Celestron Super C8+ (deforked) Atlas EQ-G Mount Celestron Onyx 80mm ED F Canon T4i (unmodified)
Photo: Qhy9 mono + qhy 5x2" filter wheel and Baader 2" LRGB, Ha, O3 and S2 filters , Meade DSI Pro 2 as guider, TS 9mm off-axis guider Binoculars: Nikon Action 12x50 Telescopes: Skywatcher Evostar 120ED f7.5 APO + TS 2" flattener Mounts: HEQ5 Pro Eyepieces: Nagler 11mm type6, Pentax XW 7mm, Televue 2X barlow 1.25"
So, last night I had a chance to get my scope out for an extended time. Sadly, it was not the best of seeing conditions, but I'll take anything!
Anyway, I have moved past the problems I had initially with polar alignment -- it's so easy, don't know how I couldn't get it right to begin with -- but have a question re: GoTo. Last night I did a 3-star alignment. My stars were, in order, Arcturus, Capella, Spica. After running this and each of the stars being way off the mark, not even in my C8 with a 36mm eyepiece, the hand controller came up and said, "Alignment May Be Poor." Yikes!
Sure enough, it was most certainly off. But, since I was looking at getting wide field astro pics, I didn't worry about it too much. After a bit I thought I would like to get some pics of Saturn at prime focus. So, moved my camera down to the C8 and popped my Bhatinov mask on. For focusing, I figured I'd use Arcturus to take my focusing images. Used the hand controller and entered Arcturus. Mount swung over and bang! Arcturus was dead center. I'm guessing because it was an alignment star I used. Anyway, got focused and used the hand controller and entered Saturn. Again, essentially dead on center. Then later used the hand controller and selected M13. Again it was dead on.
So why after star alignment couldn't find anything and then later I get some objects dead on?
Just curious if anyone has some insight on this.
Uncle Rod Uncle Rod's Astroblog: http://uncle-rods.blogspot.com/
Quote:Go-to accuracy can be different in different parts of the sky, usually due to poor alignment star choices.The current SynScan firmware does some filtering of the alignment star choices, but it is still up to you to choose good ones. Most important, the first two stars must be separated by 3 - 4 hours of right ascension.
Quote:Well that's strange. I personally have never seen such message with my heq5 pro (sirius). It is normal the first star to be way off (even out of the field of view of finder scope) but the next 2 stars are always either close to the center of the finder scope or even in the field of view of my dslr (i use it for centering and not eyepiece).
Quote:Go-to accuracy can be different in different parts of the sky, usually due to poor alignment star choices.The current SynScan firmware does some filtering of the alignment star choices, but it is still up to you to choose good ones. Most important, the first two stars must be separated by 3 - 4 hours of right ascension. Have a look at the manual's tips and use those in accepting alignment stars. If I do that, the C8 will easily put anything in the field from horizon to horizon.
Quote:Another cause of pointing errors is cone error, where your scope's optical axis isn't aligned with the mount.The biggest source of alignment error is not being able to correctly set the home position of the mount. The Atlas, when powered up, assumes that the mount is perfectly set in the home position, something that's almost impossible to do. The first GOTO you do assumes perfect polar alignment and home position.I resolve this by unlocking the clutches and pushing the scope to the first alignment star. Final adjustments are made using the hand controller buttons after relocking the clutches. This procedure aligns the scope to the hand controller's concept of where the first alignment star is located. The other alignment stars are entered as described in the manual. Assuming that I have a good initial polar alignment, this procedure has always given me goto results that place the target inside the middle 2/3 of a low power eyepiece.Phil
Quote:When a SYNTA mount/hand controller is powered up, it uses a sky model that includes the following assumptions:1. The tripod surface is perfectly level2. The date and time are a perfect match to the actual values.3. Your location is exactly what you entered.4. The mount is perfectly polar aligned.5. You have no cone error between the mount and the scope's optical path.6. The home position of the scope is perfect.
Quote:Quote:When a SYNTA mount/hand controller is powered up, it uses a sky model that includes the following assumptions:1. The tripod surface is perfectly level2. The date and time are a perfect match to the actual values.3. Your location is exactly what you entered.4. The mount is perfectly polar aligned.5. You have no cone error between the mount and the scope's optical path.6. The home position of the scope is perfect.1. This doesn't make any difference.2. This is important for go-tos to solar system objects, and the alignment stars the HC offers. It does not have to be any more precise than what your watch says.3. As above. Precision doesn't help much here either.4. The mount does NOT have to be perfectly polar aligned. The polar scope is more than adequate.5. If, like most users, you have some cone error, you use a three star alignment, which takes that into account.6. This doesn't have to be perfect, either. How close you are to home only affects how close you come to the initial alignment stars.What really matters most? Alignment star choice. Follow the tips in the manual religiously even if you ain't religious.
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Quote:Apart from the argument about how to best align this mount, I'm interested in the statement Phil made that his gotos end up "inside the middle 2/3 of a low power eyepiece."I'm used to my CG-5 and gotos tend to be VERY accurate with my mount once aligned. I would say my gotos are usually with 5' of dead center.Is the Atlas actually that bad? While goto accuracy isn't the only thing, which is why I'm strongly considering the Atlas for AP instead of my CG-5, it sure is nice.