Guiding between targets


#1

Gradually getting familiar with SGpro but I was wondering how guiding works between targets especially neighbouring ones generated by the mosaic wizard. When one tile is finished and the scope moves to the next tile how is a guide star reestablished with PHD2. Do I need to do this manually or is SGpro/PHD2 able to find a star in the guide field automatically and start the new tile so the whole masaic can complete without intervention? I guess this question applies to any target, can it find a star automatically and start guiding in preparation for starting the exposure?


#2

For any target change with slewing or auto center SGP will:

  • Stop PHD
  • Flip calibration data if needed (IE SGP detects a pier flip during the slew)
  • Have PHD acquire a guide star
  • Start guiding

So you don’t need to do anything except watch the magic happen.

It’s highly recommended to guide via ASCOM rather than ST-4 as you get the following benefits through PHD2

  • Dec scaling (changes the dec rate based on your location in the sky…important when you don’t recalibrate between slews)
  • Saved calibration (this might apply to ST-4 as well)
  • Automatic calibration flipping based on pier side

Thanks,
Jared


#3

Jared,
Will Doug need to enable the server in PHD2 (under the PHD Tools menu), or is the server enabled by default?


#4

I’m not sure if it’s enabled by default, it very well may be…but yes, it will need to be enabled for SGP to communicate with PHD.

Thanks,
Jared


#5

Yes, the server is enabled by default on new installs of PHD2. Upgrading from one version of phd2 to another will not change the setting. You can confirm that it is on by clicking Tools on the menu bar and seeing that Enable Server is checked.

I would recommend using PHD2 v2.3.0 or newer, since 2.3 has some improvements with automatic star selection when being driven by SGP. (Older versions were susceptible to seemingly random cases of “Failed to start the autoguider”)

Andy


#6

We have a new version of PHD2 coming out shortly (in the next couple of days or so) that supports connecting to the mount with ASCOM to get pointing information (like declination, and side-of-pier), but guiding through ST-4. This will allow users who prefer to guide with ST-4 to get the benefits Jared mentions, which were previously only available when connecting to the mount via ASCOM. The new version will be posted at http://openphdguiding.org/snapshots.html when it is ready.

Right, saved calibration is available regardless how you connect to the mount (ASCOM or ST-4). Check the option “Auto restore calibration” in the Global tab in the brain. Generally if you have an ASCOM connection to the mount you would want to check that option. Calibrate once (at a low declination, near the equator), then no need to calibrate again unless you rotate your guide camera.

Without an ASCOM connection to the mount, you should recalibrate when your target declination changes. For a mosaic, declination is close enough and you probably do not need to recalibrate.

Andy


#7

It’s highly recommended to guide via ASCOM rather than ST-4 as you get the following benefits through PHD2

  • Dec scaling (changes the dec rate based on your location in the sky…important when you don’t recalibrate between slews)
  • Saved calibration (this might apply to ST-4 as well)
  • Automatic calibration flipping based on pier side

I would note that in an upcoming version of PhD 2 you will be able to use the ST-4 cable interface and it will do
all of those things. I have tested it and it works although it needs one change in SGP (coming in the next version) that will allow correct guiding after pier flip.


#8

Thanks for the reply.

Does the magic work for any target (not just a target change within a sequence) when I have PHD selected as my guiding program. i.e. when any target starts will it automatically instruct PHD to find a star and start guiding and report any problems - i,e no suitable star?

So after calibrating PHD I don’t even need to tell it to start guiding?


#9

Hi Doug,

I always calibrate and start guiding with PHD2 before I start the sequence but after I have done a manual centre here.

I just tried with the simulators starting a sequence without guiding active, it tells me it will ignore frame dither and auto frame restart and then starts the sequence not guiding.

The above was without the ‘“Center on” when target starts’ ticked in the target.

With that ticked the behaviour is as described above, it will centre, then kick PHD2 into life, calibrate and start guiding - never tried that before, impressive.


#10

I have a permanent observatory Doug. I start PHD2 each afternoon and just let it work. I calibrated it a few months ago. Basically, whenever I change something with my alignment. It ‘just works’. It doesn’t matter if you swap targets, change filters… SGP/PHD2 figures it out.

Once you’re calibrated, stop guiding and just tell SGP to ‘run sequence’.


Recording Focus position During Sequence For Assisting with Flats
#11

Thanks everyone. I will give this a go on the next clear night.


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