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Old 01-09-2011, 07:22 AM
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hotspur (Chris)
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Auto Guiding Issues-Advice Sought

Hello.

Over the last two nights I have attempted some AG'ed imaging of the comet.

But the Auto guiding has been very poor,The Orion AG and software is not a fault,it is excellent. I have included some cropped images from last night,may be more experienced imagers might be able to tell what the issue could be.

I adjusted the weight,yesterday so the tube was heavier lens end,I checked speed,Backlash comp on paddle,made some adjustment through the night.The AG is doing it job,when I calibrated it does a little calculation after E-W,before going on to N-S.I really do not think there is any issue with the AG software.

It appears,I may have to pull motors off,and tighten the little bolts that adjust tension on worm-does that sound like where the problem is most likely to be

Is it likely ,this is a 'normal' issue for astro images? Unfortunately no images come to our country property any more,so I cannot pick their brains-most have moved on to other hobbies.( I am starting to see why-this is a very frustrating hobby a lot of the time)

Just looking at these images,the comet images have stars that are 'jaggered' never had that before,the on with 253 the usual trails,I did read the morning an object in the E as this was,the scope set up should have counter weight slightly heavier,I know this was not the case last night,But could re adjusting that make any real meaningful difference?

I think the issue is a bit more than weight balancing adjust.

Any thoughts or suggestions would really be good,otherwise there might be a good AG scope on the market very shortly!

Thanks Chris
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Last edited by hotspur; 01-09-2011 at 07:28 AM. Reason: spell
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Old 01-09-2011, 09:32 AM
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The first one looks like problems with backlash overcompensating. This may be due to the worm being a bit sticky. What is the software you are using for guidiing?
I have found I get better results with backlash compensation turned off as I seem to have inconsistent backlash.
I'm not sure about the middle exposure.
do you have the guider oriented so that corrections are in RA or Dec rather than needing to correct both axis when the star wanders just on RA?
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Old 01-09-2011, 09:35 AM
Alchemy (Clive)
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Chris, to help, if you have a few frames, stack them with NO allowance for shift, ie stacked on one another, this will show the general drift.

Guiding wih a side by side/ extra scope, needs all of the following.

1. Good polar alignment
2. All points of movement locked down securely ( focusers extensions rings etc)
3. No or limited flexure
4. A suitable guidestar ( not to bright not too dim)
5. Solid mounting of mount ( is it on soft ground)
6. Balancing of scope, generally a slight weight in the driving side ... Not perfectly balanced
7. Correct guiding settings, not to aggressive etc
There's probably one or two others.
I replied recently on a thread similar to this, your problem WILL be a fairly simple one, it's just finding it, maybee a set of fresh eyes on location will help, see if you can tempt someone with a BBQ Ive seen scopes with plastic add ons and sticky tape etc, although people think it's solid it's questionable. I'd love to help but I don't think were anywhere near.

I see from your bio you are using a refractor ?

Bang up a pic of you setup, at least that might give us a starting point for loose items. Or cables tangling etc

The good thing is once you've identified this issue you will go on to have a good time under the stars.

I will pop back soon to see how it goes... Let's get it sorted.
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Old 01-09-2011, 10:01 AM
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hotspur (Chris)
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re guiding

Thanks Terry and Clive.

I will post images of set up,its all in a permanent observatory set up on pier,very sold PA.

The guide scope is on top of the 4 inch refractor,towards the end,Maybe this set up is not suitable,most do 'side by side'

I will hold off pulling all the motors off and opening up the mount to fiddle with worms.I will turn off the Backlash comp as Terry mentions.

Thanks again for your suggestions,Ideally I'd like to take five minute subs and darks and use DSS and get some sort of images on a regular basis,as I have invested a bit building observatory.

Cheers Chris

Terry-using PHD orion star shoot AG
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Old 01-09-2011, 10:05 AM
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jenchris (Jennifer)
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I got that effect when my voltage was too low.
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Old 01-09-2011, 12:02 PM
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Here are images of set up,I check cables regularly for snag ups.

I use a Jaycar power supply (cost $400) it has digital display screens,shows power usage,amp draw current votage etc (very impressive looking),I run SS2K at 12.7 volts,uses less than .2 of an amp guiding and 1.43 amp when slewing.I have heard SS2K is 'Power hungry' so not sure if I should tun up votage,I am sure book says only 12.5 volts.

May b e the 'on top' guide' scope is not a good idea,and a 'side by side' arrangement is best.Yesterday I put plate on top of guide scope with 2 200 gram sinkers to weigh that end more as suggested.

Might have to send mount to Rodger Davis or Gary Mack in Melbourne for tune up,bit really cannot afford that at present-its $40 each way for postage.

