Sunday, July 21
We had no clear sky after the hunting sessions of last month. It is a matter off course because of rainy season in Japan. We cannot expect stable clear sky this month.
Concerning unconfirmed comet discovery on April 19 JST this year, the situation has progressed thanks to Vladimir Bezugly (a discoverer of C/2021 E2), Ukraine. The article was posted “Unconfirmed comet: Part 2 Sequel” page. Please have a look at. I appreciate his great effort.
Sunday, June 16,
I conducted comet hunting sessions twice this month. The first one, on Saturday, June 1, I dared to sweep the sky near the moon past waning phase, and did not identify any comet like object. The next session, on Tuesday, June 4, seven galaxies past through the field of view. Among them, NGC63 was the most impressive. From my memory I have never identified any NGC objects with double digits.
I cleaned mirrors today in two years, because dust on the primary mirror stood out. “The Dobsonian Telescope” (1997 David Kriege, Richrd Berry, Willmann-Bell) reads the reason for mirror cleaning is not to remove dust but to harmful pollutants to the mirror coatings like acidic contaminants. A small amount of dust on the mirror little affects the visibility of the telescope. The book reads over cleaning deteriorates mirror coatings. However, one wants to clean the mirror that stands out the dust.
The book includes Section 11.4 Cleaning the Optics, which explains how to clean the optics with the telescope assembled. I used to clean the optics using the method. It is true that the method is simple because one need not to recollimate the secondary mirror. However, the azimuth encoder should be removed and it is a hassle and physically hard to crawl between truss tubes.
Washing out dust on the primary mirror using tap water in the bathroom.
Washing the surface of the primary mirror using dish detergent dissolved in water and sterile cotton.
For the reasons, at least the primary mirror was brought into the bathroom and washed. On top of that, I concerned trouble of the dew removal heater installed on the flip side of the secondary mirror due to water. Considering those, both primary and secondary mirrors were removed to clean.
The Dobsonian Telescope states to use distilled water throughout the process, but I use tap water except for the last rinse after using the detergent. Firstly, I remove dust on the mirror by pouring over tap water. Secondary, dish detergent dissolved tap water is poured on the mirror. Using the sterile cotton wads, wash the surface with a circular motion from the center to the outer part of the mirror without pressure.
The book describes to dissolve one drop of the detergent for one quart of water, because two drops or more of detergent makes it difficult to remove soap film from the mirror. After washing with the detergent and the cotton, I rinse off the detergent components with tap water, and finally, the mirror is rinsed using distilled water (purified water) to avoid water droplet marks.
The secondary mirror cell was disassembled and the mirror was removed. The dew removal heater was installed on the flip side of the mirror.
It is quite troublesome to remove the secondary mirror from the cell, however, it is secure to do so to avoid getting the heater wet. The collimation shifts largely with disassembling and reassembling the cell. It is desirable to collimate the secondary mirror by setting up the telescope before the next observation. I collimated the optics today during daytime, and it was difficult to recognize the ray of the laser collimator. However, it avoids to consume extra time for the collimation in the dark at the next observation.
This year, the start of the rainy season delayed, but finally, it will come on the next week. From the next session, I will observe with fresh mind using the clean mirrors.
Tuesday, May 28
I gave a poster presentation on Unconfirmed Comet on April 18 UT, 2024, at the 52nd Annual Comet Conference at NAOJ, Tokyo, held on May 18 and 19, 2024 (participated online). I had been busy for preparing the presentation and I took a break “From Diary” last month.
I conducted comet hunting sessions six times this month. The first one was on May 4. It was foggy at the time of the arrival at the site. I waited for the recovery in my car, and there appeared breaks of clouds after 20 minutes. I set up my telescope and was waiting for the clear sky until 10 minutes after the beginning of the twilight for a half and one hour in total. As the result, it had been cloudy and I broke down the telescope and got back to home. On Wednesday May 15, the forecast was clear sky, however, I did not go comet hunting because it was overcast at home when I looked at the sky. I identified a smaller number of deep sky objects in each night during the hunting session. I overlooked some brighter objects while spotted darker ones, although it is true that the area I swept includes many darker galaxies in many cases. I think one of the reasons is that heterogenous distribution of air glow. Tsutomu Seki wrote in his book that psychological factors at the time is the cause. It is difficult to know how those factors affect observations. All I can say is effort × luck.
