Tuesday, December 01, 2020

checked Olaf's map

Had a quick look at Olaf Frohn's Solar System Missions blog post. He just updated it. I check on the three craft heading to Mars. And I noted Hayabusa 2 close to Earth!

checked out conjunctions

Did some checks in Stellarium... I want to get clear about an astronomical conjunction. There are two occasions or situations it seems...

Both images show the equatorial grids lines. I have Stellarium set into Equatorial Mode so that orients the grids nicely. North is up; east is left. 

Jupiter and Saturn in conjunction by RA

The objects can have the same Right Ascension (RA). You can see that Saturn and Jupiter are aligned on the RA axis. They are near the 20h 11m 5s mark. 

Jupiter and Saturn in conjunction by longitude

Next I zoomed out a bit to draw in the ecliptic line. I selected one of the planets to reveal the data. Note the ecliptic longitude: same. You can see the J2000 value for Jupiter: 300° 9' 40".

The time is around 9:00 AM Eastern on 21 Dec 2020. That matches up with the RASC Observer's Handbook.

heard of the collapse

And it's done... The Arecibo Observatory overhead structure collapsed. 

I had a feeling.

It seems the remain cables from one of the towers were strained then let go. That sent the main platform and azimuth arm hurtling down to crash through the spherical dish. 

The three towers, now no longer supporting the central load, succumbed to the lateral forces of the support cables, snapping their tops off.

third not last!

Well, well. Look at that.

Time and Date website using good terminology

I was checked the Time and Date website for the upcoming Moon phases.

I noticed their labelling for the "quarter" phases. In particular, they use "Third Quarter."

Thank the Universe! 

It's NOT last quarter. Sheesh.

Thank you.

Monday, November 30, 2020

delivered first Stellarium course

Ran the first online Stellarium introductory level 1 training course for RASC members. I think it went quite well. Class ratio was good, I was able to cover the planned content, the polls in Zoom worked, everyone seemed satisfied, and a bunch hung around after the class (for another hour!) where we explored a few more features and I answered questions. I think it's gonna work... Oh, and I converted 3 more for the level 2 course. That's 80% of the whole class! Wow.


Whoa. A ton of Stellarium intro course applications poured into my mailbox! Wha happened? 

Oh... The RASC weekly bulletin was mailed out. It contained a link.

Now I have to tell everyone the upcoming scheduled courses on full with a waiting list.

Sunday, November 29, 2020

looked up "conjunction"

Checked the definitions... Amazing wikipedia to the rescue:

While an appulse occurs when the apparent separation between two bodies is at its minimum, a conjunction occurs at the moment when the two bodies have the same right ascension or ecliptic longitude.  In general, the precise time of an appulse will be different from that of a conjunction.

There ya go.

last call

Ed thanked Tom and I for proofreading the RASC TC Secretary's report. Ralph had previously made updates in the shared PDF.

updated Lunar X calculator

Extracted the selenographic co-longitude values from the RASC Observer’s Handbook 2021 and updated my Lunar X calculator.

Phil Chow verified the events.

Lunar X table for 2021

Looks like there are 3 good opportunities for year 2021 to view or image the letter-X pattern on the Moon, near the first quarter phase.

  • Sat 20 Mar
  • Tue 18 May
  • Thu 11 Nov

All appear to start while the sky is still light with the peak of the event happening in twilight. Then:

  • 20 Jan
  • 17 Jun
  • 16 Jul
  • 13 Sep

are ops where the Moon is above the horizon for us near Toronto but the sky will be very bright and that may greatly hinder chances. July is borderline; maybe it will be good?

All other events occur when the Moon itself is out of sight.


Chris V check the Dial-a-Moon page for 2021 and reported that my March 20 prediction at ~6:38 pm EDT hits the mark!

Saturday, November 28, 2020

spotted Jupiter and Saturn (Bradford)

Popped outside. Saw Jupiter through the leaf-less trees. Couldn't see the partner. Called Rhonda out. She pulled the biscuits from the oven and joined me on the deck. Hawkeye saw Saturn and directed me. Up and left, 11 o'clock position, one pinkie finger width away. Ah. Got it. Nice. She asked about the orange dot up near zenith. Yep, that's Mars. Wow... nice night.

met with the prez

Met with the new RASC Toronto Centre president, Tom, to discuss the IT team's planned use Google Drive and my recommendation to specifically use Google Slides for the announcements presentation.

the Boston crew

Caught up with chas. Pitched him on a volunteer role. I had to try!

