Sky & Telescope - February 2020 - 23

S Mon
HD 261263 (10.3)

HD 261389 (10.5)
The
Christmas
Tree
Cluster

R Mon

HD 261416 (9.3)

The Cone
Nebula
HD 261447 (10.3)
HD 261231 (9.7)
HD 261661 (9.1)

HD 47888

POSS-II / STSCI / CA LTECH / PA LO M A R OBSERVATORY (2)

~1° × 1¼°

t IN NORTHERN MONOCEROS Tiny NGC 2261 is below and right of the
Cone Nebula and NGC 2264, the Christmas Tree Cluster - the star S Mon
is the bright star at the base of the upside-down tree. By the way, the
Cone Nebula is an extremely difficult visual target - have you snagged it?
Hubble's
Variable
Nebula

scope. As it turned out, I could. There are also two observations from October 2019 using my own 8-inch f/4 Dob.
One of the most valuable things I've learned from this
observing project is that getting satisfying observations of
Hubble's Variable Nebula doesn't require a huge telescope and
freezing all night under the winter sky at a remote dark-sky
site. Cold winter nights can certainly present a persuasive
argument to stay inside, but NGC 2261 is one of the best
reasons to get out there and observe anyway.

December 6, 2018
28-inch f/4 at 408×

January 1, 2019
28-inch f/4 at 408×

p ZOOMING IN You don't need a monster of a scope to spot Hubble's
Variable Nebula - its small apparent size and relatively bright magnitude
yield a high surface brightness. Use the HD stars and their magnitudes (in
parentheses) to estimate the brightness of R Mon. This image is 30′×30′.

How Long?
After looking at an online animation of images taken over
several months (see https://is.gd/HVNanimation), I had a
hunch I'd be able to see changes over the course of a few
nights. Although that turned out to be true, the shortest
timescale during which I saw definite variations was only
24 hours. That was both unexpected and exciting, because I
could see at a glance that the nebula had changed its appearance each time I observed it on consecutive nights. Observa-