Below I describe those six hunting sessions.
Thursday, May 9
Night Vision (NV) was used. I started to sweep from M2. At an altitude of 18º, I identified 10th magnitude galaxy, NGC7606. It was the only galaxy I spotted during the session.
Friday, May 10
I used NV because transparency was poor like the previous night. I began with M15. The air temperature rose from 8ºC to 10ºC during the session. Mars passed through the field of view, but no comet-like object was identified.
Saturday, May 11
I started to sweep from NGC7331 using NV. It was easy to spot Stephan's Quintet located near this galaxy. I identified NGC404, Mirach’s Ghost, followed by NGC7426 that rose as high as 33º with the magnitude of 13.5. After 30 minutes of the start of the twilight, M32, 31 and M110 entered the field of view. Thanks to the power of NV, dark lane of M31 was clearly seen.
PGC68743. The image is 60’ wide.
The Digitized Sky Survey copyright © 1994
Tuesday, May 14
I began to sweep the sky from α Aquarii using a glass eyepiece 78x, as the transparency was good. The only galaxy I spotted the night was PGC68743 with the magnitude of 13.8 (the altitude was 18º). As shown in the DSS image, the galaxy is well concentrated and it made the object easy to identify. However, there are brighter galaxies in the area I swept and it is very strange I did not spot those galaxies.
Friday, May 17
NV was used as transparency was poor. The session was started fromα Pegasi. NGC7332, a 11th magnitude galaxy, and NGC7339, a 12th one, were identified in the same field of view.
Monday, May 20
I trained my telescope at Saturn and started comet hunting. At an altitude of 18º, 13th magnitude galaxy, NGC7537, and 11th one, NGC7341, were observed.
Sunday, March 17
Among 3 times of comet hunting sessions this month, I reflect sessions on Sunday, March 10 and Friday, March 15.
Sunday, March 10
It was very cold due to wind with air temperature of -4ºC. The transparency was poor because of cedar pollen, which is common in this season in Japan. Under such bad condition, Night Vision (NV) is a powerful tool. Before the start of the comet hunting session, I observed C/2021 S3 PanSTARRS. The appearance of the comet was almost the same using a glass eyepiece and NV, because the altitude of the comet was rather high, 32º above the horizon. If the comet was at lower altitude, it is presumed the visibility of NV is better.
I began searching from an open cluster in the constellation of Scutum, M11 at 4:17am local time using NV. After 10 minutes, at 4:27am I identified a planetary nebula in Sagittarius, NGC6818. The nebula is bright with the magnitude of 9.3, but the apparent diameter of only some 20”. I did not recall ever identifying this object during the session. I noticed the nebula with the magnification of only 37x, thanks to producing sharp pinpoint image even with poor seeing. Looking at SkySafari 7 Pro, there is an irregular galaxy, NGC6822, also known as Bernard Galaxy 40’ south-southeast of the galaxy. I have identified this galaxy several times during the hunting session. This time, I could not recognize the galaxy, because the altitude was only 10º with poor transparency and using NV that is difficult to observe extremely faint objects.
The next deep sky object came into the field of view was an open cluster in Aquila, NGC6749 with the magnitude of 12.4. Although the altitude was as high as 33º, the object was rather challenging to detect eve with NV. I wondered if I have ever identified it during the searching session. After identifying two bright globular clusters, NGC6740 in Aquila and M74 in Aquarius, I completed the session.
Friday, March 15
Temperature was 1ºC with light wind, and much warmer than on Sunday. I started the comet hunting session from M22, a globular cluster in Sagittarius. After Omega nebula, M17, and a globular cluster, NGC6517, came into the field of view, a nebula like object appeared in the field. The object was not shown on SkySafari 7 Pro. An open cluster, NGC6604 was in the same field of view. I remember that I had ever identified the object, which is H II region, and is not visible using a glass eyepiece. However, I did not want to rely on ambiguous memory without solid confirmation. I turned pages of Uranometria 2000, a printed sky atlas, and found Sh 2-54 (Sharpless 2-54) was at the position with the size of as large as 1.5ºx2º. I used Aladin Sky Atlas on line, and I found the same shape of nebula on the display as that in the field of view of the telescope to confirm the object. At home, I looked into the nebula, and it is named as Simeis 3-123.
