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2017

Monday, November 13

How wonderful this clear predawn was! This was the third comet hunting session this month, i.e. the first one was Wednesday 1 and the second was Monday 6. The chill was severe and the air temperature was -2 degrees in Celsius when I arrived at the site at 3am. I found a small amount of remaining snow at the shade. I began the hunting session at 3:45am because I spent a lot of time to wear winter clothes. There was a crescent moon at the foot of the constellation of Leo, and I started the searching session with M3 in the northeast to avoid the moonlight. Under the moonlight the altitude of M3 was only 13 degrees above the horizon, but the cluster dissolved into numerous individual stars that proudly shined.

Todayfs major search area was Canes Venatici where there are uncountable galaxies. However, I could observe bright ones only due to the moonlight. The first comet-like object that I encountered was NGC4145 (magnitude of 10.8), which found to be a galaxy at a glance because of the elliptical shape and a hint of spiral structure. I did not notice NGC4151 that was in the same FOV with NGC4145.


Three galaxies on the left: from the top NGC5350, 5353 and 5354. Left: NGC5371. The image is 60f wide.
The Digitized Sky Survey copyright © 1994

Soon after the start of the session Cor Caroli, alpha Canum Venaticorum and a binary star, came into the FOV. The beauty of yellow colored primary and violet secondary was restful and peaceful, which I drank in for a while. NGC4490 and 4485 were interactive galaxies and they were deformed by the gravity of their own. After identified M94, M63, NGC5557 and 5326, I saw four galaxies, NGC5350, 5353, 5354 and 5371, in the same FOV. I observed 17 galaxies during the session and the darkest one was the 12th magnitude, i.e. NGC4326, while I looked over many 10th magnitude galaxies. The easiness of the detection for comet-like object is dependent on not only the magnitude but also the surface brightness (the degree of concentration). Nonetheless, I found myself that both of those factors cannot explain the cause of the oversight.


Night glow in Paranal Observatory in Chile. The night glow is inhomogeneous and stronger at lower altitude of the sky.
http://www.eso.org/public/images/potw1638a/

Tsutomu Seki described in his publication that the cause of overlooking is mental condition of the comet hunter of the time. Recently, I began to think that the cause is the effect of night glow. I have often recognized nonuniform brightness in the FOV of my comet-seeker. It is obvious that it was not cloud and not a part of a large nebula. It seems that the nonuniform distribution of night glow affects brightness of the background that leads to oversight of comet-like objects. On top of that, as the distribution of night glow varies with time, an object that one could not observe may be observable after a short period of time.

 At the time of the beginning of the twilight when Mars and Spica roses high above the horizon, the coldness got further severer and the thermometer on hand indicated -4 degrees Celsius. The daybreak in late autumn is lovely as temperature went down.


Friday, October 27

It has been rainy and cloudy since October 1 when I conducted the comet hunting session last. Finally, we had clear sky this predawn. It was chilly as air temperature at the site with an altitude of 1000 m above sea level was only 3 degrees Celsius. I started the session with Regulus, alpha Leo. I began with this star because I could spot 62P Tsuchinshan soon after the beginning of the session and 28P Shaumasse in the galaxy groups of Leo if I continued comet hunting toward the north.

However, actually, I had overlooked 62P. I pointed my comet-seeker at the comet using the SkySafari 5 Pro; 62P was faint and rather difficult to observe. I thought that the comet passed through at the edge of the FOV during the sweeping, but I felt something was wrong. I looked over the sky and noticed that thin cloud covered the entire sky. I could not see 62P due to the cloud in addition to bright zodiacal light.


NGC4088 (center) and NGC4085 (lower center). NGC4088 looked like paler image of this photo. The image is 30f wide.
The Digitized Sky Survey copyright © 1994

At 3:50am almost all the sky was covered with thin cloud. There was a gap among the clouds in the northeast and I trained my comet-seeker there. I identified NGC4800, 4026, 4157, 4088 and 4085 in the cloudy sky, but the break was closed in a short time. Next, I spotted NGC6643 at the north and the amount of cloud reduced except for the east.

