Comet C/2022 E3 (ZTF)
Comet C/2022 E3 (ZTF) could be observed between Feb 06 and Feb 08, 2023. In the night between Feb 06 and 07 there was a conjunction with another comet, C/2022 U2 (ATLAS), almost at the same time when ZTF crossed the th galactic plane.Index
Click on the images to jump to the larger images and videos with description.
Feb 06, 2023. ZTF and ATLAS.
Feb 06, 2023. Closest approach between ZTF and ATLAS.
Feb 06, 2023. ZTF at galactic plane and almost in conjunction with ATLAS.
Feb 06: C/2022 E3 (ZTF) and C/2022 U2 (ATLAS) near the galactic plane
On Feb 06 there was a close apparent approach between comets C/2022 E3 (ZTF) and C/2022 U2 (ATLAS). In that night ZTF also crossed the galactic plane. That unusual event was observed between 17:10 and 00:40 UTC.In the pictures below comets and stars are aligned and processed separately, also see the image processing details. For each image and video frame comet ZTF was only integrated over a period of one hour due to the volatility of the ion tail (see the videos). Comet ATLAS and the stars where integrated over the whole observation period of about 7.5h
The images where captured one day after full moon and therefore suffer from low signal to noise ratio (due to the photon noise from the bright background).
The bright background also caused other artifacts which could not be removed completely, see the documentation of artifacts.
The larger comet is C/2022 E3 (ZTF), the smaller one is C/2022 U2 (ATLAS).
The picture shows the the positions of the comets and stars at 18:40 UTC. The video spans the period from 17:30 UTC to 00:30 UTC. Please note how the ion tail changes over time.
Color information where obtained using SDSS I', R', B' filters (mapped to red, green and blue) using instruments 1-3 (see data section).
Instrument 4 was used for the high resolution luminance data.
The comas of both comets appear blue because because its turquoise light (created by photodissociation of dicarbon, see [1]) is only captured by the B' filter.
The field of view is 2.1° × 1.5° and the pixel scale is 5 arcsec/pixel.
The picture shows the positions of the comets at their closest apparent approach at 20:04:30 UTC.
The video spans the period from 17:30 UTC to 00:30 UTC. Please note how the ion tail changes over time.
This false color image is composed from SDSS I', R', B' data (mapped to red, green and blue) of instruments 1-3 (see data section)
and H-alpha, taken from another data set and mapped to red to orange.
The pictures shows the positions of the comets and stars at 22:53:45 UTC, the moment at which ZTF was on the galactic plane. 54 minutes later both comets where in conjunction (in right ascension).
That region is rich of emission nebulae which are also shown in the image.
This false color image is composed from SDSS I', R', B' data (mapped to red, green and blue) of instruments 1-3 (see data section)
and H-alpha, taken from another data set and mapped to red to orange.
The field of view is 5.2° × 4.2° and the pixel scale is 12.5 arcsec/pixel.
The field of view is 9.2° × 7.2° and the pixel scale is 12.5 arcsec/pixel.
Instrument and image
The comet was simultaneously captured with 5 instruments.| Instruments 1-3: |
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| Instrument 4: |
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| Instrument 5: |
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| H-alpha data: | From this source |
| Pixel scale: |
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| Location: | Pulsnitz, Germany |
| Orientation: | North is up (exactly) |
Image processing
- Darkfield and flatfield correction, calibration using stars
- Background image:
- Stacking with alignment to stars and dropping of outliers (in that case moving objects)
- Star subtraction
- Removing the comet residuals by masking and interpolation of the masked region
- Add previously subtracted stars
- Comet images:
- Stacking with alignment to the comet and subtraction of the stars and the background
- Background estimation by masking the comet (plus a wide border) and interpolation of the masked region
- Low-pass filtering that estimated background and subtracting it from the stacked result
- Denoising
- Shifting the components to the position at the given time and color composition
- Dynamic range compression
- Tonal correction
Artifacts
Almost all images on this page suffer from a bright background, especially the images captured on Feb 06, one day after full moon. This caused certain artifacts that could not be removed in a save (without altering the image information) and deterministic way.For a correct evaluation of the images shown above, these artifacts are documented hereinafter.
- Inaccuracy of the flatfield correction due to bending of the optics. With a dark background the effect is negligible. In the images from Feb 06 this effect is probably responsible for the green spot in the dust tail of ZTF.
- Moon light which illuminated the dew caps / telescope tube. Due to internal reflections this becomes visible in the image. Optical leaks have a similar effect. This kind of artifacts could be strongly reduced by the background correction as described in the previous section. But some of the fluctuations in the ion tail may be caused by this
- Internal reflections of bright stars which appear as small spots mainly in the NIR channel (probably because the lens is not optimized for that wavelength)
References
- Jasmin Borsovszky & Klaas Nauta & Jun Jiang & Christopher S. Hansen & Laura K. McKemmish & Robert W. Field & John F. Stanton & Scott H. Kable & Timothy W. Schmidt. (2021). "Photodissociation of dicarbon: How nature breaks an unusual multiple bond". Proc Natl Acad Sci USA. 118 (52) e2113315118. Monthly Notices of the Royal Astronomical Society. stad027.
