Focusing Statistic


#1

I am trying to understand how to get a statistic from my images that I can use for manual focusing. I normally use FWHM or HFD. I normally use the “Information Panel” in Maximdl. I have place an image in dropbox, https://www.dropbox.com/s/lrbe4erxeo3lrke/E2_15sec_1x1_L_frame1.fit?dl=0. I have read the help system and tells me to click on the “Star” icon to calculate HFR. All that happens when I do is that the HFR number in the image statistics panel changes from N/A to 0.00.

I do not have an electronic focuser and would like to get to focus by having SGP do continuous short, 5 sec, exposures calculating and displaying a statistic, FWHM , HFR or HFD for each exposure without the need for me to press any buttons in between exposures.

I have been struggling to figure out how to do this and would very much appreciate some assistance.

Ray


#2

Not sure… when I open the image you sent and click the star icon, I get this:

That said, this is not what you are after anyhow (for manual focus, this is pretty tedious):

Go ahead and take a look here:

http://mainsequencesoftware.com/Content/SGPHelp/ImageHistory1.html

When you turn image history on and then use frame and focus, you will see 3 things that are helpful for manual focus:

  • The big huge “HFR=” test in the upper left of the image.
  • The image history graph itself (the trend)
  • The lowest HFR seen (in the last 25 frames), so you know where to go to when you pass focus.

#3

Ray, I have found the following arrangement of dialogs to be very helpful.

In Frame and Focus you can click Start and it will take continuous images and display the stats as it goes.
This assumes you have loaded the latest beta version 2.5.1.6.
Earlier versions should also work with different statistics.


#4

Thanks for the help. I will give it a try tonight.

Why do you think that I get get it to compute the HFR for all of the stars, do I need to connect up a focuser for that function to work? It looks like a statistic that would be very helpful. What do you suggest that I do to troubleshoot the problem?

Ray


#5

I just got set up and tried frame and focus and image history. I am able to get continuous sequential images and the “HFR=XXX” is displayed but still it is not computing any statistics. HFR and star count are always at 0.

Ray


#6

Thanks

That is useful.

Just one question, how sensitive is the HFR calculations to the star size settings

Ray


#7

Very sensitive with the current 2.5.1.6 and 2.5.1.7 betas. See thread titled “Auto Focus Beta Consolidation Thread” for extensive details.


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