Tag: astro photography

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Comet C2020/F3 NEOWISE already visible in the evening!

Yesterday night, before going to bed, I took a brief look at the night sky. Fortunately, the forecast clouds did not yet appear. So I took my binoculars and went up to the top most window of my condo’s stair case, which is facing north.
I could not spot the comet with my bare eyes. Though with binoculars, the comet was a pleasant sight, even though it was low in the suburban light polluted sky. At this moment, the comet was a mere 5.5 degrees above the horizon.

So I rushed back down the stairs and grabbed my camera and a tripod. I intentionally did not use one of my tracking mounts, as I expected the comet to reach the adjacent roof top within a short period of time.
Within a few minutes I could capture a set of images to process. Here are the results, all captured with Sony A99-ii and 70-200mm/f2.8 tele lens at 200mm:

It is obvious that the 30x4s ISO1600 exposures are far better in noise than the 115×2.5s ISO12800 exposures. Apart from that (ignore the color cast and gradients, which result from bad calibration data), a lot of information may be pulled from the stacked images.

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Comet C2020 F3 NEOWISE

This years best view of a comet has finally been visible in my region. Weather conditions have been really favorable for a night time spectacle.
Combined with the setting across my home town Graz, viewing from top of Plabutsch (located at the eastern edge of Graz) permitted the comet to rise exactly next to the 2 antennas on the mountain top of Schöckl in 14km distance.

See how remarkably bright the comet is in the wider angle image below. This image was taken with a mobile phone camera! And the comet is clearly visible!

The timelapse video shows the comet rising at 02:38 CEST until mid of nautic twilight at 03:54 CEST. See the amazing pattern of the noctilucent clouds going in waves!

Comet C2020 F3 NEOWISE rising over mount Schöckl (1445m) near Graz, Austria
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One night of Messier and Planet hunting at home

My limited view from the balcony is not the best for astronomy. I have approximately 120 degree east to west, facing south-east across the city. The maximum altitude i may see stars with the telescope is 74 degrees. Objects positioned low in the sky are blocked by the adjacent building up to 25 degrees. So I have access to only a smaller part of the sky, with typical Bortle 5-6 visibility.

Even though conditions seem to be unfavorable to setup a telescope…
– at times, I have all the planets in view
– the moon is a wonderful sight, even though the air above the city is far from stable
– several deep sky beauties come into view almost year round
– using light pollution filters work really well under these conditions
– I may view or image every night (time and weather permitting) without the hazzle of packing, driving an hour to one of the next darker sites, setting up, …

To proof that the night sky has still a lot to offer in light polluted urban places, I collected the images below in one single night, within less than 4 hours:

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M5 globular cluster in different exposure settings

Speed of optics and exposure times have a great impact on the resulting image. Even though a higher quantity of individual exposures may improve the result, the total amount of photons collected is key.
The 715mm f/7 APO is significantly slower than the 800mm f/4 photo newton, the total capture time of 600s vs 1560s produces a significantly better result:

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Makarian Chain and Iris Nebula

Even though the dark night in June is quite short, I could capture these images of Makarian Chain around M86 in Virgo and the Iris Nebula.
Images captured near Sommeralm, 30km north-east of Graz. Night sky still suffers from light pollution. The milky way was visible, but not crisp and clear.

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Tilt Adapter for narrow band solar imaging

Imaging with narrow band H-alpha filters for solar imaging (prominences and chromosphere) requires the light beam to be almost parallel before entering the special interference filter called Etalon filter. This is achieved by i.e. telecentric systems, also extending the focal length by a factor of 2-4x. The sensor protection glass and anti-reflection glass of the camera create reflections with each other and the filter surface. Due to the parallel light beam, these reflections create interference patterns, noticable as so called Newton’s rings in the image. It depends on several different factors like sensor construction (micro lenses, …), exact angle of sensor in optical path, angle between sensor and filter / protection glass, … how strong the Newton’s rings influence the resulting images.

It is possible to reduce or eliminate this in post processing. But any minor shift in the imaging train will make it almost impossible to compensate with flat-field images.
Fortunately, there is one alternative option: tilting the camera by a few degrees (usually up to 5 degrees), to widen the distance of the Newton’s rings, where they are no longer disturbing.

As these tilt adapters have a quite steep price tag, I constructed and printed one myself. I had to create several versions, until I had achieved a proper stability as well as stray light protection. But finally, I have a working tool 🙂
If you are interested in the design, you find the 3D files and description here: https://www.thingiverse.com/thing:4301757

See how much the tilt changes the resulting image!
Hints to the images:
– The blurry look in the image with Newton’s rings results from the alignment algorithm locking on the Newton’s rings instead of surface features
– the adapter attached to the filter is a prototype without stray light protection. Hence a strip of black insulation tape was used for shade

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A splendid night out in the countryside

Last night I spent near my home town – a short 25 minutes drive – to a place I frequently used years back for astronomy. It is a quite dark spot, though the light pollution is still obvious. Nevertheless I tried to go for some deep sky objects, getting as much observation / camera time as possible in the short nights of June.

My list of objects was not too short. All of them were well placed in the sky and really nice to see :-). So here you go:
1) Hercules cluster M13 (Sony A99ii, 800mm f4, 2xTC, 27x120s, ISO3200)
2) Virgo galaxies M60, M87, M90, M100 (Sony A6000mod, 70-200mmf2.8 @ 200mm f4.5, 22x300s, ISO3200)
3) Virgo galaxy M90 – though I intended M87 😉
4) Whirlpool galaxy M51 (Sony A99ii, 800mm f4, 2xTC, 6x360s, ISO3200)
5) Andromeda galaxy M31 (Sony A6000mod, 70-200mm f2.8 @ 200mm f4.5, 5x30s, ISO3200) – I made an error in exposure time, so instead of 5×300 I ended up with 5x30s 🙁
6) Jupiter (I did not pack my planetary imaging camera – so I used the same setup with Sony A99ii and 800mm scope at 1600mm)
7) Saturn (same as Jupiter)

And far too late (at 01:30) I set up my timelapse camera for a night-to-day movie. The milkyway was beautifully placed just above the pasture. The resulting video clip is below.

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