Sara arrived home after hockey with the boys. I congratulated her.

posted late-Nov 2020 doubles

Prepared my double star "bulletin" for Nov-Dec 2020. It is a short list of suggested targets. I will share this on the RASC Toronto Centre forums. And I post here for everyone.



The Grey Months are upon us so this may all be for naught. But if you find yourself with clear conditions over the next couple of weeks, after looking at the gas giants, then try out some easy doubles for fun. For Nov-Dec 2020.

staralso known asalternate catalogue(s)
π (pi) And29 And, H V 17SAO 54033, HIP 2912
HD 223070Σ3037 Cas (Struve)SAO 20832, HIP 117227
34 PscΣ5 (STF)SAO 91750, HIP 813
HD 3125 CetD 2SAO 128831, HIP 2713
55 EriΣ590SAO 131443, HIP 21986

An interesting quality of double stars is their resistance to creeping light pollution and moonlight. So, have a go. See if you can split them and detect colour. How different are they in brightness? And please share your discoveries.

Be seeing you.

Friday, November 27, 2020

received OH '21

Woo hoo! Received the 2021 RASC Observer's Handbook! Yes! Pleaides on the cover, nice. Interesting timing on the article on pseudoscience. I'm still reeling from that flat earth YouTube video...

made binocular and telescope views

In anticipation of the grand conjunction of Jupiter and Saturn, I fired up Stellarium and made some snaps. All for 6:00 PM from Toronto.

First, the view in binoculars, jumping one week at a time. I configured the software to use 15x70 binoculars which yield a 4½ degree field. Of course, up is up and east is left.

Saturn and Jupiter in binoculars Nov 30

Nov 30, above. Elevation or altitude above the horizon about 17°. The angular separation or distance between Jupiter and Saturn is approximately 2¼°.

Saturn and Jupiter in binoculars Dec 7

Dec 7. Capricornus has come into view. Elevation 15°. Separation: 1½°.

Saturn and Jupiter in binoculars Dec 14

Dec 14. Saturn about to exit Sagittarius. Elevation 12°. Separation: 3/4° or 45 arc-minutes. About 1 degree is is typically the domain of telescopes, a low power eyepiece can show this much sky.

Jupiter passes Saturn in binoculars Dec 21

The big day, Dec 21. Also the solstice. Elevation 9°. Separation: 6 arc-minutes! Closest they have been to one another in about 400 years.

Jupiter and Saturn in binoculars Dec 28

A week later. You can see tree-tops in this snap. Elevation 6°. Separation: almost 1°; some 50 arc-minutes.

Then in a telescope. I configured the software for an 8-inch Schmidt Cassegrain Telescope with a 26mm eyepiece with produces a magnification of 77x and a field of view diameter of about 3/4 of a degree, 40 arc-minutes to be precise. Also set as in an equatorial mount. This is a mirror-reversed or laterally-inverted view. Therefore north is up and east is right.

Saturn and Jupiter in a telescope Dec 20

Dec 20, above. Separation: 8½ arc-minutes.

Saturn and Jupiter in a telescope Dec 21

Dec 21. Closest approach. Separation: 6¼".

Saturn and Jupiter in a telescope Dec 22

And then Dec 22. Separation: 10".

You can see the moons dancing about. I did not include the labels to keep the screen uncluttered... You'll want to use some software to identify all them.

Finally, I simulated the view with a 9mm and a doubler on Dec 21. Wow.

Saturn and Jupiter at high power in a telescope

If you can put magnification on it, if the view holds up (the seeing might be poor at a low elevation), it's gonna be spectacular.

Let's hope for clear skies. This will be amazing.


The YouTube video I made on Nov 14 shows the scene wide-field, say with just your eyes.

drafted piece

Drafted my next Journal article. even though I can't figure out one part of the app...

