Quote:Hey guys,I apologize in advance for the long post.As the title suggests, I use a CG5ASGT with a 100mm lens and I see trailing after only 4 minutes of exposing. Shouldn't I be able to go ~15min without seeing any trailing?
Uncle Rod Uncle Rod's Astroblog: http://uncle-rods.blogspot.com/
Quote:Thanks for the input.It is trailing. All the stars are streaks in the same direction. Even at f/5.I thought leveling was crucial.
Quote:It is trailing. All the stars are streaks in the same direction. Even at f/5.
Quote:I have seen that if you want accurate goto's then you want the mount a level as possible. At least that is what I have observed with both the cg5 and the cgem.Dan
- Jared Willson
Quote:6. Turn mount off. I am not sure if this is the way to go. If you leave your mount on, how do you get it to do another 2+4 alignment?
Celestron Edge HD 11, 190 mm Orion Mak-Newt, Astro-Tech AT90EDT Losmandy G11, NEQ6 PRO Canon 450D XSi, Modded
Quote: You don't need to turn off the mount. keep hitting undo to scroll back to the start, and the HC will once again ask you to input your data, align index marks etc. This is because your previous alignment is lost when you go through the polar align routine.
Quote: I use a CG5ASGT with a 100mm lens and I see trailing after only 4 minutes of exposing. Shouldn't I be able to go ~15min without seeing any trailing?
Quote: Are you sure 3 min @ 100mm is the max I can get out of this mount without guiding. The mount is way underloaded with my equipment.
Quote: It depends on what camera you are using too. arcseconds per pixel. If you're using a new-ish DSLR then you will likely have around 20 arcseconds pr pixel. That means your mounts PE won't make that much difference. I stay with most of the others here: Try drift alignment. I bet you'll be able to do at least 5 minutes. 10 should be doable at that scale.
Quote: For drift alignment it is advantageous to level the mount to reduce the number of iteration. Suppose I don't trust the bubble level of the CG5, where on the mount should I place the external level?
Quote: The other reason was that the bigger the drift, the smaller the "effective" imaging area. Once you stack the images, the edges look underexposed. The bigger the drift, the bigger the area that looks underexposed (because the overlap between 1st and last sub is smaller).
Quote: Another point. If I hit 'Undo' often enough, the CG5 only takes me back to a screen that reads 'Advanced GT', I don't see an option to enter all the info and do another 2+4 alignment. Not that it matters too much - turning the mount off and on again may take 1 second longer than the other way.
Quote:Are you talking about light drop off at the edges of the image? If so, that's probably vignetting due to not having 100% field illumination on the XSi sensor. Are you taking flats? That usually helps with vignetting. I don't understand what you mean by 'drift', unless you're referring to the movement of the stars from frame to frame. That kind of drift is actually a result of polar misalignment. The stars may not be trailing in the image because the exposure was short enough not to capture it, but over time the star field moves from frame to frame. That brings you back to the need for a good polar alignment.
Quote: If I replace one alignment star as you suggested, will it automatically ask me to replace the other one, and the 4 calibration stars?
Quote: I expect that limited trailing like this will be invisible (hidden by limited resolution of the lense, clipping of bright stars and seeing blur).