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My Orientation and Exposure


gnomus

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I set up the scope last night and managed to achieve approximately 10 minutes of imaging time before the clouds rolled in!

I got the following shot of Clavius/Tycho.  Unfortunately, some of it was shot through a thin layer of the incoming cloud, so it's not great - this is 200 frames of a 3000 frame capture.  I'm still very much learning.

post-39248-0-13017600-1422622769.jpg

My first question relates, I guess, to "composition".  Clearly, this image is spoiled by being somewhat "skew-whiff" (for want of a better phrase).  On the few occasions i have tried imaging the moon I have come across situations when what I see on the laptop screen is OK but I feel a strong desire to rotate the camera a little in an attempt to achieve a more pleasing composition.  I am concerned, however, that if I do that, I will not seat the camera back in the eyepiece holder in precisely the same way, thus leading to a loss of focus.  (The supplied cable with the ZWO is a little on the stiff side, and sometimes when I do move the camera in the holder, the resistance of the cable will cause the eyepiece holder adapter to unscrew a little.) I know that I could then slew off to a star to re-focus with my Bahtinov, and then come back to the area I want to image.  Is that what those folks who image the moon regularly have to do (going back and forth to a star, I mean)?  Or am I missing something obvious? 

My second question relates to exposure.  I am setting the gain on my ZWO ASI120 MM-S to exactly 50%, and am then adjusting the length of exposure by viewing the histogram and moving the sliders.  I usually end up around 5-10 ms.  I tend to err on the side of caution, however.  My histogram often has a long (and sometimes broken) "tail" on the right.  I am concerned that if I push too far to the right I will end up clipping some highlights.  This is especially so since when I "sharpen" the image (by whatever means), this seems to push bits of the histogram further to the right.   Do my exposure times (5-10 ms) seem about right, or do I need to be bolder as regards the rightwards push?  On the report generated by Firecapture I often get a max level around the 140 mark.  

Thanks in anticipation of your assistance.

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Very nice. shot.

Question1: Do it anyway. I like composing the image and twisting this way and that  helps. I would also add that one of the reasons I then chose the moonlite, was an external locking ring that allows 360 degree rotation of the entire focuser body without touching anything else. I don't bother with a mask, just zoom in on the moon surface and focus it by eye. look for the small changes in the image that kind of tell you you are close, go back and forth through to find the best place to lock the focus down.

Question2: Depending upon region and phase, then exposure will vary. again I never look at a histogram (perhaps I am doing something wrong)? I usually look at the image and see if highlights are being blown out anywhere and adjust it again by eye. would say that the exposure times are spot on. its only when you get to nearly full that I have to sometimes drop it down to around 2. 

Just what I do though. I am still learning as well ;-)

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