CCD vs Film? Lots of time vs no patience? Alright, this is your place to discuss all the astrophotography what's and what's not. You can discuss about techniques, accessories, cameras, whatever....just make sure you also post some nice photos here too!
Hi,
Another object taken yesterday night (03 Jun 2006). Not on my target list, but due to the cloud blocking all over the sky when I start my imaging session and only Omega Centauri was left in a small clear patch of the sky. Anyway, only manage to take 7 images of around 1 minute each before the cloud claim that portion of the sky too...
By the way, this time I try not using the LPR filter, but with the WO VR-1 filter (to reduce the false colour). The light pollution are quite serious on the RAW image, but still manage to reduce most of it (some dim stars seem to disappear too ) after processing. I think the colour is more accurate than using the LPR filter (the stars look greenish with LPR filter). Will try without LPR filter on nebula next time.
Have a nice day.
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Last edited by weixing on Mon Jun 05, 2006 9:56 pm, edited 1 time in total.
Yang Weixing "The universe is composed mainly of hydrogen and ignorance."
Hi,
After looking at the RAW image, it is obvious that quite a lots of the dim stars disappear and the colour balance seem not right... just wonder where did I do wrongly??? Will try to play with image processing when I got more time...
Anyway, the attachment is the RAW image (crop to same size as my processed image)... look how seious our light pollution is...
Have a nice day.
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Yang Weixing "The universe is composed mainly of hydrogen and ignorance."
try gathering more raw images, otherwise it is tough bringing out the outer realm of the globular without accentuating the background noise level. chris has done a good job correcting the colour balance and u might like to try making sure the initial background correction is all equalised - which means using levels (press CTRL+L) in PS and move the black point slider for each individual R, G, B channel near to the base of each channel histogram. Next you may want to activate curves in PS (CTRL+M) to bring out the dimmer outer regions of the cluster by adding a new curve set point, then entering input: 128, and output: 150 for a start. The output value can vary, and you may like to experiment. But it is best to do all these on a combined image rather than the individual sub frames. I would love to show you the raw image of the cluster from the CCD, but it would be mostly black! a lot of stretching needs to be done prior to processing henceforth.
try gathering more raw images, otherwise it is tough bringing out the outer realm of the globular without accentuating the background noise level. chris has done a good job correcting the colour balance and u might like to try making sure the initial background correction is all equalised - which means using levels (press CTRL+L) in PS and move the black point slider for each individual R, G, B channel near to the base of each channel histogram. Next you may want to activate curves in PS (CTRL+M) to bring out the dimmer outer regions of the cluster by adding a new curve set point, then entering input: 128, and output: 150 for a start. The output value can vary, and you may like to experiment. But it is best to do all these on a combined image rather than the individual sub frames. I would love to show you the raw image of the cluster from the CCD, but it would be mostly black! a lot of stretching needs to be done prior to processing henceforth.
Thanks... I'm not good in PS and never use the curve... will read more and try it when I'm free.
Have a nice day.
Yang Weixing "The universe is composed mainly of hydrogen and ignorance."
Hi,
Using the same final output, but change the colour balance, adjust the threshold and the level a bit. The result seem a bit better, but the background is a bit noisy.
Have a nice day.
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Last edited by weixing on Mon Jun 05, 2006 3:37 pm, edited 1 time in total.
Yang Weixing "The universe is composed mainly of hydrogen and ignorance."
[80% Steve, 20% Alfred] ------- Probability of Clear Skies = (Age of newest equipment in days) / [(Number of observers) * (Total Aperture of all telescopes present in mm)]
Hi,
Ok... I have upload another golden version in the above post. It use the same colour balance with the image in the first post, but doesn't seem as "golden" as the image in the first post... I think this is because I use the photoshop curve to reduce the red noise in the back ground.
Have a nice day.
Yang Weixing "The universe is composed mainly of hydrogen and ignorance."
"The universe is composed mainly of hydrogen and ignorance." 
