#21  
Old 05-02-2014, 06:03 PM
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Bart
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Whooo-hooo! Stars showing up in my Lodestar through the OAG!!

Had another fiddle with it and got it all working, however; guiding is terrible.
With my guide scope, I use 1 second exposures and get reasonable guiding. I notice with the OAG that the star tends to wobble around a lot and guiding is bouncing up and down. Do I need to run with longer guide exposures or trim my min and max move times etc in MaxIm? PEC? With ST4?

Any suggestions to tweak it now it is running?
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  #22  
Old 05-02-2014, 06:22 PM
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alistairsam
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Hi
What FL is the scope?
2sec would be better, difference with the guidescope and the oag is that the guidecam/oag would have a smaller image scale than the guidescope so is seeing stars at a longer FL
at 1m, mine does jump around a but thats mainly flexure in my ota.
Seeing also plays a part.

Can you post a guiding graph?

Edit: I've noticed st4 works better one part of the sky and pulse guiding in others but this might just be my rig.
Best to experiment, get it going without pec first.
Pec would only work with pulse guiding
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  #23  
Old 05-02-2014, 06:33 PM
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Bart
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Hi Alistair,

The scope is a TAK TSA 120 and with the flattener it is F7.3 which is about 876 mm. I did notice 2 seconds made it better. The mount is an EQ6 Pro with belt drive. Polar alignment is good, I wouldn't say great, as trying to adjust it with those dicky altitude screws is very hard. Polar drift is veeeerrrryyyy ssslllooooowwww!

Sorry, no graph. Will try to collect one tonight.

Cheers.
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  #24  
Old 06-02-2014, 12:49 AM
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Unhappy

Hi
How much play or slop did you leave affer the belt mod?
Mine is also an new6 pro and I've also installed rowans belt mod. I guide and image at 1m and dont have issues guiding with this graph fairly flat and mine is a 10inch newt so loads more flexure
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  #25  
Old 06-02-2014, 10:47 AM
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Got it under control!

Changed guide exposures to 2 sec, might try 3, and the calibration steps to 20 and all is very good apart from an unusual problem.

I have the filter wheel pointing up and the OAG and Lodestar pointing down. After one or two exposures, MaxIm locks up and I have to do a full reboot, re-centre etc...

If I then take the Lodestar out and stick it back in the guide scope, it goes all night. I am not willing to rotate the OAG up as I am working on a project and and don't want to have to take all my flat frames again. When my project is finished, I will set it up the other way and see what happpens although I am very happy to basically have it working.
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  #26  
Old 06-02-2014, 11:25 AM
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You can also adjust the aggressiveness setting. After autoguider is callibrated then its down to aggressiveness (probably set too high - try 6 or 7 instead of 10), guide exposure length - I find it varies - bad seeing try 1 second, good seeing go a bit longer, can't find a guide star bright enough - then you may be forced to use longer.

Polar alignment, balance are physical factors that affect guiding.

Chosing the right guide star. If you get excessive errors try picking another guide star. Make sure it is tightly focused. Try to avoid an eggy one at the sides or a double star or overly bright star.

PEC can help get round stars although it will seem to make your guide errors larger.

Perhaps a cable is coming loose upside down. Make sure the cables fit snugly or put a bit of tape on it to make sure it doesn't come loose.


Greg.
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  #27  
Old 06-02-2014, 11:42 AM
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Maybe the usb cable is coming out a bit when the lodestar is pointed down. Its good to put a band or velcro strap and fasten thr st4 and usb cable against the lodestar body.
The connectors are known to be flimsy.
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  #28  
Old 06-02-2014, 12:34 PM
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Thanks guys.

I have tried that/do that. In my research for a new guide camera I discovered the info relating to the connectors on the Lodestar and have been securing the cable from day one. I already have a GPUSB and decided to run with that as it would get rid of a cable with a potential problem and is a flawless performer so far. I see no reason to change.

I may post it to the SX forum although it is an unusual one for them even.

It would be good if I could stop it doing that as now that I have it working I would like to take advantage of it.
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  #29  
Old 06-02-2014, 03:21 PM
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Merlin66 (Ken)
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I've been using the Lodestar (with the TS cable clamp) for the past three years to guide my spectroscopes (basically similar arrangement to OAG)
It was a dramatic improvement on the QHY5 I used and it continues to work every clear night without fault.
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  #30  
Old 06-02-2014, 06:47 PM
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I'm enjoying your continual encouragement, Merlin. Can't wait to complete my first image with an OAG.
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