Drift Alignment - how far?

[whzzz28 (Nathan)]

Originally Posted by Poita

The failure of the two star align makes me think that you have the date in DD/MM/YYYY format instead of MM/DD/YYYY.

Thanks for the posts Peter.
I can confirm that it is MM/DD/YYYY. This is the first thing i checked.

I also tried the simulator. The amount of movement needed was more than i expected but i was able to align it. Next time i am out ill take a photo of the mount. I am starting to think that maybe my leg isn't pointing at the correct location. Something else to double check.

Sadly its showers forcast for the next seven days so will be awhile before i can get back out there.

[Poita (Peter)]

Ah. There is your problem right there.

Tell your mount to 'Park' and then loosen the clutches, and manually move the mount into the correct parked position (the mount not the tripod, leave the tripod where it is).
Then tighten up the clutches again.
Now the electronics in the mount are aligned with the mount itself, and you will have much better luck with the 2 star align process.

The mount has no idea where true North or South or anything is, it counts on you having the tripod pointing true south, and the elevation set to your location, and the 'Park' being when the mount is 'zeroed'.
It then aligns everything in relation to that starting point, so they need to be as close as possible.

If you park the scope, and it isn't pointing directly over the leg, then you need to move it into the correct parked position, using your hands, not using the controller. It should then remember that parked position as long as you park it each time before you turn it off.

[niko]

some good advice here - it's frustrating but hang in there, once you have it you'll be flying.

I read this - "Two hours later i get fed up and put the altitude back to what it should be and decide to move on to star alignment. Following instructions i did a two star alignment. First star: Acrux. Mount was off by a fair bit so i manually (with my hands) moved it so Acrux was centered in the scope. I then pressed OK to mark the location and then went to Sirius. Again it was off. This time i used the controls to move the mount and centre it. HEQ5 accepted it."

Not sure that you can move the mount with your hands for one star but the controls for the other...???

[Peter.M]

for the first star you can loosen the clutches and move the telescope by hand, the second star must be centered with the controler.

[Poita (Peter)]

Originally Posted by niko

Not sure that you can move the mount with your hands for one star but the controls for the other...???

That is exactly the way it should be done. Park the scope, and if it is not correct loosen the clutches and get it by hand into the parked position. Tighten the clutches and start the alignment.
When the scope is finished slewing to the first star, loosen the clutches again and centre it by hand (do not use the controller).
Then tighten the clutches, accept the first star and let it slew to the second. This time you centre it with the hand controller.

[RobF (Rob)]

Hmmm, which is probably why my 3 star alignments never used to work - I never used clutches to get first star right. And come to think of it now, I'm effectively doing that now with all the trouble I go to to get very close polar alignment before final pointing model in EQMOD now....

[Peter.M]

The pre parking is not needed if you are just going to undo the clutches and move the scope because when you park it after manually centering the first star it isn't going to be in the right spot anyway. It can't hurt I guess though.

[Poita (Peter)]

Originally Posted by Peter.M

The pre parking is not needed if you are just going to undo the clutches and move the scope because when you park it after manually centering the first star it isn't going to be in the right spot anyway. It can't hurt I guess though.

True.
I guess I was expecting that once the three star was done that a drift alignment would then ensue, in which case you'd park the scope at the end of the session to be ready for next time.

[whzzz28 (Nathan)]

Thought this was due a followup post.

On the weekend, Saturday to be exact, the weather was brilliant and i got some good quality time in with the scope.
Sadly my quality time was mared by creepy crawlies. Felt something on my head, put hand up and felt cobwebs... Went inside and checked for spider but couldn't find one. Went back outside and noticed something crawling down my arm, about the size of a two dollar coin... Yep it was a spider. After killing it i noticed a large spider building its web very close to my scope... Sigh spiders.

I am happy to say that i think i have drift alignment down pat. Not perfect, no far from perfect, but i was able to drift align.


I think what was causing me my problems were:

1. Mount was not levelled properly.
2. Mount altitude was way, way off. (7 degrees or so apparently)
3. The digital (android app) compass was showing true north to be south-west. It was actually south-east (10 degrees).

Once i fixed these three things up, i found drift alignment only required a small amount of turning and screwing to get it close.
I bought a normal compass and digital inclonometer with spirit guage, and they helped alot.

Now i am having problems with PHD guiding. Guiding is rough causing blur on long shots and guiding was impossible near the meridian (it said it was guiding... and the star just moves away as if PHD isn't sending the commands to move the mount to the mount) and the poor guiding showed in distant objects when i tried to do more than 1min subs.
I guess this is just a matter of my PHD settings not being agressive enough, although im not sure about guiding near the meridian, that seemed borked to me. Will have to do some more reading.

One last question;
I have uploaded a copy of M42 that i took (it was a jpeg shot, i didn't get raw shots of M42 before it disappeared behind the house). Is this coma/field curviture at the edges of the screen causing the star shape problems and, what looks some sort of ghosting? The stars towards the center of the image look much rounder and sharper so i am not sure if what i am seeing here is poor guiding, poor alignment, or due to lack of coma corrector and or field flattener?

http://i.imgur.com/dQk8L.jpg

-edit-
Turns out the "ghosting" (correct term was probably haloing) was due to bad stacking. Did a 2 point stack in nebulosity and got a better image. Lack of flattener on the edges is noticeable, but there still seems to be some shift, guessing guiding or alignment.

http://i.imgur.com/aC32R.jpg

Thanks for the help everyone has provided so far!