Discussion in 'STT Series (retired)' started by jerryyyyy, Jun 11, 2018.
Looked at your calibration images. The scope is moving correctly.
The signal-to-noise ratio in those frames is unacceptable for calibration. You need to find a brighter star, or use a longer exposure.
It may be possible to guide on a star with an SNR of 7, but it isn't sufficient for calibration since it has to search the whole frame for the star. Especially with the gradients etc. in those frames.
I took a look at your images. They're of insufficient quality for calibration.
Possibly more telling, their FITS headers indicate they were produced with MaxIm DL V6.16. There is a patch that only applies to V6.17 that fixes contention between guider and main image shuttering in SBIG cameras. I strongly recommend you use the upgraded software.
- Owen -
Basically back up and running. I think the ACP script selects a star for optimal brightness....
Discovered that I had to change my guider image calibration as I was using 1X files and now at 2X. Changed to simple darks.
I still have that problem with the chip, probably worse in summer, where it just goes blank and screws up the guiding for that sub. This is less with the multi-star. I see you have a new version 6.17 out. Are there any changes in multi-star worth installing?
I guess you are suggesting install.... will try. Always scary. I wonder if those bad images are the shutter problem....
Yes I would recommend installing the latest.
Did it. Having some problems calibrating the guider images. I cannot find the menu that says where you put the DARK and BIAS. I am using the simple auto-dark until I figure this out. I think it is important as it is very hot here and the guide chip is uncooled.
If you want to use full calibration, you need to use the Set Calibration command. (You can set it up with groups for more than one camera at a time, if needed.)
Thanks, found it under the Process Windows. Is this Differential Guiding new?
It's been there for a while; we put it in at the request of Alan Holmes, who developed the patented technology. Requires some hardware. We have prototypes, but haven't transitioned it to production because busy.
Jerry, did you notice if you still get the bad guide images with 6.17? I need to download the demo to try it and see if it fixes the problem, I've just been super busy lately and not had the time when the sky is clear.
Doug, we are pretty much back in business but I wanted to post a few more items here since it is the same saga. Enclosed in a tracking log annotated as well as an image of the Maxim guiding graph. Big questions is are they on the same scale? Is the tracking log in pixels or in arcsec? I put the guider graph in arcsec. Log attached as zip.
In the picture you will see the PE being corrected... cycle is about 600s. George at AstroPhysics notes that the DEC reading will give you an idea of your seeing variability... which should be the range of variability also for the RA... so a real correctable change in RA should be bigger than the reading in DEC... this is you minimal move setting.
In any case, this is all for optimal conditions and all goes out the window with a few clouds or humidity like we have here.
in San Francisco.
The scale on the graph can be set to pixels or arc-seconds, and is the same for both X and Y. Details are in the manual:
Format of the track log is in the manual:
Offsets are in pixel units. Correction numbers are in seconds - it is the actual pulse length sent to the telescope.
Thanks. Very helpful: So the Offset is in Pixels; The Correction in ArcSec/Sec; and the graph either Pixels or Arcsecs.
I can get the Excel all on the same units. say arcsec by applying the arcsec/pixel and arcsec/sec constants for my system. If it interests you, in the last two columns of the attached. Interesting to me. It is not over correcting.
Is there a unit for the brightness? A lot of my problems now seem to be reduced to the seeing in my urban area.
The correction is in whatever-your-mount's-guiding-rate-is per second.
Brightness is in ADU.
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