/aas/st_201203
https://www.nxtbook.com/nxtbooks/aas/st_201202
https://www.nxtbook.com/nxtbooks/aas/st_201201
https://www.nxtbook.com/nxtbooks/aas/st_201112
https://www.nxtbook.com/nxtbooks/aas/st_201111
https://www.nxtbook.com/nxtbooks/aas/st_201110
https://www.nxtbook.com/nxtbooks/aas/st_201109
https://www.nxtbook.com/nxtbooks/aas/st_201108
https://www.nxtbook.com/nxtbooks/aas/st_201107
https://www.nxtbook.com/nxtbooks/aas/st_201106
https://www.nxtbook.com/nxtbooks/aas/st_201105
https://www.nxtbook.com/nxtbooks/aas/st_201104
https://www.nxtbook.com/nxtbooks/aas/st_201103
https://www.nxtbook.com/nxtbooks/aas/st_201102
https://www.nxtbook.com/nxtbooks/aas/st_201101
https://www.nxtbook.com/nxtbooks/aas/st_201012
https://www.nxtbook.com/nxtbooks/aas/st_201011
https://www.nxtbook.com/nxtbooks/aas/st_201010
https://www.nxtbook.com/nxtbooks/aas/st_201009
https://www.nxtbook.com/nxtbooks/aas/st_201008
https://www.nxtbook.com/nxtbooks/aas/st_201007
https://www.nxtbook.com/nxtbooks/aas/st_201006
https://www.nxtbook.com/nxtbooks/aas/st_201005
https://www.nxtbook.com/nxtbooks/aas/st_201004
https://www.nxtbook.com/nxtbooks/aas/st_201003
https://www.nxtbook.com/nxtbooks/aas/st_201002
https://www.nxtbook.com/nxtbooks/aas/st_201001
https://www.nxtbookmedia.com