Jump to content

NLCbanner2024.jpg.2478be509670e60c2d6efd04834b8b47.jpg

Drift aligning question

Keithp

By Keithp
in Imaging - Discussion

Recommended Posts

Keithp

Keithp

Posted
Posted

Hello All,

Sky is looking good tonight so I intend attempting drift alignment for my pier mounted EQ6.

At the moment everytime I check with polarfinder I find Polaris sitting on the circle in the polar scope eyepiece, that is the large circle around the crosshairs. If I swing the scope round to view the star through the polar alignment scope the small circle has Polaris in the middle. (That is at the time indicated by polarfinder.) Now that would suggest a pretty good alignment and to be honest I've done 3 minutes unguided and no trails.

I want to nail it down exactly. Now I have purchased an illuminated eyepiece (12mm meade jobbie). This might be a difficult question to answer but....

What sort of movement would I expect the target star to move up or down the N/S axis in the eyepiece and what sort of adjustment are we looking at to counter that, say if the star drifted up or down by half the radius of the field of view?

That is after 10 mins if it had drifted one way or the other by a half of the radius what would the corrective move of the mount axis in relation to the view of Polaris be..for example to move it from the centre of the small circle in the polar scope to the edge. Do you see what I mean?

Toughie I know, many variables but this is the 1st time I've attempted this.

Regards

Keith

Link to comment
Share on other sites
  • Replies 38
  • Created
  • Last Reply
Keithp

Keithp

Posted
  • Author
Posted

Many thanks Ken,

about to start shortly. If I get a movement of the star, and assuming I'm nearly but not perfectly aligned, what sort of movement would I expect over say a 10 minute period and then what sort of correction would I apply. That is the degree of correction in relation to the movement of the target.

That's the toughie on this one. I'll post up what I do. Just looking for some initial pointers from anyone who has done this.

Regards

Keithp

Link to comment
Share on other sites
Merlin66

Merlin66

Posted
Posted

Being an Ozzie, we have no choice but to become good at drift alignment - there's no bright polar star to guide us!!

Usually you can be down to zero (well, nothing noticable!) dec movement within twenty minutes of setting up with a star in the East and on the Meridian.

Link to comment
Share on other sites
Keithp

Keithp

Posted
  • Author
Posted

:headbang:awh Ken, sorry mate never realised you were down south.. Many thanks for your pointers though.

Themos, cheers I'll try that, many thanks.

Okay what I'm going to do is suck it and see.. no disrespect to anyone who's answered on this but it looks like I'll record and see, make adjustments and see what the result is.

Let's go...camera is left in the house..

Link to comment
Share on other sites
themos

themos

Posted
Posted
Being an Ozzie, we have no choice but to become good at drift alignment - there's no bright polar star to guide us!!

Usually you can be down to zero (well, nothing noticable!) dec movement within twenty minutes of setting up with a star in the East and on the Meridian.

Hmm, I wonder if I should adapt my photographic method for the Southern Hemisphere.

Link to comment
Share on other sites
Keithp

Keithp

Posted
  • Author
Posted

okay, polarfinder has the ncp at about 09:00 ish, little bit after. I have Polaris on the line as mentioned before and if I rotate the scope round it's smack in the centre of the small circle.

Now doing the 3 star alignment to kick in the tracking... flipping full moon, maybe not the best night to try this but here we go

Link to comment
Share on other sites
Keithp

Keithp

Posted
  • Author
Posted

hmm, that was tricky but I managed it. The first target is Altair, due south and to the west of the (and forgive me if I get this wrong) but that line overhead which is 0 hours.. gulp I take a caning for that one.

okay got altair in the sights, right in the middle of the cross hairs, moved the scope east to west and made sure it goes along the horizontal lines on the crosshairs.. 10 mins and see what happens.

Now please correct me if I'm wrong but I'm looking for drift up and down, ignoring, for the moment left or right..yes?

Link to comment
Share on other sites
Keithp

Keithp

Posted
  • Author
Posted

right, now gone for mirach in the east, done the same thing, ie if I move the mount using the left and right keys it goes down a straight line on the crosshairs ie east to west as you view through the eyepiece.

Leaving it for 10 mins to see what happens

Link to comment
Share on other sites
Keithp

Keithp

Posted
  • Author
Posted

okay it's drifting up, as I look at it. Bear in mind when use the left and right keys it moves along that line in the crosshairs..

So I should move the mount so the star appears to move down in the eyepiece...

2 secs, brb

Link to comment
Share on other sites
Keithp

Keithp

Posted
  • Author
Posted
So, what's first, azimuth?

He he, I've given up for tonight...work tomorrow,.. erm azimuth?

that's left and right...on the keypad?

Sorry, appreciate your help but this is a relative newbie trying this method out. After I'd done a 3 star alignment I went for Altair, put the crosshairs on it and then moved the mount left and right on the controller and orientated the eyepiece so the crosshairs kept the star on the left to right horizontal.

And it stayed there after 10 mins... switched to Mirach in the East and did the same thing but noticed Micrach climbed up the north or upright axis on the crosshairs, bearing in mind I did the same thing ie moved it left and right with the controller and it stayed on the horizontal line.

So I need to get my head around which counter movement I need to make to sort that..or adjust it one way or the other.

Regards

Keithp

Hope it helps anyone else drift aligning.

Link to comment
Share on other sites
themos

themos

Posted
Posted

might help visualise what's going on.

Your first measurement, of a star in the South (crossing the meridian), was meant to measure your polar alignment error in azimuth. Your second, of a star in the East, was meant to measure your PA error in altitude. You saw the star climb north. That means your mount needs to lean over more so that it rises more sharply when pointing east. That means you need to reduce its altitude, that is, make it point down a bit.

Link to comment
Share on other sites
Keithp

Keithp

Posted
  • Author
Posted

anybody out tonight?

I've got lovely clear skys here so I'm getting the drift alignment nailed down...even if it takes all night. Bit of cloud so maybe not so good for the imagers out there.

Regards

Keithp

okay, it's sitting on capella, smack bang in the middle, after getting no drift from altair the other night and seeing a northwards drift on mirach and making adjustments to lower the mount I'm going to give it 15 mins and see what happens

Link to comment
Share on other sites
Keithp

Keithp

Posted
  • Author
Posted

might be getting close, no movement N or S, though it has drifted a little east. As I look in the eyepiece, going to leave it another 15 mins, get a coffee and see what happens. Maybe time to switch to a star SW.

Regards

Keithp

okay it's gone a little south, not much. About the same distance between the double lines east to west, just going to tweak it up a little

It's moved a smidgin north and east, just thought I really should put some timings on these updates for anyone else following this. Okay details are : Skywatcher 250px on eq6 pier mounted. 12mm meade wireless illuminated eyepiece. Done 3 star alignment, no probs dropped me straight on capella. Going to give it another 10 mins then switch to something in the SW. Time is 01:08

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.