Guiding Issue

[Starwiz]

This one's got me a little stumped.
The last four nights, I've been imaging the same target, the Heart Nebula.

Just after 3 in the morning each night, something bad happens to the guiding which causes the scope to slew off somewhere else.

The last four nights, this has happened at:

03:13

03:01

03:11

03:02 (last night)

These times seem a little close for it to be coincidence.

Here's what I know:

a).  The cables aren't snagging - I even re-routed the cables last night.

b).  It isn't caused by clouds - the last 4 nights have been completely clear.

c).  The target hasn't reached the Meridian.

d).  It's Malta, so Astro-darkness lasts until around 04:30 at this time of year.

Guide logs from last night attached - any help appreciated.

Thanks

John

 

 

 

PHD2_DebugLog_2020-07-28_212834.txt PHD2_GuideLog_2020-07-28_212834.txt

Edited July 29, 2020 by Starwiz

[mikeyj1]

Looks like it lost the star.  Look at star mass and SNR in the graphs, they both take a tumble at that point.

curious why the camera frame size is showing as 640x480  in your  screen shot also...

[Starwiz]

25 minutes ago, mikeyj1 said:

Looks like it lost the star.  Look at star mass and SNR in the graphs, they both take a tumble at that point.

curious why the camera frame size is showing as 640x480  in your  screen shot also...

Thanks for replying.

Yes, it lost the star, but I guess the question is, did it lose the star then drive somewhere else, or did it start driving somewhere else which caused it to lose the star?  I would expect it to be more random if it was just a lost star, but it's happening every night around the same time.  I've just had a thought that I've probably chosen different guide stars on different nights, so I will have another go tonight, but will select the same guide star as last night to see if the times it goes wrong are closer.

I'm using 2 x 2 binning on the guide camera, so I guess that's why it's showing as 640 x 480 instead of 1280 x 960.

Thanks

John

[michael8554]

Hi John

To find out if the egg or the chicken came first you should upload the guidelog and the debug log to the PHD2 help site.

They can tell from the debug log, I can't tell which it was.

Upload instructions are in the PHD2 Help tab on your computer.

https://groups.google.com/forum/?fromgroups=#!forum/open-phd-guiding

Some strange settings John.

Focal length is entered as 1000mm.

Are you guiding with the 50mm Mini ? That's 162mm.

Or using an OAG on the 200P ? That's 1200mm.

PHD2 will compensate for the 2x2 Bin setting, you don't need to.

All night long the logs say the guidestar was Saturated, even during the excursion when the star Mass and SNR dropped very low.

And there weren't any Star Lost messages.

You have Star Mass Tolerance disabled - so what setting was there for star detection in Advanced Setup ?

Why was the star Saturated ?

PHD2 auto selects a good star, so did you select one yourself ?

Or was it a result of the star detection setting being wrong, or because your exposure at 3 seconds was over exposing ?

Michael

[Starwiz]

4 hours ago, michael8554 said:

Hi John

To find out if the egg or the chicken came first you should upload the guidelog and the debug log to the PHD2 help site.

They can tell from the debug log, I can't tell which it was.

Upload instructions are in the PHD2 Help tab on your computer.

https://groups.google.com/forum/?fromgroups=#!forum/open-phd-guiding

Some strange settings John.

Focal length is entered as 1000mm.

Are you guiding with the 50mm Mini ? That's 162mm.

Or using an OAG on the 200P ? That's 1200mm.

PHD2 will compensate for the 2x2 Bin setting, you don't need to.

All night long the logs say the guidestar was Saturated, even during the excursion when the star Mass and SNR dropped very low.

And there weren't any Star Lost messages.

You have Star Mass Tolerance disabled - so what setting was there for star detection in Advanced Setup ?

Why was the star Saturated ?

PHD2 auto selects a good star, so did you select one yourself ?

Or was it a result of the star detection setting being wrong, or because your exposure at 3 seconds was over exposing ?

Michael

Thanks Michael, some good considerations for me to look at in there.

I'm now using OAG on the 200P which is 1000mm (F5).

John

[Richie092]

Are you on mains power or battery?

[alacant]

On 29/07/2020 at 10:22, Starwiz said:

last four nights, this has happened

Hi.

Move the Ra and Dec gears to different teeth; rotate each say, 90° and reset the home position. There's probably a rough patch or a missing tooth on one of the worm wheels.

Cheers and HTH.

[Starwiz]

9 hours ago, Richie092 said:

Are you on mains power or battery?

The mount is running from mains, imaging camera cooler from battery, so not caused by a low battery problem.

Thanks

John

[Starwiz]

6 hours ago, alacant said:

Hi.

Move the Ra and Dec gears to different teeth; rotate each say, 90° and reset the home position. There's probably a rough patch or a missing tooth on one of the worm wheels.

Cheers and HTH.

How do I move the gears to different teeth without taking the mount apart?  Won't it end up on the same tooth/gear for the dodgy position anyway?

I don't know how the mechanics of the NEQ6 work, but can take a look at the strip-down instructions so I understand it better.

Thanks

John

[michael8554]

18 minutes ago, Starwiz said:

How do I move the gears to different teeth without taking the mount apart? 

I think Alacant meant unclutch RA and Dec first, then move the mount, reclutch. 

Then slew to the setup position, the worm is now on a completely different section of the wormwheel. 

Or vice versa, slew first, , unclutch, move to setup position, reclutch. 

Michael 

[alacant]

1 hour ago, Starwiz said:

move the gears to different teeth

Hi.

No need to dismantle the mount.

Mount in home position. Clutches engaged.

- move the mount between say 70° to 120° in both Ra and Dec.

- loosen the setting circles

- disengage clutches

- set the home position using a bubble level.

- spin the setting circles until you have something sensible such as ra and dec at zero.

- lock the setting circles.

That's it.

HTH

 

 

[Starwiz]

1 hour ago, michael8554 said:

I think Alacant meant unclutch RA and Dec first, then move the mount, reclutch. 

Then slew to the setup position, the worm is now on a completely different section of the wormwheel. 

Or vice versa, slew first, , unclutch, move to setup position, reclutch. 

Michael 

 

40 minutes ago, alacant said:

Hi.

No need to dismantle the mount.

Mount in home position. Clutches engaged.

- move the mount between say 70° to 120° in both Ra and Dec.

- loosen the setting circles

- disengage clutches

- set the home position using a bubble level.

- spin the setting circles until you have something sensible such as ra and dec at zero.

- lock the setting circles.

That's it.

HTH

 

 

Many thanks, it make sense now.

John