#1  
Old 18-09-2011, 01:09 PM
hotspur's Avatar
hotspur (Chris)
Registered User

hotspur is offline
 
Join Date: Apr 2009
Location: south east QLD,Australia
Posts: 2,867
operating PHD-advice sought.

Hello.

I am trying to get up into AGing,but having a few issues.Made some progress,but still getting egg stars.Some advanced astrophotographer
with a great wealth of tech skills,recently visited and checked gear-did som tightening of RA and DEC on mount.But the guiding still produced eggs.

Fiddled with PHD brain settings.But not much joy.The backlash clearing of the dec,seemed to take a long time.I have since been advised by a another astronomer,that dec is usually where issue arise.And that trying it without dec correction turned on,or only N or S correction.May be a path to a solution.

So will try that.What do the Dec alogrith-low pass and resist switching mean,and how to apply/not apply them?

What 'min motion pixels' should a very small 'finder guider; 200 mm guide scope be set at?

Also what calibration step should a small 200 mm finder guider be set at?
some say 1000 plus other say lower than 500.

So,really unsure of the above settings and how to apply them,to try and get nice round stars at 5 min subs.

Did a bit of reserch-sounds like issues in PHD-dec settings are not uncommon.

I have a Vixen GPD2 mount that is always on pier in an observatory-so PA is very much lined up well,and checked.

Any ideas,suggestions or links would be well received-thanks,Chris
Reply With Quote
  #2  
Old 19-09-2011, 05:46 PM
gbeal
Registered User

gbeal is offline
 
Join Date: Oct 2004
Location: New Zealand
Posts: 4,345
I use a finder-guider, and it plate-solves at less than 200mm, mine is 176mm. While I can't help too much with all the settings questions, I d suggest trying something a bit bigger than 2000 for the calibration steps. In my case I use about 2700, but the end result is that the star has to move a bit, and not stay still, try it and see.
Gary
Reply With Quote
  #3  
Old 19-09-2011, 09:31 PM
DavidTrap's Avatar
DavidTrap (David)
Really just a beginner

DavidTrap is offline
 
Join Date: Jun 2009
Location: Brisbane
Posts: 3,032
Chris,

I've been thinking that if the auto guiding speed was set to 2, that may have meant that the "long" calibration step was shifting the star a long way, and that's why it completed the calibration in just 2-3 steps.

Try 0.5x and a long calibration time.

DT
Reply With Quote
  #4  
Old 19-09-2011, 10:12 PM
mithrandir's Avatar
mithrandir (Andrew)
Registered User

mithrandir is offline
 
Join Date: Jan 2009
Location: Glenhaven
Posts: 4,161
Chris, aim for about 10-15 steps in each direction for calibration. If it takes less, decrease the max step. If it takes more, increase it.

Somewhere in the 1500-2500 range will probably get it right, but I've never used a guide scope that short so you'll need to experiment.

You will do best with the guide scope slightly defocused. This reduces the effect of the guider trying to chase the seeing.

I know from experience that min motion works at 0.1 pixels with a 400mm guide scope. On a reasonable night, set min motion to something in the 0.1 to 0.5 pixels range and watch the graph. Tweek the value up and down to get the smoothest line.

It is not exactly a black art, but it isn't something you'll get right in a few minutes, and every combination of guide scope, guide camera, and mount behaves differently.
Reply With Quote
  #5  
Old 20-09-2011, 07:11 AM
hotspur's Avatar
hotspur (Chris)
Registered User

hotspur is offline
 
Join Date: Apr 2009
Location: south east QLD,Australia
Posts: 2,867
re phd

Thank you Gary,David and Andrew.

Was up till 1 am this morning try a few things.Changed the speed to.05,not much change,turned off DEC,no change.tried north only dec,about the same.
Tried south only and went from 1000 to 1200.seemed to be some sort of improvement.Only after 12 am,and the battery in camera going flat-(and so was the operator).Ther was a fair amount of smoke in sky-not sure if this is going to affect it.Also what exp speed for AG'er was using 2 sec.But 1 sec might be better?

