10 replies to this topic

[Procyon]

Magnification, Exit Pupil and Eyepiece preference for Comets

 

Not all comets are the same, sure, but have you guys and gals found you keep turning to a specific magnification/exit pupil/eyepiece or telescope for Comets? I've always preferred a telescope for Comets but I guess binoculars work fine too. It's been a while since I've looked for a comet but last time I did, I seem to have preferred 30mm and 40mm widefield types with a 3mm-4mm Exit pupil in my f/10 SCT. 90x - 70x magnification.

 

I'm wondering if a Refractor might be the better telescope at even lower magnitudes. How do you guys prefer viewing a comet when it starts coming in? Or is it test every eyepiece on hand and leave the best one in?

 

This came to mind after seeing a telescope named: Celestron CO-62 Cometron in the classifieds. 

62mm f/4.8 with an included 25mm Kellner eyepiece. That's 12x magnification 5.2mm Exit Pupil.

 

Than again, there's the famous Explore Scientific 152mm David H. Levy Comet Hunter Maksutov-Newtonian Telescope,

152mm f/4.8 with an included 30mm eyepiece. That's 23x magnification, 6.6mm Exit Pupil.

 

Have I missed much all this time going with too strong of a magnification? 

 

https://www.bresser....lescope-4852740 <----------Always loved looking at this scope, must have never looked at the stats though, lol.

Edited by Procyon, 15 May 2025 - 07:42 PM.

[Sketcher]

Magnification, Exit Pupil and Eyepiece preference for Comets

 

Not all comets are the same, sure, but have you guys and gals found you keep turning to a specific magnification/exit pupil/eyepiece or telescope for Comets? Sure binoculars can be used, but they're...boring for the job?

Wow!  Where to begin?

 

You were dead-on with that "Not all comets are the same" sentence fragment.

 

I've been observing comets for more than 50 years.  For a period of time, I hunted comets.  Long ago I lost track of how many comets I had seen.

 

And what's with that binocular comment?  Many of the brighter comets have been best observed with binoculars.

 

For comets, the size of one's true field of view in relation to the comet's apparent size is often of greater importance than magnification and exit-pupil.

 

Back in the days of visual comet hunting, magnification, true field of view, and apparent field of view were all three of major importance.  But those days are pretty much gone.  So, I'll not waste time and space going into those details here and now.

 

For my comet observations these days, depending of course on the specific comet and its apparition at the time, I prefer using one or more of the following:

 

1) naked-eye

2) 8x42 binoculars

3) 20x80 binoculars

4) 25x100 binoculars

5) 80mm f/5 achromat refractor

6) 130mm f/6.4 apochromat refractor

7) 152mm f/6.5 achromat refractor

 

 

That's quite a range of instrumentation.  But as you noted: "Not all comets are the same".

 

In general, in my opinion, an SCT is one of the worse telescopes to choose for observing comets -- in general.  The brighter, more spectacular comets are going to be too large for the limited true fields of view -- in general.  While the telescopes mentioned above all have wider field capabilities in addition to the ability for increased magnification when it's called for.

 

So, again, in general, true field of view is more important than magnification and exit-pupil in getting better cometary views.

 

Consider Comet NEOWISE from a few years ago:

 

 

The above is one of my rough, at-the-binocular sketches of Comet NEOWISE.  At the time, from my "seriously dark" sky the comet's tails extended out (if I recall correctly) about 12 degrees behind the comet's head.  How many telescopes can accommodate visual fields that large?  I made use of my 8x42 binoculars with their 8-degree fields of view.  Even then, it took two binocular fields to accommodate the entire visual extent of that comet.  Oh, and NEOWISE was far from the largest (in visual extent) comet that I've observed over the years.  (That honor would go to Comet Hyakutake -- with a tail that stretched in the neighborhood of 90 degrees across my sky).

 

Of course, sometimes a narrow, higher magnification, true field of view is desirable -- like this close-up view of Comet Hale-Bopp's inner coma made with my 130mm f/6.4 apochromat:

 

 

For comets one ought to have access to relatively flexible, in terms of fields of view and magnifications instrumentation.  Forget about exit-pupils -- mostly.  Though I do find it generally better for me and my skies to not employ exit-pupils that get much larger than 4mm.  But that's more about me and my skies than it is about comet observation in general.

[Procyon]

Wow!  Where to begin?

 

You were dead-on with that "Not all comets are the same" sentence fragment.

 

I've been observing comets for more than 50 years.  For a period of time, I hunted comets.  Long ago I lost track of how many comets I had seen.

