Again, we have no clear sky and I could not have comet hunting session this month, and there is no prospect to have a fine day in the near future. In these days even if the weather is fine in daytime, it turns into cloudy late at night.
I took a look at the number of comet hunting nights in July for the latest 10 years, i.e., in 2011 and after. One night in 2020, three nights in 2018, five nights in 2015, three nights in 2014 and one in 2013. In the other year nil. The searching activities in 2017 and before were done in Tohkamachi, Niigata.
I picked up the record on Wednesday, July 22, 2015, the month when I spent as many as five days for comet hunting. There is no description on the day (today 6 years ago) in "My diary" on my web page.
Wednesday, July 22, 2015
Observing site: Tsunan-town, Niigata, moonless night
I started the comet hunting session with Deneb Kaitos, β Ceti, at 2:25am. Galaxies identified were NGC61, 61A, 84, 86, 589, 615, 681, 720, 908 and 701: ten galaxies in total. I think NGC589 was misprinted and NGC596 is correct.
At 2:46am I changed the eyepiece from Ethos 21 mm, 97x to Planokular 30 mm with Paracorr because of poor seeing.
The session was completed at 3:25am but it was interrupted for 20 minutes for some reason (not recorded in my dairy). As a result, the total time for the session was 40 minutes.
NGC681 and 701. The image is 60' wide.
The Digitized Sky Survey copyright © 1994
NGC151. The image is 60' wide.
The Digitized Sky Survey copyright © 1994
I checked some of the galaxies I observed using a map. I saw NGC681 (magnitude of 11.8 with the surface brightness SB of 13.6 mag per square arcmin) and NGC701 (12.2 with SB 13.5), while I overlooked NGC151 (11.6 with SB of 13.4). NGC151 has brighter magnitude and SB than those of NGC681 and 701.
However, as you see in the photos NGC151 has a bright central core with faint spiral arms. I can imagine that the central core looks like a star and arms are too faint to recognize through the telescope. Consequently, I overlooked the object.
I often disappointed to have overlooked bright galaxies with the magnitude of 10th to 11th. Nevertheless, I seldom did that due to lack of overlapping of the FOV during the comet hunting session. In some cases, it is caused by the inhomogeneous distribution of SB in the object that is difficult to infer from the numerical data or poor sky condition. The same holds true for comets; it is challenging to predict the comet is visible or not based on the magnitude data alone.
Many periodic comets with the single digit designation numbers are in the eastern sky at predawn. I expect clear sky in the coming month.
Sunday, June 27
I conducted a comet hunting session only once this month on Monday June 21. It was moonless at predawn on that day, and I expected to observe a lot of galaxies in the eastern sky. In my experience the transparency is often excellent in June if we have clear sky.
Nearly seven weeks have passed since I visited the observing site last. Before I knew it the season has progressed; the constellation of Scorpion was about to set that was the meridian transit in May when I arrived at the site. The Milky Way was rising toward the zenith from the southwestern horizon.
I tried to observe 7P Pons-Winnecke prior to the comet hunting session. It took some time to identified the object, though it was reported as the magnitude of 9.7 in a certain web site. In actuality, the magnitude was 12th with the apparent diameter of 0.2'. The image was similar independent of the eyepieces used: Night Vison 37x or Ethos 21 mm 97x. Though I had a plan to enjoy observing other comets, I did not, because I spent too long time for observation of 7P. Instead, I used the time for the hunting session.
I have started the searching session, but I could not encounter any galaxy. The only galaxy I observed was M74, and I was disappointed. I did not observe any galaxies with 10th magnitude or brighter, probably due to poor transparency.
I read back my diary in June last year, and it was found that I comet hunted only once but that I identified some galaxies with magnitude of 12th to 13th. In 2019, I observed three times, but few galaxies were observed due to nasty weather and moonlight. In 2018, twice and observed many galaxies with 13th magnitude or brighter and a planetary nebula.
I have lived in Tohkamachi, Niigata, until 2017. In June 2017, I went to on a comet hunting session twice and identified several galaxies. In 2016, I observed more than a dozen of galaxies during the three times of the session.
I will not conduct a comet hunting session this month any more because of moonlight. I expect clear sky in July.
Saturday, May 29
The days of the comet hunting sessions in this month was only three, Monday May 3, Tuesday 4 and Thursday 6. The Japan Meteorological Agency said we have entered the rainy season on Saturday, 15 May, 20 days earlier than the 30-year average, but it had been cloudy and rainy for one week prior to their announcement. All the three days that I conducted comet hunting sessions were moonlit. In the eastern sky at predawn in this time of the season we see less DSOs and the moonlight made it more difficult to observe them. All DSOs that I identified during the three days were merely M15, NGC7177, M55 and M75. On May 4 it was impressive that some two dozens of the Starlink satellites with the magnitude of 12th to 13th passed through the FOV.
