Multiple Question from New User

Hello.

I am somewhat familiar with automation software but new to ACP. So far I have been able to setup the preferences on the first night and run a brief session on the second night.

Guiding:

1. Does the ACP guiding algorithm a try to avoid guiding on saturated guide stars? I saw this happening although it could have been an initial guide star choice through clouds that later cleared.

2. I understand that if "automatic dither" is checked the dither amount is 1 pixel. I suppose if I want to change that value I can do so by editing the #dither line in the plan txt file, correct?

3. Of the 2 images I capture last night using automatic dither, I noted the shift from one image to the next was excessive. Would you explain why? Here is a link to the imaging log:

http://tinyurl.com/34ouang

4. Would you explain "guide cycle time?" I don't know what to use for this value.

Horizon:

1. Is there a way to edit the local horizon other than freehand?

2. How accurate does the local horizon need to be?

Shutdown:

1. I am uncertain about using the shutdown procedure. I am using a Takahashi NJP Temma 2 mount (ASCOM Temma 2 driver) and remotely controlled Pier-tech retractable pier and Tele-station (roll-off roof observatory). At the end of a session I would like ACP to turn off camera cooling but I like to "park" the mount myself. I need to make sure the mount is in the proper "park" position and the pier is retracted before I close the roof. Is this possible?

2. On a similar subject, does ACP stop mount tracking after various tasks (ie capturing flats, lights, biases or darks)?

Planner:

1. If I setup a plan to capture biases and/or darks (or a second target) after a target run , will it postpone the capture of the calibration frames (or second target) if the light frame plan runs over it's scheduled time period?

2. Tonight I have a plan to take 30, 1 sec bias (dark) frames. Why does Planner estimate that this will take 23 minutes?

Thank you very much.

Gordon Mandell

Hi Gordon,

I'm a long-time ACP user (actually I think I'm customer #8). I'll do my best to answer. Bob will probably want to add more info.

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1. Does the ACP guiding algorithm a try to avoid guiding on saturated guide stars? I saw this happening although it could have been an initial guide star choice through clouds that later cleared.

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Yes, 2 ways. First, PinPoint shouldn't see a badly saturated star as potential guide star. Second, the process is to first take an exposure at a "medium" length (I think 5 sec is the default), then it scales the actual guide exposure to meet the minimum SNR (I think 3.0 is the default). So, it is possible you'll see a saturated star in the initial exposure, but highly unlikely in the actual guiding.

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4. Would you explain "guide cycle time?" I don't know what to use for this value

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It's actually probably my fault that that's there at all! In the old days, some guiders had a very long cycle between exposures that needed to be accounted for. For most current guiders, there is virtually no delay between guide cycles, therefore this number should be very short (less than 1 second).

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1. Is there a way to edit the local horizon other than freehand?

2. How accurate does the local horizon need to be?

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Regarding accuracy, I think it depends on your situation. If you've got lots of obstructions, the more accurate you are, the more efficient ACP can be - e.g. ACP will avoid the problem areas as best you define them.

There is a user application to help automate the horizon-creation process. You can check it out here:

http://forums.dc3.com/showthread.php?t=3111

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1. I am uncertain about using the shutdown procedure. I am using a Takahashi NJP Temma 2 mount (ASCOM Temma 2 driver) and remotely controlled Pier-tech retractable pier and Tele-station (roll-off roof observatory). At the end of a session I would like ACP to turn off camera cooling but I like to "park" the mount myself. I need to make sure the mount is in the proper "park" position and the pier is retracted before I close the roof. Is this possible?

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The possibilities to control the shutdown process are virtually endless! But, if what you're trying to do is manually control shutting things down, the easiest way to do it is to use the #quit directive at the end of your Plans instead of #shutdown. #quit just stops the telescope from tracking, but leaves everything else for you to do manually. #shutdown warms up the camera, shuts it down, and slews the mount/dome to its park position (as defined in the driver).

