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Old 27-08-2015, 07:02 PM
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PRejto (Peter)
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Guide Software That Will reacquire Lost Star?

I'm perhaps on an impossible quest in an attempt to automate my two scopes on one mount. I would love to use FocusLock with both of my scopes each of which has an ONAG + guide camera. I can automate scope 1/camera 1 through CCDAP5 and with a sync program can trigger images to be taken through camera #2. With this setup I can dither the 2 cameras and I can acquire a guide star easily in scope 1. The guide star is a big problem in scope 2. At the beginning of a session I can manually find a guide star (used only for focus, not guiding) but if I am not present when the scope slews to a new target I cannot think of any automated way to find a new guide star for scope 2. Consequently FocusLock will no longer maintain focus for camera #2.

Thus the question; is there any guiding program that will automatically search out a guide star if the originally selected guide star is lost? I was thinking that a similar sort of situation might occur if a guide star is lost due to clouds. Suppose that the guide star is hidden for 30 min or so. Obviously in that case there would be no guiding corrections but the mount would continue in RA. But one couldn't assume that the guide star would remain in the tracking box when the clouds parted. Will any guide program take a full frame image in that situation and try to hunt down the "missing" star? If so, then there might be a way to find a star when the mount slews to a new target making the guide star disappear in scope 2.

Thanks,

Peter
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Old 27-08-2015, 08:30 PM
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CCDsoft will continue to try to locate the guide star and I have found it often reacquires it if the polar alignment is good and the guide star is still in the guide box. Best to not use subframing in that instance.

It is my complaint about PHD2 which seems to lose the guide star very easily and does not even attempt to reacquire as far as I can tell. Although it may be there are settings I can tweak for it to work better.

It does great guiding but loses guide stars too easily.

Greg.
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Old 27-08-2015, 10:15 PM
Garbz (Chris)
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Will any guide program take a full frame image in that situation and try to hunt down the "missing" star? If so, then there might be a way to find a star when the mount slews to a new target making the guide star disappear in scope 2.
PHD2 can be asked to auto-select a guide star by hitting alt-s. That feature is already baked in. The server interface allows connecting programs to be alerted if a guide star is lost and allows programs to automatically start guiding in which case an appropriate star will automatically be selected.

Some programs that interface with PHD2 already do that. Failing that it should be trivial to make a standalone program that listens for PHD2's "Starlost" event and then sends the "Guide" event back to basically tell PHD2 to try find a star and resume.
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Old 28-08-2015, 09:08 PM
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Thanks Chris and Greg.

That is exactly the info I have been looking for!

I'm particularly interested in trying out PHD2 for this purpose. Chris, you wrote "Some programs that interface with PHD2 already do that." Are you able to mention any programs that do exactly that together with PHD2?

Thanks,

Peter
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Old 29-08-2015, 09:46 AM
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I'm particularly interested in trying out PHD2 for this purpose. Chris, you wrote "Some programs that interface with PHD2 already do that." Are you able to mention any programs that do exactly that together with PHD2?
SGPro will do this. It enters a recovery mode if the guide star is lost (say due to cloud) and will repeatedly recheck to see if a guide star can been re-acquired. If so it will automatically resume the guiding and the imaging sequence.
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Old 29-08-2015, 04:00 PM
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Thanks for the info Richard!

Peter
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Old 30-08-2015, 06:44 AM
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I had a bit of a play with PHD2 last night. Things didn't go too well. First images returned from my ST-i looked very odd. Barely any stars showed up in the camera FOV so I disconnected and connected to TSX which on the same FOV showed many stars. Went back to PHD2 and only a single bright star looked like it could be guided on. I tried different gain settings and finally was just barely able to see other stars but they remained very faint even with greatly incresed exposure time. Perhaps this was due to the inability of PHD2 to bin the camera 2x2. Not sure. Even at 1x1 the ST-i is quite sensitive. I also tried with and without darks and this hardly made a difference. Any ideas from any of you familiar with this program?

Thanks!
Peter
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Old 30-08-2015, 08:26 AM
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phd2 automatically scales the display to the brightest star, so some of the dim looking stars would probably have been quite suitable for guiding - put a box over one and see what SNR you get - more than about 4 is usually OK on mine.

Darks are a very good idea and easy to implement. median noise reduction is also worthwhile.

from the manual:
"The next control to the right is a slider for adjusting screen stretch and contrast, essentially a "gamma"a djustment. PHD2 automatically adjusts the display accounting for the darkest and brightest pixels in the image, and the slider is used to fine-tune the display to better see the stars in the field of view. This may be useful, for example, if you are trying to focus the guide camera for the first time and need to see the large, out-of-focus star image. Moving the gamma slider only makes the display brighter or dimmer
for your viewing. PHD2 always uses the raw pixels from the camera for guiding, and moving the gamma slider has no effect on guiding. A display of "completely white" or "completely black" is usually an indication that no stars are available in the field of view. "
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Old 30-08-2015, 05:32 PM
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Thanks Ray,

Big help. After all reading the manual is a very advanced concept!

Peter
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Old 30-08-2015, 07:16 PM
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Thanks Ray,

Big help. After all reading the manual is a very advanced concept!

Peter
thought you might enjoy that
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Old 31-08-2015, 11:37 AM
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SGPro will do this. It enters a recovery mode if the guide star is lost (say due to cloud) and will repeatedly recheck to see if a guide star can been re-acquired. If so it will automatically resume the guiding and the imaging sequence.
Interesting you mention this. I don't use SG myself but one of the biggest gripes of astrofest this year was that a lost guidestar caused an aborted sequence and people on the field were looking for a solution with great anger.
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Old 31-08-2015, 11:52 AM
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Interesting you mention this. I don't use SG myself but one of the biggest gripes of astrofest this year was that a lost guidestar caused an aborted sequence and people on the field were looking for a solution with great anger.
I figured it out after I got back.
There is a setting for "recovery" that's supposed to solve that. Haven't tested yet.

I know I lost a lot of imaging time on the Tues night because guide star lost and sequence paused but didn’t start again when guide star regained. Did some reading, and it appears there is a feature to be enabled that wasn’t on mine. See here, the section on “sequence recovery” http://www.mainsequencesoftware.com/...equencing.html

Basically, you just need to have the box checked under Tools->Options, Sequence Settings tab.
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