Why is guide needed for darks?


#1

Maybe I just do not know how to set it up, but it seems that SGP will not allow one to set up (as a target), a set of darks to be done before a target that contains a light. It tries to do things that make no sense for darks, such as insisting that the guider be running.

I also tried this as part of a target containing lights (as the first item). It still insists on running the guider. Taking darks while waiting for full dark or the object to be high enough (in which case guiding might not be possible if the object is blocked) is a very common procedure. How can this be done without unnecessarily running the guider (or can it)?

Am I missing some setting or procedure or is this not possible?

If not currently possible, consider it a feature request. Basically to treat darks the same before a set of lights as it treats them after a set of lights and not try to or expect to be able to guide or to be in any particular sky position.


#2

If SGP detects any active lights it will require the guider. The 2.3 implementation with PHD doesn’t allow us to start the guider from nothing. Because of this if you have lights we require that that guider is active and guiding before beginning.

Since you already have darks in their own target, just disable the target with the lights and then run the sequence. Since the lights aren’t active SGP shouldn’t require the guider.

Thanks,
Jared


#3

The 2.3 implementation with PHD doesn’t allow us to start the guider from nothing. Because of this if you have lights we require that that guider is active and guiding before beginning.

Wow. OK. Never mind darks for a moment, what you seem to be saying is that one can’t have the system wait and then start imaging an object at some point in the night? That seems to be what you are saying if the system cannot start the guider from nothing (I am assuming here that PhD 2 has a calibration loaded from a previous session). If that is the case, then what is the purpose of this?:

Your reply also seems to imply that future versions will be able to do this.

Have I got this right or am I misinterpreting something?

Since you already have darks in their own target, just disable the target with the lights and then run the sequence. Since the lights aren’t active SGP shouldn’t require the guider.

So if I do that, it will not need to do anything with the scope/mount/guider before executing the darks?

I assume this would also apply to other static frames such as flats and bias, correct?


#4

Technically you can have it wait to start a target, you just have to have PHD guiding. If it’s dark you can point to some random area, start PHD and wait. But currently SGP will not start guiding “from scratch” as the PHD socket server does not have this functionality.

The Start/End times can be used with multiple targets. For instance if your first target started immediately you could have a second target that started at 2am. We can switch targets and start guiding just fine.

Yes, 2.4 with the new PHD2 API will have the ability to start guiding from scratch. You will need to have PHD open and your equipment connected, but everything else will be automated. The first release of 2.4 will likely not have the ability to do this, but it is something we will add.

Correct, assuming you don’t have any functionality in the events that needs the mount (parking at a specific area for flats). But flats, darks and bias frames by themselves have no reliance on the mount or guider.

Thanks,
Jared


#5

In that event, what does it do if the first target completes quite a bit before the second target is due? Stop Guiding? Stop Tracking? Both?


#6

Good to hear that will be added. It is fairly important to be able to do that and have complete automation.


#7

Continues tracking and waits for your start time. We were planning on having it park between targets…but that would cause you a lot of issues we may make this behavior user selectable.

Thanks,
Jared


#8

Just to be sure I understand:

  1. I image Target One by starting the guiding and have it run the first target light frame events .
  2. Target One finishes but Target Two is not yet set to run so:
    a) It stops guiding.
    b) It continues tracking
  3. Target Two time arrives
    a) Starts guiding
    b) Starts images

Are we talking about V 2.3 in the above, or V 2.4?

BTW, for what it is worth, I do think that maybe stopping tracking might work with the Paramount (dunno about other mounts) whereas parking will not. Stopping tracking is what ACP does in similar situations. That might avoid the mount getting into trouble during a wait. Perhaps allow user selectable park/stop track/continue track.


#9

Mostly correct. PHD will continue guiding. Then when it’s target 2 time SGP will slew and reacquire a guide star.

I would prefer to have my equipment parked between targets. I’m sure others would prefer tracking just stopped and others may be indifferent. Which is why when we get around to this we’ll likely make it an option.

Thanks,
Jared


#10

I tried the “start capture” option last week on a couple of targets that I wanted to image after I wanted to turn in. The first night, I started the guider at the first target and let it run. On the next night, since the target wasn’t in a good position at the time I wanted to start, I started the guider at an alignment star, then placed it in pause via the guider control panel in SGP. I did this as there was cirrus in the area that was supposed to clear by imaging time and didn’t want the guider walking of or doing other strange things due to clouds. Both nights seemed to work fine (my Ha post of NGC 6888 is the result of night 2). This seems like a practical option to leaving the guider guiding.

Frank Z…


#11

OK, so in (current) Version 2.3 it will keep guiding on the first target until time for the next target, then slew and point and such and start guiding again on the new target.

But in Version 2.4 it will be able to stop guiding (and also park or stop tracking if desired) after target one and then start guiding again with target 2.

Have I got that right?


#12

Interesting, Thanks!

Jared, does that sound like a reasonable option for V 2.3 until V 2.4 has the capabilities discussed? It looks like one is essentially setting up a “dummy target” (although not necessarily a “target” in SGP) where you start guiding and then pause it and then allow the “real” target to resume the guider and start as scheduled.


#13

Hey Jared,

So you’re saying I’m getting lucky when I start SGP with my shed closed and parked? My standard ‘go’ is with a ‘start time’, roof closed, PHD2 connected but not guiding… It works all the time minus that last shot with 2.3.13…

I am calibrated already of course.


#14

So you’re saying I’m getting lucky when I start SGP with my shed closed and parked? My standard ‘go’ is with a ‘start time’, roof closed, PHD2 connected but not guiding… It works all the time minus that last shot with 2.3.13…

I am calibrated already of course.

“Curiouser and curiouser!” In fact, I kinda do recall trying a “cold start” one night and having it work, but then later it didn’t…

I will try it again tonite if this wind goes down…


#15

OK, it has been cloudy here until tonite but I just tried a timed start and it started imaging just fine with the current versions of SGP and PhD2. I had a previous night’s calibration from a different object loaded into PhD via a profile.

The only thing I did in PhD was to connect the equipment and take darks.

The only things I did in SGP were:

  1. Connect equipment
  2. Prefocus manually
  3. Pressed “Run sequence”

It started just fine at the specified time and is now off and running.


#16

No, that workflow is supported. Sorry, I lose track of features some times. As long as your start time is in advance SGP will sit there and wait until your first target it started. At which time it will un-park your scope and open your obs, slew to your target and acquire a guide star. This is essentially handled as a target switch.

Thanks,
Jared


#17

OK, cool. Hope to have enough data for the first SGP taken images by the end of the June new moon.


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