spectroscopy slit function

[Jfisher6626]

I had my first successful night using alpy600 and asroart but I have some remaining questions
on this particular functionality. when I activate the slit function and mark star ,my screen looks different
than the instructions. the cross is tilted and much smaller. How do I know that guiding has been activated and is there anyway
to increase the size of the guide window?

thanks john

[fabdev]

Hi, it seems to me that the rectangle chosen is too big, it looks like 100x100 pixel, it should be 30x30 pixel instead. Doing so, when the guide window is resized, the pixels become visible and it's possible to move the star with sub-pixel precision over the slit. I suggest also to try a "normal" guide session, to verify that the pulses are correctly send and received by the mount.
Fabio.

[Jfisher6626]

Thanks , let me see if I have this correct. Once the star is in the window, I use the edge arrows to get the cross on the slit,then use the hand controls to move the star over the cross? Thanks j.

[fabdev]

Yes, that's correct. The star could be moved with the "pulses" buttons (from the Telescope Window), or just with the actual keypad of the telescope. Once the star is 2-3 pixels near the cross, it can be automatically "captured" if you enable the RA and DEC checkboxes for autoguide.
I suggest to align better the camera, with a rotation less than 5 degrees (for generic autoguide, rotation does not matter, but for slit autoguide, when the "cut star" is used to guide, a low rotation is mandatory).
When preparing the cross over the slit, remember that it's possible to move the cross by 0.5 pixels pressing CTRL+Click and by 0.1 pixels pressing SHIFT+CTRL+click
Fabio.

[Jfisher6626]

Thanks. Finally got a clear night so I’ll try again. But is it necessary to do a calibration first? I’m using a Ioptron cem 70 and Alpy and thinking of exposure of less than 5 min. So will it track without calibration in slit mode? Thanks. John

[fabdev]

Hi, if it's a mobile setup, a calibration is recommended every night. If it's a fixed observatory, once per year is enough.
I suggest to start with some autoguided exposures (not in slit mode) just for testing, and compare them with exposures of 5 minutes unguided.
Fabio.