Astroart 7.0 SP4

[fabdev]

Hello, a new minor version of Astroart is available:

Version 7.0 SP4 - June 8, 2020
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* New feature. Full-frame autoguide on multiple stars.
* New feature. Syncronization between two sessions for sequences.
* New feature. Focusing with a spectrum reference line.
* New feature. Focusing with the Bahtinov mask.
* New feature. "Connect all" command for instrumentation.
* Improved. Some incompatible DATE-OBS FITS keywords are supported.
* Improved. More options for autoguide.
* Improved. More script functions.
* Bug fix. Apply Macro on 8 bit files changed the extension in some cases.
* Bug fix. Percentage of rejected pixels by sigma not shown in the Log.

Download at: http://www.msb-astroart.com
The installer will update also the documentation, by the way:

To "Connect all" the instrumentation with a single click, press CTRL + Left Click on the Setup button, a list will appear with the instruments to be connected.

For the Bahtinov mask focusing, the method is available in the menu of the subframe focusing. See also Wikipedia: https://en.wikipedia.org/wiki/Bahtinov_mask

From the menu, it's also possible to focus on a spectrum reference line, where the width of the line is used to estimate focus.

It's now possible to synchronize three cameras: two Astroart sessions which are taking sequences, plus an autoguide system in dithered mode. Select "Master" in a session and "Slave" in the other. The session which is guiding (or which is controlling the external autoguide software) must be selected as the Master one.

For the new autoguide see the next post:

[fabdev]

Astroart 7 SP4 contains a new full-frame autoguide, with the additional features:

• Usage of all stars. If several "good" stars are present in the field, then those stars are used to autoguide, just like when stacking a sequence of images.

• Automatic exposure time. If the star is too faint, then the exposure time is increased to an optimal value. If the star is too bright then the exposure time is decreased.

What is a "good" autoguide star? The classic S/N Ratio was not optimal to define it, the reason is that in amateur astronomy the strongest source of noise is light pollution, which is not included in the formula of the classic S/N.

For this reason a new metric, based on PSNR was used. The noise is now measured directly on the image, so all contributions (light pollution, thermal current, readout noise) are evaluated at the same time. The PSNR is usually defined in decibel, e.g. 20 Log(Signal / Noise) here is an example for three stars.

For more information about PSNR see this internet search: https://www.google.com/search?q=image+psnr

Automatic exposure time

The exposure time is controlled by three Time values and three PSNR values:

At first an exposure of Initial seconds is taken. If no stars have an Optimal PSNR then the exposure time is increased to achieve that optimal PSNR, obviously the increment is limited by the Max exposure time. Then another exposure is taken, if no star has at least the Minimum PSNR, then the procedure is declared failed and it's terminated.

For those rare cases where the star is too bright, so it's brighter than the Maximum PSNR, the exposure time is decreased to reach again the Maximum PSNR, but not less than the Min exposure time. This prevents blooming and gives a better frame rate to the autoguide.

Scaled dark frames
If the camera needs dark frames, the variable exposure time poses a problem, how to correct it? To solve, a new scaled dark frame algorithm was created and it's active by default.

For more information, see the updated documentation.

[AstroBernd]

Hello Fabio,
i was excited to find out you implemented a Bahtinov mask Focusing method. This will be very helpful for Hyperstar focusing, so i am very excited to have it available in AA7! Thanks a lot!
I tested it quickly with the simulator, but could not understand how it works. I can not test on the scope right now, as it is getting dark much too late her north of the Alps. There are several blue and yellow dots jumping around and two new small tiles in the upper left hand corner of the Focus window.

Screen shot Focus Window Bahtinov

How is the process to do the focusing? Could you pls. give a short explanation? Looking forward to using it.
Appreciate your help
Ciao
Bernd

[fabdev]

Hello Bernd,
the six dots are automatically placed on the six spikes of the Bahtinov mask (which are not present in your screenshot, see the Wikipedia link above for some examples). To view the six spikes you need a bright star.
The buttons place the dots nearer or farther the star. Usually there's no need to click the buttons unless they are misplaced for some reason (at beginning they are placed at 50% of the radius of the subframe).
The procedure is the same of other focus methods, the range is still 0-1000 where 1000 means perfect focus.

[AstroBernd]

Thanks Fabio, for the quick reply. That makes perfect sense.
Looking forward to test it out on a bright star (the example was obviously w/o a Bahtinov mask).
Thanks a lot

[Gary Clayton]

I had some issues last night trying to recalibrate my mount (Ioptron cem25P) with SP4, I could see and hear the mount moving as it calibrated the axis, but I kept getting "your mount is moving to slowly" and your "mount is not moving in dec" messages. I then tried calibrating/guiding with PHD2 with no issues so back to Astroart which again gave me the same massages, I did manage to get it calibrated after 4 attempts though and the guiding was very good, as I had been using SP3 with no issues before hand I was wondering if this is just "new behavior" ?.

[fabdev]

Yes, in SP4 you will see notifications in the status bar if the apparent telescope speed is lower than 0.75 pixels per second or higher than 12.0 (telescope too fast). As a general rule, If the speed is too slow, then the guide pulses will be too long and this will decrease the frame rate so the "efficiency" of the whole exposure time. If the speed is too fast then the guide pulses will be too short (milliseconds) and they will not be precise.

Maybe you could check in the mount the guide sideral speed, if it's slow (0.1X sideral for example) you could increase it, you could also verify with PHD if this gives better guide statistics.

If instead you prefer to keep that speed, I suggest to increase in Astroart the duration of the calibration pulses, from 800 to 1500 ms or more. This will probably permit the calibration at the first attempt, but the notifications will remain.

[fabdev]

instead, for some Active Optics it's recommended to decrease the calibration pulses to 500 ms, otherwise it's possible that the limits are reached during the calibration procedure.

[fabdev]

The demo version of SP4 was released today:

http://www.msb-astroart.com/

[AstroBernd]

After the summer w/o photgraphing (thru the scope at least), i tried out the Bahtinov function in the focussing aid. It works great!
Thanks
Fabio