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Humingbird; Asteroid Sherrod (Mag. +19.2)

Posted: 15 April 2018

Open: Saturday, 14 April 2018, 1833 MST
Temperature: 82°F
Session: 1221
Conditions: Clear

Equipment Used:
12" f/8 LX600 w/StarLock
2" 24mm UWA eyepiece
Focal Reducer

1840 MST: LX600 ON, StarLock OFF, High Precision OFF.

This Black-chinned Humingbird came to visit the observatory:


Viewed Venus, 102X.

1850 MST: I stepped outside of the observatory and reclined on the observatory patio bench.

1853 MST: sunset.

1900 MST: observatory dome OFF (onto the POD Zenith Table; PZT):

photo photo

1927 MST: set up the D850 DSLR for faint asteroid imaging after the end of Astronomical Twilight (2018 MST). I mounted the DSLR on the 12" telescope at prime focus + focal reducer.

My first planned target would be Asteroid 117736 Sherrod (Mag. +19.2). I had been planning to image this very faint asteroid for several weeks when it was brighter than Magnitude +18, but clouds and the Moon always seemed to interfer with my plans. I didn't hold out much hope of being able to image Asteroid Sherrod this night at its Magnitude +19.2 with my DSLR. The asteroid is named for my friend Dr. Clay Sherrod of Arkansas Sky Observatories. Here are Dr. Clay (left) and myself on 4 October 2002 at the "2nd Annual Mighty ETX Star Party" held in conjunction with the Illinois Dark Skies star party:


1938 MST: returned to the patio bench to "watch the stars come out". 1952 MST: returned to the observatory.

I tested using the D850 DSLR touchscreen to start/stop long exposures as my ShutterBoss III Wireless Remote has been returned to Vello for warranty service. The touchscreen worked fine and no vibrations were introduced by touching the camera. (The D850 also has a built-in intervalometer which I will test out on a future session.)

2010 MST: the Zodiacal Light was visible in the western sky.

Slewed to the star Denebola and SYNCed the AutoStar. Focused on the star using a Bahtinov Mask. 2014 MST: Wi-Fi ON. Used the iOS app SkySafari 6 Pro on my iPhone 8 Plus to GOTO Asteroid 117736 Sherrod. 2015 MST: StarLock ON.

2017 MST and 2117 MST: took StarLock autoguided, 5 minutes, ISO 6400, White Balance 4000K, exposures of what I hoped would be Asteroid Sherrod (Mag. +19.2). After doing some significant post-processing I determined that I did indeed capture Asteroid Sherrod:


This animated GIF shows the very faint asteroid movement over the one hour interval:


Look closely near the center of the image and you will see the asteroid moving a short distance at a diagonal left-to-right. Seeing was not ideal this night (hence the elongated stars in one image) so I was thrilled to be able to image Asteroid Sherrod. And its Magnitude of +19.2 makes it the faintest object I have imaged with a DSLR at Cassiopeia Observatory.

After imaging Asteroid Sherrod the telescope was slewed to another faint asteroid. Unfortunately, breezes began getting strong and seeing quality was further reduced. I tried imaging but autoguiding was too erratic for good tracking. I gave up. I will image this asteroid on a future session.

2141 MST: StarLock OFF, Wi-Fi OFF.

2150 MST: dome ON.

2156 MST: LX600 OFF.

Close: Saturday, 14 April 2018, 2203 MST
Temperature: 53°F
Session Length: 3h 30m
Conditions: Clear, breezy

Exactly 11 years ago I spent two nights at "Oracle Observatory". You can read my report here: 13-14 April 2007.

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