Anyhow thanks for all your suggestions of a fix-Chris
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Old 01-09-2011, 12:51 PM
Alchemy (Clive)
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Had a look at the pics

Check these points for movement, just apply a moderate amount of pressure up down and sideways

1. Camera to ( is it an off axis guider or a flip thing) , and how is it attached, screw or compression rings.

2. Compression rings ... Or is it just 2 point screws behind focuser, screws are notorious for movement.

3. Did you relock the focuser after focusing, check focuser movement

4. Atachment points for the scope to mount, check everything as they can come loose over time, particularly in a permanent place

5. Ok your guide scope looks like it's cantilevered over the end first glance would suggest it's not rigid, plus the weights on it .

6. Focuser itself , if you get any visible movement it's going to be a little difficult,

With one of your images, there's a sudden jump in the stars, plus movement, if I had this on my setup, I'd wonder if a cloud had gone over and blocked it momentarily, but it does suggest a mechanical failure of a fairly sudden sort not backlash.

Get back as far as these things.... And be critical
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Old 01-09-2011, 01:41 PM
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Ok Clive will look at those points and try to improve on them.

I just found a page in SS2K manual,that mentions Backlash comp should be on O when AGing,as Terry suggested.

I had it on 250,and went to 300,so may be this could be a part of the problem.Also I now remember I have seen people hook these SS2K up to car batteries-which are 13.8 volt and have no issues,so may be I have had not enough power,Also there was some cloud around last night,also lots of smoke from grass fires-the stars were 'twinkling'.

So will have ago with Backlash at zero,and see what happens.It does appear the configeration of guide scope on top is not as good as side by side,So will have to change that.

Thanks for help-Chris
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Old 01-09-2011, 02:34 PM
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Very good. Make sure the orientation of the guider is set to make corrections in N/S or E/W direction only rather than at a diagonal.
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Old 01-09-2011, 03:25 PM
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Quote:
Originally Posted by Terry B View Post
Very good. Make sure the orientation of the guider is set to make corrections in N/S or E/W direction only rather than at a diagonal.

Thanks Terry-may be all the pieces are falling into place,You mention 'rather than at a diagonal' and only a n/s or e/w correction,I am unfamilar with that setting in PHD AG.

From the sound of it,it may be on the diagonal,as I hear the AG 'shunting' a fair bit.And looking at image two suggests 4 different directions of movement?

Anyhow-maybe it could be a not so large issue that will warrant sending mount away or getting a AG side by side plate.

Clive,the plate G scope is on is 9 mm thick aluminium.but still may have flex that could be apart of issues.

Also,will look into voltage I can operate this SS2K at,it may be it would function better at higher voltage.

Thanks all for you helpful suggestions,Chris
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Old 01-09-2011, 03:29 PM
Alchemy (Clive)
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Quote:
Originally Posted by Terry B View Post
Very good. Make sure the orientation of the guider is set to make corrections in N/S or E/W direction only rather than at a diagonal.
Absolutely, correct aligning is most important.
.............................

Setting of 0 may be the way to go, I know when I watch the guide frame as it's guiding if it's too aggressive it will swing back and forth overshooting.

Looks like you need a clear night to try it all out.
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Old 01-09-2011, 03:39 PM
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Quote:
Originally Posted by Alchemy View Post
Absolutely, correct aligning is most important.
.............................

Setting of 0 may be the way to go, I know when I watch the guide frame as it's guiding if it's too aggressive it will swing back and forth overshooting.

Looks like you need a clear night to try it all out.

Yes,I have noted that back and forth movement,so it does appear one or some settings are incorrect-thanks Clive and Terry-Will go through these.

Unfortunately the smoke is real bad this arvo,so no astronomy tonight.

One thing I will have to have is a new procedure on BL settings-when slewing set it,when going to AG set it to 0.

Will wait till better sky condition is about-but will miss out on the comet.

Thanks-Chris
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Old 01-09-2011, 06:57 PM
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Quote:
Originally Posted by hotspur View Post
You mention 'rather than at a diagonal' and only a n/s or e/w correction,I am unfamilar with that setting in PHD AG.
Chris
Chris - what Terry means is the Autoguider should be square to the RA & Dec axes. It means that if the scope "drifts" in RA it only has to correct along that axis (usually across the chip), rather than detecting it as movement both across and up or down the chip.

The easiest way to do this is make sure the sockets and light on the back of the autoguider are square to the telescope. If you're looking at the screen on PHD and use the buttons on your hand controller to move E-W & N-S you want to see the stars on the screen move horizontally then vertically on the screen. (It's a mechanical setup, not a software setup/option)

Keep at it Chris - it's a frustrating hobby, but eventually you'll get it sorted out. You've come a long way in Astro by yourself - no reason why you can't sort out astrophotography as well!

DT

Last edited by DavidTrap; 01-09-2011 at 06:58 PM. Reason: added a bit
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Old 01-09-2011, 07:53 PM
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Quote:
Originally Posted by DavidTrap View Post
Chris - what Terry means is the Autoguider should be square to the RA & Dec axes. It means that if the scope "drifts" in RA it only has to correct along that axis (usually across the chip), rather than detecting it as movement both across and up or down the chip.

