Astroart Forum

I have experience continued consternation with the focus routine. I have only once seen a single pixel in the middle of the focus field despite having readouts of the fwhm at less than 1.5.
I have been manually focusing but will be changing to autofocus.
Just like the instructions; take an image, draw a square around a star, after one has picked the binning at focus length. I have tried with my own active images, post imaging session images and your learning images. IN none of these cases do I get an example like that in your manual. Help please and thanks. cjacobson

cjacobson wrote: ↑

03 Apr 2020, 02:09

I have experience continued consternation with the focus routine. I have only once seen a single pixel in the middle of the focus field despite having readouts of the fwhm at less than 1.5.
I have been manually focusing but will be changing to autofocus.
Just like the instructions; take an image, draw a square around a star, after one has picked the binning at focus length. I have tried with my own active images, post imaging session images and your learning images. IN none of these cases do I get an example like that in your manual. Help please and thanks. cjacobson

Can you provide details of your scope, camera and focuser?

scope can be either a c14 hyperstar using a starlight xpress sxvm25c or a 175 f8 triplet reduced to a fl of 1050 and again a starlight xpress camera either sxvr m25c or sxvm25c.
I have tried various binning and exposure . lenghts. really all i ever see is the shuddering window of multiple little squares. It is hard to pick out which might be come a star or single square despite getting readouts of 1.5 or less FWHM. What am I doing wrong? this should be so simple. thanks cjacobson

cjacobson wrote: ↑

03 Apr 2020, 19:16

scope can be either a c14 hyperstar using a starlight xpress sxvm25c or a 175 f8 triplet reduced to a fl of 1050 and again a starlight xpress camera either sxvr m25c or sxvm25c.
I have tried various binning and exposure . lenghts. really all i ever see is the shuddering window of multiple little squares. It is hard to pick out which might be come a star or single square despite getting readouts of 1.5 or less FWHM. What am I doing wrong? this should be so simple. thanks cjacobson

I would not use binning when using the Hyperstar and possibly not when imaging at ~1050mm EFL.

The software assisted focus or autofocus readout can be inaccurate if the scope is grossly defocused. A simple Hartmann mask can help to achieve rough focus.

For me a typical focus session using the main camera:

click on the focus/guide tab

Take an unbinned ~3 second exposure. For a Hyperstar this might be a ~1 second exposure

Draw a small box around a suitable star

Click on the focus button. For Hyperstar I would probably try and use a ~.5 sec exposure and maybe less.

The star should be displayed in the focus window. you can experiment with the different focus algorithms by clicking on the small triangle beside the focus readout number. I find that SmD seems to be most consistent.

The star will not come to a sharp point, but will display as a tight group of pixels. Focus is achieved when the displayed value reaches a consistent maximum.

thanks I'll try your ideas next clear night. cjacobson

I opened up several images with small stars, placed the square around them in AA6 and AA7. same result no consent square just an oscillation square of white and dark squares in the focus box despite readouts of less than 1. I looked for this little triangle you mentioned next to the readouts. I could not see it. there is a triangle that can be used to change the szie of the focus window. So where is it?? What is the SmD? I just want to solve this. I can not even fine a utube video describing a focus routine. c jacobson

Well, try with the FullFrame Autofocus routine. Is much better than the old AA6 autofocus routine.
I'm using this routine in my observation unattended runs and I'm pretty satisfied. However my set up is different from yours (LX600 14") having a longer focal length.
I obtained the best results by using the SmD (small disk) option. In case you will use the FullFrame Autofocus it is not necessary to draw a square around a star. BTW, I'm using the focuser driver by ASCOM.
As Dunmunro explained a rough focus is in any case necessary to get a good result.
Regards.

Alessandro

cjacobson wrote: ↑

05 Apr 2020, 03:06

I opened up several images with small stars, placed the square around them in AA6 and AA7. same result no consent square just an oscillation square of white and dark squares in the focus box despite readouts of less than 1. I looked for this little triangle you mentioned next to the readouts. I could not see it. there is a triangle that can be used to change the szie of the focus window. So where is it?? What is the SmD? I just want to solve this. I can not even fine a utube video describing a focus routine. c jacobson

Have you updated AA7 to SP3? You should do this ASAP.
I've attached an image with a red arrow pointing to the triangle. There is a detailed help page on focusing and focusers. Click on the camera control settings tab and then click on the blue question mark to get the help menu.

Does it work with the Camera Simulator ?
Just like in the image above.

I have resolved this problem with the help of you all and Fabio. I was trying to do this on my own previous images until it was pointed out that I needed to be live. It worked just fine the other night live with a bright star using my refractor at f6 with a bayer matrex narrow band filter( OPT's). I think my previous attempts were marred by a too short image acquisition time and or a too dim star. Hence the checkered board pattern which I demonstrated to myself on a dim star on my successful nite.
Thanks all.