An
original technic for planetary acquisition* with ASTROSNAP (PRO)
* easily adaptable to the following
objects : Sun, Moon, DSOs, Microscopy, Fluorescence etc...
revised 24/12/2009
Everything started with a question ...
What quality difference is to be seen between the two following pictures of Jupiter ?
I hope you agree that there is not much ... nevertheless then have been taken in completely different ways !
Mainly, the AVI which was the source for the (L)eft image weight 446Mo and the one for the (R)ight image only 10Mo, thats 50 times less ! Wow ! Much place could be saved for working or archiving purpose on one's hard disk ! Even and older PC can handle many files that size !
Moreover, the full process of registration/optimisation with Registax2 took a couple of min for R- and a long time for L-AVI !
The secret is obviously the small number of frames
in R ! But then how to overcome the apparition of much noise after wavelettes
for example ?
AVI-L has 841 images for a total time of 90s (BTW, always use short times
for Jupiter, as rapid rotation would blur the details otherwise). AVI-R has
only 44 frames for the same overall time !
Lets see the aspect of the RAW frames in each :
L image is very noisy, R image is nicer as much less noisier, almost looking as an image output from registration ..
How come ? Did I use a super brand new webcam ?
Not at all ! Maybe now you have guessed ...
I did the' acquisitions using powerfull functions of Astrosnap :
- Zone creation for guiding and saving
- soft guiding
- histogram (only Astrosnap Pro)
- Focus windows with values and graphs
- Flux mode reaching full speed
- Software integration
- Powerfull timelpase
- DCT (calculated JPG size) image selection on the fly (before integration
step)
- Clipped AVI savings (Only Astrosnap Pro, otherwise use BMPs)
Here follows the complete procedure (Jupiter near opposition is used, adjust for other celestial objects) :
(translation work in progress)
1) Set camera parameters (here TUCam or TUCam II Pro advices) :
Set the color camera vertically in order to be able to correct for atmospheric refraction more easily. Rotation will be done later at the end of registration.
If available, set sharpness mode, noise=0
Lum : 40-50, gamma 0, saturation 100
Open histogramme
Set 10 fps, speed & gain Auto
Uncheck Auto
Set gain at about 75-80%, or more if necessary
(It is a must in order not to get onion skin artefact around the planetary disk
at the end of processing !
Set speed to have a nice image on screen and max level in histogramme near 200
ou a bit more but avoid at all time saturation. Attention : an end of curve
as a vertical wall is to avoid absolutely too ! The slope should be ~45°
downwards !
Close the window. In APro, go from "source" to "Result"
Hit "flux" (not useful in WDM camera mode) to capture a maximum number
of images.
Take all your time to get a precise focusing taking the turbulence into account.
Do it many times ... Try to get close to the best value in the "focus"
window.
2) Set zones and software guiding :
Now return to "source"
Select a guiding zone (red line) which encercle the object or a smaller well
contrasted structure (Moon, sunspot)
Choose a saving zone with a good margin of 20%. It is a good idea to have both
size multiple of 4 for best compatibility with codecs (HuufYUV, XVID...)
Start guiding in "sum of axis" or "contour" mode
3) Set integration mode and levels :
Goto "Result"
This powerfull function of Astrosnap, already used for DSOs does a live registration
with a very good quality, at least when the sky is clear with nop wind and seeing
is good
Choose integration mode loop***, with about 20 images to start (NB: also very
useful for focusing of dark subjects : use 2 - 5 fps, auto limits then manual.
This lessen the visual effects of the turbulence and improve contrast. Eg. Venus
in UV or Near IR, DSOs, etc...)
Set the limits to get a well contrasted image without saturation !
*** Attention be sure this mode is selected
4) DCT and time lapse :
Except for Jupiter (maximum number of images wanted in a short interval) you can use the "Image quality select/DCT" fonction to eliminate the bad images before saving.
Set the sequenceur with a generic name, (AVI if using
AstrosnapProshareware otherwise BMP or JPG)
Choose a 4 or 5 digit format
Then "save once", "all the nn frames (here 20)" for the choosen time
(90s max for Jupiter) or the number of images you want (>=2000 for UV-Venus)
Start acquisition
5) Last :
Process as usual !
Comments & questions welcomed.
Lost object (bad guiding, clouds) ? Stop integration and restart it. Be really
sure you are again in continuous mode !!
Result too noisy ? Increase number of integrated images up to 100
Best quality wanted ? Use correlation mode (value 10) in software guiding
(requires fast PC)
Impossible to refresh full page mode ? Stop "integration", "DCT",
etc...
Result image stays the same ? Verify DCT (not too high, on red) or worse
integration on "unique" mode !!
Problem to recenter zones ? Stop following object
Examples of realisation (Registax5 will do better work than this old Registax2 version !):
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Saturn, 03/28 2004 |
Venus, 03/28 2004 |
Soleil HAlpha at near sunset 03/29 2004 ! |