As I have confirmed many times, Night Vision (NV) is more effective for visual comet searching than the conventional glass eyepiece under the moonlight. Both C/2020 R4 ATLAS and C/2020 T2 Palomar looked brighter with NV than with Ethos 21 mm.
Number of days of comet hunting for the last 10 years.
Though in Niigata where I have lived until March 2018, we had many fine days in May, conversely, in Kumamoto we have less clear sky. This is the fourth year for me after the moving to Kumamoto. In the first year, 2018, there were many fine days in May but I comet hunted only two days, because of busyness just after the moving and the tight schedule of my job.
I have enjoyed the hunting session from last autumn to the end of April very much. The total searching hours and the times of the sessions for 7 months from October 2020 to April 2021 were 74 hours 45 minutes and 58 days with monthly average of 8.3 days, respectively, which were higher than those of the annual records after 2008 (cf. Fig. 2 in Diary in 2019). I think the major cause is that the rate of fine days at the observing site in Takamori Town where I started to use since last August is high.
If the volcano Aso becomes active, I cannot use the site because of the fall of the volcanic ash. May the world be peaceful so that God in the volcano does not get angry.
Sunday, 18 April to Wednesday, 21 April
I have comet hunted four consecutive days at predawn, and total days of searching were seven days this month. I utilized Night Vision for all the four days, because transparency has been poor due to yellow sand from the continent and other causes like pollen originated from various kind of plants that are common in spring in Japan.
Sunday
Air temperature was 2ºC. I saw a small number of stars at a low altitude with the naked eye, but could do a lot of them using NV with the zero magnification. I felt cold with wind. I observed two comets prior to the hunting session. C/2020 T2 Palomar was 12th magnitude, apparent diameter of 1' and DC=6. C/2020 R4 ATLAS was estimated as the magnitude of 11th, 3' and DC=4. Those values were determined by intuition using NV instead of using comparison stars.
I began the session with Saturn focusing on the zodiac. I observed only three DSOs: M72, NGC6926 and M2. NGC6926 is a galaxy in the constellation of Aquila with the magnitude of 12.5. I could notice the object because it came into the FOV at the altitude of 31º above the horizon that was fairly high. M2 were resolved into stars even at the center and was impressive. I found that the air temperature dropped down to 1ºC.
Monday
Temperature was low, i.e. 2ºC, like the day before, but I felt warmer due to the wind less condition. I started with M2 so that the seeping area overlapped with that on the previous day. I identified only two objects: M15 and NGC7177, a 11th magnitude galaxy in Pegasus. The moment when I saw the galaxy, I estimated it as 12th magnitude due to poor sky condition. I found frost on the grass at the site, and air temperature was 1ºC when I completed the session.
Tuesday
It was warmer than yesterday with air temperature of 4ºC. NGC7177 was the start point of today's searching area that connected with that on Monday. Again, only two DSOs were identified. NGC7217 is a 10th magnitude galaxy that looked bright. I spotted NGC7331 (9th magnitude) 14 minutes after the start of the twilight. There is Stephan's Quintet 0.5º SSW of NGC7331. I could not spot it during searching but it was easy with attention. I identified it during the twilight and it would be impossible to see it with a glass eyepiece. Mt. Sobosan appeared with its holy silhouette in the morning-glow when I was taking down my comet seeker. The mountain has different appearance unless it is hidden in the clouds. You can compare the photo below with those in this year and the year before in Diary. This is wonderful observing site that can be called as "sacred place".
Mt. Sobosan in the morning glow.
Wednesday
Air temperature was 8ºC. I stared with NGC7331 to overlap the sweeping area with that of the day before. I also observed Stephan's Quintet in the same FOV. The Milky Way in Cygnus and Lacerta was magnificent. The FOV was filled with neat stars. NGC7242 is a galaxy in Lacerta with the magnitude of 12.9 that I identified at an altitude of 24º. The galaxy forms the galaxy group but the other galaxies was invisible due to dark magnitude of 14th. Then, I spotted M32, M31 and M110 at an altitude of 12º. M110 was evident with NV. I tried observing it with the glass eyepiece, Ethos 21 mm. M110 looked fairly faint with Ethos 21 mm. Gamma Andromedae with the altitude of 4º came into the FOV 32 minutes after the beginning of the twilight, but I could not enjoy the beauty of the star as NV is in monochrome. Again, I changed the eyepiece from NV to Ethos 21 mm. The golden colored primary star and the light blue companion flickered by the scintillation. How wonderful they were! I was satisfied with it and finished the session.
