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Stardaug
professor emeritus
Reged: 08/03/08
Posts: 549
Loc: Ontario, Canada
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I've had some more time to experiment with the All Star Align in firmware 4.18 now. I'm not entirely convinced it's better than the old wedge align routine having used it more now.
I've tried a number of scenarios for alignment stars and polar align star. Although Celestron says you can use any star(s) I don't think this is the case as experimenting with a number of stars in different areas of the sky produced vastly different results.
So what I'm wondering is what alignment stars do others use for the All Star Align? What star do you use for the polar align routine? My best results so far have been using Enif for the polar/wedge align.
This has been discussed a bit before but I'd like to open up the discussion again. Hopefully get some better results with the polar/wedge align end of it.
Cheers.
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"Keep looking up!"
Shawn / Ontario, Canada
Celestron CPC800 SCT w/XLT & GPS // Skywatcher Equinox 80ED F6.25 500mm APO // Canon Rebel 350XT unmodded // Milburn EQ Wedge (a Meade model modified to fit my CPC)
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Chris Rowland
sage
Reged: 02/28/05
Posts: 344
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Stars near the zenith aren't good because rotating the mount in azimuth doesn't move the stars, just rotates them.
Stars to the East and West aren't good because the altitude adjustment moves them in the same direction at the azimuth adjustment.
The optimum seems to be stars near the meridian.
How does this match your tests?
Chris
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Roy Salisbury
sage
Reged: 05/26/09
Posts: 413
Loc: Las Vegas, NV
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I found the new alignment process it to only be "easier" but not necessarily better or worse. And depending on when I start will dictate what stars I use. I stay away from Polaris just because I also use the "Live View" on my DSLR for centering, and its a bit hard to see when the LCD is obscured by the base of the scope.
I pick that I can easily identify and use them. Something bright and easily named. Say like Deneb and Vega. I'm not necessarily using them for "perfect" alignment, but something to get me started in the right direction.
But I rarely ever stop there. I end up doing an iterative alignment (about 5 or 6 iterations) using whatever stars are recommended by my AstroPlanner software, and then do a quick check with PemPro. All in all I spend about 30-45 min on alignment (and initial focus) and it usually gives me enough to get the field rotation under control and let the autoguider do the rest.
Roy
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Scope: CPC 800 / AT66ED
Cameras: Canon 500D / QHY9M / SSAG
Hualapai Valley Observatory
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Stardaug
professor emeritus
Reged: 08/03/08
Posts: 549
Loc: Ontario, Canada
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I've tried a few different situations and yes stars near the meridian do tend to be the best choice, hence why Enif seems to work for me.
I also tried using Fomalhaut and Diphda which are lower to the South/SSW, near the meridian and ended up making unusual adjustments in ALT especially to achieve a polar alignment which ended up actually be way out.
Celestron indicated to me that any alignment stars could be used, even though the HC says the stars are to far east or west. So does this mean doing a star align using to far east or west is okay if you then use a star near the meridian for the polar alignment?
Would we use stars near the meridian for alignment and also one of these for polar alignment then? Or choose a different one?
I think Roy may have it right when he says about getting a rough polar alignment and using that to further refine it.
Oddly enough I found redoing the polar alignment has me making adjustments again even though I just did it. I would have thought it would end up where I had previously left things.
Thanks for the feedback thus far!
Cheers.
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"Keep looking up!"
Shawn / Ontario, Canada
Celestron CPC800 SCT w/XLT & GPS // Skywatcher Equinox 80ED F6.25 500mm APO // Canon Rebel 350XT unmodded // Milburn EQ Wedge (a Meade model modified to fit my CPC)
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Stardaug
professor emeritus
Reged: 08/03/08
Posts: 549
Loc: Ontario, Canada
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So last night I tried using Algenib and Scheat for the alignment and then Scheat for the polar alignment. The HC said the stars were to far east, west for best polar alignment. This being said, I went ahead any how with it. I was able to get 3min unguided images through the 80mm F6.25. 5min exposures displayed trailing.
With the old polar alignment routine I was able to achieve 5min unguided images. Unfortunately the old polar alignment routine is no longer available in the 4.18 firmware from what I can see.
So I guess we're still left with having to tweak the polar alignment further. It would be nice though I think if a polar alignment routine existed that was accurate. At least more accurate than the current All Star Align.
Anyone else have some experiences to share?
Thanks!
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"Keep looking up!"
Shawn / Ontario, Canada
Celestron CPC800 SCT w/XLT & GPS // Skywatcher Equinox 80ED F6.25 500mm APO // Canon Rebel 350XT unmodded // Milburn EQ Wedge (a Meade model modified to fit my CPC)
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astrovienna
sage
Reged: 12/04/06
Posts: 249
Loc: Vienna, VA
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I just experimented with this for the first time last night, and was pretty flummoxed when I chose Pollux as my star. The az and alt movements were too confusing with a star low in the northeast. But then I just picked Polaris as my star, and I think it was pretty much the same as the old routine.
Kevin
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The Hole in the Trees Skybox
CPC1100 on a Milburn wedge
C8 Phoenix (1985 Super C8+ remounted on a Nexstar GPS fork)
Meade DSI II Pro
DMK 21AU04.AS
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Stardaug
professor emeritus
Reged: 08/03/08
Posts: 549
Loc: Ontario, Canada
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I used Algenib and Scheat the other night for the all star align and Scheat for the polar align. I had better results this time even though the HC indicated star(s) were to far east or west - perhaps actually not liking the altitude of these stars but based on what the HC was giving me options for in the EQ Auto Align these are what I chose.
Pointing at the pole and looking through the CPC 800 with a crosshair EP, Polaris was outside the FOV and the two stars I could see nearest center appeared to rotate around the center fairly good. A little off but not bad.
I took the opportunity to experiment with Iterative Polar Alignment. I synced on Capella and did a goto for Polaris. Nudging Polaris halfway in the FOV toward center using the wedge adjustments and then slewed back to Capella, centered and synced on it, with a goto back to Polaris, repeating these steps.
I definitely noticed the goto on Polaris positioning it closer to center with each iteration. I did however get to a point where I could not refine it any closer to the crosshair center.
Cheers.
--------------------
"Keep looking up!"
Shawn / Ontario, Canada
Celestron CPC800 SCT w/XLT & GPS // Skywatcher Equinox 80ED F6.25 500mm APO // Canon Rebel 350XT unmodded // Milburn EQ Wedge (a Meade model modified to fit my CPC)
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