At 4:25am I observed C/2017 O1 ASASSN (9th magnitude, diameter of 6f with a tail), C/2016 PanSTARRS (13th, 0.5f) and 62P (10th, 4f). I resumed the hunting session from the positon of 62P, i.e. in the constellation of Leo. After identifying NGC3641, M95 and M96, I was clouded out again at 4:52am. At 5:00am I tried to observe 28P through a small break in the clouds, but 23minutes had passed since the beginning of the twilight. I could see nothing at the positon of the comet, however, I spotted 28P using the Lumicon comet filter!

It was satisfactorily session, though there were a lot of clouds. When I was taking down my comet-seeker Venus rose and shined lovely just above the horizon.


Monday, September 4

It has been nasty weather for exactly one month. When I got back to my motherfs house in Shiga Prefecture in the middle of August in gObonh, the sky was clear and we enjoyed watching Saturn and globular clusters. Contrary, in Tohkamachi, we have had no fine days.

This year there were few cloudless nights even if the forecast predicted fine weather. I did not expect clear sky this predawn, but when I got up I found starry sky out there that seemed to be miracle for me. As I planned I conducted the comet hunting session at the farmland behind my residence, because there was little expectation for fine weather and did not get up early. The moonset was 2:57am local time and the start of the twilight was 3:48am, which meant the dark night was only 51 minutes. I went out and set up my comet-seeker quickly, and I could begin to searching at 3:10am.


NGC1999 (lower left) and the southern part of M42 (upper right).
The image is 60f wide. The Digitized Sky Survey copyright © 1994

The constellation of Orion rose rather high above the horizon when I started the session. I thought that the area along the ecliptic must be swept by the comet hunters all over the world, and I dared to begin with Orion that is away from the ecliptic. Unintentionally, I trained my telescope on the constellation of Orion, and I peered into the FOV. Accidentally, I noticed there was an object that looked like a reflection nebula. I identified the object using the SkySafari 5 Pro, and it turned out to be NGC1999. At the same time I saw a nebula drawing a large arc on the northwest of NGC1999, and I moved my comet-seeker to the nebula. I found it to be M42. The arc was the loop-shaped area of the southern part of M42. At home I learned that NGC1999 has a gholeh at the center, and I remembered that I was sure to have observed the hole with a high magnification in the past.

I continued the session and the Orionfs Belt came into the FOV. I could see the Horsehead nebula with conscious observation, not to mention NGC2024 (Flame nebula). NGC2167 in Monoceros seemed to be a reflection nebula. A star was surrounded by a faint nebula. The winter Milky Way around the region was beautiful. The next object that came into the FOV was M78 and I also noticed NGC2071 that is near M78.

I spent for one hour and ten minutes for todayfs session, and completed when Venus rose high in the sky. The site was behind my house but I observed the winter Milky Way at 20 degrees or higher above the horizon that meant the transparency was pretty good. I was content with the hunting session for the first time in a while.



Friday, August 4

I got up at 0:40am and looked at the sky. The amount of cloud was 40%, but transparency was good. I headed for the observing site but on my way to the site I noticed that it seemed to be cloudy. I parked my car and confirmed the sky condition: I could see only a few stars. I did not expect to conduct a hunting session satisfactorily, but anyway I drove to the site.

I completed setting up my comet-seeker before 2am, but only one star was in the sky to align the digital setting circles (DSC): when Capella appeared Polaris was hidden by a cloud, and both Capella and Aldebaran got behind a cloud when Polaris was shining. I was patient and finally, I could finished the alignment of the DSC at 2:20am.

At 2:22am I observed C/2015 ER61 PanSTRRS. The magnitude was 11th with a diameter of 1.5f. It looked much darker than actual brightness since I observed the comet through thin cloud. I saw C/2017 O1 ASASSN1 for the first time: mag. 10 and diameter of 8f. The comet had large apparent diameter like Comet Ikeya-Murakami upon discovery with darker brightness. There were breaks of clouds in the direction of those two comets but they disappeared behind clouds soon. I started the comet hunting session; wherever there was a gap of cloud I trained my comet-seeker and swept. I could not concentrate on the session because the amount of cloud was 80 to 90% and the breaks of clouds were filled soon. I was forced to sweep the other part of the sky.


