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).
Greetings. This turned out to be a broad enough topic that I ended up writing a blog post about it. Please give it a read and let me know if you have any additional questions!
Edit: The blog post was somehow truncated when it got posted. I’ve asked the staff to fix this for me. It should be resolved shortly.
Brian
I’ve just noticed that one of the talks at the Annual Meeting is titled " T CrB: Brightest Nova in Generations." If the star doesn’t actually brighten by the time of the meeting … will the title have to be changed?
(sorry – I’ve been monitoring this star for so long that I’m starting to grow impatient and rather annoyed by it)
MWR
After you read the blog post, please let me know if there is anything else you’d like me to include. I thought I got everything, but I came to realize I didn’t say “submit your data!” anywhere…
Please check comp star number 42 in the chart pasted in your blog entry. I thing it should be numbered as 41 according to the text.
Yes, that’s correct. Thanks. I’ve updated the post!
Thanks Brian for your blog article on T CrB. I believe ir clears up several of my confusions, but what’s more important, offers a clear guideline of what to do to make the most of it.
I am more attracted to DSLR/CMOS/CCD photometry, but in the case of a recurrent nova, I feel the temptation of doing Visual Photometry, because I feel like its a one in lifetime event, so just enjoy the ride, keep records as good as possible.
I wish everyone here in AAVSO a fulfilling experience with T CrB.
Patrick Kavanagh,
CopernicusClub,
Mexico
We are getting to the point where I am wondering about the probabilities that T CrB can just go from a high-state to low-state and back to a high-state with out any outburst. Maybe my question will get the olde symbiotic to finally pop! Some of us of an age probably remember the build up for comet Kohoutek and the fact it didn’t live up to expectations… happens more than one would think in astronomy! Keeping fingers crossed that it does the outburst thing before solar conjunction… rapidly approaching…
Jim (DEY)
Come on T CrB!!!
We’re counting on you!
Well, there’s always the lunar eclipse…