January 14, 2019
28-inch f/4 at 408×

January 30, 2019
8-inch f/3.3 at 164×

sk yandtelescope.com * FEBRUARY 2 02 0

23



https://www.is.gd/HVNanimation http://www.skyandtelescope.com

Sky & Telescope - February 2020

Table of Contents for the Digital Edition of Sky & Telescope - February 2020

Contents
Sky & Telescope - February 2020 - Cover1
Sky & Telescope - February 2020 - Cover2
Sky & Telescope - February 2020 - 1
Sky & Telescope - February 2020 - Contents
Sky & Telescope - February 2020 - 3
Sky & Telescope - February 2020 - 4
Sky & Telescope - February 2020 - 5
Sky & Telescope - February 2020 - 6
Sky & Telescope - February 2020 - 7
Sky & Telescope - February 2020 - 8
Sky & Telescope - February 2020 - 9
Sky & Telescope - February 2020 - 10
Sky & Telescope - February 2020 - 11
Sky & Telescope - February 2020 - 12
Sky & Telescope - February 2020 - 13
Sky & Telescope - February 2020 - 14
Sky & Telescope - February 2020 - 15
Sky & Telescope - February 2020 - 16
Sky & Telescope - February 2020 - 17
Sky & Telescope - February 2020 - 18
Sky & Telescope - February 2020 - 19
Sky & Telescope - February 2020 - 20
Sky & Telescope - February 2020 - 21
Sky & Telescope - February 2020 - 22
Sky & Telescope - February 2020 - 23
Sky & Telescope - February 2020 - 24
Sky & Telescope - February 2020 - 25
Sky & Telescope - February 2020 - 26
Sky & Telescope - February 2020 - 27
Sky & Telescope - February 2020 - 28
Sky & Telescope - February 2020 - 29
Sky & Telescope - February 2020 - 30
Sky & Telescope - February 2020 - 31
Sky & Telescope - February 2020 - 32
Sky & Telescope - February 2020 - 33
Sky & Telescope - February 2020 - 34
Sky & Telescope - February 2020 - 35
Sky & Telescope - February 2020 - 36
Sky & Telescope - February 2020 - 37
Sky & Telescope - February 2020 - 38
Sky & Telescope - February 2020 - 39
Sky & Telescope - February 2020 - 40
Sky & Telescope - February 2020 - 41
Sky & Telescope - February 2020 - 42
Sky & Telescope - February 2020 - 43
Sky & Telescope - February 2020 - 44
Sky & Telescope - February 2020 - 45
Sky & Telescope - February 2020 - 46
Sky & Telescope - February 2020 - 47
Sky & Telescope - February 2020 - 48
Sky & Telescope - February 2020 - 49
Sky & Telescope - February 2020 - 50
Sky & Telescope - February 2020 - 51
Sky & Telescope - February 2020 - 52
Sky & Telescope - February 2020 - 53
Sky & Telescope - February 2020 - 54
Sky & Telescope - February 2020 - 55
Sky & Telescope - February 2020 - 56
Sky & Telescope - February 2020 - 57
Sky & Telescope - February 2020 - 58
Sky & Telescope - February 2020 - 59
Sky & Telescope - February 2020 - 60
Sky & Telescope - February 2020 - 61
Sky & Telescope - February 2020 - 62
Sky & Telescope - February 2020 - 63
Sky & Telescope - February 2020 - 64
Sky & Telescope - February 2020 - 65
Sky & Telescope - February 2020 - 66
Sky & Telescope - February 2020 - 67
Sky & Telescope - February 2020 - 68
Sky & Telescope - February 2020 - 69
Sky & Telescope - February 2020 - 70
Sky & Telescope - February 2020 - 71
Sky & Telescope - February 2020 - 72
Sky & Telescope - February 2020 - 73
Sky & Telescope - February 2020 - 74
Sky & Telescope - February 2020 - 75
Sky & Telescope - February 2020 - 76
Sky & Telescope - February 2020 - 77
Sky & Telescope - February 2020 - 78
Sky & Telescope - February 2020 - 79
Sky & Telescope - February 2020 - 80
Sky & Telescope - February 2020 - 81
Sky & Telescope - February 2020 - 82
Sky & Telescope - February 2020 - 83
Sky & Telescope - February 2020 - 84
Sky & Telescope - February 2020 - Cover3
Sky & Telescope - February 2020 - Cover4
https://www.nxtbook.com/nxtbooks/aas/st_202406
https://www.nxtbook.com/nxtbooks/aas/st_202405
https://www.nxtbook.com/nxtbooks/aas/st_202404_qr
https://www.nxtbook.com/nxtbooks/aas/st_202404
https://www.nxtbook.com/nxtbooks/aas/st_202403
https://www.nxtbook.com/nxtbooks/aas/st_202402
https://www.nxtbook.com/nxtbooks/aas/st_202401_aus
https://www.nxtbook.com/nxtbooks/aas/st_202401
https://www.nxtbook.com/nxtbooks/aas/st_202312_aus
https://www.nxtbook.com/nxtbooks/aas/st_202312
https://www.nxtbook.com/nxtbooks/aas/st_202311
https://www.nxtbook.com/nxtbooks/aas/st_202310
https://www.nxtbook.com/nxtbooks/aas/st_202309
https://www.nxtbook.com/nxtbooks/aas/st_202308
https://www.nxtbook.com/nxtbooks/aas/st_202307
https://www.nxtbook.com/nxtbooks/aas/st_202306
https://www.nxtbook.com/nxtbooks/aas/st_202305
https://www.nxtbook.com/nxtbooks/aas/st_202304
https://www.nxtbook.com/nxtbooks/aas/st_202304_qr
https://www.nxtbook.com/nxtbooks/aas/st_202303
https://www.nxtbook.com/nxtbooks/aas/st_202302
https://www.nxtbook.com/nxtbooks/aas/st_202301
https://www.nxtbook.com/nxtbooks/aas/st_202212
https://www.nxtbook.com/nxtbooks/aas/st_202211
https://www.nxtbook.com/nxtbooks/aas/st_202210
https://www.nxtbook.com/nxtbooks/aas/st_202209
https://www.nxtbook.com/nxtbooks/aas/st_202208
https://www.nxtbook.com/nxtbooks/aas/st_202207
https://www.nxtbook.com/nxtbooks/aas/st_202206
https://www.nxtbook.com/nxtbooks/aas/st_202205
https://www.nxtbook.com/nxtbooks/aas/st_202204
https://www.nxtbook.com/nxtbooks/aas/st_202203
https://www.nxtbook.com/nxtbooks/aas/st_202202
https://www.nxtbook.com/nxtbooks/aas/st_202201
https://www.nxtbook.com/nxtbooks/aas/st_202112
https://www.nxtbook.com/nxtbooks/aas/st_202111
https://www.nxtbook.com/nxtbooks/aas/st_202110
https://www.nxtbook.com/nxtbooks/aas/st_202109
https://www.nxtbook.com/nxtbooks/aas/st_202108
https://www.nxtbook.com/nxtbooks/aas/st_202107
https://www.nxtbook.com/nxtbooks/aas/st_202106
https://www.nxtbook.com/nxtbooks/aas/st_202105
https://www.nxtbook.com/nxtbooks/aas/st_202104
https://www.nxtbook.com/nxtbooks/aas/st_202103
https://www.nxtbook.com/nxtbooks/aas/st_202102
https://www.nxtbook.com/nxtbooks/aas/st_202101
https://www.nxtbook.com/nxtbooks/aas/skywatch_2021
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/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