M77 (lower left) and GC1055. I could have noticed the dark lane of NGC1055, if I had carefully observed.
The image is 60f wide. The Digitized Sky Survey copyright © 1994


NGC1363, a small galaxy (center). The image is 30f wide.
The Digitized Sky Survey copyright © 1994

At 2:55am I observed C/2017 O1 again as the cloud around the comet disappeared. Without a filter it looked the same as I observed at 2:30am. But with the Comet filter the comet had a coma 5f in diameter with a tail 3f in length. The sky got completely cloudless straightaway and I aimed my telescope higher altitude. M77 and NGC1055 came into the FOV. I saw faint halo surrounding the nuclear of M77. After that I identified NGC1087, 1090, 1421 and 1337. I compared the actual FOV with SkySafari 5 Pro
to confirm the function of the encoders that I tuned the other day, and accidentally noticed that NGC1363 was in SkySafari 5 Pro. In the actual FOV I found NGC1363 with ease. The data indicates the galaxy has a magnitude of 13.1 with an apparent diameter of 0.9f, however, the diameter was 0.3f visually that makes it impossible to spot the small galaxy during a hunting session. The sky have been cloudless until when I completed the session at 3:45am. The clear sky lasted only less than one hour, but I was content with a grareh sky condition that I finally met.


Saturday, July 22

Bad weather
I feel there is a trend of bad weather in the past few years, and transparency is poor even if it is fine. I did not confirm the trend based on the statistical analysis, but some comet hunters told me that they had the same impression. I comet hunted last on June 20, i.e. I could not comet search for more than one month because of nasty weather; if it was cloud less, I could not search due to poor transparency.

Three photos below are taken from my house. From top to bottom Dec. 30 in 2013 (fair with good transparency), Jun. 1 in 2014 (fair with poor transparency due to yellow sand from the continent), and Jul. 22 in 2017 (cloudy with poor transparency probably due to high concentration in aerosol). In the photo taken in 2013 a mountain range 30 km away from my house is clear (indicated by a square), contrarily, it is not visible in the other photos.


Dec. 30 in 2013 (fair with good transparency)


Jun. 1 in 2014 (fair with poor transparency due to yellow sand from the continent)


Jul. 22 in 2017 (cloudy with poor transparency probably due to high concentration in aerosol).

I exactly do not know the reason why the increasing trend of the days with poor transparency, but I think the concentration of aerosol is getting higher for unknown reasons. The web site below can simulate some different kinds of aerosol concentrations and may give clue for this topic.
http://sprintars.riam.kyushu-u.ac.jp/forecast2.html


Aerosol forecast at 15:00 JST, on 21 Jul. 2017

Improvement of 46 cm comet-seeker
Last year I replaced the focuser of 46 cm comet-seeker because it was broken. The old one was light weight but made by plastic: the Phase 4, AstroSystems, CO, USA. From the beginning I was afraid the durability but was satisfied with the product since it worked well for 15 years. Please refer to this page on the series of improvement of my come-seeker.

The pole seats and the wedge method was used to connect the truss poles and the top ring (secondary cage), however, there was a defect that the alignment shifted at an altitude of over 60 degrees. Also, the method requires long screwing length that is a bit annoying. To solve those defects I adopted the crush-tube method. One end of the pole was crushed in 10 cm long and overlapped poles are fixed by the bolt and nut. Along with it the insulator that covers the poles was also replaced with the new one: from thick one for water pipe to thin black one. The alignment was improved but not perfect and it seems to shift a bit over 70 degrees in altitude. After the improvement there is no clear sky. Now it is rainy season, but I am looking forward to clear sky with high transparency after the end of the rainy season.


Monday, June 5

I conducted comet hunting sessions seven times in May, but I could not satisfied with them all because of poor sky conditions: moonlight and hazy air. Today the moon set at 2:03am and the twilight began at 2:35am, therefore, the dark night lasted only some 30 minutes. However, the transparency was fair and I expected pleasing session. I wondered if how many galaxies I could identify during the session around the Great Square of Pegasus.