 

For my comet observations these days, depending of course on the specific comet and its apparition at the time, I prefer using one or more of the following:

 

1) naked-eye

2) 8x42 binoculars

3) 20x80 binoculars

4) 25x100 binoculars

5) 80mm f/5 achromat refractor

6) 130mm f/6.4 apochromat refractor

7) 152mm f/6.5 achromat refractor

 

 

That's quite a range of instrumentation.  But as you noted: "Not all comets are the same".

 

In general, in my opinion, an SCT is one of the worse telescopes to choose for observing comets -- in general.  The brighter, more spectacular comets are going to be too large for the limited true fields of view -- in general.  While the telescopes mentioned above all have wider field capabilities in addition to the ability for increased magnification when it's called for.

 

So, again, in general, true field of view is more important than magnification and exit-pupil in getting better cometary views.

 

Of course, sometimes a narrow, higher magnification, true field of view is desirable -- like this close-up view of Comet Hale-Bopp's inner coma made with my 130mm f/6.4 apochromat:

 

For comets one ought to have access to relatively flexible, in terms of fields of view and magnifications instrumentation.  Forget about exit-pupils -- mostly.  Though I do find it generally better for me and my skies to not employ exit-pupils that get much larger than 4mm.  But that's more about me and my skies than it is about comet observation in general.

Nice, nice, good to hear from someone who's been observing them for a long time. I removed my bino comment, because you're right, I went back in my notes and had forgotten my nights watching Comet Lovejoy. For example, here's a note of mine I found somewhere: I saw it (Comet Lovejoy, 2015) using my 8x42, 12x50 and 15x70 binoculars. It seems as if with the 8x42 that I got a tiny glimpse of the nuclei or coma?

 

So yeah, kind of a dumb comment the way I wrote it, I use Binos in the day quite a bit, what I really wanted to say is I prefer to observe with a telescope at night. But the binos are needed sometimes. 

 

I think I've seen 4 or 5 comets. I did originally buy a telescope (10" Dob f/4.7) in 2009 to try and find comet Lulin. I never found it lol. 

 

Some other notes I found:

 

26 January 2015 With an 8 Edge

Saw comet Lovejoy again, in a Delos 12 Like a nice cloudy faint fuzzy, with maybe a bit of green. Not sure. Maybe Greyish-Green. I immediately made out the faint fuzzy in the finderscope and than in the 31mm Aspheric, than in the 17.3mm Delos. I saw it better in the 10mm Pentax XW but it was still a faint fuzzy, as expected though. 

 

13 August 2018 With an 11" SCT
Saw Comet 21P/Giacobini-Zinner last night at 2am eastern from a Bortle 1 zone, this made my night, exactly as Havasman described it, greenish tint, could make out a long extended tail and the core. It took magnification quite well at 175x and over but looked great at 75 and 95x.

 

I do remember that night thinking I wish I had a TV 56mm Plossl with me. For lower magnification.

 

Next time one comes around, I'm taking out refractors and binoculars for sure. In other words, big TFOV, low magnification preferred, most of the time. Thanks.

Edited by Procyon, 16 May 2025 - 09:00 AM.

[Ernest_SPB]

I do not see any specifics in comet observing comparing to other deep sky objects.

Magnification/FOV selection is going from angular size, brightness of the object and background.

Moreover to discover comet, overview it, trace tail and investigate head usually required very different magnifications   

[Jon Isaacs]

I do not see any specifics in comet observing comparing to other deep sky objects.

Magnification/FOV selection is going from angular size, brightness of the object and background.

Moreover to discover comet, overview it, trace tail and investigate head usually required very different magnifications   

 

I find that comets behave quite differently than galaxies and other DSOs.  I believe this is because of they are quite diffuse and have poorly defined boundaries.  Galaxies are typically best viewed at exit pupils around 2mm but with their faint tails, it just seems like comets are best viewed at relatively low magnifications. 

 

A diffuse object without vague edges, increasing the magnification decreases the surface brightness gradient which makes the boundaries even more vague.  I find large apertures and smaller exit pupils are generally only advantages with relatively dim comets where the tail is not visible. Brighter comets are best viewed in binoculars... Comet Hyakutake, was discovered in 1996 by Yuji Hyakutake using Fujinon 25x150 binoculars.  

 

Jon

Edited by Jon Isaacs, 16 May 2025 - 07:57 AM.

[Procyon]

 

 

Oh, and NEOWISE was far from the largest (in visual extent) comet that I've observed over the years.  (That honor would go to Comet Hyakutake -- with a tail that stretched in the neighborhood of 90 degrees across my sky).

