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iPhone Star Cluster Astrophotography:
Trapezium, M79, M41, M50

Posted: 18 January 2018

Saturday night, 13 January 2018, was cloudy and windy. Monday, 15 January, was forecast to continue being cloudy, but surprisingly it was clear. However, I had a very early morning commitment the next day so wasn't able to go out to the observatory. Tuesday, 16 January, clouds returned, along with strong winds. The sky cleared the morning of Wednesday, 17 January, with a clear night in the forecast.

Open: Wednesday, 17 January 2018, 1822 MST
Temperature: 60°F
Session: 1186
Conditions: Mostly clear, breezy

Equipment Used:
12" f/8 LX600 w/StarLock
2" 24mm UWA eyepiece
1.25" 15mm eyepiece
2" 30mm eyepiece

iPhone 8 Plus

1830 MST: LX600 ON, StarLock OFF, High Precision OFF.

Viewed M42 (Great Nebula in Orion), 102X. The sky was still too bright for good viewing of the nebula, but the Trapezium star cluster was nice. Viewed the Trapezium, 163X.

Mounted the iPhone 8 Plus on the 15mm eyepiece using the Levenhuk adapter. Took this unguided image of the Trapezium, afocal 163X, using the iOS app NightCap Camera (ISO 4000, 1/25sec):


I then viewed M79 (globular cluster), 163X. I would image it (and two open star clusters) later this session when higher in the sky for my iPhone Messier Catalog Astrophotography Album.

1922 MST: the Zodiacal Light was very visible from my dark sky location. I could see it almost all the way to the zenith.

2001 MST: StarLock ON.

Took the following StarLock autoguided iPhone images using NightCap Camera:

M79, afocal 163X (Long Exposure, Light Boost, ISO 8448, 1/3sec, 1 minute exposure)

M41, afocal 81X (Long Exposure, Light Boost, ISO 4000, 1/3sec, 1 minute exposure)

M50, afocal 81X (Long Exposure, Light Boost, ISO 4000, 1/3sec, 1 minute exposure)

Removed the iPhone and viewed the open star clusters M44 (the Praesepe), M46, M47, M48, and M67. I will image these with the iPhone on a future session.

2039 MST: StarLock OFF.

2045 MST: LX600 OFF.

Close: Wednesday, 17 January 2018, 2054 MST
Temperature: 49°F
Session Length: 2h 32m
Conditions: Partly cloudy

On my previous two reports I discussed imaging Asteroid (1761) Edmondson. The asteroid was named for Dr. Frank Edmondson, who was the Chairman of the Indiana University Astronomy Department for many years, including when I was an undergraduate working on my astrophysics degree. He was also from my hometown in southern Indiana. Click to learn more about Dr. Edmondson. I am glad I was able to image his asteroid.

One thing that has frustrated me for years is getting a precise repeatable DSLR camera orientation when attaching it at prime focus (with and without the focal reducer). For most imaging the camera orientation is not critical, but when imaging comets, asteroids, and planet moons over a period of days, having the same field-of-view orientation makes it easier to accurately align multiple images during post-processing. I tried applying some markers on the 2" visual back, 2" prime focus camera adapter, and 2" focal reducer, but due to the shapes of these items it was not possible to place the markers without a lot of parallax showing up when aligning them. I welcome thoughts from readers who may have solved this camera alignment problem. Thanks.

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