Thursday, November 26, 2020

watched Contact again

Watch Jodie Foster's Contact tonight. There it is, 8 minutes in, the Arecibo Observatory... (sniff).

plotted planet mags

Figured out the magnitudes of all the planets for the next year, the next 13 months. It helps one compare all the big solar system objects at once. 

Added in a couple of asteroids (dwarf planets, minor planets, whatever) that dance around the brightness of Neptune.

magnitude graph for all planets in 2021

Data from SkyTools 3 Pro ephemerides. Composted in Excel.

Venus (the white line) climbs to almost -5 next fall. Looks like Jupiter (orange) opposition is around August 2021. Mars (red) is fading, fading, fading away. Look at that weird symmetrical pattern with (grey) Mercury! The green dashed line is the human vision threshold.

There ya go! Vesta (purple) climbs into naked eye range in Q1 2021. Whereas Ceres (brown) is never visible to the Mark I eyeball.

This ties back to my post "how many planets can you see?" made on 19 Nov.

I had a "it's in the handbook" moment today so I skimmed the RASC 2020 Observer's Handbook. I thought there WAS a graph like what I've done for all the planets for the whole year but I didn't see it... I was sure that was a feature. Maybe I missed it.


Found it! Page 96 of the 2020 edition...

Ah. They do not include the outer ice giants nor minor planets. Their chart goes to mag +2 and a bit.

It'll be fun to compare mine above to the 2021 RASC chart...


Check out the freaky graph by Mallama and Hilton on the Sky & Tel measuring planet magnitudes page...

Wednesday, November 25, 2020

choose EDT!

Holy Universe.

Spotted the headline from CP24:

Ontario passes legislation to make daylight time permanent

Quickly scanned the article.

All right!

All we need to do is coerce Québeckers and New Yorkers and we're good!

helped at the annual meeting

Helped at the annual general meeting for the RASC Toronto Centre, immediately following the talk. I served as Zoom host, admitted the members, and ran the Zoom polls to permit the member voting.

Hung around for the new president and chair's signing authroity meeting and made a quick on-the-fly poll.

Saved the chat content.

In a quick meeting after the meeting with Ralph and Tony, I verified the holder of the shirts...

helped at speaker night

Helped at the speakers night meeting for the RASC Toronto Centre. I served as Zoom host, admitted the backstage crew (used the doorbell again), verified the OSB links, interacted on the YouTube channel, and put questions to the lecturer Dr Daniel Seigel. Then saved all the chat content, Zoom and YouTube.

Learned from Dr Seigel that I need to update my slides. When I do a general astronomy talk, I should not say that the heavy elements (like gold) come form supernove but rather neutron star mergers.

Little anxious at the end as we ran long and I was to host the annual general meeting...

Raw video is on the channel.

refined processes

Sorted some issues with the National Observing Committee chair. Developed some improved workflows.

found another link error in the Journal

I downloaded the December 2020 edition the RASC Journal.

Looks like another great issue and I look forward to reading many of the articles. There is a big one on light pollution that looks amazing. That should be very informative.

cover of the December 2020 Journal
But I was very disappointed on reviewing my Binary Universe column article. Once again, the hyperlink to the software is not working. And this time, it's my fault! Somehow, the target link embedded in the tinyurl.com URL shortener hyperlink is broken. There's an extra space character. I don't know how this happened. I thoroughly tested the link. I was trying to avoid a repeating problem when the PDF versions of the Journal are altering the long links that I provide in the original word processor document. I was trying to avoid the problem and I made it worse!

Do not use:

Copy and paste the Google Play store link below into your browser. Please use:

Or click the hyperlink version below:

Breathe, breathe... No one died. 

In this column, I shared discoveries using Daff Moon, a rich and robust program filled with good astronomical information. I wanted precise Moon lunation age (from the New Moon phase) down to minutes and seconds. It offers much more. Also, it is an astounding application in terms of design. This is how to do it right on a mobile device. I used version 3.00 by Evgeny Fedorischenko on my Android.


James E to the rescue again! Thank you!

He said he'll personally check hyperlinks in future editions.

He told me to avoid shorteners (while confessing they exist in the Handbook).

He said he would repair the current Journal.

He said he'd have a new MailChimp issued.

Thank you very much!


A big shout-out to Kevin the founder of tinyURL.com.

He fixed the link reference!

