Guiding and Drift Alignment - One star Drift?

[CKemu]

Getting in to CCD / Narrowband imaging and with the tighter field of view I am trying to hone my drift align method. As despite some success, I am having to fight field rotation and some egging of my stars:

M27 - Hubble Palette and Natural Colour by Chris Kennedy, on Flickr

Whilst I have been always fine tuning my mount's Alt/Az drift using a Southern star, never actually gone about adjusting the Dec drift via the wedge using an Eastern star, which I concluded has left me with PHD fighting harder than it should. Most of my research has found guides that use the diagonal, which I don't use, as I make adjustments using the etched 12mm eyepiece, straight in the tube. I find this easier, if star drifts down, I move the star right, and if it moves up I move it left.

Thus reading guides on the web make my orientation and brain spin - until I found this:

http://www.astrotarp.com/drift_method.htm

Almost everywhere goes on about using an Eastern star (or western), yet the above method makes sense to me and saves extra mucking around

One star, due South, 20 degrees or so above horizon:

Alt/Az Wedge Adjustment (First motion is drift, second is correction)
Star Up, move Left
Star Down, move Right

Dec Wedge Adjustment (First motion is drift, second is correction)
Star Left, move up
Star Right, move Down

So unless someone can point out a glaring problem with this method, this makes sense to me...

I would presume that the Dec adjustments would be more sensitive/faster if I was facing East/West - but still doable facing South, just the angle is 90 degrees offset, hence the above motions/corrections.

[Thalestris24]

Hi

Drift alignment is easy to do with the PHD2 drift alignment tool

Louise

[michael8554]

How much of the left or right drift will be due to your RA drive not being exactly 100% ?

Using EW and S stars the error is always up or down.

Michael

[ollypenrice]

If you have the camera in, why take it out to drift align? I do it via the camera and the crosshair on the capture screen, which is ultra-accurate as well as easier. (The camera can see more stars then the eye, too.) For a camera method tutorial this takes some beating. http://www.andysshotglass.com/DriftAlignment.html

Olly

[Davey-T]

Does a southern star start drifting the other way once past the Meridian ?

Dave

[KyleStoke]

Hello the method i use is as follows and works very well.

Using PHD 1

1) i find a southern star perform the normal guiding calibration

2) once that is complete i go into the brain switch of dec guiding

3) then i guide on the southern star switch on the graph and switch it from RA/DEC  to DX/DY this will show the graph either drifting above or below the line on the DY line

4) if it drifts up then i tighten the left azimuth knob (looking at mount from the north side) pushing the mount to the east, if it drifts below the line the tighten the right

5) repeat the tightening of the azimuth bolts until the DY line stays in the center of the graph. 

6) slew scope to a star in the East and re-calibrate with dec guiding back on auto.

7) once calibrated switch dec guiding back off

8) enable the graph in DX/DY again and see which way the DY line drifts

9) if the DY drifts below tighten the altitude bolt to raise mount height, if above lower mount height. 

10) repeat until DY line stays in the center of the graph. 

I know this seems confusing, maybe they way i have written it but in practice it is very simple. I have also assumed the wedge is adjusted in the same way as an EQ mount never used one so i don't know.

With this method i very easily achieve 15 minuet subs and probably a lot longer if i wanted to

Good luck Kyle

[Thalestris24]

Hello the method i use is as follows and works very well.

Using PHD 1

1) i find a southern star perform the normal guiding calibration

2) once that is complete i go into the brain switch of dec guiding

3) then i guide on the southern star switch on the graph and switch it from RA/DEC  to DX/DY this will show the graph either drifting above or below the line on the DY line

4) if it drifts up then i tighten the left azimuth knob (looking at mount from the north side) pushing the mount to the east, if it drifts below the line the tighten the right

5) repeat the tightening of the azimuth bolts until the DY line stays in the center of the graph. 

6) slew scope to a star in the East and re-calibrate with dec guiding back on auto.

7) once calibrated switch dec guiding back off

8) enable the graph in DX/DY again and see which way the DY line drifts

9) if the DY drifts below tighten the altitude bolt to raise mount height, if above lower mount height. 

10) repeat until DY line stays in the center of the graph. 

I know this seems confusing, maybe they way i have written it but in practice it is very simple. I have also assumed the wedge is adjusted in the same way as an EQ mount never used one so i don't know.

With this method i very easily achieve 15 minuet subs and probably a lot longer if i wanted to

Good luck Kyle

It's much easier - 'user friendly' - with the phd2 visual tool

Louise

[KyleStoke]

Hi Louise

I had a quick read about the PHD2 one and decided to stick to what i know as it works but i will download it and have a play at some point, in fact i might do it now as the weather forecast is for rain

[Steve Ward]

I've always found this method very simple and straightforward ... http://www.cloudynights.com/page/articles/cat/articles/darv-drift-alignment-by-robert-vice-r2760

[Thalestris24]

Hi Louise

I had a quick read about the PHD2 one and decided to stick to what i know as it works but i will download it and have a play at some point, in fact i might do it now as the weather forecast is for rain

Hi I guess there's no reason why you can't use PHD2 tools but guide with PHD 1, if you prefer You don't have to think much when doing PA with the drift align tool

Louise

[KyleStoke]

Yea just installed and it looks very straight forward

[CKemu]

I've read the posts above (finally) and will be giving the PHD drift align method a go, looks pretty reasonable to me, my Alt/Az drift align with a Southern star has been bang on for ages now, can get it to not move over periods of 15 minutes, but my E/W has never worked well - so here's hoping Thank you all for your feedback.

[Thalestris24]

Hi

The East or West drift align is to get the altitude correct. Normally one would do the southern drift first for azimuth, then the East or West, followed by a re-check of the southern azimuthal alignment. The idea is to check alt and az more or less independent of one another. It's important to get a good PHD2 calibration first since that tells PHD2 the relationship between the guide scope and the mount, and it's really the mount one is aligning.

Good luck!

Louise