When you get to the point where you want to automate some of the shutdown process, I'm sure we can help with that.

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2. On a similar subject, does ACP stop mount tracking after various tasks (ie capturing flats, lights, biases or darks)?

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ACP will stop tracking after executing virtually everything it does. The exception to that is when certain scripts are run manually from the console (I think the only ones are syncscope.vbs, findbrightstar.vbs, and calibrateguider.vbs).

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1. If I setup a plan to capture biases and/or darks (or a second target) after a target run , will it postpone the capture of the calibration frames (or second target) if the light frame plan runs over it's scheduled time period?

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No, it won't. It just works through the Plan sequentially. Therefore, it's important to get your timing's reasonably close in Planner's setup so that doesn't happen. This is most important when doing dawn flats, since the window for taking them is reasonably short.

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2. Tonight I have a plan to take 30, 1 sec bias (dark) frames. Why does Planner estimate that this will take 23 minutes?

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Look through the times in Planner under Tools, Preferences. These are what's driving the calculation. After you run a few Plans, you can analyze the logs and change the values to match your system. I think the defaults are fairly conservative.

I didn't answer anything about dithering since I don't regularly use that functionality.

I hope this helps - and you enjoy using ACP!

Regards,

Jim McMillan

Jim --

All I can say is WOW! Thanks so much for answering this myriad of questions. They are good questions too! I'm tied up on another issue today and have less bandwidth than the last few.

Thank you very much Jim. Your detailed explainations and suggestions were extremely helpful. I have previously read your article on autoguiding prior to knowing that your work was used in developing ACPs autoguiding algorithms. I refer to your article often.

I am currently running a session and after some tweeking of the guiding settings I'm seeing better results tonight.

Thank you for the link to the horizon editor. I was able to import my horizon from TheSky into ACP with minimal trouble (although I think the editor has some peculiar behaviors).

As far as the shutdown procedure. It seemed to work for me last night as I wanted. It warmed the camera and parked the mount after the dawn sky-flats were taken. The park position was where the telescope was pointing when the last sky flat was captured (which is fine). I was then able to manually unpark the mount, slew it to it's proper "home" position, park the mount, lower the pier and close the roof while watching on the observatory webcam. Perfect!

I'm slightly confused about your answer regarding how ACP handles 2 targets. Are you saying that if the first target run is longer than expected that ACP will abandon this target run to start the second target run on time? Or that the second target run will start after the first is completed regardless of the scheduled start time for the second run? I assume the latter and how that might interfere with a series of dawn sky-flat frames.

One problem that I am seeing tonight (similar to last night) was that after the initial autofocus run, the telescope slew to an incorrect location for the first image using an Ha filter. After that, the target was centered correctly when the camera took 2 additional images with the O3 filter before another autofocus run (I am using filter offsets). Starting with image number 2 and thereafter (so far) target centering and dithering look good. I'm not sure if I have something set up wrong in the preferences or what. After the current session completes I will analyze the images and post the log to show what I mean. Any thoughts?

Thank you again.

Gordon

Hi Gordon,

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I'm slightly confused about your answer regarding how ACP handles 2 targets. Are you saying that if the first target run is longer than expected that ACP will abandon this target run to start the second target run on time? Or that the second target run will start after the first is completed regardless of the scheduled start time for the second run? I assume the latter and how that might interfere with a series of dawn sky-flat frames.

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The latter - e.g. the second target run will start after the first is completed regardless of the scheduled start time for the second run.

Regarding the other problem, I'm thinking based on your other post that turning off CA solved the issue. CA is kind of a software kludge to deal with hardware problems. Most mounts prefer CA off, so nothing unusual there.

Regards,

Jim

Thank you so much Jim.

FYI to new folks, we are closed on the weekend and Mondays are usually spent handling support and pre-sales questions.

Thanks Jim and Bob.

Gordon