Juan Jose Pueyo wrote:Supernovae within the reach of amateurs have magnitudes usually between +12 and +18. So far, using the Alpy600 with Atik 314L+ (for spectrum) and Atik Titan (for observation and guidance) I have reached magnitude +14. The telescope is a SC8" at f/6.3. The problem to go lower is that I have to see the object, to keep it in the slit of the spectroscope, and guide it if possible. Is there a way to improve in that regard? How to get a better view of faint objects?
Cheers Juan José Pueyo
Hi Juan José,
To guide on faint targets I offset guide using another star in the field. (I use PHD2 for guiding but it should be possible to do this with other guider programs.)
First I take a deep image of the field from the guider camera (typically 20x20 sec, aligned and stacked) and measure the difference in pixels X and Y between the star I want to guide on and the target. I also note the X Y coordinates of the centre of the slit.
I then add the XY offset to this, place the guide star at this position and start guiding. I usually then take a long guider exposure, say 15 sec to check everything is ok before starting a long exposure on the spectrum camera (typically 1-2 hours in 600 or 1200 seconds exposures)
Here is an example from last night of a 15 second exposure from the guide camera. (SN2022fuc at mag 16.5) The guide star was bright enough to use shorter exposures for guiding.
- sn2022fuc_guider_15sec.png (192.55 KiB) Viewed 7407 times
I use the same technique for extended objects like galaxies and nebula and for comets and asteroids where PHD2 can be programmed to automatically change the offset to keep the target on the slit
Cheers
Robin
