dithering

[Curtis H. Croulet]

In Planner, how do I enable dithering? I don't see it.

[Yves Laroche]

Curtis,

please see the attached picture from Tools --> Preferences menu.

--Yves

Dithering.jpg

[Curtis H. Croulet]

Yes, I found that and set it. But it gives me no control over dithering -- pixels to dither, frequency. And I'm not clear that it's being applied. Other questions have come up. If ACP Planner is separate from ACP, then why do I need ACP? It appears to me also that Planner and ACP don't provide for temperature control of the camera. My previous experience is with CCD Commander ($99), which can shut down, cool, and warm up the camera. It also provides control over dithering.

Update: I'm not sure how force it to focus or to designate a focus star. I suspect I'll finish up the night with CCD Commander.

[Yves Laroche]

Please refer to the ACP's help information below.

--Yves


#DITHER Offset each image in a repeat-set by some small amount away from the original target location. Works for both guided and unguided images. If no parameter is given, ACP uses a value of 5 main imager pixels for dithering (see below). Normally, this value will be appropriate for achieving the noise reduction effect of dithering. Dithering is done by generating two uniform random numbers ranging from minus to plus the "amount". One is applied in the X direction, the other in the Y direction. Note that you must supply a value for the guider's plate scale in order for ACP to calculate main imager pixels for guided dithering. If you fail to do this, a warning message will appear in your run log and dithering will be in guider pixels.

If given, the parameter specifies the maximum amount in each axis of this offset in fractional pixels. A parameter value of 0 disables dithering. The random offsets are applied independently in X and Y and are always relative to the initial position. For example:
#DITHER ; Automatic dithering
#DITHER 3.0 ; 3 pixels dither on the image
#DITHER 0 ; Disable dithering

[Curtis H. Croulet]

Thank you, Mr. Laroche. I tried ACP Planner for the very first time tonight on the Horsehead Nebula (TEC140 scope, QSI 683 camera). I think it dithered. It also focused. I don't know how it focused, but FocusMax reported successful focus. If ACP eliminates the need to hunt through TSX for a suitable focus star, which must then be designated in CCD Commander (go-to, plate-solve, focus), then that will be a definite plus. Unfortunately, I also had something that looks like RFI in the images. At first I thought it was caused by ACP, but retrying the same area with CCD Commander yielded the same result. I shut everything down and unplugged/replugged some USB connectors. I think the problem is solved. In almost eight years of owning this camera, it's the first time I've seen anything like this. Strange.

One anomaly with ACP Planner: although my "plan" was set to shoot 12 ea 300 sec exposures, it kept going after the twelfth exposure. It shot 20 exposures before I cut it off to look into the RFI problem. I will double check the guider image scale setting.

[Curtis H. Croulet]

Feeling my oats, I tried to create and run another "plan." I had an awful time getting it to run. The allotted time for it to start came and went, but nothing happened. It required a complete shutdown and reboot to get the "plan" to go. When the "plan" finally ran, it went to focus. ACP chose a star that was too bright, whereupon ACP simply gave up and went to the object (galaxy NGC 2903) to do the imaging). Since FocusMax is pretty specific about the brightness of a star for focusing, ACP should be sensitive to those parameters. Is there any way to set focus parameters in ACP, to prevent it from selecting an unsuitable star?

[Bob Denny]

Curtis -- Have a look at these instructions on how to attach files to your posts. Then please attach the plan and the resulting ACP run log where it had a terrible time. The logs are located in My Documents\ACP Astronomy\Logs\yyyymmdd\ ​I need to see the plan and the problems in order to help.

You might want to look at FocusMax's "AcquireStar" function which will allow it to be far smarter in picking the focus star. I am surprised, though, that ACP picked one that is too bright. Anyway the time spent to get FocusMax to focus by itself (without ACP running at all) and using its AcquireStar feature will be worth it.Test at multiple random places in the sky, not to include Sirius or other ultra bright stars. With ACP (with and without FocusMax AcquireStar) you will never need to manually select and designate a focus star. ACP is true automation :-) :-)

[Yves Laroche]

You are welcome Mr. Croulet.

--Yves

[Curtis H. Croulet]

Thank you to Bob and Mr. Laroche for your replies. I could not get AcquireStar to work. Its setup looks quite complex, which is probably why I never bothered with it before. I'm not even sure what it's supposed to do. Note that I have the last of the freeware versions of FocusMax. In any event, I am going to retire from working with ACP for awhile. My QSI camera appears to be dying. I get lots of noise and herringbone patterns. As recently as three days ago it worked perfectly, as it has since 2012. I have to make some decisions: send it off for repair (which I understand means a trip to Portugal) or buy a new camera. But this isn't the forum for that. Thank you all.

[Yves Laroche]

Sorry Curtis but I can't help you with AcquireStar. I'm not using it but tested it many years ago. If I remember correctly, the AcquireStar feature pass all the control of choosing the focus star (according to its settings) and the autofocus process to FocusMax. If not using AcquireStar, ACP manage the acquisition process (choosing the right star) and just let FocusMax doing the autofocus process.

By memory, in using AcquireStar you must connect FocusMax to the ASCOM telescope driver. FocusMax needs to know where the telescope is pointing. Also the FocusMax telescope must be calibrated first.

Maybe other person here can share his experience with this AcquireStar feature.

Hope that will help you a bit.

--Yves