NGC7769, 7770, 7771. The image is 30f wide.
The Digitized Sky Survey copyright © 1994

I began with the session from Markab, alpha Pegasi, at 1:55am. Air temperature was 4 degrees in Celsius that was low at this time of the year, though the site is over 900 m above sea level. Soon after the start of the session, the first galaxy of this session, NGC7743 (mag. 11.4) had come into the FOV. An owl hooted as if it had announced there was still some time until the beginning of the twilight. When the twilight started I identified the second galaxy, NGC7678 (11.8). I was somewhat disappointed because I could not observe many galaxies as I expected. Nonetheless, NGC7769 (12.0) and 7771 (12.1) were came into the FOV at 2:49am. The SkySafari 5 Pro indicated another galaxy, NGC7770 (13.6) near NGC7771. I looked at the positon and I easily noticed NGC7770. I was glad I could identified those galaxies with an altitude of 20 degrees, but I had no idea why I did not notice the other 11th magnitude galaxies within the search area. I overlooked even 10th magnitude one, NGC7814. I think this was probably due to the low altitude and small apparent diameter of the objects. I always have doubts like this, and I wonder if the capability of my comet-seeker is not enough to detect dark objects considering the aperture.

After 36 minutes of the start of the twilight, C/2015 ER61 PanSTARRS have come into the FOV. The comet had a tail with the magnitude of 8th. I continued the session and finished when Venus was in the FOV. A cuckoos chirped in replace with the owl. What a fresh daybreak! Air temperature dropped to 2 degrees in Celsius.


Tuesday, May 2 and Wednesday, May 3

I conducted comet hunting session three times in April, but I updated my web page only once on April 1, because I had been very busy. One of the reasons was that I have been in Vienna to take part in General Assembly of European Geosciences Union (EGU) as a forest hydrologist not as an amateur astronomer.


Venue of EGU in Vienna.

I took off on Monday, May 1, to recover from the jet lag. I tried to go to the observing site for non-snow season without expecting disappearance of snow. I could not go beyond the point with the altitude of 600 m due to snow cover. As the altitude of the site is 962 m, it probably takes one more week until the disappearance of snow. I use the temporal observing site with the altitude of 575 m until the snowmelt of the summer site.


The observing site with the altitude of 575 m where there remained some snow cover on May 1, 2017.

Tuesday
I was scheduled to get up at 1am, but I wake up at 0am because of the jet lag. I felt I could not sleep anymore, and I headed for the site. I was ready to observe at 1am. Prior to the comet hunting session, I enjoyed observing bright comets. Comet 41P Tuttle-Giacobini-Kresak was 7th magnitude, DC = 2, diffused, and the wide tail was not distinct with the length of 0.1 degrees. I could recognized the existence of the comet using a 7x50 binocular. C/2015 V1 Johnson was 6th magnitude, DC = 4, the beautiful tail extended as long as 0.7 degrees. I noticed the tail with ease using the 7x50 binocular. The brightness of these comets were determined by intuition and not objective.

I started the comet hunting session from the east at 1:20am, specifically from Altair, because the southeastern sky was very bright. I wondered what the source of the light pollution was. Did a ski resort still open through the night? I noticed the southeast is always bright at this time of the year. During the session the DSOs that I identified were NGC6934, M2, NGC7006, M15 and NGC7177. All of them except for the last one were globular clusters. I identified NGC7177 (mag. 11.2) when it was at the altitude 39 degrees 15 minutes after the beginning of the twilight. Nonetheless, the impressive moment for me at the session was when C/2015 V1 Johnson came into the FOV. I noticed that the object was the comet in a moment. Spotting a comet, even if it is a known one, gives me an inspiration.

I often come across wonderful double stars during the session, but I have seldom confirmed the names. During this session, I identified a double star. It was Gamma Delphini. The primary star was golden with the secondary being dull golden. I checked the color of them at home using the Internet; the primary was golden as I observed, but the secondary was unexpectedly light blue. The golden color of the primary looked like that of Golden Hall, Musikverein in Vienna where my wife and I enjoyed the concert. I wondered how long the star has been shining. In comparison with the period, the lifetime of the Hall must be as short as a blink of an eye.


Golden Hall, Musikverein in Vienna.

Wednesday
Following yesterdayfs session, I conducted one this predawn also. I began with NGC7177 that was the last DSO I identified yesterday. This galaxy looked a mere faint stain because of poor transparency. During the session I identified Veil Nebula in Cygnus. Last year I installed a filter slider on the focuser on which three filters are attached: IDAS LPS-P2, Lumicon Comet, Lumicon OIII. The nebula was not clear due to haze but applying the Comet or OIII filter improved the contrast dramatically and made the image wonderful.


