Guiding issue

[Ivor]

I experienced a new problem last night and I'm hoping for some suggestions to sort it out. As it has been nearly 4 months since I last did any imaging I'm quite prepared to accept it's simple oversight on my part.

For imaging I set my kit up as follows:

Start EQMOD
Start Cartes du ciel
Start AA5
Align mount to 3 stars
Goto to target
Focus
Start guiding via ASCOM using a Lodestar
Take subs.

Previously I used PHD to guide but I want to move to AA5 so I can use the dithering functionality. 

I picked the Lodestar as the guide camera in AA5 and the plot looked pretty good, so I went ahead with producing the subs however the results weren't what I expected.

Guiding plot



Resulting sub


I also tried PHD for the guiding however it came up with an error about insufficient movement in the DEC plane, which I think is a clue to the problem but doesn't explain the guiding output from AA5.

Any suggestions?

Thanks

[The Thing]

Hi Ivor,

I assume PHD and AA5 calibrated the guiding OK? Looks like guiding commands are not getting through on one axis.
Check the guide rates in EQMOD (top right when display is expanded). And check both axes are enabled!
Try using PHD's mount control panel to slew in each direction - it is a good test to see if guiding commands are getting through as this sends guide pulse commands so you won't see it but will hear the motors.

If using PHD get a copy of PHDLab and monitor what PHD is doing. It has a similar plot to the AA5 one you have shown plus all sorts of graphs and measures including PA error.

Hope that helps

Duncan

[Rocket Pooch]

It's not the software or you would not be able to guide like that, I'd check for snagging cables or something loose.

[The Thing]

Maybe you were guiding on a hot pixel, hence the tiny corrections, meanwhile the image drifts. That would also explain PHD's objection as the 'star' wouldn't move. Folks are always posting cries for help about just this on the Stark Labs Yahoo Group.

The first half of the AA5 graph section looks like you were using a star hence the larger excursions and then these disappear as the star as lost and the adjacent hot pixel latched on to instead. So you end up with defined stars from the guided section with trails after the hot pixel was picked up.

Any more theories?

[julian]

you could also check the guide speed in EQmod.
When I image near the zenith I have to change the speed
From 0.25 to 0.5

Julian

[Ivor]

Some good suggestions here, thanks. If I escape the clutches of Canary Wharf early enough I'll have a play tonight if the clouds hold off of course!!

[Carole]

When I image near the zenith I have to change the speed
From 0.25 to 0.5

Julian

Where do you change this speed Julian, I ask because I've had some recent problems near the Zenith.  Is this in PHD the "looping" speed thingy, or are you talking about something in the handset or something else entirely.

Carole

[The Thing]

When I image near the zenith I have to change the speed
From 0.25 to 0.5

Julian

Where do you change this speed Julian, I ask because I've had some recent problems near the Zenith.  Is this in PHD the "looping" speed thingy, or are you talking about something in the handset or something else entirely.

Carole

See below re:EQMOD Guiding Speed

[JonH]

That sub looks as though not all of the stars have trailed and seems like it wondered off for only a portion of the sub rather than for the whole duration.
I suppose it depends on whether all the subs were like this or just this one but is it possible you knocked the scope, or as there is a plain/satellite trail threw the middle perhaps threw some shear luck the plane or satellite passed right over the guide star and it tried to follow it?

Jon

[Rocket Pooch]

Its got stuck on something, then freed then guided on the star, done it myself.

The only other thing is the mount is sticky or slack, which might be the PHD issue.  Or your cable is loose.

It's not the software.

[Rocket Pooch]

That sub looks as though not all of the stars have trailed and seems like it wondered off for only a portion of the sub rather than for the whole duration.
I suppose it depends on whether all the subs were like this or just this one but is it possible you knocked the scope, or as there is a plain/satellite trail threw the middle perhaps threw some shear luck the plane or satellite passed right over the guide star and it tried to follow it?

Jon

In AA if the guiding software would have locked onto a satellite the adjustments in the pixel scale would have been off to one side adjusting to the movement of the satellite.

[julian]

Hi Carole

Here is a link to EQmod guiding. I would send you a screen shot but I need the scope to be connected.
http://eq-mod.sourceforge.net/tutindex.html

Julian