He was being awesome.

Tuesday, November 24, 2020

built a hub page

Built a new "hub" page, gathering all the Stellarium course information together. This will make it easier for RASC members. One stop shopping. It also gives a platform for discussing future courses.

checked scripting shortcuts

A participant asked about scripts at the end of the Stellarium webinar. What they are, if I had used them, and how to stop them.

I explained they are sequences. We can make Stellarium do a series of actions automatically and I had used them in the past during astronomy presentations to automate activity in the application while I spoke over the steps. It's been a while but it was very much like programming. (I didn't say it at the time but they are like macros in spreadsheets. The Stellarium script language reminds me a bit of JavaScript.)

He correctly noted there are built in scripts, ready to go. See the Configuration menu (F2) and the Scripts tab. Quite a few actually, such as the analemma. Or triple shadow instances on Jupiter past and future (Ctrl d, then m, then 1).

I started to show my keyboard shortcut list but remembered that I had specifically not included the scripting ones.

Here they are:

  • run or start a script: Ctrl d then the assigned letter code(s)
  • pause a running script: Ctrl d then p
  • resume script execution: Ctrl d, r
  • stop a script: Ctrl d, s
  • show the script console window: F12

Note 1: For the Ctrl d keypress, do the usual process, i.e. hold Ctrl and tap d. Then, for the subsequent steps, let go of the Ctrl and tap the letters or numbers required.

Note 2: Keyboard shortcuts for starting a macro are defined by the script developer. Not all scripts have shortcuts assigned.

Maybe I should include these in my next shortcut update...

During the webinar Q&A, I also showed the built-in shortcut list in the tool, emphasising F1, the only key you need to memorise.


Scripts files or SSC files (on Windows) are in the Program Files folder, the Stellarium app folder, and the Scripts subfolder.

another article on telescope sales

Noted an article on the Kitchener CTV News web site entitled Telescope sales surge amid COVID-19 pandemic. By Stephanie Villella a staff videographer.

The KW Telescope store is shown. Cool.

Shannon Cameron said "The phone at KW Telescope has been ringing off the hook lately." She made some good points: "I think because it's a safe thing to do, it's also educational, it's fun, and you can do it in your own backyard."

listened to radio article

Heard through RASC circles of a piece on CBC. Specifically, from The Current. It's called How astronomy has provided stress relief and a sense of community during pandemic

It's a fantastic piece. The journalist was really good and the host asked good questions. I found it uplifting and inspiring. And it is confirming too...

Enjoyed Hilding's words. It's intriguing hearing yet another report that astronomy equipment is flying off the shelves. RASC is featured too—yeh.

Little Julia is so sweet!

filtered comets in Stellarium

OK. Think I figured it out...

After delivering the webinar on the basic and intermediate features of Stellarium 0.20.3, a participant asked the following question:

How do you specify comet criteria to import?

I quickly accessed the Configuration settings, Plug-ins, and the Solar System Editor and conducted an Online Search for C/2020 S3, found it, loaded it, and located it in the sky.

The questioner reiterated her query which I had jumped the gun on.

She specifically wanted to know HOW to review a list of comets with the intention to ONLY importing those that were viable, doable, given her skies, instrument, etc. I.e. maybe filter by magnitude before importing.

Oh. I had not carefully read the question.

So I headed back into the Configuration, SSE. This time I showed the Lists tab. I selected the "MPC's list of observable comets" and hit the Get button. Right. Now we had a list.

The difficulty here is that list of dozens or hundreds of comets does not show any particulars such as absolute magnitude or coma size or surface brightness or distance from Earth...

The user is in a bit of a lurch here. In Stellarium, must one select all the comets and then assess each on a case by case basis? Are some of these "observable" comets going to be magnitude 18 or 20? Why import them? Likely there will be a bunch out of range.

I shared that I'm a dyed-in-the-wool SkyTools fanatic and over there, it's easy. I gave a quick demo. Start the app, go to the Current Comets list. Update manually, if using version 3. Sort by apparent magnitude or surface brightness. Note the size column. Apply horizon and time frame constraints, as necessary, considering one's location. Select interesting (bright) targets and add 'em to an observing or imaging campaign list. Nice (although, now that I think on it, that's quite a number of steps).

