Astroberry/EKOS Focusing with a EFW

[TerryMcK]

I have had a few failures recently with some of the data captures specifically with my OIII filter in conjunction with my ZWO ASI 5 position EFW filter wheel.

It helps if the manual on EKOS is read for time to time rather than blindly just diving in with both feet as I did! It turns out that I was missing out setting the filters autofocus in the EFW settings.

Clicking that little box above opens up this below

What I hadn't done is click the auto focus box against each filter. I have done that now as seen from the screen capture.

Previously my sequence settings were something like this:

1. Capture target 1 in Ha. Make sure focus box is ticked.
2. Capture target 1 in Sii. Make sure focus box is ticked.
3. Capture target 1 in Oiii. Make sure focus box is ticked.

etc. I expected it to change to the filter in the job when focusing.

What it was actually doing on every job was setting the initial filter for auto focusing to whatever was set in the focus module. In my case Ha.

 

Once focused it would then switch the filter to Oiii etc as determined by the respective sequence job and acquire the images. However my Oiii filter is not parfocal with the Ha and Sii filters which are very close. Hence I got a couple of runs of Oiii out of focus!

So now I have read the manual I now know that when the filter is changed it will automatically switch to the focusing module, perform an auto focus, when complete it will switch back to the sequencer and carry on with image acquisition,

Once I have worked out what the actual filter offsets are (I don't know them for sure yet) I can then enter them into the Offset column. This means I can choose one filter to always perform the autofocus - Select Lock Filter to make sure this is always used. Uncheck all the other filters autofocus boxes. Then when a different filter is selected the focuser will move the relative number of ticks and (hopefully) that filter will then be in focus (assuming backlash is compensated for in the focuser).

Now my scheduled jobs still look the same but I only set the focusing job on the initial job in the list

The next job and all subsequent ones look like this

Notice the focus box is unchecked. It will automatically focus using the filter selected in the job instead from now on.

There are many ways to set schedule sequences up and I have chose this way as it seems to work ok.

BTW the naming convention I use for sequences is Filter-Gain-Time-Number of captures. So OIIIG111T180C40 means

• OIII filter
• Gain 111 (that's the default on the 183MM)
• Time in seconds 180
• No of Captures 40

I always set offset to 8 so don't record that in the name of the sequence.

So the moral of the story is sometimes you should read the manual. Hope this helps anybody diving in to the Astroberry Kstars/Ekos or Stellarmate/Ekos systems.

 

 

 

Edited September 19, 2020 by TerryMcK

[MarkAR]

And the hard part is getting consistent results when finding the offsets. Definitely setting the backlash will help.

Edited September 19, 2020 by MarkAR