Sh 2-54 is a large nebula. The round shaped nebula at upper center is Simeis 3-123, while open cluster at lower center is NGC6604. The image is 1º wide.
The Digitized Sky Survey copyright © 1994
Sh 2-54 and NGC6604 are shown in Uranometria 2000, but Simeis 3-123 is not.
Sometimes, it is time consuming to identify object when I use NV, because I can see some objects with NV that are not visible using a glass eyepiece. However, from the opposite point of view, it is enjoyable I can observe invisible objects using conventional glass eyepiece, like NGC6334, Cat’s Paw Nebula, easily using NV.
Tuesday, February 27
I comet searched four times this month. I pick up impressive observation out of them.
Thursday, February 8
Moonless night with air temperature of －2ºC. It was very cold when the wind blew. The Milky Way rising above the eastern horizon was bright enough to take it for clouds.
I observed 62P Tsuchinshan 1 prior to the comet hunting session. I estimated the comet as the magnitude of 9th, the diameter of 5’, the degree of concentration (DC) = 4, and the tail length of 5’ using a glass eyepiece, 78x, while the comet looked mag. 11th, dia. 4’, DC = 3, tail length 2’ using Night Vision (NV). It was reconfirmed that this comet is exception of my empirical rule that short-periodic comets look brighter with NV. C/2021 S3 PanSTARRS was observed as follows: mag. 10th, dia. 2’, DC = 5, tail length 2’ using glass eyepiece, while mag. 9th, dia. 2’, DC = 7, tail length 2’ using NV. Regarding this comet, NV had a better visibility in comparison with the glass eyepiece.
The southeastern sky at the end of the hunting session. A comet at the center slightly right is C/2021 S3 PanSTARRS. SkySafari 7 Pro.
Moon rose up to 1º above the southeastern horizon at 6:00 local time.
SkySafari 7 Pro.
I searched the sky using the glass eyepiece with 78x. I started to sweep the sky from M10, a globular cluster in the constellation of Ophiuchus at 4:44am local time, and ended at 6am when M11, an open cluster in Scutum, entered the field of view (FOV). When I finished the session, I was impressed by a beautiful scenery: a thin moon and Venus shinning in the low southeastern sky.
Monday, February 13
Moonless night with good transparency. The air was warm with the temperature of 1ºC. I could spot M13 rose as high as 55º above the horizon with naked eyes in direct vision. Before starting the comet hunting session, I observed Omega Centauri. The cluster looked bright and powerful using NV as usual, but tonight it was fine and beautiful using the glass eyepiece.
I began sweeping the sky fromπ Scorpii using the glass eyepiece with 78x. I identified 18 globular clusters in total including M4, M 80, and NGC6144, and several open clusters. During the session, C/2021 S3 PanSTRRS came into the FOV. M9 was seen in the same FOV. Rising to the altitude of 27º, the comet had a fine tail. I estimated it as 9th mag. dia. 6’, and the tail length of 6’.
Saturday, February 17
Moonless night, air temperature of 0ºC with light breeze. I enjoyed observing C/2023 A3 Tsuchinshan-ATLAS before starting the comet hunting session. The comet was well concentrated and easy to observe. The magnitude was 13th with the diameter of 0.5’, and DC = 3. I am looking forward to seeing what the appearance will be in the future.
I tried observing the antennae of the Antennae Galaxies using NV, but it was unsuccessful. It is said that the 60 cm telescope is required to observe.
I began to searching from C/2021 S3 PanSTARRS located near the center of the Milky Way using the glass eyepiece 97x. The summer showpieces, M8, M20, M22, M16 and M17 came into the FOV, which are scattered in gorgeous and countless stars, i.e. Large Sagittarius Star Cloud. The three parts of the Trifid Nebula, M20, was clearly seen in spite of the low altitude of only 14º above the horizon.
M23. The image is 1º wide.
The Digitized Sky Survey copyright © 1994
Usually, less impressive star cluster, M23, popped into the FOV with stars shining powerfully like fireworks today!
