This “new” star is definitely worth to log. It was the brightest nova in Sagittarius (German Schütze) more than 100 years, and the brightest anywhere in the sky since Nova Centauri 2013.

Classical novae are not all alike. However, their underlying mechanism is the same: a white-dwarf star collects gas, mostly hydrogen, from a close companion star that’s overflowing its gravitational boundary. As the fresh hydrogen builds up on the white dwarf’s surface, the bottom of this layer becomes compressed by the dwarf’s powerful gravity. upagainEventually the layer’s bottom becomes dense and hot enough to ignite in a runaway hydrogen-fusion reaction, which quickly spreads around the whole star — the layer becomes an H-bomb in the form of a thin shell. The brightness typically jumps by 10 magnitudes.  The white dwarf eventually settles with the gas stream from its companion resumes, and the cycle begins anew. In a supernova, by contrast, an entire star explodes completely and for good.

For the picture a 50 mm lens is best:

Length FOV (Angles in degrees)
Format 35mm & Full Sized e.g.Canon 5D APS-C e.g. Canon 60Da
Horizontal Vertical Diagonal Horizontal Vertical Diagonal
10mm 122 100 130 99 76 109
11mm 117 95 126 94 71 104
12mm 113 90 122 89 66 99
14mm 104 81 114 80 58 90
15mm 100 77 111 76 55 86
17mm 93 70 104 69 49 79
18mm 90 67 101 66 47 76
19mm 87 65 97 63 45 73
20mm 84 62 95 61 43 70
24mm 74 53 84 52 36 61
28mm 66 46 75 45 31 53
30mm 62 44 72 43 29 50
35mm 54 38 63 37 25 44
45mm 44 30 51 29 20 35
50mm 40 27 47 26 18 31
55mm 36 25 43 24 16 29
60mm 33 23 40 22 15 26
70mm 29 20 34 19 13 23
75mm 27 18 32 18 12 21
80mm 25 17 30 17 11 20
85mm 24 16 29 16 11 19
90mm 23 15 27 15 10 18
100mm 20 14 24 13 9 16
105mm 20 13 23 13 9 15
120mm 17 11 20 11 7 13
125mm 16 11 20 11 7 13
135mm 15 10 18 10 7 12
150mm 14 9 16 9 6 11
170mm 12 8 15 8 5 10
180mm 11 8 14 7 5 9
200mm 10 7 12 7 5 8
210mm 10 7 12 6 4 8
300mm 7 5 8 5 3 5
400mm 5 3 6 3 2 4
500mm 4 3 5 3 2 3
600mm 3 2 4 2 2 3
800mm 3 2 3 2 1 2
 1000mm  2.1  1.5  2  1.4  0.9  1
(1) 36x24mm 35mm film frame/FX sensor size – Field of View Crop Factor = 1
(2) 23.6×15.7mm APS-C/DX sensor size – Crop factor = 1.5
 Formula:
Field of View (in degrees) = Sensor size ÷ Focal Length X 57.3°The scale factor 57.3° is just 360° ÷ 2 pi. By the way this formula is likely less accurate for very short focal lengths. But let’s use my D60a camera and 940 mm telescope as an example, DPReview gives the sensor size  as 22,3 mm × 14,9 mm. Use each dimension separately in the formula:

  • 22.3 mm ÷ 940 mm X 57.3° = 1.36°
  • 14.9 mm ÷ 940 mm X 57.3° = 0.91°