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Old 06-07-2017, 12:19 AM
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Jewel box NGC4755

Jewel Box is one of the youngest know open clusters in the constellation Crux with just over 100 stars. The cluster got named (but not discovered) by Herschel who described it as "... a superb piece of fancy jewellery".

This is a further test of our home-made Cam86 CCD camera.

About 1h of 2min exposures taken with Cam86 on ED80 on NEQ6. No field flattener. Flats and darks subtracted. The camera was not cooled and the sensor was running at about 12C. Seeing was bad and the imaging location was few km from the CBD. Stacked with DSS and processed with StarTools.

I also tried using drizzle for the first time. The ED80 + Cam86 gives about 2.64 arcsec/pixel. I could see some minor improvement with 2x drizzle. I have to try 3x drizzle but StarTools wants 24GB of RAM to process such huge images

I am tempted to add diffraction spikes to get to more jewelery-like appearance

I am wondering how to improve the image (apart from the obligatory going to a darker site). Clearly a night with a better seeing would have been advantageous. Would shorter exposure times prevent the brightest starts from being overexposed and give more "resolution" in star separation?

Any comments/hints are greatly appreciated.
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Old 06-07-2017, 01:11 AM
raymo
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Yes, try 45 or 60 secs instead of 120, and your colour is [in my opinion]
over saturated, highlighting the blown out red stars.
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Old 06-07-2017, 11:21 PM
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Thanks Raymo. I usually do deep sky imaging which requires long exposures and going below 2min just seemed too short.

And I can see what you mean by blown out red stars.
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Old 07-07-2017, 03:31 AM
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Indeed, photographing clusters tend to overexpose easily. I tried this one, Omega Centauri or h and chi Persei but they all overexposed.
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Old 07-07-2017, 03:28 PM
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rcheshire (Rowland)
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Still, a very nice result...
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