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Old 05-09-2020, 02:10 PM
Dazzled by the Cosmos.

Dennis is offline
Join Date: May 2005
Location: Brisbane
Posts: 11,126
UKS1 (UK Schmidt 1)

I recently replaced my JMI Motorised Focuser with the Primalucelab ESATTO 2” Focuser as I discovered that my focus was shifting over a period of 1 hour or so of imaging. The JMI focuser was loaded with the weight of a Tak x0.8 Reducer, USB Colour Filter Wheel and ASI1600 Camera. I initially thought it may be temperature related, but in the end concluded it was more likely a mechanical issue, I was simply asking too much of the JMI.

Whatever it was, it has now been fixed so as a test target, I selected one of the brighter Milky Way Globular Clusters, UKS 1 (magnitude 17.29) to compare to a previous effort, which saw me rejecting a lot of out of focus frames due to the gradual focus drift as the scope tracked the objects higher towards the zenith.

Over a couple of nights under Bortle 6 skies in Brisbane, I took the following:

LUM: 30 secs x 120 (60 Mins)
RED: 30 secs x 40 (20 Mins)
GREEN: 30 secs x 40 (20 Mins)
BLUE: 30 secs x 40 (20 Mins)
IR807: 60 secs x 30 (30 Mins)

The ‘scope is a Tak Mewlon 210 F11.5 DK with Tak Reducer/Flattener x0.8. A plate solve gave me a measured focal length of 2080mm at F9.9.

I threw all the frames into the Batch Processing Script of PixInsight, adding Bias, Darks and Flats and PI took care of the change in camera orientation and framing over the 2 nights, as I have to set up and tear down each night.

I added the IR807 as a Luminance Frame in PS CC, which brought out the faint UKS-1 and the even smaller and fainter Crouch-1 (VVV GL001), which I believe was discovered independently by Steve Crouch and professional astronomers.

Steve Crouch’s independent discovery images can be found here:

The last 2 images (annotated) have been rotated 90 degrees CCW to better show the 2 faint Globs.

I wasn’t game enough to explore the depths of PI to figure out where the blue star halos were coming from in my images.


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