NGC7311 (upper center) and Stephanfs Quintet (lower right).
The Digitized Sky Survey copyright © 1994

There are many galaxies in the constellation of Pegasus, the major search area today, however, I encountered only two, NGC7217 and 7331, except for NGC7177 from which I started the session. NGC7177 came into the FOV following 10 minutes of the start of the twilight. I could manage to recognize Stephan's Quintet that is 0.5 degrees south southeast of NGC7331 with attention. In the latter half of the searching session, the transparency got worse with time and hazy. I completed the session when Venus rose on the eastern horizon.


Saturday, April 1

We have had no clear sky at predawn for just four weeks. During the period I got up at predawn a couple of times, but I was clouded out.

I went to skiing and on a hiking to a snow-covered mountain last month. It takes some 15 minutes by car to Joetsu Kokusai Ski Resort where one of the nearest ski field from my residence. At the top of the field air temperature was below zero degree Celsius and snow quality was pretty good. At the lower part, however, snow was granular and poor quality with few skiers.


The highest point of Joetsu Kokusai Ski Resort. It was snowing in the morning.


The hiking course was Mt. Sakato-yama (37.059034N, 138.898435E ) where I usually enjoy mountaineering. It is 30minutes drive from my house to the parking at the foot of the mountain where 165 m above sea level (a.s.l.). For me it is 50 minutes-walk (in summer 40 minutes) from the parking to the top (634 m a.s.l.). On Monday, March 20 the snow depth at the parking where many city houses were was around 1 m, while at the top 2 m.


Toward the top to the Mt. Sakato-yama. It was cloudy in the morning.

After getting back to the parking from the top I saw a wonderful scene that the top of the mountain and houses were reflected on the surface of a pond. It was refreshing and looked like European one.  One month has passed since I observed 41P/Tuttle-Giacobini-Kresak  last. I have yet spotted C/2017 E4 Lovejoy nor C/2017 E1 Borisov. All of them are getting brighter. I hope clear skies in Apirl.


Mt. Satato-yama (a peak at upper center).


Tuesday, February 28, Wednesday, March 1, and Saturday, 4

At predawn we had clear sky three out of five days. I must say it is rare that we have gso manyh clear days at this time of the year.

Tuesday, February 28
Air temperature reached as low as -7˚C that was the lowest record in my comet hunting session this winter.
Prior to the session I observed 45P/Honda-Mrkos-Pajdusakova, 41P/Tuttle-Giacobini-Kresak and C/2015 V2 Johnson. This is the first observation of 41P and 45P for those returns. The image of 45P was extremely diffused and it looked like M33 under a bit poor sky condition. With careful observation I noticed the comet had the west ward tail with a length of 0.6˚. I estimated the parameters of the comet as DC=0, dia. > 10f, and mag. 8th by intuition. Another periodic comet, 41P has a tail with 11th magnitude. The tail of C/2015 V2 got wider in comparison with that on January 7, and the magnitude of the comet was 11th. It is interesting that each comet had its own trait.


45P/Honda-Mrkos-Pajdusakova, C/2015 V2 Johnson, 41P/Tuttle-Giacobini-Kresak and C/2015 ER61 PanSTARRS. The drawings were made at home after the observation based on recollections.

I began the session with M4, a globular cluster in Scorpius, and finally, I identified 18 DSOs. The catalog data of NGC6325, a globular cluster, shows the magnitude is 10.5 with apparent diameter of 4f, but for me it looked 12th magnitude with the diameter of 1f that was faint enough to have had been overlooked. After the start of the twilight, I trained my comet-seeker at C/2015 ER61 PanSTARRS. When I observed the comet on January 22, I could not recognized it without a filter, and I managed to observe the comet with the comet filter. After observing C/2015 ER61, I made a 10-minute searching identifying 3 globular clusters, and completed the session at 5:18amlocal time. The last globular cluster that came into the FOV was NGC6401 in the vicinity of Saturn but Saturn was out of the search area.