So upping this calibration step,could be a good thing-try up to 1500-2000 tonight,and decfocus slightly as Andrew suggests.Thanks chaps-Chris
Reply With Quote
  #6  
Old 22-09-2011, 05:35 AM
Alchemy (Clive)
Quietly watching

Alchemy is offline
 
Join Date: Jul 2007
Location: Yarra Junction
Posts: 3,044
Hi chris, just applying some logic here, I notice you are trying all kinds of settings. Generally PHD works "out of the box"
If like yourself, you are using a very short FL guidescope the only thing you should need to change would be the sensitivity of detection..... If standard was .5 of a pixel then you might use .2 of a pixel.
Corrections are applied to the main scopes image which is common to all users, ( ie regardless of guidescope, all users of FL around yours will achieve the same effect with the same correction, a .5 slew for .6 of a sec will always have the same result, there is no need to apply a larger or longer corection because of the guidescope) My own experience was to simply drop the aggression until it was no longer overshooting and causing that egging effect.
I'm reading that you have eliminated all flexure ( substantial anyways as some always exists).
To me if you couldn't achieve a decent result using the above method, it should be a mount problem.
That might be over-simplifying it but I hope you can see the logic.
Reply With Quote
  #7  
Old 22-09-2011, 10:27 AM
hotspur's Avatar
hotspur (Chris)
Registered User

hotspur is offline
 
Join Date: Apr 2009
Location: south east QLD,Australia
Posts: 2,867
re phd

Yes Clive

I thought PHD worked out of the box too.But it appears that AGing is a black art-I have been trying for months to get this guiding,But it looks like calibration step needs to be around 2000 for this small guide scope-I will try that and reduction in movement step.That will bring me to the end of things I can do,If that does not work,I seriously think I will ditch the lot and get out of astronomy all together-and move on to other photography.
Reply With Quote
  #8  
Old 22-09-2011, 11:33 AM
Alchemy (Clive)
Quietly watching

Alchemy is offline
 
Join Date: Jul 2007
Location: Yarra Junction
Posts: 3,044
I sense your frustration. Hopefully it wont come to that.
Reply With Quote
  #9  
Old 22-09-2011, 12:47 PM
hotspur's Avatar
hotspur (Chris)
Registered User

hotspur is offline
 
Join Date: Apr 2009
Location: south east QLD,Australia
Posts: 2,867
Quote:
Originally Posted by Alchemy View Post
I sense your frustration. Hopefully it wont come to that.

Yes,rather frustrated-had two very advanced astronomers who have very highly technical fields of employment come up and help,but still egg stars.
Will see what these final few settings bring-but I cannot afford to send mount away to be fixed,if that's the case-will move on.

One of my school teachers used to say "If at first you don't succeed try and try and try again;if that fails time to move on-no use becoming an extremist!"

After 6 months of battling these AGing and have no joy-I have given my self till Xmas to get it right,after that I'll ditch the lot and buy a 7D for birding-seem to be making some progress on that direction of photography.
Reply With Quote
  #10  
Old 22-09-2011, 01:54 PM
Alchemy (Clive)
Quietly watching

Alchemy is offline
 
Join Date: Jul 2007
Location: Yarra Junction
Posts: 3,044
Do a run of guiding, with the output disabled and log the data.... You will need to do for say 30 mins no need to take a photo, can you email me the log file?
Reply With Quote
  #11  
Old 22-09-2011, 03:35 PM
hotspur's Avatar
hotspur (Chris)
Registered User

hotspur is offline
 
Join Date: Apr 2009
Location: south east QLD,Australia
Posts: 2,867
Quote:
Originally Posted by Alchemy View Post
Do a run of guiding, with the output disabled and log the data.... You will need to do for say 30 mins no need to take a photo, can you email me the log file?
Ok,Clive-I did down load that PEPpec program-not sure where the computer down loaded it too.But will keep trying with getting AG going-for a few more weeks.
Reply With Quote
  #12  
Old 23-09-2011, 08:18 AM
hotspur's Avatar
hotspur (Chris)
Registered User

hotspur is offline
 
Join Date: Apr 2009
Location: south east QLD,Australia
Posts: 2,867
re guiding.

Finally got some guiding going last night!

Tried 253,but the speed setting on controller had switched to 3.5 AG speed.So that threw things for first few images.By the time I got it sorted,the object was almost over head.Did not really do any good.

Went to M45,nice angle in sky,had a fiddle -

the Cal step was set to 1400

min mot .05 RA agres 60%

and I de focused guide stars a bit,It was getting late,the seeing
had much improved.First couple of images a bit eggy,but as time went on
and it all settled down.Starting getting nice round stars even when cropped right in. Was doing 3m 30 sec exp.and ended up with around 12 good images,I took 4 darks along the way-I could even PP this data-and will attempt in DSS.

The RMS value was showing .15.I was told this value is important to monitor,in good seeing another astronmer is getting .09 with this sort of set up.

The graph started to look less 'saw tooth'. Not sure what the main reason was that it all started to work.But my thoughts are de focusing guide star,the improvement in seeing conditions,followedby setting changed to 1400.

I'll post some images and crops of centre area.

Thanks for all the help and pointers everyone-Chris
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 04:36 PM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Advertisement
Bintel
Advertisement
Testar
Advertisement