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Monthly archives: április, 2019

Saturn – 2017-06-04, reprocessed 2019-04-30

I reprocessed an image of Saturn, recorded in 2017. Looks like Saturn too was made with the N150/750, but for certain, my only color camera was the Scopium webcam, a rather modest piece.


A Jovial Family – 2019-04-23

With my big gun I observed Jupiter and its four big moons in a very pleasant position. From left to right we see Io, Ganymede, Callisto, Ganymede’s shadow and Europa. The only thing missing from this great vista is the Great Red Spot, as it is frequently missing when it should not.

The gear: ASI 224MC, TS Optics ADC, Barlow, N 250/1200, HEQ5.




Saturn 2019-04-25

I imaged Saturn with the ASI 224MC, TS Optics ADC, Barlow, N 250/1200, HEQ5 setup. 60k frames went into the planet (it doesn’t really get motion blur like Jupiter) and a few frames of 200ms into the satellites. Enceladus was at (or below) the noise limit, however, I added it onto the final picture. Below some more pictures with at around 10k frames each.



ACO 1656 Coma Galaxy Cluster – 2019-03-30

Coma Cluster, ACO 1656

Using my usual deep sky gear, N 150/750, Baader MPCC Mark III, Canon 1100D mod, HEQ5 with the IDAS LPS D2 in place, I imaged the Coma Galaxy Cluster, ACO 1656. I acquired a relatively modest amount of expos, 9×4 minutes at ISO 3200, from the haystack in Dângău Mare.

Obviously, I used my photo planner to plan this job.


ACO 1656 [galaxyCluster in Com] Coma Galaxy Cluster   ø76.6′ [simbad] 400mm, 600mm, 750mm



Jupiter’s family – 2019-04-07

At 02:35UTC I imaged the giant and its moons with the fairly new N 250/1200, TS Optics ADC and ASI 224MC.

G, C, I, E and Jupiter


Markarian’s Chain, 2019-03-30

Markarian’s Chain

I already had two attempts at imaging Markarian’s Chain, see here and here. Now I let my gear to shoot 22×5 minutes at ISO 3200, using the  N 150/750, Baader MPCC Mark III, Canon 1100D mod, HEQ5 with the clip in IDAS filter. I also added some data from 2017. Location: Dângău Mare, Cluj, Romania.


catalogs name type const mag
M 86, NGC 4406 Gxy Vir 9
M 84, NGC 4374 Gxy Vir 9.4
NGC 4438, Arp 120 The Eyes Gxy Vir 10
NGC 4473 Gxy Com 10.1
NGC 4477 Gxy Com 10.4
NGC 4435, Arp 120 The Eyes Gxy Vir 10.8
NGC 4461 Gxy Vir 11.1
NGC 4458 Gxy Vir 12.1
NGC 4443 Gxy Vir




Safe php acos, astronomy

I’m posting because of a very frustrating issue I stumbled upon while developing my photo planner: php’s acos function has an undocumented (yet found by others) behavior. It can return NaN, in a way that breaks a JSON. The PHP manual says (2019-04-02) Return Values: The arc cosine of arg in radians — and nothing about a NaN scenario. Nothing. On forums, it can be found that the function returns NaN when the argument is out of the range [-1, 1]. And as it turns out, due to rounding errors in the float, this can happen. Very, very, very annoying.

I have the following lines of code, obviously for astronomy, calculating the arc distance, in degrees, from radec pairs, in degrees.

function arcdistdeg($ra1, $dec1, $ra2, $dec2){
  $cosA = sin(deg2rad($dec1)) * sin(deg2rad($dec2)) + cos(deg2rad($dec1)) * cos(deg2rad($dec2)) * cos(deg2rad($ra1 - $ra2));
  return rad2deg(acos($cosA));

And this function returned NaN for perfectly valid input values (around NGC 4103). So the obvious solution was to force the range with a safe_acos function, similar to

function safe_acos($n){ return acos(min(max($n,-1.0),1.0)); };

Very, very annoying.


The Whale Galaxy

The Whale Galaxy

On 2019-03-30, from Dângău Mare, I imaged the Whale galaxy, a well known target. I used my N 150/750, Baader MPCC Mark III, Canon 1100D mod, HEQ5 setup, with the IDAS LPS D2 filter in place, and captured 26×4 minutes at ISO 3200. It was surprisingly easy to process the resulting images.

C 32, NGC 4631, Arp 281 [galaxy in CVn] Whale Galaxy, Bálna-galaxis, Herring Galaxy, Herring Nebula 9.1m ø15.5′

The bright companion to the left is

NGC 4656 [galaxy in CVn] Image it together with the Whale galaxy 10.2m ø15.1′ [wiki] [simbad] 750mm

And the Whale’s “breath” is

NGC 4627, Arp 281 [galaxy in CVn] 12m ø2.6′ (tovább…)


Jól kalibrált monitoron mindegyik számnál elkülönülő árnyalat látszik. Ha mégsem látszanak, akkor a megjelenített képek színhiányosan rajzolódnak ki. A monitort valószínűleg kalibrálni kell.

You should see distinct shades for each number. If those shades are not clearly visible, the displayed pictures will lack accuracy. Your display most likely needs to be calibrated (brightness, gamma, contrast etc.).