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D850 DSLR 12" LX600 Image Scale Tests;
Jupiter & Galilean Moons

Posted: 30 June 2018

Friday, 29 June 2018, dawned partly cloudy, and the clouds increased during the day with some wind. As sunset approached there were some clear areas so I decided to go out to do some astrophotography tests.

Open: Friday, 29 June 2018, 1908 MST
Temperature: 83°F
Session: 1262
Conditions: Partly cloudy, breezy

Equipment Used:
12" f/8 LX600 w/StarLock
2" 24mm UWA eyepiece
2" 2X PowerMate
1.25" 3X TeleXtender
1.25" 9mm eyepiece


1915 MST: LX600 ON, StarLock OFF, High Precision OFF.

Viewed Venus, 102X.

I then began setting up to do some image scale astrophotography tests with the D850 DSLR on the f/8 12" LX600 telescope. The following images of Venus were taken at prime focus, prime focus + 2X PowerMate, prime focus + 3X TeleXtender, and eyepiece projection 271X (9mm eyepiece). The prime focus image was taken at 1/640sec, ISO 100; the other three images were all at 1/160sec, ISO 100. The images are all full-frame; the insets show the apparent size of Venus in the original 8256x5504 full sized images. The images are unedited except for being converted to black-n-white.


Based on these tests I have decided to purchase a Televue 2" 4X PowerMate in the near future.

1938 MST: sunset. Time approximate as the sun set behind some clouds.

1948 MST: viewed Jupiter, 102X. Three moons were visible. The Great Red Spot was just rotating into view.

1951 MST: all four Galilean Moons were now visible as the eclipse of Europa had just ended.

I mounted the D850 DSLR at prime focus + 3X TeleXtender. This is a single frame cropped image of Jupiter and the four Galilean Moons, 1/30sec, ISO 2500:

Mouseover or tap on image
Mouseover or tap on image for labels

The details on Jupiter's disk are pretty good considering this was a single image. The Great Red Spot and the cloud bands show very clearly.

I then did a video recording of Jupiter (DX 1080p 120fps, 1/125sec, ISO 2500). This is a stack of 119 frames using Lynkeos:


2007 MST: ended imaging due to clouds.

2009 MST: I noticed a strange looking blue cloud surrounding the planet Venus. I took this D850 photo (f/3, 1/40sec, ISO 1600, FL 38mm):


I assume that this blue cloud was very high in the Earth's atmosphere, and so was still picking up the less refracted blue light from the Sun (which was well below the horizon). The reddish cloud to the left is lower in the atmosphere, and hence being illuminated by the refracted red light from the Sun. Venus is the bright dot at the right of the blue cloud.

2020 MST: the breezes had calmed down now, but the clouds were in much of the sky.

2025 MST: last look at Jupiter, 102X.

2026 MST: LX600 OFF.

Close: Friday, 29 June 2018, 2040 MST
Temperature: 80°F
Session Length: 1h 32m
Conditions: Partly cloudy

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