M1 Pulsar

[Alex Swartzinski]

Hello everyone, I'm happy to be a new member of this fantastic forum! There's lots of great DSO information on other websites, but having a dedicated place to discuss observations is great.

I raise the topic of M1's Pulsar. I've heard of observations in apertures ranging from 13.1" to 30". I'm trying to figure out how realistic is it to see this object in a 15" or a 16" based on your experiences.

Could seeing be a determining factor in nailing this tricky star? I've heard of observers with scopes over 20" struggling to see this object. If this truly is the case then any teen-sized scope seems questionable to make the observation. I'm thinking that seeing limitations might explain this disparity in aperture like M87's jet.

It seems like I would need an exceptional night at very high power while knowing exactly where to look if this one is possible.

What are your experiences with the crab pulsar?

[ScottH]

First of all, good to see you found your way over to hear, Alex!

In my opinion, seeing the Crab Pulsar (PSR B0531+21) is several notches more difficult than seeing the central star in M57. You see, the pulsar has an almost 2 second amplitude in which it goes from magnitude +16.6 down to...well, I'm not exactly sure. And to make matters worse, it is at least half a magnitude fainter than the foreground star just 5" to its northeast. Howard Banich had a good article on the Crab Nebula itself in the February 2019 issue of Sky & Telescope.

Here is a story for you. About 10 days ago, I used a 36-inch dob for all night (10 hours of full darkness). At the beginning of the night, the SQM-L read 21.15 near the zenith and the seeing was very good. So good, in fact, that at 970x the central star inside the Ring Nebula was visible with direct vision and the fainter star nearly due east was visible with averted vision!! I mean, the dang Ring felt like it nearly filled the field of my 110 degree AFoV eyepiece! Eight hours later, I observed the Crab Nebula. The SQM-L was reading 21.05 (moisture that I could feel and see was the culprit) and the seeing had lost a notch. At 664x, the Crab's Pulsar was visible, but it seemed not quite stellar and was only really visible as faint "something" just off the brighter and much more noticeable star with averted vision. Using the same telescope a year before, I had spent three times longer looking for the pulsar and failed.

So from my limited experience, the Crab Pulsar is harder than you might think. Possibly because it is actually "blinking" at us all the time. But I have it on my list to at least try for it in my 16-inch to see how hard the brighter (maybe +15.9?) star is to see.

Scott H.

[Alex Swartzinski]

Good timing Scott! I just saw your recent CN post about this very pulsar.

Your 36" story does not give me much hope for this object. I hadn't considered how the magnitude 16.6 nature of this object doesn't remain constant, but it is literally pulsating so that makes sense!

I don't think the likelihood of a 15" or 16" scope is very high, but if it's possible for a 16" to achieve then I think you have a good shot at it with your 36" experience. Knowing the field and what to look for really helps!

[Howard B]

Hi Alex,

Like Scott mentioned, the Crab Pulsar is a difficult target even for fairly large scopes. I've seen it in a 20-inch several times, and I agree that the seeing has to be quite steady, because you'll need high magnification to have any chance of seeing it and the star that appears next to it.

However, I don't think the rotation of the pulsar effects its visibility though. It rotates at 30 times per second, and that's something our eyes don't normally respond to. The two-second amplitude Scott mentioned was the result of a rotating shutter made by Dan Gray that rotated just a tiny bit slower than 30 times per second, and that rotation is what produced the apparent two-second amplitude from brightest to almost invisible that we saw. This was on the 90-inch Bok telescope on Kitt Peak a decade ago, so although I'm likely to never see it that well again, it was one of the most incredible things I've ever seen through a telescope.

[Norman]

Hello together,
With 12" under very good transparency and Seeing of 2 a Little condensed very weak tiny smudge appeared, Sometimes a very weak star has peaked through.
So, it appeared to me having seen sort of the "combined" light of both Stars, meanwhile the foreground Star shows itself the one or other moment. I know both Stars are Not close enough for this effect but i don't know how to describe the Observation better.

Magnification was 425x.
On occasion with very good seeing i will give it a try with around 700x on EQ platform and then i will see :-)

Damned, German Auto correction is driving me Mad ;-)
CS
Norman

[Alex Swartzinski]

Wow Howard, I can't imagine seeing a pulsar rotate! That's an experience you will never forget. What a clever way to allow our eyes to sense the rotation too...

Your observation is incredible Norman! Seeing the light from both stars and picking them out as stellar points is very impressive. 12" scopes seem to pack an incredible amount of power for how manageable they are. High power and a great night seem to be key. Have you repeated this observation before?

I wonder if this object is similar to M87's jet. Technically possible, but very tricky to do unless the seeing is perfect...

[Norman]

Hi Alex,
Up to now i did not repeat the observation but i have it on my list :-)

I only saw the foreground star shining through but i will give my best supported by EQ platform at very high Power one day :-)

CS
Norman

[ScottH]

First of all, I want to thank Howard for explaining the "2-second amplitude" he wrote about in his article. I see now that it was self created. If the "chopper" had been even slower, then the amplitude you would've seen would've been even longer.

Alright. On the night of 21st, one of the last objects I looked at with my 16-inch was the Crab Supernova Remnant. But first, I had tried to see the brighter star next to the pulsar with my 10-inch 24 hours before. At 260x and 400x, I couldn't quite see it. You might think that is odd considering it is a few tenths of a magnitude brighter than the faintest star I've seen in the 10-inch, but there isn't a lot of contrast since the glow of the Crab is BRIGHT.

Okay, back to the 16-inch. At 300x, I could see the star. I had waited until the SNR was directly overhead and my SQM-L was reading 21.5 mpsas. At 600x, things really got interesting. The "seeing" was quite good and 45% of the time, when I used averted vision to look at the star at the Crab's center, it was stellar. But another 40% of the time it was clearly not. It was an obviously elongated glow. I could see a fainter companion on one side of it but couldn't separate it. Then, much to my utter amazement, 15% of the time I would see for a few moments two distinct stars staring back at me. During those moments, I estimated the PA using nearby field stars and when I studied my image (attached), I found that I was only a few degrees off. There isn't a doubt in my mind that I split the pulsar from the brighter star because I did it at least four times. The seeing would get so sharp that those stars were just little pinpricks -- even at 600x.

I won't be offended if some people think I didn't split it. I can hardly believe myself since I've had a bear of a time doing it with a friend's 36-inch!!! But at least log it that I was able to detect it as a distinct elongation off the brighter foreground star at 600x (an APM 3.8/110) in a 16-inch dob on a tracking platform (that last part is critical, in my opinion), please. So, I'd say that Alex S. has a shot at least doing that with his 15-inch.

After my "feat", I blasted my night vision by observing nearby Mars for 10 minutes at 600x (very nice). Then I started taking it all down since I was tired and getting cold.



Scott H.

[ScottH]

Here is an image I drew up to help me find the Crab's Pulsar.

post-251696-0-55019700-1669254495_thumb.jpg