Plate solve and frame and focus question


#1

Hi everyone,

I have finished setting up my focus points and a consequence the offsets for my 5 position filter wheel (Ha, OIII, R, G, B). I use green filter for autofocus and plate solving.

I have a question about the sequence because after I ran the frame & mosaic wizzard to create new sequence, I started sequence and plate solve failed because stars were completely out of focus. I had wrongly assume that SGP would auto-adjust the focuser to the right green filter focus position before plate solving but it did not.

I read the forums and notice that a lot of people are using the manual frame and focus before kicking off the sequence which will do a plate solve afterward. Is that correct? Do I need to run’frame and focus’ to set the focuser to the right the right focused position so I can ultimately start the sequence and get the plate solving done that way?

Thank you


#2

It’s a good idea to have the scope close to focus before starting a sequence. It doesn’t have to be perfect.

But from your description I wonder if you are understanding filter offsets correctly. SGP will not set the focuser to a defined step position for each filter. Filter offsets are the relative difference, in steps, between two filters when those filters are in focus. So let’s say your green filter is perfectly in focus at 10,000 steps. But your blue filter is perfectly in focus at 10,100 steps. The filter offset is +100 and that means whenever the filter wheel moves from green to blue the focuser will be racked out 100 steps, and when the filter wheel moves from blue to green the focuser will be racked in 100 steps.

In the above scenario in the “Define Filter List” you would set the blue filter “Focus Pt” to be +100 steps above whatever number you have in there for the green filter. It doesn’t matter what these numbers are as long as the relative difference is correct. So for example you could set the green filter “Focus Pt” at 4000 and the blue filter “Focus Pt” to 4100.


#3

Hi Joel,

Thanks for the clarification. Given that I have identified a focus point for Green filter (let’s call it a close to focus point), I would have thought the ‘Adjust per filter’ option would have set my focuser automatically to a ‘close to focus’ position with filter green, so the plate solving would have been successful.

But if I understand correctly, you are saying that I need to manually move the focus to ‘close to focus’, so when I start the sequence which will automatically go into plate solving with green filter, the plate solving is close to focus and it can successfully solve plate, right?

Best,

Miquel


#4

Correct. You need to manually move the focuser to close to focus. SGP does not do that automatically.


#5

Perfect. Now, it is clear. I will add that my sequence notes.

Thank you so much for your help,


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