So, planning tools... well, it's in their DNA to apply criteria to gauge the viability of seeing celestial targets.

Told my participant that I'd get back to them.


This question kicked off a round of research...

It made me realise or consider that part of this is the LOADING of ALL possible or potential comets into an application or tool first then applying geographic and time-of-night constraints... Of course, Greg Crinklaw's algorithms are very sophisticated taking into account atmospheric conditions, local light pollution, observer age and experience.

True absolute magnitude needs to be distilled to apparent magnitude. So that raw list from the MPC must be loaded. Then the software can calculate the apparent values...

I looked in the Stellarium manual (for version 0.20.3). The PDF with 350 plus pages. And nothing obvious. Hrmm.

I wondered what the criteria was for MPC "visible comets." Visited IAU's Minor Planet Center web page for Observable Comets. It says "This page lists links to orbital elements and ephemerides of (potentially) observable comets." Nope. I could find an explicit answer to that.

I looked in the Stellarium wiki. Nope. Nothing. Sheesh.

I checked the Stellarium Google Groups. Huh. Only 6 convos total with "comet" in the content. 

I looked in Stellarium forum on the developer side. Dog's breakfast.

Hopped into the Stargazers Lounge discussion on Software. Didn't see anything after a few quick searches.

Similar outcome in the Cloudy Nights forum on Astronomy Software & Computers.

Like earlier Google searches, most threads were how to load a comet. Nothing about filtering or analysing before importing. Or getting a short list of good candidates by magnitude criteria. Nothing about the MPC's criteria. 

I returned to CN, logged in, and created a post. I apologised if the question had already been answered. I explained the situation. I asked if the "new" Astronomical Calculations Window came into play noting I did not a lot of experience with it. I asked pointed questions:

Do you have to load all "potentially" "observable" comets into Stellarium as a starting point?

Then is there a way to know which ones are seriously attainable for your location, light pollution, instrument, etc?

After about 60 minutes, there were 30 views of my question but no replies in CN.

I pinged Chris V for ideas.

Then I fired up Stellarium (version 0.18.0), with a hunch in mind... I did the following:

  1. Loaded cometary data.
    1. Accessed the Configuration window (F2).
    2. Clicked the Plug-ins tab.
    3. Selected the Solar System Editor option. Mine is already active, loading automatically at startup so I was ready to go.
    4. Clicked the Configure button to open the SSE. The Minor Solar System objects dialogue box appeared.
    5. Clicked the Solar System tab.
    6. Clicked the Import orbital elements in MPC format... button. The Import data dialogue appeared.
    7. Ensured the Lists tab was active.
    8. In the type options, I clicked Comets.
    9. In the source section, I chose MPC's list of observable comets from the list.
    10. I clicked the Get orbital elements button. The Import data box changed to show Objects found.
    11. I clicked the Mark all button to load every one of the "observable" MPC comets into Stellarium.
    12. I closed all the config boxes.
  2. Set up for good comet viewing conditions.
    1. Set the location to a dark-ish site. I used Collingwood, Ontario.
    2. Set the date and time to early November 2020. When that somewhat bright comet flew through Orion. C/2020 M3 (ATLAS).
  3. Tried the new-ish calculator tools.
    1. Accessed the ACW (Astronomical Calculations Window).
    2. Ensured the Position tab was active.
    3. Set the object filter (at the top-right) to Solar system objects: comets.
    4. Ticked the Use horizontal coordinates check box, so to get altitude values.
    5. Used the spinner to Show objects brighter than magnitude 14. I can see to about mag 14 in my 8-inch SCT.
    6. Hit the Update positions button at the bottom.

Look at that.

Astronomical Calculations Window - Positions - showing comets

I'm impressed.

I've dabbled with the ACW but it was really good to have a specific use-case.

This makes me consider the "observable" comets in Stellarium / the MPC is like the "current" comets feature in SkyTools (who knows, might be same source). So probably brighter than magnitude 16 or 18 or something like that.

Then Chris replied. He did similar things but went into the ACW's WUT. That's the What's Up Tonight tab.

  1. I clicked the WUT tab.
  2. Clicked comets in the category list.
  3. Adjusted the magnitude limit spinner.

There you go.

