Overlay masks

CCD cameras (CMOS/CCD), DSLRs, telescope mounts, focusers, autoguiders, domes, Roll off roofs, etc..
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keving
Posts: 53
Joined: Thu Dec 14, 2017 4:49 am

Tue Oct 09, 2018 5:25 pm

I am having trouble using the 'overlay grid' to mark the position of the slit in spectroscopy. I see that, depending on which side of the meridian I am on, it flips the coordinates of the grid centre point - I dont actually find this helpful!.

But asssuming this is an intended behaviour, I was wondering if I could make use of an 'overlay mask to do the sam thing. I can't see any reference to these in the help pages - can someone explain what they are please - and could I use it to mark the spectrograph slit?
Thanks
Olivier Thizy
Posts: 11
Joined: Fri Aug 04, 2017 8:24 am

Wed Oct 17, 2018 12:53 pm

Kevin,


I once used a Acq_masq.msqtxt file which included:
<Cross>
364,278
""
Arial,10
FF0000
2

Can't remember if I had to put the name of that file in the camera tab or in the general parameters of the software. Check on both...

But now I am only using the right clic on the image to position the cross. I dont care if it is approximative as the coordinate of the fibr (or slit) is given at the autoguiding. The cross is thre just to help in manual moving target near the fiber tip or slit.


Cordialement,
Olivier
keving
Posts: 53
Joined: Thu Dec 14, 2017 4:49 am

Fri Oct 19, 2018 1:06 pm

Many thanks Olivier

I see you can use overlay masks in two ways
(i) directly from the right-mouse context (it's the last item on themenu) or...
(ii) As an option in the Software setting/camera recording menu

In (i) the mask is not persistent, so no use for setting star position (in a continuous loop)

(ii) could work, but I see the y-coordinate is inverted with respect to the readout I get from the mouse position on the image. I am hoping this wont be telescope-position dependent like the simple crossed lines...

I guess I could try a simulated telescope experiment....

For Hamza: I reverse engineered the syntax of the mask, but some docs would be handy ;)

Kevin
keving
Posts: 53
Joined: Thu Dec 14, 2017 4:49 am

Fri Oct 19, 2018 1:21 pm

In simulation, the overlay grid seems well-behaved (with a simple line pair or a maks). There is no flipping or mirroring of the grid centre when the scope moves across the meridian. I would like ot see if others have seen this behaviour (with a real scope or in simulation)

Kevin
keving
Posts: 53
Joined: Thu Dec 14, 2017 4:49 am

Sun Oct 21, 2018 4:45 pm

Also, in a real session, the text mask seems to remain in the same position irrespective of pier side - great!

Kevin
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