drift alignment, east/west drift

[Pete Presland]

hi all, i have been using the drift alignment technique for quite a while now. but since upgrading to the synscan set up in the summer, i have really struggled with east to west drift, the north/south drift seems fine.is this periodic error or something else?

the reason i have been re-checking the alignment is because, despite a succesfull 1st guided image it has been a nightmare since.PHD seems to go through the calibration ok, i get a "green cross" to tell me its guiding on the star selected, but it looses this star within seconds.

i am using a 200PDS on a HEQ5synscan, and a QHY5/finder guide scope

[Pete Presland]

i dont think the cable connections are wrong, but just to check its -

QHY5 st4 to the st4 port on the mount

QHY5 to USB on laptop

HEQ5 handset to laptop

[bamus]

could you attach PHD log from this session?

[ollypenrice]

How are you doing your drift alignment?

There's a very good technique for fast drift alignment in azimuth when you can see the celestial equator looking south at the Meridian, as most people can. (It also works for Alt polar aligning but needs the celestial equator to be visible east or west, which can be harder.)

Point due south at the celestial equator and take a 20 sec sub. During the sub slew slowly in RA for ten secs and then back for ten secs. This will leave vee shaped star trails on the image. You simply adjust in altitude until the out and back traces of the vee lie one on top of the other making a single line per star. Then you're aligned.

Olly

[ollypenrice]

Note on the above. Sorry, error! You adjust in Azimuth, of course, while exposing a sub to the south.

Not awake yet!

Olly

[russellhq]

How are you doing your drift alignment?

There's a very good technique for fast drift alignment in azimuth when you can see the celestial equator looking south at the Meridian, as most people can. (It also works for Alt polar aligning but needs the celestial equator to be visible east or west, which can be harder.)

Point due south at the celestial equator and take a 20 sec sub. During the sub slew slowly in RA for ten secs and then back for ten secs. This will leave vee shaped star trails on the image. You simply adjust in altitude until the out and back traces of the vee lie one on top of the other making a single line per star. Then you're aligned.

Olly

I thought the celestial equator crosses the horizon in the due east and due west direction? Is this what makes it difficult?

Sorry if that's a daft question, but I'm still learning the ropes as they say.

[martin_h]

[russellhq]

Thanks martin, that's what I thought it looked like. So I'm still confused how you can pick a star on the equator in the east and west direction?

[martin_h]

Thanks martin, that's what I thought it looked like. So I'm still confused how you can pick a star on the equator in the east and west direction?

You just need one as low as practical in the East/West

[ollypenrice]

The point is that the Celestial Equator can be very low or even hidden by the terrestrial horizon in the east and west while it is still visible in the south. The photo method I described is often only practicable in the south (for adjusting Azimuth) so you need another method for doing Altitude using stars in the E or W.

You can't pick a star in the E or W on the celestial equator if you are too far north, hence my suggestion that you use the photo method only in the south. Even at my Lat (44.19) I can't get to the CE in E or W. If you use the photo method well away from the CE you get strange curved star trails - or I did! (Might just be me...)

I know these things cause brain strain!!

Olly

[russellhq]

Thanks olly, much clearer now.

[skybadger]

So the equator of the sky is the ecliptic and the meridian is the local highest point. For stars on the meridian, track and adjust azimuth, for stars on the equator on the east or west horizon, track and adjust altitude.

Cheers

Mike

[skybadger]

Erm, I didn't.mean that ecliptic thing. I knew there was something wrong with it the.moment ii wrote it. The overall message is that it is ok to pick something higher in the east and west as long as. You expect more iterations to home in on alignment.

[Pete Presland]

thanks for all the replies!

i am doing the drift alignment by using an illuminated 12mm reticle. so i can use the DSLR method to check the alignment at the meridian & as low down as practicle in the east?

[Pete Presland]

could you attach PHD log from this session?

hi here is the attached file,there are a lot of numbers there!

PHD_log_16Oct12.txt

[themos]

That log file shows that PHD has no control over the mount, the star just drifts off somwhere no matter what commands PHD thinks it is sending. Try PHD's manual control and see if you can make the star move in every direction. If you can't, there's something stopping the commands reaching the mount.

[bamus]

]

That log file shows that PHD has no control over the mount, the star just drifts off somwhere no matter what commands PHD thinks it is sending. Try PHD's manual control and see if you can make the star move in every direction. If you can't, there's something stopping the commands reaching the mount.

if this was true, calibration would fail strait away. this is not the case in this example.

in order to solve your issues make sure polar aligment is quite good and do following things in phd:

- reduce length of calibration step (would guess to around 2500ms). you have got only 3-4 calibration steps in each direction. Optimal amount is about 15.

- reduce minimum motion value to 0.06. you have got 0.50 which is well too much for finder guider.