 

 

Must have been a heck of a sight! 

 

Comet Hyakutake

 

Comet Hyakutake (formally designated C/1996 B2) is a comet discovered on 31 January 1996. It was dubbed the Great Comet of 1996; its passage to within 0.1 AU (15 Gm) of the Earth on 25 March 1996 was one of the closest cometary approaches of the previous 200 years. Reaching an apparent visual magnitude of zero and spanning nearly 80°, Hyakutake appeared very bright in the night sky and was widely seen around the world. The comet temporarily upstaged the much anticipated Comet Hale–Bopp, which was approaching the inner Solar System at the time.

 

Hyakutake is a long-period comet that passed perihelion on 1 May 1996. Before its most recent passage through the Solar System, its orbital period was about 17,000 years, but the gravitational perturbation of the giant planets has increased this period to 70,000 years. 

 

Discovery

The comet was discovered on 30 January 1996, by Yuji Hyakutake, an amateur astronomer from southern Japan. He had been searching for comets for years and had moved to Kagoshima Prefecture partly for the dark skies in nearby rural areas. He was using a powerful set of binoculars with 150 mm (6 in) objective lenses to scan the skies on the night of the discovery.

 

Earth passage

Hyakutake became visible to the naked eye in early March 1996. By mid-March, the comet was still fairly unremarkable, shining at 4th magnitude with a tail about 5 degrees long. As it neared its closest approach to Earth, it rapidly became brighter, and its tail grew in length. By March 24, the comet was one of the brightest objects in the night sky, and its tail stretched 35 degrees. The comet had a notably bluish-green colour.

 

The closest approach occurred on 25 March at a distance of 0.1 AU (15 million km; 39 LD).[4] Hyakutake was moving so rapidly across the night sky that its movement could be detected against the stars in just a few minutes; it covered the diameter of a full moon (half a degree) every 30 minutes. Observers estimated its magnitude as around 0, and tail lengths of up to 80 degrees were reported. Its coma, now close to the zenith for observers at mid-northern latitudes, appeared approximately 1.5 to 2 degrees across, roughly four times the diameter of the full moon. The comet's head appeared distinctly blue-green, possibly due to emissions from diatomic carbon (C2) combined with sunlight reflected from dust grains.

 

Because Hyakutake was at its brightest for only a few days, it did not have time to permeate the public imagination in the way that Comet Hale–Bopp did the following year. Many European observers in particular did not see the comet at its peak because of unfavourable weather conditions.

 

https://www.cloudyni...kutake-in-1996/

 

https://en.wikipedia...Comet_Hyakutake

 

Edited by Procyon, 16 May 2025 - 08:26 AM.

[Sketcher]

Must have been a heck of a sight! 

 

Comet Hyakutake

It was indeed!

 

I've occasionally shared my story of Comet Hyakutake here on CloudyNights.  I was living under a pristine sky.  Forecast was for clouds on the magical best night.  So, I set no alarm upon going to bed (under a cloudy sky).

 

I just happened to wake up around 3am.  The moon had set by that time.  The outdoor temperature was minus 17 degrees F.  I got up and looked out my south-facing door and immediately saw a star-studded sky and an immensely long, bright, greenish tail that stretched from my zenith toward my south horizon.  I stepped out a bit farther in an attempt to see the comet's head, but only saw more of the tail, narrower and brighter.  I again stepped out even farther but just saw more and brighter tail.  So, I rushed to my north-facing door, looked out, and finally caught sight of the monstrous comet's head!!

 

I immediately woke up my wife and son (3am on a weekday when we had either jobs to go to or school to attend).  I instructed them to get dressed without turning on any lights.  The three of us then went outside (on snow-covered ground) and stood in awe of the majestic sight.

 

I had the forethought of taking out my 8x42 binoculars, but after a brief look realized that the naked-eye view was really the only way to take in the sight.  At times I stood facing north looking toward the comet's head.  At other times I turned my back to the comet's head in order to check out where the tail appeared to end.

 

We've seen two total solar eclipses, an all-sky rapidly changing colorful aurora display and other fantastic astronomical sights, but all three of us were in agreement that that sight of Comet Hyakutake was, for us, without any doubt, our most memorable astronomical sight.

 

My wife wrote a poem about comets, with special attention to comets Halley, Hyakutake, and Hale-Bobb.  I've often posted the part about Hyakutake:

 

Hyakutake,
You took my breath away,
And used it for a veil that stretched
Behind you and burned the
Starry sky with its cold grandeur.
Breathless then, I stood and stared
Finally, I understood
The awe the ancients felt
When they beheld a comet.

