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Collaborative astro-photography projectIn astrophography, a picture can increase in quality as exposure time and individual exposures grow. If one amateur astrophotographer can pile up to several tens of hours, several astrophotographers may be able to pile up... a lot more ! The genuine idea comes from a project coordinated by Yuriy Toropin on M51, on which a processing was performed by Maxim Usatov, that can be seen here : http://www.bcsatellite.net/bao/m51.html
Particpants of this project come from the Webastro french-speaking community.
Discussions take place on the Webastro forum
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The concept - Gather raw material taken by several amateur astronomers
- Combine this material onto a higher SNR (signal to noise ratio) than one astronomer can easily do alone
- Try to produce a really "good looking" picture ;-)
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The method - Find a common object to shoot, accessible by several astronomers with various photo setups.
- Define some shooting "rules"; in order to gather "similar" raw images from the same objects (orientation, field of view, ...).
- Assemble all these images using appropriate pre-processing software, to produce high SNR pictures
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How do we proceed...A choice of an object is made, easy enough to be pointed at our latitudes (so that the object passes above 45° declinaison angle). The object must not be too wide, so that it can enter in the field of view of each photographer, with hardware setup that can vary from one to another. It must also not be too tiny, so that its structure can be detailed with sufficent definition. Individual exposures (raw pictures) can be taken either with a digital camera or with a CCD camera. In case of CCD, different planes have to be provided (L, R, G, B, and even exposures with interference filters). Calibration data have to be provided as well (dark, offset, flat). Depending on imaging device and focal length of instrument, picture sampling will change. indivudual exposure characteristics have to be well known, so that they can be resized before being stacked altogether. Additionally, photographers with a finer sampling (more focal lenght or smaller CCD chip) may concentrate on the luminance channel in order to improve image definition. Photographers with a lower sampling may concentrate on R,G et B layers, which are less demanding in terms of resolution. Individual exposures are then shared online, so that every participant can access them to start pre-processing (registration, stacking) or processing them (with an imaging software such as Photoshop).
Preliminary testingAs numerous questions arise when considering stacking heterogeneous images, a stacking test was made in order to validate the stacking procedure. ShootingAs a first attempt, the choice was made on the NGC 891 galaxy. This is a moderate sized object, but which structure can be reasonably detailed with amateur equipment. Raw material is shared in the FITS format, so that it can be used by every participant.
| Contributor |
Instrument |
Focal
(mm) |
F/D |
Camera |
Pixel
size (µm) |
Sampling
(arsec/pixel) |
Exposure
time (min) |
Raw images |
| Remy Gallet |
Newton 150 |
750 |
5.0 |
DSI Pro II |
8.50 |
2.30 |
- |
- |
| Orion_BG |
Newton 200 |
1000 |
5.0 |
Atik 314L+ |
6.45 |
1.33 |
- |
- |
| Goto24 |
Orion ED 80 |
600 |
7.5 |
Atik 314L+ |
6.45 |
2.21 |
- |
- |
| Tiflo |
Newton 250 + paracorr |
1380 |
5.5 |
Canon 500D |
4.70 |
0.70 |
- |
- |
| Sambogosse |
C11 XLT + Red. 0,63 |
1980 |
7.1 |
Atik 4000 |
7.40 |
0.77 |
L:55m - RGB : 54m |
Brutes + dark/flat/offsets  (98 Mo) |
| Bradisback |
Newton 250 |
1200 |
4,7 |
Atik 4000 |
7,40 |
1,27 |
- |
- |
Project StatusIndivudual exposures are in progress...
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