Astronomical Calculations Window - What's Up - showing comets

I actually think Chris's method is better. Mostly because it works for the entire evening; the Positions tab is sensitive to the specific hour and minute.

A little thing I don't like in the WUT is that you're restricted to one category at a time... Oh well.

Anyhoo, there's the answer.

Yes, sorta. While you cannot filter comets at the import stage, you can get Stellarium to filter "potential" comets based on magnitude. Load all current comets then use the Astronomical Calculations Window to make a short list by magnitude value. 

That's pretty good.

I'll list my webinar peeps know...

cascading effect

Stumbled across a post on Cloudy Nights in the Astronomy Software & Computers forum while searching on "Stellarium comet".

user: ordep (get it?)
Vendor: Simulation Curriculum (makers of SkySafari and StarryNight)
Loc: Toronto
Posted 09 July 2020 - 03:12 PM

I contacted the Minor Planet Centre today and asked them to update the data for this comet.  Should be correct now across all astro apps that use this data.  It shows Mag +1.5 in SkySafari Plus for example (after updating).  Pedro 

Ah ha. Another reason for discrepancies for comet magnitudes when comparing one software tool to another. 

The source is found to be wrong, someone reputable reports it, the data gets fixed, but it takes a while for the update to cascaded into the tools...

I share the thread, if you're interested.

This relates to my long post on comet magnitudes back on 23 Jul.

to speak on doubles in April

The Seven Ponds Astronomy Club of Dryden, Michigan booked me to speak on double stars. They saw my "unnoticed treasurers" talk on the RASC TC YouTube channel. I'm scheduled to deliver an online presentation on 24 Apr 2021.

Whoa. There it is, on the slate! That was quick.

Seven Ponds Events for early 2021

The event page is up and running.

double stars talk page

Cool! They used my Albireo shot!

Monday, November 23, 2020

powerful and vast

Delivered my Stellarium Training Series webinar on the software basics, plus a couple of advanced features, via a Zoom meeting. about 25 attendees, RASC members from around the country. Went well, no hiccups. Good questions.

One participant sent a quick note.

Thanks for the info Blake, and the presentation.  I unfortunately had to bail just as you were getting to the questions.  I have had Stellarium for some time and frequently use it.  But, truthfully, I had no real sense of its power and the vast number of features.  So, thanks for opening my eyes and encouraging me to take my first steps down the rabbit hole....  :-)

That's pretty satisfying.

And welcome to the strange land...

clinic confirmed

Heard from Celia. She confirmed that Richmond Hill approved the RASC Toronto Centre telescope clinic for Sat, Jan 9, 2021 at 1-3 pm at Oak Ridges community centre. Assuming we're not in a big lockdown...

Sunday, November 22, 2020

learned of shipping company issue

Phil C sent out a note to RASC TC members via the forum.

The delivery of the 2021 Observers Handbook [is] quite late this year.  The good news is that all [have] now been sent out as of yesterday, Nov. 21...


Shipping company trouble...

let's look into comet C/2020 S3 (Erasmus)

OK. Let's try to get ahead of this one...

Comet C/2020 S3 (Erasmus).

I'm always been sceptical of people promoting an "amazing" or "incredible" new comet that you gotta check out now, you won't believe what's going to happen next!

Bah. Humbug. Click bait.

the crazies

I first saw a new item about this late last night/early this morning with some feed item showing up on my Android phone.

KQED urged us to check out a "Once-in-a-Lifetime Comet Is Visible Now in Pre-Dawn Sky." Please! That's a large dose of selling newspapers with a headline like that. Now the article itself seems fairly balanced. I'm being generous here. The author appears to be well-informed and did some decent research. But I wondered, did the editor write the ridiculous headline?

Some key points. Ben Burress says in the opening paragraph, you "may" be able to see the comet. From the get-go, setting expectations in a good way...

He tells us where to look and cautions the reader that it will be low and faint. Suggests using obvious Venus as a jumping point and using your hand as a measuring stick (though he forgot to say you must extend your arm). He hints, somewhat, that it might be possible to see visually. Er... I dunno about that. But then quickly recommends binoculars (but doesn't suggest stabilising them). He does give a rather fair description of how it might look in binos. "Cotton ball." I like it.

