Image all night using filter offsets - first attempt at drag script. It works!

I like to use filter offsets to maintain focus with narrowband filters instead of focusing in real time. I feel it works better for me, but I know it is not supported in Voyager. So, I made a drag script to automate filter offsets. The script:

  • The goal is to create as efficient an image capture system as possible without sacrificing quality. Where I live, every second counts! The less the mount has to point around for focus and start and stop guiding the better, in terms of time spent collecting data.
  • Is for a single target, imaged all night. It can be easily modified to run from a certain time to another and you can run multiple scripts per night if you want.
  • You can choose which filters to run, exposure times, and how many times to run each filter per ‘cycle’
  • One cycle is: Precise point, Focus using Localfield and L filter, Start guiding and dither immediately, Run user defined filter sequence with focus updating itself for each filter… repeat all night until dawn.
  • Precise pointing at the start of each cycle creates an automatic meridian flip when needed

Please take a look and let me know if you see anything I did wrong. I ran the script last night and it worked very well. My questions:

  • Do I need to first ‘Aquire guide star’ and then Start Guiding? Or can I just Start Guiding?
  • Is there a way to create a decision based on the end of Astronomical night? Currently there is just a wait for the start of night, but no way to trigger events at the end of the night that I could figure out. In the script, the user defines the end of the night but I would like to automate that part
  • Please let me know if you see places I can do things better/more efficiently

Thanks for looking! The script is available for anyone to use and modify as they choose. The attached script uses the NGC 7000 as the target.

StartToShutdownoffsets_NoAmNeb.vos (322.8 KB)


Hey Mike. Thanks for sharing this. I feel the same was that you do about efficiency – any time my shutter is not open, I am looking for ways to speed up processes.

Looking forward to studying your script. (I am traveling and am a Mac user, so will have to wait until I get home to look it over.)


Ed Beshore

after some years you will understand that is not this the beatiful of Astrophotography … my personal tought !

1 Like

Hi Leonardo. No astrophotography if the shutter is not open!

A good topic to discuss over some good Italian wine and Fonduta Valdostana! Hope we can do it someday.

Cheers, Ed

if you want to always have shutter opened, remove it !
Is the best solution to solve the hurry up problem :slight_smile:

All the best


I will put in my vote for Leonardo’s method, at least with my equipment.

I have a carbon fibre tube newtonian, and a short tube refractor (Not carbon) and find that while both are quite stable in terms of focus, regular focus runs simply produce better data. With my NB filters the time taken with Robostar to slew to and center a focus star, make the focus run, slew back and continue imaging is about the same as a localfield focus run through a broadband filter.

I might lose the equivalent of one or two narrowband subs a night to extra focus runs but compared to how I was imaging before using Voyager, the data I am getting is better, a good tradeoff IMO.