Hello everybody,
All of us are very excited with the prospect to witness T CrB’s outburst soon. But I have a [silly] question about how should we capture the data during the outburst.
As far as I know, the outburst takes place in a very short period of time, and will have a large V amplitude, about 8 V, if I am not mistaken. The question is: how do we adjust the sub exposure times to avoid loosing linearity?
Cheers,
Enrique (BETB)
Hi Enrique,
That’s a great question! T CrB is going to be really challenging to observe. The AAVSO has some guidance prepared for when the eruption occurs, but haven’t released it yet. I’ll ask Elizabeth to post it to the forums early next week.
Regards,
Brian
If your exposures are controlled with software that allows you to expose accoring to a pre-programmed “plan” or “schedule” , perhaps it is wise to interleave the sequence with some exposures that are “too short” for the star in it’s current state but more adequate when it begins to rise. So, say, if your normal exposures are (just for the sake of an example) 10 sec every minute or so, why not do something with this cadence:
10 sec, 1 sec , 1 sec,1sec … 10 sec, 1 sec 1sec 1,sec …
The rationale for the group of shorter exposures is to have at least 3 sec per data point to manage scintillation better. While T CrB is not doing anything special, you would probably just throw away the 1 sec exposures when doing the photometry. If you notice (after the fact) that is was rising during a session, you will instead throw away the 10sec exposures once they are saturated, but at least you have some more data covering the rise and this buys you some time to react until it has risen enough to saturate even the shorter exposures. Yes, this multiplies the data needed to be stored by a small factor but I think it’s a good insurance premium against frustration in the event of T CrB rising.
In case you are observing with a larger aperture scope and your exposure time is already kind-of super short, you might consider looking at the data that your guide scope with its smaller aperture gives. Maybe that is also useful in case of T CRB rising…provided you can force it to save images, at least once-in-a-while.
I have been doing visual estimates for several stars just to keep my long, many decades of visual estimating variables and comet magnitudes in practice.
I also have been testing and experimenting using wide-field camera lenses and DSLRs on bright stars, 6th and brighter and for a few objects from the Alert Notice #859 to get procedure, defocus amounts to cover the Bayer matrix sampling problem, etc. understood and under control. Doing this visual and wide-field camera practice will hopefully allow good photometry to be obtained of not only T CrB when bright but for any other objects like an unexpected bright nova or super nova!
Jim (DEY)
Great advise, @Bikeman ! Thanks so much for your comment.
Hello, Jim! Thanks! This is also an alternative, although unfortunately I do not have a DSLR or APS-C sensor handy for the moment (just my trusted IMX533 mono camera).