| Both sides previous revision Previous revision Next revision | Previous revision |
| en:ost:ccds:astrofotografie [2016/10/25 23:49] – [Darkframes + Flatfields] rhainich | en:ost:ccds:astrofotografie [2021/06/21 13:16] (current) – [Photography with a DSRL] rhainich |
|---|
| |
| ====== Astro photography ====== | ====== Astro photography ====== |
| The OST can, of course, be used for astro photography. Since two of our [[en:ost:ccds:grunddaten|CCD cameras]] are equipped with filter wheels, they can take pretty pictures -- this article shall be a short manual for this and it shall document our progress in the=is field. It shall still grow, get more details etc., so it's not considered complete so far. :-) | The OST can, of course, be used for astro photography. Since three of our [[en:ost:ccds:grunddaten|astro cameras]] are equipped with filter wheels, they can take pretty pictures -- this article shall be a short manual for this and it shall document our progress in the=is field. It shall still grow, get more details etc., so it's not considered complete so far. :-) |
| |
| The images can be found in our [[en:ost:gallery|gallery]] -- click on the pictures to see more details on their exposure time, filters, dates, etc. | The images can be found in our [[en:ost:gallery|gallery]] -- click on the pictures to see more details on their exposure time, filters, dates, etc. |
| | |
| * useful webpages: | * useful webpages: |
| * [[ttp://www.calsky.com/|CalSky]] | * [[https://telescopius.com | Telescopius]] |
| * [[http://simbad.u-strasbg.fr/simbad/|Simbad]] | * [[http://simbad.u-strasbg.fr/simbad/|Simbad]] |
| * further websites can be found [[en:etc:links|here]] | * further websites can be found [[en:etc:links|here]] |
| |
| ==== Filter choice ==== | ==== Filter choice ==== |
| There are several different filters available for our cameras (see [[en:ost:ccds:grunddaten|here]]). Please note, that filters have transmission curves that absorb most of the photons, so the exposure times are getting (much) longer. Depending on the object, some filters are more useful then others. For emission nebulae, e.g., narrow band filters (H-Alpha/Beta, OIII) are especially useful. For stars und galaxies, broad band filters (U/B/V/R/I) mare usually more sense. To construct a (pretty) RGB image later on, best use the B, V, and R band filters. | There are several different [[en:ost:ccds:grunddaten|filters]] available for our cameras. Please note, that [[en:ost:ccds:grunddaten|filters]] have transmission curves that absorb most of the photons, so the exposure times are getting (much) longer. Depending on the object, some filters are more useful then others. For emission nebulae, e.g., narrow band filters (H-Alpha/Beta, OIII) are especially useful. For stars und galaxies, broad band filters (U/B/V/R/I) mare usually more sense. To construct a (pretty) RGB image later on, best use the B, V, and R band filters. |
| | |
| ==== Exposure times ==== | ==== Exposure times ==== |
| * extend here -- maybe a small galery | * extend here -- maybe a small galery |
| * [[http://polaris.astro.physik.uni-potsdam.de/gallery/2015.05.21/ngc188_sample_inverted.jpg|40min exposure]] -- stars until V $\sim $ 18mag can be observed | * [[http://polaris.astro.physik.uni-potsdam.de/gallery/2015.05.21/ngc188_sample_inverted.jpg|40min exposure]] -- stars until V $>$ 18mag can be observed |
| |
| |
| ==== Darkframes + Flatfields ==== | ==== Darkframes + Flatfields ==== |
| *Darkframes | *Darkframes |
| * attach the protective cover to the telescope | - attach the protective cover to the telescope |
| * switch off the light in the dome | - switch off the light in the dome |
| * per filter (for the observation) take a number (3 or more) exposures with equal exposure times | - per filter (for the observation) take a number (3 or more) exposures with equal exposure times |
| *Flatfields | *Flatfields |
| * select the same filter as used for the "science" observation | - select the same filter as used for the "science" observation |
| * attach (carefully!) the flatfield foil (from the lab room , 1.113) and switch it on (power supply in the locker in the dome) | - attach (carefully!) the flatfield foil (from the lab room , 2.009) and switch it on (power supply in the locker in the dome) |