Wednesday, March 1
It was as chilly as yesterday with the air temperature of -6˚C. I started the session with Eta Ophiuchi so that the search area overlapped with that of the previous day. When M9 came into the FOV I looked at SkySafari 5 Pro and noticed that there is a dark nebula in the vicinity of the globular cluster. Again I peered into the FOV and actually, there it was; the number density of stars are different between the right and left side of M9.


M9, a globular cluster in the constellation of Ophiuchus. There is a dark nebula on the lower right. The image is 1 degree wide.
The Digitized Sky Survey copyright © 1994


An emission nebula in Sagittarius, NGC6595. The image is 15f wide.
The Digitized Sky Survey copyright © 1994

I could identified an emission nebula, NGC6595, because I saw a faint blur of light around a double star. Showpieces of DSOs like M22 and M17 went through the FOV with the gorgeous background of stars. I finished the session with wonderful view of those objects.

Saturday, March 4
On weekends the light pollution is getting prominent at the usual observing site. This is because Kandatsu Kogen Ski Resort, some 18 km away, opens through the night.


Advertising of all night opening of Kandatsu Kogen Ski Resort.
http://www.snowjapan.com/japan-ski-resorts/kandatsu-kogen

The service finishes at 4am local time, but the light at the ski field remains crazy bright after the time. In the past the resort was once closed because it went bankruptcy and the managements have changed a few times. Now, it features the service of all night, but it is annoying for me. I headed to the observing site that was different from usual one to avoid the light pollution caused by the resort. At the usual site the direction of the pollution is on the southeast but at todayfs site on the south-southeast.

I began with M17 to overlap the sweep area with that of 3 days ago. However, around 10 minutes later, I was discouraged by the light pollution originated at the ski resort that made the FOV bright. I recovered from the negative sense and I resumed on the east where less polluted. A globular cluster NGC6760 and two planetary nebulae, NGC6781 and 6804 have come across the FOV. NGC6781 is worth observing 11th magnitude nebula with an apparent diameter of 2f. On the contrary, the 12th magnitude nebula, NGC6401, has the apparent diameter of only 0.5f. I could noticed NGC6401 as I employed the magnification of 97. If I used 68x or 78x as I did in the past, I would have overlooked NGC6401.

In snow season, light pollution from ski resorts in addition to snow light makes the sky brighter. Another disadvantage in winter is that I cannot go for the site with high altitude due to snow. I am longing for disappearance of snow.


Sunday, February 5

When I arrived at the observing site at 2:10am local time, air temperature was -2˚C. It was not very chilly. The transparency was inferior, and a shine of Scorpius that began to rise on the eastern sky looked very weak probably because of the poor transparency. Light pollution caused by ski fields around the site made the situation worse.

At the comet hunting session on Friday, Jan. 20, transparency was very bad and the moonlight boosted the light pollution. On top of that, there was a large amount of clouds and I could not concentrated on the session. On Sunday, Jan. 22, wind got stronger with time, which caused snow drifting. I was forced to stop the comet hunting session in 50 minutes. Snow drifting is a phenomenon that snow particles on the surface of the snow cover are blown and drifted by wind. I found more than 100 snow particles on the surface of the primary mirror upon taking down of my comet-seeker. Snow particles did not melt as air temperature was -6˚C. I could even blow them using a rubber bulb dust blower. Having said so, I quitted removing them because so many particles were on the mirror. I decided to leave the mirror in the mirror case to sublimate them. I have experienced such a situation once per winter more or less.


Snow drifting. Even if the sky is clear, snow particles on the snow cover are blown that causes poor visibility. 
© Copyright William Starkey@http://www.geograph.org.uk/photo/2182100

Today transparency was not good just like Friday, Jan. 20, but cloud cover was less. I began the session with theta Centauri on the southeast to avoid the light pollution originated by ski resorts in the southeast. The transparency got worse as time went that made a contrast in the FOV poor. At 4:34am NGC5728, an 11th magnitude galaxy in Libra, was in the FOV. Because of bright background the image of the object was faint that might be overlooked. However, surprisingly, the transparency improved drastically at around 4:50am local time. Scorpius that was high in the eastern sky shined vividly. I had an illusion as if I had moved to another dark site, since the change in the sky condition occurred within a few minutes.