As seeing was rather good, I could enjoy clear star image without swelling regardless of the magnification of 97x. It was a comfortable session.
Monday, January 22
I have comet hunted 5 times this year. I described some impressive observations among them.
Friday, January 5
I searched under the moonlight; the moon had just passed the last quarter. I noticed Venus rose above the horizon at 4:37am local time. The altitude was only 0.4º that meant the observation site has a good visibility to a very low altitude.
I started comet hunting using Night Vision (NV) 37x from α Librae. The first deep sky object I identified was NGC5634, a globular cluster in the constellation of Virgo, and the second was NGC5812, a galaxy in Libera. When I confirmed the galaxy with a digital map, SkySafari 7 Pro, it displayed a comet in the same field of view (FOV). The comet turned out to be C/2023 A3 Tsuchinshan-ATLAS! The comet is expected to become a great comet in this fall. Even though it was under the moonlight, I thought I could confirm the comet visually, because I knew Alan Hale, a discoverer of C/1995 O1 Hale-Bopp, succeeded to observe it visually using a 41 cm reflector on December 18, 2023, via comets-ml: https://groups.io/g/comets-ml . I increased the gain of NV and I was sure to see the comet. It was 14th magnitude with an apparent diameter of 0.2’ that looked like a planetary nebula. I changed the eyepiece to the glass one, i.e. Ethos 17 mm, and the image was the same as that of NV. I lasted the searching session hoping that the comet would become great.
SkySafari 7 Pro displayed that C/2023 A3 Tsuchinshan-ATLS and NGC5812 were in the same field of view. The circle represents the field of 1.1º.
Thursday, January 11
As always, I enjoyed observing some objects prior to the comet searching session. I thought I would enjoy because both transparency and seeing were rather good.
I could spot C/2021 S3 PanSTARRS that was condensed easily at 4:41am, although the comet was only 4º above the horizon. I felt it was firmly discoverable during a hunting session. On the contrary, the comet was difficult to observe using Ethos 21 mm 97x, as it was diffused, and it was challenging to spot it during sweeping. The comet looked 11th magnitude through both eyepieces, but there was significant difference in visibility between the two.
Omega Centauri, a globular cluster that is the most beautiful in the sky, rose as high as 6º in altitude. When I observe M13, the most beautiful globular cluster in the northern hemisphere, I feel use of a glass eyepiece is better than that of NV. The glass one allows a greater number of stars visible in the cluster. In contrast, NV is always better for ω Centauri. This time, ω Centauri looked dynamic with Ethos 21 mm, 97x. However, using NV the cluster looked brighter and all the stars, which must have consisted of hundreds, were on and off due to scintillation! I have ever observed this object many times, but it appeared the most impressive this time.
I spotted a couple of wonderful double stars during the session. One was β Scorpii and another wasνScorpii. Those companions looked green and light blue, respectively, and impressive. One can enjoy double stars only when glass eyepieces were applied, because NV cannot reveal the color of stars.
Tuesday, January 16
I used NV as it was hazy at low altitude. I began to search from C2021 S3 PanSTARRS located at the constellation of Lupus. Between the comet and the globular cluster M4 in Scorpius, there is no particular bright deep sky objects except for NGC5897, a globular cluster in Libra. Contrary, there are numerous globular clusters beyond M4, i.e. the east at the horizontal coordinates. I encountered one of those globular clusters named 1636-283 (ESO 452-SC11) for the first time. The visual magnitude in SkySafari 7 Pro is 12.0. The appearance using NV was a globular cluster without doubt and I felt the magnitude indicated in SkySafari was appropriate. Nonetheless, in the photo of DSS the object does not look like a globular cluster, and there is no description in Guide 9. A scientific paper on the cluster said, “one of the faintest and least studied stellar clusters of the Milky Way” https://doi.org/10.1093/mnras/stx2174 .
Most globular clusters around the region beautifully resolve into stars using NV. Among them I always feel M19 wonderful. Stars with pinpoint image appeared tightly packed in spite of the low altitude of only 11º.
ESO 452-SC11. The image is 15’ in width.
The Digitized Sky Survey copyright © 1994
Both the glass eyepiece and NV have their features, and I can enjoy observing each of them. I must say it is hard to decide which is better on the potential of the comet discovery.