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Quote:The real problem I am having is exposures over 10 minutes when imaging with C-11. The star trails (or elongated stars) get bigger with longer exposure. Is it because of heavy OTA plus guide scope or the left directional button as descibed in first paragraph? C-11 plus guide scope weighs 38 pounds. I made sure the equipment I have do not have flex issues especially on guide scope. I use clam shell tube rings instead of three screws tube rings for that reason. If PHD Guider keeps the guide star where it supposed to be, then why am I getting star trails (or elongated stars) longer than 10 minutes exposure with C-11?Thanks,Peter
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Quote:I'm no SCT expert but my imaging buddy just installed mirror locking bolts on his C11 because no matter how much flexure he eliminated, how tweaked his guiding was, etc. he couldn't overcome the slight movement of his mirror over a 10 minute exposure. He had oblong stars. If that's your problem, rather than double stars or something like that, I think it could very well be mirror shift.
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Quote:David,Even with the C-11 alone, it's still heavy and very difficult to turn the latitude bolts and not worth the risk damaging the bolts or threads in mount. Thanks for the suggestion. Probably drift alignment with smaller scope is more accurate than using Polar scope. When I use polar scope, I use polar finder software and once I align Polaris where it should be in polar scope, I rotate RA to make sure Polaris remains in circle. I thought this method is pretty accurate. I guess I thought wrong.And the east heavy balance thing, you said mount needs to be CW heavy when imaging east of meridian. What about imaging west of meridian? Should it be Scope heavy?Thanks,Peter
Quote:I understand your problem with the Alt bolts. I owned an Atlas and it was always a concern.And you're correct, you want to be scope heavy if your object is west of the meridian for the same reason...keeping the worm engaged.I don't think your tripod is too weak, however how is it set up? Is it on concrete or on the lawn? If it's on concrete or asphalt, you need vibration dampeners under the legs. Actually, the lawn is the best place because it's so stable. You just have to have conditions very close to perfect because of the loading on the Atlas.David
Quote:This was my original target before I started having problems. Later that night I imaged M1 as shown earlier in this thread.NGC891C-11 at F/10, 2800mm F/L2 frames of 15 minutes each1 frame of 10 minutesImagine what this would look like if I had image it all night with 15 minutes (or longer) each frame!!!! If I only knew exactly the issue I am having. Peter