A pair of galaxies in Libra, NGC5898 (right) and NGC5903. The image is 15f wide.
The Digitized Sky Survey copyright © 1994

After that, the DSOs that came into the FOV were NGC5834 (globular cluster), a pair of galaxies NGC5898 and 5903, 5897 (g. c.), 5986 (g.c.), 6072 (planetary nebula), M80, and M4. All of them were 11th magnitude or brighter, and I could not identified darker galaxies in Libra, i.e. 12th magnitude or darker, at all. My observing site at the snowy season is 425 m above sea level, while 960 m in none snowy season. In addition to the altitudinal difference, snow light and the light pollution of the ski fields degrade the limiting magnitude in winter.


Weekly forecast. Japan Meteorology Agency
http://www.jma.go.jp/en/week/323.html

In January and February it is lucky enough in my city if we can conduct comet hunting sessions two days per month, and in that sense it was a satisfactorily winter session today. It is expected that bad weather will last through one week from now on.


Saturday, January 7 and Sunday, January 8


Saturday
A weather forecast said clear sky at predawn, while another predicted cloudy. I believed clear sky and got out of my bed in the wee hours, but the entire sky was covered with the clouds and I could not see any stars at home. Even so, I drove to the observing site expecting starry sky at predawn.

Upon arriving at the site at 3:05a.m. local time, I saw some stars through breaks in the clouds. Under the air temperature of | 6˚C it took much time to wear my polar shoes and clothes. At 3:50a.m. I was ready to observe but I could not align Nexus DSC, because stars to align with were invisible behind the clouds. At 3:55a.m. Spica and Arcturus appeared from the breaks in the clouds and I could manage to align the DSC. There was a band shaped gap of the clouds at an altitude of 5˚ to 20˚ above the horizon between the southeast and the south and I swept the area, though 90% of the entire sky was hidden by the clouds. I identified IC4296, a 10th magnitude galaxy in the constellation of Centaurus, but the other galaxies nearby were not observed due to drifting thin clouds. In 20 minutes the area was behind the clouds, and I turned my comet-seeker some 10 degrees eastward to last the hunting session.


Interactive galaxies NGC5426 (lower galaxy) and 5427. The image is 15f wide.
The Digitized Sky Survey copyright © 1994

At 5:06a.m. an interacting galaxies in Virgo NGC5426 (mag. 12.1) and 5427 (11.4) came into the FOV. Both of them are spiral galaxies but I could not see the structure. It may be perceived when they rise higher in the sky. The amount of clouds declined with time, but it was kept more than 60% through the session. That meant when I swept the sky from the altitude of 40˚ to the horizon I could see the star less than half of the path and the rest of the sky was cloudy.

I stopped the session for a while and observed C/2015 V1 Johnson. I saw this comet for the first time. It was 11th magnitude with a tail of 2f long, which looked a typical beautiful gcometh shape. At 5:30a.m. I turned my comet-seeker at C/2016 U1 NEOWISE. The altitude was only 5˚ above the horizon. It was a 7th magnitude having a short tail of 1f. I have observed the comet on 25 November for the first time: 13th magnitude with a diameter of 2f. It got surprisingly bright since then. After observing the come I completed the 2-hour of session.

Sunday
In a sharp contrast with yesterdayfs sky, the sky was cloudless today. Having said so, transparency was poor and C/2015 V1 looked as if it had reduced the brightness by one magnitude, though the actual magnitude must be unchanged.

The light pollution from the Ski Resort in the direction of Naeba was not very conspicuous yesterday. Contrary, it was boosted by aerosols, the causative agent of poor transparency in the form of particulates, and the entire eastern sky was polluted. I started the session with M5 to avoid light polluted area, i.e. the southeast. In 10 minutes I applied the light pollution filter, IDAS LPS-P2, to improve the contrast in the FOV. The DSOs I identified were M12, M10 and M14 only. In the area I searched there are some 11th magnitude of galaxies but I could detect none of them.

After the beginning of the twilight I observed C/2016 U1 NEOWISE but the image was humble and dark in comparison with that of yesterday. Nonetheless, usually, weather in January is harsh and it is norm that there is no days that I observe in the month. I must say it was lucky that I conducted comet-hunting sessions two consecutive days.



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