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10-02-2011, 07:56 AM   #46
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Here is one from last night where I mounted the camera on top of my telescope. It was a lot easier to get some good stuff in the shot but focus remain troublesome. I can not comprehend why focus at infinity is worse than almost infinity? well, a couple of 10 second exposures at ISO 1600 is an ok method to tune it in.



90 second exposure, ISO1600 at 250mm

10-02-2011, 08:51 AM   #47
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QuoteOriginally posted by Zorglub Quote
Here is one from last night where I mounted the camera on top of my telescope. It was a lot easier to get some good stuff in the shot but focus remain troublesome. I can not comprehend why focus at infinity is worse than almost infinity? well, a couple of 10 second exposures at ISO 1600 is an ok method to tune it in.
I'm going to guess this is an autofocus lens. I have some that focus past infinity too. The point where you are focused is the true infinity.

Nice result. I'm glad to finally see some of these types of photos.

10-02-2011, 08:51 AM   #48
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That's amazing detail - the spiral arms are visible, as well as M32 and M110. To be able to lock the stars like that - at 250mm over 90 seconds - is quite a feat.

Last edited by JayBee; 10-02-2011 at 10:37 AM.
10-02-2011, 09:57 AM   #49
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Very nice, but "on top of my telescope" where you not using the O-GPS1 but a motor driven telescope mount for this shoot?

10-02-2011, 10:47 AM   #50
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The motorized drive option crossed my mind, but I do know that getting something as faint as M31 into the camera's field of view is nearly impossible using just the camera's viewfinder (with my eyes anyway). Using an aligned scope and camera setup makes it a lot easier. But I'm seeing about as much star movement at 12mm and 120 seconds as in Zorglub's 250mm shot. I've yet to try the DA 50-135, but maybe with the help of my right-angle finder I can lock in on Andromeda.
10-04-2011, 03:16 AM   #51
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@Jeff, Thanks for for the info!

@Gimbal, I used the telescope and mount for finding the galaxy, then I switched off the mounts motors and let the O-GPS1 do the tracking.

@JayBee, On the topic of star movement I get very good results in some shots but mediocre in others. I will try to investigate if there is any pattern on my next outing.
10-04-2011, 03:59 AM   #52
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QuoteOriginally posted by Zorglub Quote
On the topic of star movement I get very good results in some shots but mediocre in others. I will try to investigate if there is any pattern on my next outing.
That is my (so far limited) experience as well. It would be interesting to know what went wrong with the shoots that failed to track successfully. The reasons could be that the heading is wrong, the pitch/roll angle being wrong or the focal length reported by lens not being right. How accurate is the focal length reported by a zoom lens?

I did some tests with the compass recently. I checked the heading to some known landmarks, first with google earth and then with the camera. After a "normal" calibration (the heading rotation performed on the tripod to get a smooth 360 degrees turn) I got a perfect heading to one landmark, but a few degrees off to another.

I then did a second calibration and was off by 10 degrees.
After a third calibration the first landmark was perfect again but the second landmark was still a few degrees off.

Another question is how the heading is affected when the camera pitch (up/down) angle is changed.
10-04-2011, 05:28 AM   #53
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QuoteOriginally posted by Zorglub Quote


1 minute exposure at 250mm aimed at the Pleiades
mooie foto, bedankt.

hier in holland te vaak bewolkt,

dus nauwelijks sterren gezien

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