Hello!
So I’m sure you get this often so I’ll be brief. I’ve done about 4 years of astrophotography and I’m now looking to turn my telescope (newtonian skywatcher 750mm) to doing some long term observation for stars.
I do have a few questions however…
From the intro information on the site, a lot of it seems to be just using your eye… Isn’t that wildly inaccurate at times? I think of these like natural haze in the summers, the moon, our own clouds? How do people who collect the data compensate for this?
For me, I’ll be using my telescope and ASI camera to do my imaging with probably shorter exposures…? This also is another question in terms of a variable (no pun intended) isn’t merelyl the exposure time going to factor in how bright a star is…? Even if I keep all of my exposures the same length…someone else who’s doing the observing may use a longer/shorter exposure time and that would put both of our sets of data in conflict?
Wouldn’t the data from someone observing with their eyes vs someone with a telescople also be wildly different? Wouldn’t someone with a telescope be able to pick up on wait milder drops/spikes as opposed to someone just using their eye? How are the two married together?
Welcome to the wonderful world of astronomy -real astronomy ;).
I am more fan of using a camera, although I have in high regards those who practice visual observing. I also started as an astrophotographer, and, although pretty pictures are exciting, photometry (and spectroscopy!) are far more exciting and fulfilling.
I strongly recommend you to take the CHOICE courses. But, as I know, you want to get started now. I then shall recommend you the manuals I have attached for you in this post. You can start with the one related to CCD/CMOS imaging (answering your question of other post, I prefer mono cameras than color cameras, they are more sensitive and useful for science purposes IMHO).
The idea here is to literally get data. Photometry is the measurement of light, and we are interested in how the light emmited by stars (and other objects) changes with time. So, the images that you will get should be treated as data, numbers, measurements that are useful to derive the nature of the celestial objects that we study. Bottom line, the approach is quite different from mere astro imaging.
Again, you should take some CHOICE courses, but we’re here to help. You can ask for an authorized mentor that will help you get started.
Answering your question number 3, which is indeed a very good one.
Visual observing can be done with your naked eye (for very bright stars), and using your eyes with the aid of binoculars or telescopes.
As Roy pointed out, you can access a chart with the field of view (FOV) that shows the location of the variable star you want to observe, and the available comparison stars that are close to it not only in position, but in brightness as well. Comparison stars are stars that are known for their brightness stability or for their very little variability*. The brightness estimation is made when you compare your variable star (target) with, lets say, a slightly dimmer and a slightly brighter comparison star’s brightness. Seasoned visual observers can estimate magnitudes with a precision of 0.1 magnitude (or some better, I believe).
How does this marry with observations done with a photometer or a CCD/CMOS sensors? It turns out that the V photometric filter used by these devices is equivalent to the range of wavelengths in which our eyes are more sensitive (V comes from “visual”). Although visual observations are not as precise as the “electronic” ones, the correct use of statistics and, therefore, uncertainty evaluation, turn visual observations useful.
I hope this answers your question.
Cheers,
Enrique Boeneker
(BETB)
*In the past years, with the introduction of CCD and CMOS sensors, many very low amplitude variable stars (stars with very low brightness change) have been discovered. A very good example of these are delta Scuti stars.
Sorry for the delay in response, but thank you for the warm welcome!
Hey, I love a good course and tutorial so I’ll definitely go through it. I’ve been wawtching a few youtube videos that I believe are from AAVSO already. I really appreciate it!
Actually one follow up question (Thanks so much for your time) You provided the monochrome CCD manual…someone else on here said because I’m shooting in color, I should use the DSLR manual…which do you think I should follow? I’m shooting with an astrophotography CCD camera, but it’s full color. So Not a monochrome and not a DSLR
Along with everyone else’s suggestions, I would recommend applying to get a mentor. Mine (Ray who chimed in above) was extremely helpful. They are there for you to ask questions of and point you in the right direction.
That way you can get your feet wet a bit before jumping into one of the courses, which can be a bit of a water hose of information.
Also, don’t just look at the CCD photometry course, but also think about the classification and light curves course (manual above post by Enrique), Arne’s best practices course as well as Ken’s Vphot course. All very helpful.
Yes, and that manual is good for monochrome CMOS and CCD cameras. Although you have a very nice full frame CMOS camera, your sensor is color (so it has a Bayer matrix over the sensor with three different colors, the famous RGB). So you should follow the instructions contained in the manual for DSLR photometry, which you will find appropriate for the camera you have now.
In the future, when you are ready to merge to a monochrome sensor, you can buy a camera with a cropped sensor (no need to buy a full frame if it is out of your budget). Monochrome sensors paired with photometric filters are great for photometry.
So, go ahead and follow the instructions of the DSLR photometry manual.