 

One of my Comet Hyakutake sketches:

 

 

. . . and two very different views (sketches) of Comet Halley.  The first was my first sighting of Comet Halley.  The second was after it had grown substantially in both brightness and apparent size:

 

 

 

Those Halley observations were made with an old 8-inch SCT that I once owned.  That last sketch shows the disadvantage of using a telescope that's unable to provide a wide enough field of view to show the full visual extent of a comet.

 

So, really, for comets, as others have mentioned, different comets, at different times, and for checking out different aspects of specific comets; different fields of view will be needed in order to get the kind of views that one might desire.  It's really not possible to specify one telescope nor one eyepiece when comets can be so different in size, brightness, etc.

 

When a comet comes along that you want to check out, just use whatever you happen to have in order to get the best views that the equipment you have can provide you with.

 

Oh, I might as well take advantage of my online time here and put in another plug for my wife (who passed away about 10 mounts ago).  Below are photos of a tapestry that she made.  She talked me into sketching things in the manner that she wanted them -- which I happily complied with.  She gets full credit for everything else!

 

 

 

Of course, as some will recognize, parts of this tapestry have been inspired / modeled after the famous (and very large) Bayou Tapestry -- with Comet NEOWISE replacing Comet Halley, among other modifications.

[Refractor6]

  I traveled to where I live now to observe Comet Neowise with my brother to take in the whole spender of it...naked eye going across a good portion of the sky under the dark skies here was unforgettable....

[PKDfan]

Comet Hyakutake is one of my top three visual experiences. I was in Vancouver and went to a dark area near Burns bog and found a very dark spot and watched it slowly move across the sky with about a 100 degree tail. Its my eternal punishment that i had no optical aid.

It was momentous in a gargantuan stature sense that resides very brightly upon recall.

Hale Bopp was brighter and weirder but Hyakutake was unforgetable.

My Bushnell Broadfield 8×40's ten degrees is tailor made for another bright comet.

Telescopically i'd have my Evolux Barlowed Zoom for 30-80X and for high resolution maybe 9Morpheuus and 100X in my F/9.

Jon is correct it depends upon coma and nucleus brightness.


Nice memory flashback.


Lance
CSS

[Procyon]

Comet Hyakutake is one of my top three visual experiences. I was in Vancouver and went to a dark area near Burns bog and found a very dark spot and watched it slowly move across the sky with about a 100 degree tail. Its my eternal punishment that i had no optical aid.

It was momentous in a gargantuan stature sense that resides very brightly upon recall.

Hale Bopp was brighter and weirder but Hyakutake was unforgetable.

My Bushnell Broadfield 8×40's ten degrees is tailor made for another bright comet.

Telescopically i'd have my Evolux Barlowed Zoom for 30-80X and for high resolution maybe 9Morpheuus and 100X in my F/9.

Jon is correct it depends upon coma and nucleus brightness.


Nice memory flashback.


Lance
CSS

Funny. A Bog huh? What were you doing there lol. Nice name to it though, Burns Bog.

10 degree binos, that's what I need : ) I've been searching for a 7x35 Sears type for some time now, perhaps the ones you mention may be even better, thanks for bringing them up Lance.

What the heck was I doing in 95-97 to have missed those nice comets. Probably crazy teenage/young adult stuff. I do remember hearing about Haley's comet in the 80's and Hale Bopp in the 90's though. First time I read about Hyakutake. That's a nice memory you have.

Edited by Procyon, 19 May 2025 - 12:41 AM.

[PKDfan]

Funny. A Bog huh? What were you doing there lol. Nice name to it though, Burns Bog.

10 degree binos, that's what I need : ) I've been searching for a 7x35 Sears type for some time now, perhaps the ones you mention may be even better, thanks for bringing them up Lance.

What the heck was I doing in 95-97 to have missed those nice comets. Probably crazy teenage/young adult stuff. I do remember hearing about Haley's comet in the 80's and Haley Bopp in the 90's though. First time I read about Hyakutake. That's a nice memory you have.

Thanks Procyon !!

The bog area is huge around a thousand acres and near fertile fields so very little LP and was my go to spot for some dark skies and only 15-20minutes to get there from Vancouver. Back then the LP wasn't as bad as now and pretty decent amount of stars for a metropolitan area.

I really really hope for another closeby bright coment now that i've got all of the equipment to penetrate their disguises.

Seeing it move and that huge tail was life changing for me and i swore to collect the optical aid to explore them in detail.

Hale-Bopp was crazy too but couldn't hold a candle to Hyakatuke.


Lance
CSS