Forgive the newbie question here, I have been reading a LOT and learning as much as I can. I come from the astrophotography side of things... and so I am just starting to try exoplanet transit viewing with NINA and a great system they have. Haven't got a full clear night yet, but am running some images through HOPs and just getting used to some things.
1. I run a RASA 11 with a 1600mm monochrome camera right now. My understanding is this is a good choice? fast images in the 15-60 second exposure range will give me more data? am I correct in that assumption?
2. Filters? I am used to astrophotography right now with RGB HSO filters. I read some say to use Red if you only have those? would Ha be a good choice? I am finding my exposure times for calculated ADU are really low on some stars with exposure lengths around 10 seconds?
again, newbie at this, but looking forward to trying a few of these things...
Hi Josh--
The RASA 11 is fine for variable star photometry, as is the mono CMOS camera. For photometry, you can get started with a V filter (it's yellowish-green and somewhat matches the color response of the human eye) for exoplanet transits, and add a B and I filter later for other types of photometry. You can check the Exoplanet section for more details on exoplanets. Exoplanet transits are great, but the amplitude of the variation is small and you need to schedule your observing run for a time when the transit is predicted to happen.
If you have not done variable star observations before, I tell folks to get acquainted with photometry by observing short-period pulsating variable stars. You can observe one or more complete pulsations in a single night, and the star is always changing. They go through a large range of brightness in a few hours, so you really see something happening, and you begin to get a feel for what your equipment can do.
A couple years ago I did an observing project with two high-school students. It was COVID time then, so they had to observe remotely and get images taken with my RASA 11 taken at my place and save on Dropbox. The students analyzed the images at their homes. We observed without filters because our goal was to pinpoint the time of maximum brightness in the star's pulsation cycle. We did a video for the 2020 webinar series:
Aug. 8, 2020: Short Period Pulsators
Topics and panelists:
- Introduction – Eric Hintz (2 minutes)
- Types of Short Period Pulsators and why do they pulsate – Eric Hintz (15 minutes)
- Why do we want to study SPP – Eric Hintz (15 minutes)
- The AAVSO Legacy Observing Program – Gerry Samolyk (15 minutes)
- Student Study of the SX Phe Variable XX Cygni – Richard Berry (15 minutes)
- Cadence in Modern SPP Observing – Eric Hintz (10 minutes)
- How can YOU get involved? – Eric Hintz
Q & A (20 minutes)
I'm not sure how to find the video of the webinars, but I know they recorded it. And you're right that the exposure times can be short: we shot an image of XX Cygni every 10 seconds from dusk to dawn for three weeks in June 2020. That was a lot of images! The science result was 23 new times of maximum light, so we added more data points -- and some of the best -- to the long-term change in its period (due to stellar evolution).
Photometry often sounds complicated when you're new to it, but it really not if you get into it with observing projects that are not super-finnicky about filters while you develop the observing skills you need for doing first-rate photometry.
Welcome aboard...
Richard
Richard,
First, as a new observer who's installing the mount into the observatory this weekend to embark on some variable star photometry, thanks for that reply about focusing on short period pulsators. It's great to have direction like that as I just try to get myself up to speed with my first light curve and start learning from there.
Here's a link to the webinar you referenced: https://www.youtube.com/watch?v=6l5_vD-eGm4
I have to go do the actual work that pays for mounts and telescopes now.....but I've bookmarked that to watch this evening as well.
Thanks,
Mike
Thanks for the detailed response, this helps and I will certainly look at variables. I have been working with NINA which sort of takes all the work out of everything, calculating transit times, exposure lengths, makes it very simple. I can schedule it all to run when needed, and started a few exoplanet runs, but get caught mid-way with clouds or something. I was running data through HOPs software, tried EXOTIC but found not as easy, and seeing light curves really show dips on HAT-P-20b (really easy target I believe). I get caught up taking DSO images instead.
From the reading I see, if I want to just try to capture these variables and exoplanets, I can use really any filter such as Red or Green?... but if going to submit any actual scientific data then probably have to jump to more filters like V or B? I'm just a hobbiest on this having fun, but maybe down the road I'll invest in some specific filters for this.
thanks again for the info.
I'm fairly new as…
Josh:
I'm fairly new as well and have recently been where you are now. By working with a mentor and gradually increasing my abilities I have been able to contribute (in a small way) towards published papers and am very near to submitting EP transit observations and analysis to TESS FOP Group 1.
One route you might want to take is to get an AAVSO mentor to assist you through this process. Also the CCD Guide and the Exoplanet Guide (Dennis Conti) are great resources. I agree, working with shorter focal lengths and SPP's is a great way to start developing your skills and methods. Gradually working you way up to the more difficult and accurate observations.
Enjoy the journey,
John
DJCA
PS: What is HOPs softare?
HOPS is just like EXOTIC, it's just a simple program to process the images. It's pretty nice and creates really nice light curves. worth checking out: https://www.exoworldsspies.com/en/
I have read through Dennis Conti guide, I"m starting into the AAVSO guide. I didn't know about this mentor assistance, will check on that... thanks
Hi Josh--
You can use your tricolor green filter as an "approximately V" filter so long as you stick to observing programs that are not color sensitive. Right now photometric filters are just coming back onto the market after being "eclipsed" by Covid supply chain issues.
--Richard
thanks, I gave it a try last night on Qatar 9b, which is pretty small. But 18s exposures, used my green filter and about 4 hours worth... sheesh, 21Gb over 700+ images, but pretty cool.
This looks like it captured it, here is the data: https://www.asgastronomy.com/wp-content/uploads/2022/02/full_model-scaled.jpg
What I couldn't figure out is the expected time and my time were off by about an hour... is that what the O-Cminutes = 57.4 is showing here? I'm guessing I did something wrong, but I would just be thrilled if this does show my first exoplanet :)
P.S. If I need to move this thread somewhere or discuss elsewhere, happy to, it just started in the instruments/equipement area.