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Old 15-08-2010, 04:48 PM
Alchemy (Clive)
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Guiding how much time between guide corrections.

Hi all

Being as I am wanting to do more off galactic plane images, where those guide stars can be just a little harder to find, I am after others info on how they guide, in particular, time between guide corrections, ..... Normal, out there if you have to , and did it work if you pushed the time out a bit.
If you could also give an idea of your mount and FL that would help fill in the picture.

I normally use 1 sec corrections, on a g11, FL 900 plus No problems, am wondering if 2 or more seconds works well enough.

Too wet and cloudy here to trial and error at the moment, and once the good weather gets here I don't want to waste too much time on things that are not going to work.

Thanking you in advance

Clive
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Old 15-08-2010, 05:13 PM
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multiweb (Marc)
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Depends on the guider type and guiding scope FL. With a QHY5 guiding through a finder or an ED80 at prime focus (600mm FL) or a newt 5" F/5 at 650mm FL I never had a problem finding a bright enough star at 1s and over, even 3s. With an OAG on the C11 at F/10 (2800mmFL), 1s would be the minimum to pick up a star with the QHY5. With the SX-lodestar I can pick up stars at F/10 still with 0.5s exposures if I take darks. That's what works for me with my G11.
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Old 15-08-2010, 07:46 PM
Alchemy (Clive)
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Originally Posted by multiweb View Post
Depends on the guider type and guiding scope FL. With a QHY5 guiding through a finder or an ED80 at prime focus (600mm FL) or a newt 5" F/5 at 650mm FL I never had a problem finding a bright enough star at 1s and over, even 3s. With an OAG on the C11 at F/10 (2800mmFL), 1s would be the minimum to pick up a star with the QHY5. With the SX-lodestar I can pick up stars at F/10 still with 0.5s exposures if I take darks. That's what works for me with my G11.

I have been until now guiding with a ed80 and an imaging source camera the mono 640 x 480 version, and have found situations where no suitable guidestar was found. Note I have recently purchased a faster scope to try to help somewhat, having had good succsess with 1 sec guiding I have been reluctant to extend beyond that,

What I am trying to qualify, is how far out one can extend the guide time, with respect to my mount or a similar one....... I have to confess I have not done a periodic error measurement on the worms I have but it seems pretty reasonable, given I have had no issues with out of round stars with the 132 scope. Using PHD guiding which has performed fine

I note you had 3 sec updates..... How well did that go?

Clive
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Old 15-08-2010, 08:05 PM
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multiweb (Marc)
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Quote:
Originally Posted by Alchemy View Post
What I am trying to qualify, is how far out one can extend the guide time, with respect to my mount or a similar one....... I have to confess I have not done a periodic error measurement on the worms I have but it seems pretty reasonable, given I have had no issues with out of round stars with the 132 scope. Using PHD guiding which has performed fine

I note you had 3 sec updates..... How well did that go?

Clive
Provided you are very well polar align and balanced and there's no wind, so minimum drift or seesaw motion, you can very easily guide with a G11 every 4-5s and get a smoother guiding than every 1s. As a general rule the least amount of corrections you (have to) do the better your guiding will be.
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Old 16-08-2010, 08:58 AM
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wasyoungonce (Brendan)
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I run PHD with 2-3s guide subs with a guide scope of 70mm & 6.2Fl.

While guiding accuracy appears good I appear to be getting some hunting or hysteresis..aka overshoot with guiding. Its not as smooth as it should be.

I'll be playing with this soon to see if I can smooth it somewhat.
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Old 16-08-2010, 11:21 AM
Alchemy (Clive)
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Thanks for the info

Marc, I had a look at the lodestar, seems good stuff too, however I will be sticking with the current unit I have, it's good to know you have been able to guide with 4-5 sec gaps.


WYOnce, sorry don't know your name.... I use PHD too, I had to drop my aggresiveness to 10% to stop overshooting, I got that back and forth swinging otherwise creating out of round stars, I am going to have to experiment with longer steps, as or seems some have succsess this way,
I used the graph in PHD to try to work it out scientifically, no hope , and to get the settings they suggested... 50 units of something ( it was a while ago) it was worse than how I was doing it, so I gave up on that.
Had a look at the program you have posted the pics of ..... Freebie too......
If you could give an explanation ???? Looks very detailed, might download it later, how does it hook up... Through PHD ???

Clive
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Old 16-08-2010, 11:26 AM
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Quote:
Originally Posted by Alchemy View Post
I had a look at the lodestar, seems good stuff too, however I will be sticking with the current unit I have, it's good to know you have been able to guide with 4-5 sec gaps.
The only reason I got the lodestar is to drive the AO. I need a fast frame rate to be able to correct many times per second. The lodestar is sensitive enough to still pick up a star at a fast frame rate. For any other type of guiding a QHY5 mono will cover all bases without a glitch.
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Old 16-08-2010, 11:52 AM
Alchemy (Clive)
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Adaptive optics, super fast guiders, you're right up there with the high tech stuff Marc , the electronic side of imaging is screaming along, I even noticed QHY coming along with a 14 megapixel OSC to be released soon. $$$$$$ something I just don't have enough of , mind you if I wait that little bit longer maybe something else will come along even better.

I am going to give 2 sec guiding a try next time we have decent weather and see how it goes, that SHOULD give me stars in any field allowing the framing I want,

The only thing with that high speed guiding is the interface with the computer or is it completely integrated with the AO unit ?
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Old 16-08-2010, 11:59 AM
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Quote:
Originally Posted by Alchemy View Post
WYOnce, sorry don't know your name.... I use PHD too, I had to drop my aggresiveness to 10% to stop overshooting, I got that back and forth swinging otherwise creating out of round stars, I am going to have to experiment with longer steps, as or seems some have succsess this way,
I used the graph in PHD to try to work it out scientifically, no hope , and to get the settings they suggested... 50 units of something ( it was a while ago) it was worse than how I was doing it, so I gave up on that.
Had a look at the program you have posted the pics of ..... Freebie too......
If you could give an explanation ???? Looks very detailed, might download it later, how does it hook up... Through PHD ???

Clive
Hi Clive. I'm Brendan...although but there is more than one Brendan..so.."hey you" will suffice.

I'll drop RA aggressiveness as you said and do some testing ..when the clouds clear. Could be some time.

EQMOD blokes devolved PECPREP (that I know of) but it can be used to analyse other mounts. In fact it has the settings for other mounts, including the G11, already built in the program.

You can use it to analyse PHD log files..just enable "log file" in PHD. Later when importing this log file to PECPREP enter the DEC value of the target log. So it can adjust the sine angle values of the data.

There is lots written on the web about using PECPREP and how to pdf's are on the EQMOD site for PREPEC at the bottom of the page.
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Old 16-08-2010, 12:10 PM
Alchemy (Clive)
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Thanks Brendan , got the PDF at 31 pages it will take a while to digest.
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Old 16-08-2010, 12:16 PM
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The only thing with that high speed guiding is the interface with the computer or is it completely integrated with the AO unit ?
Well... still sorting out cabling. You still have to go through USB. The guider connects to the laptop via USB (like a QHY5 in PHD), then USB to serial to AO then AO direct to mount guider port. So the guider takes a pic (throught the AO glass) then sends it to the laptop. The software drives the AO to tilt. If out of range (+/-25px approx. depending on image scale) the AO bumps the mount (not the guider). That's the last bit I haven't figured out yet.
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