Quote:
Originally Posted by netwolf
Damien thanks for your write up, just to confirm are you saying we should not do any star alignments on the mount goto control at all before running alignmaster?
For my g11 I did a cold start to clear any pointing model, and do the first star align. Then I start the alignmaster process. I would think if you don't do this then the first star you goto with alignmaster maybe quite far of. The reason I did the single star align is that this is the process you do when you use the inbuilt POlar alignment assist on the Gemini 1. That process is similar to alignmaster so I thought perhaps same rule applies, but it maybe wrong here. But the bigger problem I have is that when I get to the part were u manually align azi and then alt, I can't get the star in the middle of the bullseye in PHD.
Best I can do is get it on the horizontal or vertical centre lines respectively for az and alt.
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Hi NW,
It's all about getting the physical mount as best as you can polar aligned.
I ensure that the mount is level and at the correct angle using a protractor and compass for my location. If this is not as close as you can get by eye, any polar alignment will be harder to do. It's about the mount and the earth, not the sky at this point.
Once done, I don't worry about any star alignment and go straight into Alignmaster and use my guide scope and camera to see the stars.
So, when using Alignmaster, and after slewing and centering the first 2 stars that you selected in the list, Alignmaster slews away from the star for the first axis and asks you to adjust to bring it back. When you adjust and bring the star back, the star will not go into the middle of the bullsye because you are not well polar aligned yet, this is normal. You need to bring the star back just on the line and do this slowly and carefully as you do not want to overshoot the line as backlash will then cause issues if you go past and bring it back.
I put the star right in the middle of the line. Repeat this for the other axis and again, the star won't go right in the centre of the bullseye yet, but put it right in the middle of the other axis line.
Make sure you do these steps using the mount adjusters and not the hand box. When I say middle of line, I mean that the line is in the middle of the star.
Once done, you will not be polar aligned yet as you need to do it a few times as it gets closer each time. Now as I think I mentioned in the previous posts, after you have picked the 2 stars from the list, then centred with the handbox on both those stars, at this point and before you click on the Alignmaster button to do the alt/az adjustments, you will see the numbers at the bottom of the Alignmaster screen, and these tell you how close to good polar alignment you are, if they are very low, then you are done, if they are high, then continue, to to do the alt/az adjustments on the mount and repeat until the numbers are low.
As soon as they are low, shutdown Alignmaster without doing any other
steps. When I first used Alignmaster, I didn't know about the numbers and was always adjusting the mount as the last step, but this is not correct as Alignmaster calculates whatever it does after you have centred the stars, not after adjusting the mount. It is like after the mount has been adjusted manually, the next run of Alignmaster checks this when you centre the stars and reports on the alignment. You will notice that each time you do this, the star will get closer and closer to the centre of the bullseye each time, which is a sure sign that polar alignment is getting better and better.
Again the numbers I look for for both axix should be 00:00:20 or less. Once I got them down to about
00:00:07 but usually I get between 00:00:30 and 00:00:12. Anyway anything below 00:00:30 should not matter that much as PHD will tighten up the rest.
Now your mount is nicely polar aligned, you can do the scope part. I then with my scope, don't even bother with the automatic 2 or 3 star aligment, rather, I go to the star of my choice, and use the bullseye in PHD to centre it and select that star in the scopes handbox database, and use the hand box to sync the star. I do this on 3 sometimes 4 different stars, and once done, I then tell the scope via the hand box to slew to one of the stars I have already sync with and hit goto, it then slews directly to the star.
On my scope, at that point in time because it is the first time that I have told the scope to do a goto, it kicks in the GPS and gets the co-ordinates for my location. The scope now knows what it is looking at and where it it located. If you don't have GPS, then your location in LAT and LON needs to be accurately entered into the mount. Also the time, date and daylight savings info.
All this takes a little time but a few extra minutes settting up, makes everything ready for great tracking/guiding.
By the way, I have the Meade LX200GPS on an equitorial wedge for my setup.
This works for me everytime, unlesss Murphy is hiding somewhere about. The issue I have if I do an auto star alignment after polar aligning, is the scope sometimes does not slew very accurately to the star that it should and I have a camera that does not clear the fork mount so I have to be careful. Putting my scope in the home polar position at startup did help a bit but the way I describe above, works everytime.
Different mounts do different things but the concepts are the same. I have heard that on some EQ mounts, auto star alignment rather that manual works well so good luck and see how you go.
Cheers,
Damien.