But then Ben trumpets this is a 2500 year period comet which we must rush outside to look at now 'cause it's your last chance. Here we go... That's steering into sensationalism. 

Happily the author gets back to facts including it's likely origin. Oh, look at that. Ben quotes NASA's Solar System Dynamics page. Excellent: a reporter referring to a reputable source (assuming you believe NASA). That's where the 2500 orbital period data came from. And Ben uses this to justify the once-in-a-lifetime soapboxing exclamation.

Goes on to discuss the bad harbinger aspects of comets. Then builds it up a little, the potential for a collision, to conclude with a somewhat calming, "relax." Oh boy.

Were you (my reader) worried about this comet hitting the Earth?! I wasn't. 

Am I to trust you (Ben) about near-Earth objects and whether they are going to kill us or not? Um, respectfully, I will consult the scientists.

Roller coaster. Some good stuff here but a lot of hyperbolic remarks.

Keep in mind during all this, this is a FM radio station.

serious amateurs

Items showed up in the RASC national listserv this morning including an observing report. Good, so it truly is a visible comet. 

Ron M started things off.

Near Venus in morning sky.  According to Space Weather Mag 7,? perhaps going to mag 5.?? Dec 12 perihelion.??  Very long tail.  All we need is clear skies...

(I don't know what Ron did to produce all the non-translatable characters.) It's too bad that we're in the beginning of The Grey Months in the northern hemisphere of the third rock from the Sun but it sounds like if you work at it, you might see it.

Curt N shared.

I spotted it in 15x63 binos and 8" Dob last weekend.  A few days later, after not seeing P1 NEOWISE, I had Erasumus [SIC] in the Dob and noticed a larger coma and hints of extended elongation.

An 8-inch telescope. Good stuff. More good level-setting information.

OK. Now to some hard data.

good comet sites

Off to Aerith.net by Seiichi Yoshida, specifically the current weekly comet page.

Now it is very bright as 7.6 mag (Nov. 17, Carlos Labordena).  It will approach to Sun down to 0.4 a.u. on Dec. 13, and will brighten up to 6 mag.  It will be unobservable soon.

Remember, he's in Japan. Latitude around 36° north.

A few more details... 

Discovered on September 17, 2020 by Nicolas Erasmus with the Asteroid Terrestrial-Impact Last Alert System (ATLAS) search program. Nicolas works at the South African Astronomical Observatory (SAAO) and studies near-Earth asteroids. There's the moniker attached to the comet. (I wonder why ATLAS wasn't used...)

Seiichi's finder charts show it moving quickly eastward, exiting Corvus, skirting Hydra, heading toward Libra and Scorpius. Very low for us in Ontario.

The magnitude graph shows measurements currently in the 10 to 9 range. You will need magnification or long exposures to get this, right now.

The prediction graph shows it peaking around 6. I consider 6 the magic number for borderline visibility with Mark I eyeballs. In dark sky locations free from light pollution, an experienced observer may be able to see down to magnitude 6.5. And to be very clear, that's for POINT SOURCES. Comets have bright cores but the coma and the tail, extended objects, are much fainter...

Over to Comet Chasing at Skyhound (maker of the amazing SkyTools). The comet is listed third. The quick synopsis says:

C/2020 S3 (Erasmus) has brightened rapidly.  It will reach periehlion [SIC] on December 12, when It is predicted to reach maximum brightness of magnitude 6.8.

That's below normal human vision limits.

The detailed section notes:

C/2020 S3 (Erasmus):  A morning comet visible in small telescopes. 

I always like Greg Crinklaw's rapid one-liner. What kind of gear do I need to see this comet? And how early do I have to get up?

The by-line reads: 

This comet begins the month [of November] in Sextans at magnitude 10.0.  Look for a 4' coma.  It should brighten rapidly, moving into Libra by month's end.

As of November 21, for people at a latitude of 55 degrees, S3 is "Very low in the southern sky during morning twilight at ~06:00." And for humans near 40°, "Low in the eastern sky during morning twilight at ~05:30." So that's a bit better news for astronomers at N44.

The finder chart produced by SkyTools 4 echoes what Seiichi showed.