The easiest way to do this is make sure the sockets and light on the back of the autoguider are square to the telescope. If you're looking at the screen on PHD and use the buttons on your hand controller to move E-W & N-S you want to see the stars on the screen move horizontally then vertically on the screen. (It's a mechanical setup, not a software setup/option)

Keep at it Chris - it's a frustrating hobby, but eventually you'll get it sorted out. You've come a long way in Astro by yourself - no reason why you can't sort out astrophotography as well!

DT
Ok,David-thanks for that.

Just had a quick peak at the writing and sockets on back of AG.It did look like it was slightly tilted.Can easily rotate guide scope tube in rings to line up.

So by doing those E-W N-S visual checks using manual,and seeing stars move straight up and down left and right-should confirm that issue of diagonal movement is sorted?

So from this thread-we have clearly identified two mistakes-Backlash setting not a zero-confirmed,and diagonal movement most likely.both of these seem fairly routine to go over and make corrections.

Not sure about the other possible causes mentioned,but clearly have something to go forward with.

Thanks All.
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Old 01-09-2011, 07:56 PM
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Quote:
Originally Posted by DavidTrap View Post
Chris - what Terry means is the Autoguider should be square to the RA & Dec axes. It means that if the scope "drifts" in RA it only has to correct along that axis (usually across the chip), rather than detecting it as movement both across and up or down the chip.

The easiest way to do this is make sure the sockets and light on the back of the autoguider are square to the telescope. If you're looking at the screen on PHD and use the buttons on your hand controller to move E-W & N-S you want to see the stars on the screen move horizontally then vertically on the screen. (It's a mechanical setup, not a software setup/option)

Keep at it Chris - it's a frustrating hobby, but eventually you'll get it sorted out. You've come a long way in Astro by yourself - no reason why you can't sort out astrophotography as well!

DT
Well said David.
This is exactly what I meant. It is a mechanical thing not a software choice. Good luck with it Chris.
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Old 01-09-2011, 08:25 PM
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Quote:
Originally Posted by Terry B View Post
Well said David.
This is exactly what I meant. It is a mechanical thing not a software choice. Good luck with it Chris.

Thanks Terry.

I am feeling a bit more confident now,the two points you bought up in the thread-Backlash at zero and diagonal movement.I did not have an awareness of.So these might be the last two steps I have to address before I am up and running.Clive has also bought up some very useful point to look at too.

And the power supply,Jen mentions-I will ask on the Yahoo SS2K group about voltages for SS2K.(although I find those yahoo groups a bother to use,and rarely go there).

Will have to wait till a clear night comes and I will have another go.

Cheers Chris
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Old 01-09-2011, 10:16 PM
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Originally Posted by Terry B View Post
Well said David.
This is exactly what I meant. It is a mechanical thing not a software choice. Good luck with it Chris.
PHD does not care if the guide cam is square. It measures both the X and Y movement as it calibrates the mount.

Having it square does make it easier for you, to because making a RA or Dec adjustment mean the guide image only moves horizontally or vertically.
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Old 01-09-2011, 10:25 PM
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Originally Posted by mithrandir View Post
PHD does not care if the guide cam is square. It measures both the X and Y movement as it calibrates the mount.

Having it square does make it easier for you, to because making a RA or Dec adjustment mean the guide image only moves horizontally or vertically.
It is true that phd or other guide software can correct in both directions at once but if there is inconsistent backlash it will cause more jumpy guiding if there are corrections in both axis with each guide impulse. It also makes it much easier to work out where the tracking errors are with the mount. If you are well polar aligned there should be very little Dec correction needed and what there is should be in 1 direction. The RA corrections should be more even and not prone to backlash problems.
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Old 02-09-2011, 08:02 AM
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Quote:
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It is true that phd or other guide software can correct in both directions at once but if there is inconsistent backlash it will cause more jumpy guiding if there are corrections in both axis with each guide impulse. It also makes it much easier to work out where the tracking errors are with the mount. If you are well polar aligned there should be very little Dec correction needed and what there is should be in 1 direction. The RA corrections should be more even and not prone to backlash problems.

Yes,Andrew-the AG can work both at once,I can hear lots of 'stops and starts' noise from the mount,I see slight up and down and 'jumpy' movement on screen.So will make sure AG camera is square,I looks slightly tilted at present.To check-I'll leave as is-and do the check David Trappet mentions,and then adjust the AG scope so its square.

I had the backlash set at 300,and now know it needs be at 0.Just wondering what speed the AG speed needs to be set at in the paddle,I have it on 2.5,may be too high??? should I set it at 1.5??

A while back,I had cable connection issues,and could not get anything to talk to each other.Now its like there has been too much information and over corrections and with the faults that I have made with BL etc,too much going on has caused poor tracking.

Thanks all-Chris

Last edited by hotspur; 02-09-2011 at 08:05 AM. Reason: detail
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Old 02-09-2011, 12:14 PM
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Terry is quite correct - it shouldn't affect PHD if it's not square - it will just make things look bad on the screen.

What are you options for AG speed? Mine has 0.25x, 0.5x and 1x sidereal rate for guiding corrections. I don't think it would make too much difference as PHD will "calibrate" at what ever speed you have set.

DT
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