Thursday, March 18
A comparison of visibility between a glass eyepiece and Night Vision: for C/2020 T2 Palomar and C/2020 R4 ATLAS
This is the fifth comet hunting session in March. I have observed C/2020 T2 Palomar and C/2020 R4 ATLAS before the searching session. In recent days I used NV instead of glass eyepiece because transparency has been poor due to disperse of Japanese cedar pollen with that of other plants. Though I have already observed the two comets, one of the objectives to see them was to compare the visibility of the glass eyepiece with that of NV.
First, I observed C/2020 T2 with the glass eyepiece, Ethos 21 mm, 97x. I trained my telescope at the comet using SkySafarai 6 Pro, a digital map, which was connected with Nexus DSC. At a glance I could not notice any comet-like objects in the FOV. I tried to compare the arrangement of stars in the FOV with that on the map to identify C/2020 T2. It took several minutes to confirm the position of the comet that was at an altitude of around 70º: at higher altitude the accuracy of locating object gets worse for Dobsonian. Though what I observe was not a comet-like object but a star-like one with the magnitude of 13 to 14, I was sure it was C/2020 T2. Then, I saw C/2020 R4 ATLAS employing the same eyepiece. It was easy to observe in spite of the low altitude of some 12º above the horizon. I estimated the comet as 10th magnitude, apparent diameter of 3' and DC=2 by intuition.
I changed the eyepiece to NV with 37x and aimed my telescope at C/2020 T2. I noticed an object that could be recognized as a comet at a glance, and observed as a magnitude of 12, apparent diameter of 1' and DC=7. I was sure to be able to spot the object of this image during my hunting session. I trained my comet seeker at C/2020 R4 with the same eyepiece, and I surely notice the existence of the comet, but somewhat hard to see it due to lower magnification in comparison with the image seen by using Ethos 21 mm. It looked darker than using the glass eyepiece and estimated as the magnitude of 11, apparent diameter of 2' and DC=2.
Which eyepiece is better for comet hunting, the glass eyepiece or NV?
The answer: it is dependent of nature comets and as I have ever written it also depends on the sky condition things like moonlight and the degree of light pollution. As Tsutomu Seki's famous quote, there is no secret plan to discover a new comet.
I have spent some 15 minutes for the above-mentioned observation, and finally, I was ready to start the comet hunting session at 4:18am. I began with Altair, alpha Aquilae, using NV. All the DSOs I identified were globular clusters. They were only three: NGC6934, M2 and M15. All were resolved into stars with NV. It was impressive that some stars of M2 at the periphery were resolved even though it came into the FOV at the altitude of only 6º.
View of Mt. Sobosan from the observing site after burning the dead grass in the field.
Movies: burning the dead grass in the field
https://www.youtube.com/watch?v=nSuDaaJipyI
Four days ago, the dead grass was burned in the field around the site, and we are seeing drastic change in landscape. On the photo taken last month there was Japanese pampas grass in front of Mt. Sobosan, but it completely disappeared on the one shown above taken today; it looks like a shot from another site. Thanks for the burning. It keeps a good view of the site.
Friday, February 19
I arrived at the observing site at 3:45am. The condition was wonderful with air temperature of -8 ºC, no wind and the snow depth of 3 cm. Though the snow depth was merely 3 cm, I had to shovel the snow to some extent, and it took more time to set up my telescope than usual. I spent as long as 50 minutes after arrival to prepare the session, though it takes half an hour to do under the normal conditions. When I lived in Niigata it also took some 50 minutes to set up the telescope after the arrival during the winter season with snow.
Prior to the comet hunting session, I observed Omega Centauri, a globular cluster. The cluster was about 9º above the horizon, and it was easy to spot with the naked eye. The view was awesome with 46 cm 78x using Planokular 30 mm and Paracorr.
To turn my eyes to the southeastern horizon, the central part of our galaxy shined like clouds and the Milky Way extended to the northern sky. In the middle of it, just under Altair, Mt. Sobosan displayed a sacred silhouette. How beautiful the scenery was!
I employed a glass eyepiece because it was moonless night with good transparency. I reached a conclusion that the glass eyepiece is better than Night Vison (NV) under the condition that the night is moonless and transparency is fair, because the glass eyepiece is more sensitive to blue-colored comets and unlikely to overlook them. Nonetheless, I used a combination of Planokular 30 mm with Paracorr 78x instead of Ethos 21 mm 98x due to poor seeing. At 4:40am I began with the azimuth of Rasalhague, α Ophiuchi. That was to say, the altitude of the star was 41º above the horizon at that time, and I searched the area from the same azimuth as the star with the altitude of 30º or less only.
