Overscan area

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apintole
Posts: 4
Joined: Sun Aug 08, 2021 4:24 pm

Overscan area

#1

Post by apintole »

Good morning,
my camera is QHYCCD268M. Once I took some flatfield frames I wondered why Pixinsight wouln't accept them for calibrating. The reason why were different dimensions of lights and flats. Whereas both were taken in 6252x4176 format and 1x1 binning chosen in "Format and Zone" panel, I got the flats in 6280x4210 format which includes the overscan area. I do not remember what options else i chose when I happened to get those flats. What option might have caused taking overscan frames?

Anyone got a clue? Thanks in advance
Heinrich
GlennB
Posts: 9
Joined: Tue Jan 09, 2018 6:33 am

Re: Overscan area

#2

Post by GlennB »

I'm a new user. But in the setup window there was a box allowing one to select Overscan. Now I know what that does so thanks for this.
I suppose best to deselect Overscan.
GlennB
apintole
Posts: 4
Joined: Sun Aug 08, 2021 4:24 pm

Re: Overscan area

#3

Post by apintole »

I wanted to follow your hint, but I couldn't find the checkbox you mentioned. Could you please explain how to get there?
Maybe I couldn't find this checkbox, because Sharpcap adapts its user interface to the camera connected. Are you using QHY268, too?
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admin
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Re: Overscan area

#4

Post by admin »

Hi,

this is a peculiarity of some QHY cameras. The extended area is available when the camera is used in video mode, but not when the camera is in still mode.

The camera will be used in video mode when

* The 'Live Mode' button in the toolbar is selected *AND*
* The 'Force still mode' control is set to OFF

The camera will be used in still mode when either

* The 'Live Mode' button in the toolbar is deselected *OR*
* The force still mode control is set to ON

I am currently unable to design code to set the same resolution in both live and still mode (or rather, I can set the same resolution, but there is no way to work out if exactly the same pixel on the sensor would be used at location (0,0) etc between the two modes).

cheers,

Robin
GlennB
Posts: 9
Joined: Tue Jan 09, 2018 6:33 am

Re: Overscan area

#5

Post by GlennB »

It was a checkbox in the ASCOM side of things.
I havent seen it since of course.
I'm using a 410c. Yet to see first light.

Robin,
Surely if its an option in ASCOM to deselect overscan then there must be something in software?
As a work around, if we just shut liveview then the issue wont appear, right?

GlennB
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Re: Overscan area

#6

Post by admin »

Hi Glenn,

as far as I can tell, what SharpCap does in the case of using the camera in still mode (or with the 'force Still Mode' option set) is pretty much the same as what the ASCOM driver does when the 'Remove Overscan Area' box is checked. If you send me a log from SharpCap when using the camera in SharpCap direct access (not ASCOM) mode, I can check the details on this. Annoyingly, with my 294C, the 'Remove Overscan Area' box is not enabled in the ASCOM driver, so I cannot test properly.

My biggest remaining issue is that I cannot make the live video mode resolution match the still mode resolution accurately (with pixel layout within the image on the sensor matching too)- that's not a problem that the ASCOM driver deals with as it always runs in still mode.

cheers,

Robin
GlennB
Posts: 9
Joined: Tue Jan 09, 2018 6:33 am

Re: Overscan area

#7

Post by GlennB »

Well the "problem" is moot really.
Liveview produces files which include extra columns of pixels compared to Still Mode.
So the solution is to do setup procedures with Liveview - framing. Then for image capture just click on Liveview to change to Still Mode - then setup the imaging run, use framing shots to recheck things.
Only use Still mode for imaging.
GlennB
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