Hi,
I am interested in DSLR photometry. I have a Canon 1100D with a few prime lenses (85mm and 200mm). Currently I am just using a tripod but am getting an iOptron SkyTracker soon so I'll be able to do longer exposures. I have read through the tutorial and had a few questions.
I think I should practice on some stars (probably Mira) that are well-observed to see if I can get some accurate data first. I have been playing with IRIS but find it not very intuitive. I was going to jump in and just buy AIPWIN but would rather not spend $100 to discover whether or not it's the best software for me (since I don't see a demo available with that software). I know there are other free programs out there. If I'm going to just focus on some LPV's initially, is it OK to just take individual exposures? Or is stacking always recommended? I am used to DSS for astrophotography already, is that acceptable for calibration with darks, etc...? For the actual analysis, I've heard of Muniwin as another free option, and APT, but that one isn't listed in the tutorial. I don't want to go too far down a path with something that isn't recommended for AAVSO contributions.
Thanks in advance for any help ... I'm sure I'll have a million more questions as I progress! Of course, just becoming interested in this endeavor had caused my normally clear San Diego skies to cloud up for the next few days! ;)
Good morning Boltzie.
I do photometry with a modified webcam ccd, and I found it the equivalent of a DSLR (although less format and less dynamic range). I recommend the IRIS software is the best and it's free, you can debayerizer and make the calibration of the images, and if you do photometry batch of images, for individual measures into a single image is better Astroart 5 demo version allows photometry and does not expire.
Otherwise, to practice before a view stars, performs photometry of stars constant brightness (stans not variables in the same field calibration you use to determine the coefficients), for you to check the dispersion in your measurements, and stability atmospheric along night, and how this influences the accuracy, the greater the air mass differences are.
here are the manuals in English Iris
http://www.astrosurf.com/buil/us/iris/iris.htm#tutorial
I have an application developed for the transformations of DSLR o CCD color (RGB Fotocalc)
http://olichris.jimdo.com/rgb-fotocalc-software/
but so far I have not finished translating the English, on the other hand, does not correct the air mass for individual stars, just for the image field, and I use the camera mounted on the telescope and the field is small . DSLR lens difference air mass in stars the better the spreadsheet of citicen sky
http://www.aavso.org/dslr-observing-manual
I appreciate the
Gracias!
I appreciate the reply, olichris. I will continue to work with IRIS and get some standard starts under my belt first to make sure I'm able to get good values.
One further question: Is it always worth transforming the values for submission? I guess I'm asking if the TG results are considered valuable or not. (maybe depending on FOV and variable star type?)
Since my Spanish is extremely basic, I think I'll have to rely on the spreadsheets on this website as opposed to your software for transformation assistance. But please let me know if you get it translated at some point. I'd love to be able to check it out.
Thanks again!
hello Boltzie.
the transformation is important if the star under study has a different color than the star of comparison, if both have the same color as the deviation is minor and negligible for the same colors. channels as our cameras are not exactly the johnson band, then this setting to take these. here I leave a link where this is explained in great detail in English. I summed up in one of the chapters of a manual supplement'm doing my software but this in Spanish and I'm finish.
http://reductionism.net.seanic.net/CCD_TE/cte_alternative.html
if the spreadsheet of citicensky is excellent and is explained in English, but not get the link to resend not record the address of the page citizesky.
Here you can see a video of how my software works, is in Spanish, but maybe if you take away the audio and pictures can only see intiur in question.
https://www.youtube.com/watch?feature=player_embedded&v=hg0RFHZHZ0U
Here a video of how to use the tool to generate scripts to run on the software to add iris image sequences into groups to form individual images for measurements in both single-mode and interlaced mode.
https://www.youtube.com/watch?v=_RTtgl-eNY8
Thank you for the
Hi Oliver,
Thank you for the links. I have been watching your videos and am able to basically follow what you are doing and it is very helpful.
Are these the spreadsheets you mentioned on CitizenSky? (bottom of pages) http://www.citizensky.org/content/calibration-beginner and http://www.citizensky.org/content/calibration-intermediate
(It also states that CitizenSky has been relocated to the AAVSO site, but nothing regarding CitizenSky has been updated in two years, from what I can tell http://www.aavso.org/citizensky)
Thanks again.
These are exactly the links Scott, that spreadsheets are exelentes, the second is the better, I take from this second the idea of plotting errors for my software (with appropriate reference Brin Kloppenborg in the manual that'm finishing). I have an friend who is translating the English videotutoriales (Dr. Katherine Vieira. - Astronomy Research Center "Francisco J. Duarte"), but still are not complete videos and even fewer translations.
the only detailed as you mention, the air mass is corrected to set the whole field, not the individual, need-star klentes DSLR with short focal length, but for DSLR mounted telescope is magnificent.
Is only a matter of a few days so that those who here perform photometry DSLR you write more recommendations.
Thanks again Oliver,
Another question if you don't mind: If taking a single measurement of a LPV, I have read that it's best to take multiple subs (to average out scintillation, etc...) . What timestamp should be used for such an observation if only one value is submitted? The first, last, or average timestamp of the images? (assuming I had, for example, 10 images total that lasted a total of about 5 or 10 minutes)
Thanks
I've seen and I also do, is averaging groups of 10 images, not just blink, but to compensate for the distrubution of pixels due to the structure of the RGB matrix with small errors in monitoring (Jittering) , becomes more composed Uniforms image underexposures, because each pixel position they picked the color pixels with others where in l image was interpolated color is added. time is the average time for the add pictures.
another thing is that as LPV have great breadth, must change the star comparison for different moments of brilliance, looking stars from the nearest to the brightness of the variable (less than 0.5 mag), but also to be the recommended used by all in order to avoid differences in the zero point when combining observations with those of other observers.
Hi Boltzie,
You should average the midpoint times for each of your subs to obtain the proper time to report with your measure. There are some shortcuts that you can take if all of your subs are equally spaced in time, but the average-midpoint method always works.
Arne