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DaveS

Making Flats with Sequence?

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Having (Cross fingers, touch wood) got Sequence playing nicely I see there is a facility for making Twilight Flats.

 

Does anyone use this method? If so have you encountered any hitches in getting good data? Any tips/

 

TIA

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Can't help with your specific question, as i haven't tried it myself. But i don't see why it wouldn't work.

I was wondering myself if i can make sequence trigger my ASCOM flat field LED panel somehow :/

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I regularly use Sequence to make Dusk flats.  It works well if you know what to do.  A few points worth noting:

 

1. As soon as you check the "make dusk flats" box, a window will pop up asking for the configuration file which should be used (and which you must have set up previously).  If the sun angle has reached 0 degrees, the scope will start to slew immediately after you select the configuration file.  Therefore, you need to open the roof before selecting the file!  Sequence does not automatically open the roof in this mode (for some strange reason....).

2. The START @TIME and RUN NOW keys play no part in taking flats.  As already stated, the scope will start to slew as soon as the dawn flats box is checked, the config file is selected, and the sun has reached 0 degrees. (It would help if this was stated in the User Manual!)

3. The configuration file is set up under the settings window.  The exact parameters will obviously depend on what filters are installed.  In my case, I have L,R,G,B,OIII,Ha,SII.  I find that for dusk flats the correct order is SII,Ha,OIII,R,G,B,L and the opposite for dawn flats of course.  My NB filters are 6 nm.  I find that if I set 5 flat exposures per filter the timing works well and I get a full set of flats.

4. Using a front illuminated CCD, RBI may be an issue.  If you normally use pre-flash, you should turn it off for sky flats and then use dark optimisation for calibrating the flats.  At least, that works for me.

 

Stephen

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I should have added that if you want to make dawn flats, you cannot just add this on to the end of a normal sequence.  After the normal imaging sequence has finished, Sequence will close the roof.  It will not automatically re-open the roof even if the dawn flats box is checked.  Therefore, if you want to avoid a roof collision you need to wake up in time to open the roof manually!

 

Stephen

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