- if it doesn't help, increase max RA and DEC motion to 500.

[Pete Presland]

thanks again to your replies, am i right in saying that looking at the log these are the calibration steps?

RA+ (west),1,-8.2,-6.4,526.3,501.6

RA+ (west),2,-16.4,-12.8,518.1,495.1

RA+ (west),3,-24.6,-19.4,509.9,488.6

RA- (east),3,-32.8,-25.8,501.7,482.1

RA- (east),3,-41.1,-32.1,493.4,475.8

RA- (east),3,-49.1,-38.5,485.4,469.4

Dec+ (north),1,-7.6,-7.2,469.5,455.7

Dec+ (north),2,-15.6,-13.6,461.5,449.3

Dec+ (north),3,-23.9,-20.1,453.2,442.8

Dec- (south),3,-32.2,-26.6,444.9,436.3

Dec- (south),3,-40.4,-33.0,436.7,429.9

Dec- (south),3,-48.7,-39.5,428.4,423.4

[bamus]

thanks again to your replies, am i right in saying that looking at the log these are the calibration steps?

RA+ (west),1,-8.2,-6.4,526.3,501.6

RA+ (west),2,-16.4,-12.8,518.1,495.1

RA+ (west),3,-24.6,-19.4,509.9,488.6

RA- (east),3,-32.8,-25.8,501.7,482.1

RA- (east),3,-41.1,-32.1,493.4,475.8

RA- (east),3,-49.1,-38.5,485.4,469.4

Dec+ (north),1,-7.6,-7.2,469.5,455.7

Dec+ (north),2,-15.6,-13.6,461.5,449.3

Dec+ (north),3,-23.9,-20.1,453.2,442.8

Dec- (south),3,-32.2,-26.6,444.9,436.3

Dec- (south),3,-40.4,-33.0,436.7,429.9

Dec- (south),3,-48.7,-39.5,428.4,423.4

correct

[bamus]

having another look I must admit that I was wrong in my previous post. there must be something wrong with connection or mount. Last value in RA and DEC calibration steps should be almost same. in your case mount is not bringing back star to start position. are you sure mount was tracking?

[Pete Presland]

it seems to go through the calibration, albeit very quickly, i then get the "green" cross to indicate calibration successful. it then looses the star almost immediately.do cable connections i mentioned sound ok?

[bamus]

it seems to go through the calibration, albeit very quickly, i then get the "green" cross to indicate calibration successful. it then looses the star almost immediately.do cable connections i mentioned sound ok?

you do not need to conect handset to laptop if yo are using st4 cable to connect camera to the mount. are you using on camera option to connect to mount?

your calibration inst correct. values dx and dy in last steps in RA- and Dec- should be same as first steps RA+ and DEC+ . have a look here on correct example:

Direction Step dx dy

RA+ (west) 1 0 -0.2

RA+ (west) 2 0 0

RA+ (west) 3 0 0

RA+ (west) 4 0 0

RA+ (west) 5 0 0

RA+ (west) 6 0 0.1

RA+ (west) 7 -0.1 0.1

RA+ (west) 8 0 0.1

RA+ (west) 9 -0.1 0.1

RA+ (west) 10 -0.1 0.3

RA+ (west) 11 0 0

RA+ (west) 12 0.1 0

RA+ (west) 13 0.1 0

RA+ (west) 14 0.2 0

RA+ (west) 15 0.2 0

RA+ (west) 16 0.2 0.1

RA+ (west) 17 0.4 0.3

RA+ (west) 18 0.2 0.1

RA+ (west) 19 0.5 0.3

RA+ (west) 20 1.2 0.6

RA+ (west) 21 2.1 0.3

RA+ (west) 22 3.5 0.3

RA+ (west) 23 4.7 0.4

RA+ (west) 24 6.4 0.7

RA+ (west) 25 7.8 0.8

RA+ (west) 26 8.9 0.8

RA+ (west) 27 10.4 0.6

RA+ (west) 28 12 0.6

RA+ (west) 29 13.5 0.5

RA+ (west) 30 15.4 0.4

RA+ (west) 31 17 0.3

RA+ (west) 32 18.5 0.1

RA+ (west) 33 20.1 0.1

RA+ (west) 34 21.7 0.1

RA+ (west) 35 23.3 0.2

RA+ (west) 36 25.3 0.3

RA- (east) 36 25.9 1.4

RA- (east) 36 25.9 1.7

RA- (east) 36 26 1.9

RA- (east) 36 25.9 1.7

RA- (east) 36 26 2

RA- (east) 36 26 2

RA- (east) 36 26 2

RA- (east) 36 26 2

RA- (east) 36 25.9 2

RA- (east) 36 26 2

RA- (east) 36 25.9 2

RA- (east) 36 25.9 2

RA- (east) 36 25.9 2

RA- (east) 36 25.7 1.9

RA- (east) 36 25.4 1.7

RA- (east) 36 25 1.6

RA- (east) 36 25 1.4

RA- (east) 36 24.7 1.5

RA- (east) 36 24.5 1.6

RA- (east) 36 24.2 1.8

RA- (east) 36 24 1.8

RA- (east) 36 22.8 2

RA- (east) 36 21.8 2

RA- (east) 36 20 2

RA- (east) 36 18.4 1.9

RA- (east) 36 17.3 1.6

RA- (east) 36 16 1.6

RA- (east) 36 14.2 1.3

RA- (east) 36 12.5 0.8

RA- (east) 36 10.8 0.6

RA- (east) 36 9.1 0.6

RA- (east) 36 7.5 0.3

RA- (east) 36 5.9 0.3

RA- (east) 36 4.1 0.1

RA- (east) 36 2.3 0.1

RA- (east) 36 1.1 0.1

Dec+ (north) 1 -0.1 0.9

Dec+ (north) 2 0 2

Dec+ (north) 3 0 3.1

Dec+ (north) 4 0 4.1

Dec+ (north) 5 0 4.8

Dec+ (north) 6 0.1 5.7

Dec+ (north) 7 0.1 6.5

Dec+ (north) 8 0.1 7.3

Dec+ (north) 9 0.1 8

Dec+ (north) 10 0 9.1

Dec+ (north) 11 0.2 10.2

Dec+ (north) 12 0.1 10.9

Dec+ (north) 13 0.3 11.8

Dec+ (north) 14 0.2 13

Dec+ (north) 15 0.2 13.9

Dec+ (north) 16 0.3 14.7

Dec+ (north) 17 0.2 15.4

Dec+ (north) 18 0.3 16.2

Dec+ (north) 19 0.3 17

Dec+ (north) 20 0.3 17.9

Dec+ (north) 21 0.5 18.7

Dec+ (north) 22 0.3 19.9

Dec+ (north) 23 0.3 20.7

Dec+ (north) 24 0.5 21.5

Dec+ (north) 25 0.7 22.5

Dec+ (north) 26 0.6 23.4

Dec+ (north) 27 0.6 24

Dec- (south) 27 0.5 23

Dec- (south) 27 0.5 21.9

Dec- (south) 27 0.4 21.3

Dec- (south) 27 0.2 20.5

Dec- (south) 27 0.3 19.3

Dec- (south) 27 0.2 18.4

Dec- (south) 27 0.1 17

Dec- (south) 27 0.1 16.4

Dec- (south) 27 0 15.3

Dec- (south) 27 -0.1 14.3

Dec- (south) 27 -0.1 13

Dec- (south) 27 -0.1 12.1

Dec- (south) 27 -0.4 10.7

Dec- (south) 27 -0.2 10

Dec- (south) 27 -0.4 8.7

Dec- (south) 27 -0.3 7.9

Dec- (south) 27 -0.6 6.7

Dec- (south) 27 -0.5 6.6

Dec- (south) 27 -0.5 5.8

Dec- (south) 27 -0.5 4.7

Dec- (south) 27 -0.6 4.2

Dec- (south) 27 -0.7 2.7

Dec- (south) 27 -0.6 2.3

Dec- (south) 27 -0.6 1

Dec- (south) 27 -0.7 0.5

Dec- (south) 27 -0.7 -0.9

Dec- (south) 27 -0.7 -1.6

[themos]

You can do this inside without dark skies: Set up as normal and try to use the manual PHD controls (Tools -> Manual Guide). Put the calibration step up to 1000ms so that each press of of the direction buttons generates a nice long pulse. Hitting "North" repeatedly should produce a noticeable rotation in declination. Which menu entry under Mount have you selected? If you're going through the guide camera, you need to select "On camera".

[Pete Presland]

you do not need to conect handset to laptop if yo are using st4 cable to connect camera to the mount. are you using on camera option to connect to mount?

your calibration inst correct. values dx and dy in last steps in RA- and Dec- should be same as first steps RA+ and DEC+ . have a look here on correct example:

yes i am using the "on camera" option if i do not connect to the handset, does the pulse signal go via the QHY5 to the mount?

could underline the valus you mean on the exmple

pete

[Pete Presland]

You can do this inside without dark skies: Set up as normal and try to use the manual PHD controls (Tools -> Manual Guide). Put the calibration step up to 1000ms so that each press of of the direction buttons generates a nice long pulse. Hitting "North" repeatedly should produce a noticeable rotation in declination. Which menu entry under Mount have you selected? If you're going through the guide camera, you need to select "On camera".

i will try the manual direction buttons tomorrow evening, Putting the calibration step "up to 1000ms" to am i right in thinking the lower this is then the longer it will pulse for?