Ryderscope
22-08-2015, 11:31 PM
Funny how I came in from starting a project to capture data on NGC7009 on Wednesday night, logged on to IIS and there was Maurice's great catch of this nice little PN (http://www.iceinspace.com.au/forum/showthread.php?t=137767). A good benchmark to strive for that it will be a challenge even at my 2m focal length.
The reason for my post is to seek some guidance on the exposure times that I should be using. I am a little unsure on this object as it seems to concentrate a lot of light into a small space so the normal calculations don't seem to quite fit. I am imaging with a GSO RC10 and QSI683. Image scale is approximately .56 arc "/Px and about a half degree field of view. I thought that I would post my questions here to see what the consensus is before I get too far down track on this one.
I have captured data so far in LRGB Ha and O3. No SII as yet. I found that my normal exposure times of around 10 minutes subs for LRGB and 20-30 minutes for Ha O3 were way out as the images were saturating in the QSI683. I toned this down by adjusting the exposures so that the ADU count of the data in the actual object were in the range of 15k - 25k. Note that this is for the un-stretched image. I have attached screenshots of the 200x zoom on the raw un-stretched data. The exposure times that I finished up with were Ha 600s; O3 180s; RGB 300s; L 120s. Particularly notable was how much I had to drop down the exposures on the Luminance and O3.
So my question is, should I tone down the exposure times even more or does this sound about right? I couldn't find many examples of images taken with CCDs and different filters so I don't have much to go on. Any assistance would be greatly appreciated.
The reason for my post is to seek some guidance on the exposure times that I should be using. I am a little unsure on this object as it seems to concentrate a lot of light into a small space so the normal calculations don't seem to quite fit. I am imaging with a GSO RC10 and QSI683. Image scale is approximately .56 arc "/Px and about a half degree field of view. I thought that I would post my questions here to see what the consensus is before I get too far down track on this one.
I have captured data so far in LRGB Ha and O3. No SII as yet. I found that my normal exposure times of around 10 minutes subs for LRGB and 20-30 minutes for Ha O3 were way out as the images were saturating in the QSI683. I toned this down by adjusting the exposures so that the ADU count of the data in the actual object were in the range of 15k - 25k. Note that this is for the un-stretched image. I have attached screenshots of the 200x zoom on the raw un-stretched data. The exposure times that I finished up with were Ha 600s; O3 180s; RGB 300s; L 120s. Particularly notable was how much I had to drop down the exposures on the Luminance and O3.
So my question is, should I tone down the exposure times even more or does this sound about right? I couldn't find many examples of images taken with CCDs and different filters so I don't have much to go on. Any assistance would be greatly appreciated.