I noted the text on the PDF file. "C/2020 S3 (Erasmus) (Comet). Magnitude: 8.66 Coma Diameter: 3.9' SBr: 20.3 Mag/arcsec² Earth Distance: 1.0 AU." That's a big coma.

Wait! Look at the surface brightness number! That's what comet fans in their easily excitable states often overlook. This is the light spread out for the comet's entire area, nucleus, coma, and tail(s). And mag 20 is super dim. Photographic target.

Remember, Crinklaw updates this page monthly.

Finally, let's visit the COBS web site. This is a relatively new tool in my kit. The great thing about the Comet Observation Database is that recent and current observations, often with measures, show up day by day.

Now, their light curve chart with visual and photographic measures is more optimistic. Recent observations are in the high 6 range with the peak cresting 4. Ah. This might mean we'll get some naked eye viewing opportunities (again, in good conditions, away from bright lights) like we enjoyed for C/2020 F3 (NEOWISE).

Comet C/2020 M3 (ATLAS), by the way, remains a bit brighter, for the moment. And is maybe a touch easier to spot, though dimming, between Orion and Taurus (thus a night-time object).

Ron M referred to Spaceweather. While not primarily a comet web page, they nevertheless showed a lovely image of this comet. See the dedicated page to enjoy a large version of the two-panel shot by Gerald Rhemann. Awesome. Look at that long tail. Note: Gerald used an ASA Astrograph 12" f/3.6 telescope with a FLI ML 16200 camera. "Exposure time: Mosaic of 2 panels LRGB 12/4/4/4 min. each." That's a big fast 'scope with a 24 minute exposure.

showing it in software

I loaded the comet data into Stellarium 0.18.0 for Windows. I emphasised the path for the next 4 weeks. Departing The Crow, running along the border between Virgo and Hydra, passing through The Scales (USA needs those right now)... The plot or trace runs from today to the solstice, Dec 21. Oh. And the green line is the horizon.

comet C/2020/S3 path for next 4 weeks from Stellarium

What do you notice? Yes, very good. It's going down! The sun diver is getting lower in the sky every day. 

That's good on one hand: closer to the Sun means brighter comet. But lower means many bad things too: closer to the Sun in a brightening pre-dawn sky, potentially dangerous to view with magnification as is draws closer to our bright star, lower in your eastern horizon to be potentially blocked by mountains, trees, churches, skyscrapers, rocks, ducks, and clouds. And if you do get a clear sightline (say, over a lake) on a cloud-free day (which won't happen until Wiarton Willie tells us), you'll be punching through a lot of air. More atmosphere, more airmasses means more dimming, aka atmospheric extinction, therefore an effective drop in magnitude or brightness.

Now a chart from SkyTools 4.0j Visual Professional. I show dates.

comet path plotted and labelled with SkyTools

So, again, a consistent path plotted. Good stuff. Good data there. With the dates showing, we can see the comet enters Libra around November 30 and is beside the Sun around December 15.

Oh, and I did see the "very long tail" in SkyTools, at least for today... (not visible in the wide-field image above).

I don't mean to dampen your spirits. Go look, carefully look, while you can, with at least binoculars, but I daresay it will become increasingly difficult in the coming days. Then impossible in mid-December.

There's this delicate balance. Comets need to be close to the Sun to show off their fancy tails and colourful comas but they need to be high enough in a dark sky for us to catch a glimpse.

official sources

You can keep tabs on alerts at the ATLAS web site.

Here is data about the comet from the MPC, the Minor Planet Center web site. The report states "N. Erasmus reports his discovery of a comet on four 30 second exposures taken on Sep 17 UT by ATLAS-MLO (T08), noting a 13" coma."

Visit the SSD web page and browse on "C/2020 S3" for more info. From an official source. Data supported by over 400 observations.

Hope this helps. Happy hunting.


Check out my July blog posts on deciphering comet names and understanding comet magnitudes.


Here's another screen snap from SkyTools. The view tomorrow morning at 5:00 AM EST.

telescope simulation of the comet

Zoomed in on the comet. The ring is the field of view for a 12" telescope with a 25mm eyepiece.

invited more RASCals

Opened up the Stellarium basic webinar to the entire RASC, issuing a notice on the listserv.