SCT Polar Alignment

[mick pinner]

This may be a ridiculous question but when setting up an sct on a wedge for polar alignment does it, when you are standing behind the scope face North or South? l have been trying to follow some instructions l found on the web but when facing South the position of the scope according to the Dec circle does not match up to where it should be.

[[1ponders] (Paul)]

Yeah Mick it can be a bit of a pain.

When you orientate the ota it should point in the same direction as the forks, not at 90 deg to them. The forks and ota should then point towards the SCP (your control panel should be on the south side as well). At certain times of the day/year the fork and ota will be rotated so that they are upside down and you will have to rotate the diagonal so that you can look through the forks. I'd suggest not trying to align on Sig Oct. Rather get it as close as you can to south with a good gestimate and then drift align. Once you have drift aligned then simply sync on a handy star, rather than run through the polar alignment routine of the LX200.

[mick pinner]

thank you Paul l think that makes sense.

[[1ponders] (Paul)]

It had me totally lost when I first put my LX200 on the wedge. If you don't know how to already, learn to drift align. It made life so much easier for me when aligning the 200.

[beren]

There's some good info here in relation to wedge mounted SCT drift aligning here http://www.users.bigpond.com/lansma/...nment%20method
Scroll down to the bottom , the only thing is I'm sure i rotate the Azimuth wedge knobs opposite to what he says

I would definitely forgo the Meade polar alignment method where you have to centre sigma octanis , it will just frustrate you and if you plan to do imaging drift alignment is needed for the accuracy.Ok its going to be frustrating at first but take it easy and after a few times times will get quicker and quicker.

Here's my procedure anyway {hope you have a illum reticle-you really need one to effectively do this}

1.get your wedge/ota lined approx like so

http://img.photobucket.com/albums/v1...n/0c4afb99.jpg

http://img.photobucket.com/albums/v1...n/a738a92a.jpg

http://img.photobucket.com/albums/v1.../polarhome.jpg

{image above sourced from-http://www.californiastars.net/lx200gps/tips.html}

make sure everything is balanced and dec/ra locked and you have the scope in polar mode and not Azimuth in the settings.

2.Using your controls centre a brightish star and put in your reticle eyepiece {make sure your diagonal is lined up square} and rotate it so the star selected moves parallel to the cross-hairs in RA and Dec. Might take a couple of minutes.

3.Okay now your ready , start first with the Azimuth adjustment.Pick a star slightly east of the meridian or slightly north {look right above you }.Put the star on the horizontal line{ near the centre of the eyepiece} so its bisected . First up the star is going to move fairly quickly up or down until its fined tuned. If the star moves up you need to move the wedge west by turning the Azimuth knobs clockwise. Take small turns so you can re-centre the star without it disappearing from the FOV.You will probably need to do this a few times before the drifting drops considerably , i use a stopwatch to gauge how will I'm going , your aim is to get the star from drifting up and down so it stays on the horizontal cross-hair for a min of 5min ie: don't worry about drift in RA/ left to right that's a symptom of your mounts tracking and has no bearing on polar alignment.If the star moves down rotate the knobs anti-clockwise.Be prepared to spend time practicing this, it can be frustrating but gradually the time taken will drop {plus you have a OB }

4.Okay once your satisfied pick a star about 30 degrees and zero declination above the eastern horizon and centre it and bisect it on a cross-hair. Tilt your head so your eye is flush with the cross-hairs and watch if the star moves up or down , you need to adjust the Altitude knobs so the star moves opposite to the drift.If the star drifts up you need to adjust the mounts elevation down by rotating the altitude knob clockwise {as you are facing it }etc. Same deal with the Azimuth adjustment you need to this until a min of no movement for 5min.

5.Okay bad news you need to go back and double check the Azimuth adjustment , shouldn't be to bad but its good to retrace your steps and fine tune it .

6.Final step is to get the GOTO working.Select a familiar star that is reasonably high and centre it in the eyepiece and bring its name up on the keypad. Once you are ready hit GOTO , the scope will slew off in one direction and stop and say its got its target.You need then to re-centre the star carefully and then hit the SYNC button.Everything should be ready to rock and hopefully gotos will be nice and accurate which is a good indication of a good polar alignment.Note however that I have a GPS scope and when i hit GOTO at the start of the process the scope gets its date and time info automatically , I'm not sure how the classic models fare.

I hope this info is accurate because I'm always a little rusty with remembering the sequence of turning the ALt/az knobs Once you practice it a few times you should have no dramas

Stuart