| * please note, the flatfield foil must evenly illuminate the whole aperture of the telescope | - please note, the flatfield foil must evenly illuminate the whole aperture of the telescope |
| * take a number of exposures with short exposure times (around 3 seconds), prevent the CCD from overflowing | - take a number of exposures with short exposure times (around 3 seconds), prevent the camera chip from overflowing |
| | |
| ==== Data reduction / Stacking ==== | ==== Data reduction / Stacking ==== |
| |
| * Useful Software: Fitswork | \\ |
| | **Data reduction by means of //[[http://www.fitswork.de/software/softw_en.php|Fitswork]]//:** |
| - drop bad raw frames (note the total exposure time) | - drop bad raw frames (note the total exposure time) |
| - create Masterdark(s) (for diff. exp. times) | - create master dark(s) (for different exposure times) |
| - create Masterflats (for diff. filters) | - create master flats (for different filters) |
| - create Masterflatdarks (subtract the Masterdark with the Flat's exp. time from the Flats) | - create master flatdarks (the subtraction of the flatdarks from the flats takes place automatically) |
| - subtract the Masterdark from the raw images | - subtract the master dark from the raw images |
| - add up the images (for each filter) | - divide that images by the corresponding master flats |
| - devide that image by the Masterflatdark | - add up the images (in each filter) |
| - if needed, compensate for different exposure times | - if needed, compensate for different exposure times |
| - mark common objects in the images | - mark two common objects in the images |
| - combine the RGB-image (with offsets) | - combine the exposures to a RGB-image (with offsets) |
| - if the offsets are not good enough, mark the regions and shift the color layers relative to each other | - if the offsets are not good enough, mark a characteristic region (e.g. a star) in the RGB-image and shift the color layers relative to each other |
| - define black background (rightclick) and the whiteness (stars) | - define the background color to be black (right click) and maybe choose one star to define the white balance (right click) |
| - cut the image | - cut the image |
| | |
| ==== Postprocessing ==== | ==== Postprocessing ==== |
| * in the finishing one can adjust things like contrast, saturaion, hue, white balance etc. to reveal more details | In the postprocessing one can adjust things like the contrast, the saturation, the hue, the white balance etc. to reveal more details. |
| -via fitswork: Bearbeiten->Farbfunktion | * via //Fitswork//: Edit -> Color functions |
| -via PS/Gimp ... see there ;-) | * via //PS/Gimp// ... |
| |
| ===== Photography with the DSRL ===== | ===== Photography with a DSRL ===== |
| * if the correct adapter (T-Ring) is available, one can also make use of the Canon EOS at the telescope | We also have a Canon EOS 700D, which is a digital (single) reflex camera (DSLR). This camera allows for very short exposure times (until 1/4000s), while our CCDs only allow for a minimal exposure time of 0.09s. Accordingly, this camera is useful for objects that require short exposure times. Please note that those objects need to be bright enough for such short exposure times. The field of view of the DSLR is larger compared to the other [[en::ost:ccds:grunddaten|cameras]]. |
| * such exposures can be interesting for short time exposures, as the CCDs only allow minimal exposure times of 0.12 seconds | |
| * interesting objects: | Interesting objects are e.g.: |
| * planeten | * planets |
| * the moon | * the Moon |
| * comets | * comets |
| * cranes, trees, buidlings etc. (daytime) | |
| |
| ===== Photography with the Webcam ===== | We also have an article on [[en:dslr:tethered_shooting|controlling DSLR cameras using a computer]] :-). |
| | |
| | <WRAP center round info 60%> |
| | **Our new camera, the QHY600M, is a CMOS camera and therefore also allows much shorter exposure times than the old CCD cameras and on the other hand does not have the disadvantages of a DSLR camera, such as a high dark current. More about this when we have more experience... :-).** |
| | </WRAP> |
| | |
| | ==== Lucky imaging how-to ==== |
| | This part will hopefully be filled soon... |
| | ===== Photography with a video camera ===== |
| * we own one of these, too ;-) | * we own one of these, too ;-) |
| * see lucky imaging howto | |
| * to be continued... | \\ |
| | **To be continued...** |