Anonymous
Unregistered
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Try as I may, I haven't been able to see Pease 1 - the planetary nebula residing in M15. Has anyone seen it? Being only 1" across does it show as anything other than stellar?
Sam
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Echo
Post Laureate
Reged: 09/29/03
Posts: 3320
Loc: So Cal
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Sam,
I have never seen it but you might want to try "blinking" with an OIII filter. Just pass the filter over the top of the eye piece and see what changes. I've done this for very faint ones and it does bring them out. Let me know what you find. I love planetaries and will have to add this to my list.
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Queen of GOTO
Life is short.... get a massage!
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Anonymous
Unregistered
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A good pic help to see Pease I,
http://voltaire.csun.edu/roland/m15.html
It's at "10 oclock, half an inch from the center on my 15 monitor.
It's really small object. Need some power and OIII filter as mention Echo. Also, but I don't know it, the orientation help, you must know it thanks to a good pic, you stop the tracking of your scope and see the direction the objects take. Spend times.
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Anonymous
Unregistered
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Tina- Thanks for the blinking idea. I usually observe planetary nebulae that don't require blinking but I think you're right this one probably does.
Diabolo- Great link! I get a much better idea of what I should be looking for. And it looks like I need to use a lot of magnification, need dark skies and a night of excellent seeing.
Sam
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Echo
Post Laureate
Reged: 09/29/03
Posts: 3320
Loc: So Cal
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Sam,
I tend to push my scope to it's limits. I've been pleasantly surprised at times so I never tell anyone not to try for things. I've found some planetary nebulae that I should not be able to see using blinking. It may be just a slight change in shape, but you'll be able to separate it from the stars if you really study it and "blink" a few times.
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Queen of GOTO
Life is short.... get a massage!
Edited by Echo (11/14/03 12:17 PM)
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12588
Loc: Cumberland, R I , USA42N71.4W
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Sam,
Think this thru for a moment.
You say this is a 1" object. It is obviously very faint, not just faint but probably around 11th or 12th mag. Also, it is an extended object.
Start with 1" resolution. To see moderately bright stars of 1" requires a scope that has a Rayleigh Limit of less than 1". So that's at minimum a 150mm. Now start putting the resrtictions on that. For an object 3-4 mag fainter than moderately bright stars it takes about 50% more aperture to see the same thing. That brings us up to a 225mm scope. But this is not just 9th or 10th mag. it is even fainter and it's not a point source it's extended. So add another 50% now we are talking about a 300mm scope. So my figures are unless you have at least a 12" scope you are not going to see a 1 arcsecond extended object.
Anybody seen it with less then 12"? less than 9?
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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Anonymous
Unregistered
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Edz,
Thanks for the reality check - I had a sinking feeling that it wasn't possible with my aperture and sky conditions but there's only one way to test ourselves and our equipment.
I have a question with regard to your resolution analysis using Rayleigh Limit. Would Rayleigh Limit be the best measured metric to use in a theoretical speculation concerning the visibility of a small (<1”), yet extended, object? The reason I ask is because I would think you wouldn’t need to achieve resolution in order to see an object. Granted if the object is in our line of sight with other objects, outside of the Rayleigh Limit of our scope, then we wouldn’t be able to discern the object as a separate entity but if it’s not “near” another object wouldn’t you still be able to observe it?
Hope I made some kind of sense.
Sam
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12588
Loc: Cumberland, R I , USA42N71.4W
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Hi Sam,
Well, your not splitting it like a double, but you still need to resolve it. And in this case it is very small, small enough that it will almost always be smaller than the resolving limits of most scopes. And resolution decreases on extended objects.
There are some papers written that go into an explanation of how large an extended object needs to be before the eyes can detect it. In some cases the size of the object (or the size that you need to magnify it to) needs to be many times the size of the resovling limits of your scope.
Acuity of the detector, the eyes, diminishes rapidly with faint light. This certainly fits the bill. Not only is it very faint, it's an extended object. But it's so small it would be seen almost as if it were a point source. So for the sake of simplicity, treat it as if it were a very faint point source.
Assume you have pretty good acuity and you can see separation in moderately bright stars (easier than extended objects) when than are magnified to an apparent separation of 180 arcseconds. For example a 3" double magnified 60x. Certain conditions will require you to magnify the object larger before you can see it. If it's fainter, if it's an extended object such as a crater on the moon or a small feature in one of Jupiter's belts. So as soon as acuity starts dropping, you need far more magnification and you need an instrument that can provide the magnification without blurring the object.
For an extended object like that your acuity may drop by several times maybe 3x or 5x. So imagine if you had to magnify that image 3 x 180 or 5 x 180. You would need a very large instrument to keep such high magnification in the optimum range of 24Dinches to 30D inches. Using Using the best case 3x180 = 540 assuming 30D, 540/30 = 22 inch instrument. Even if your instrument was the best made and you could drive magnification up to 50Dinches, which is fine for double point sources but usually not fine for extended objects, you would end up with at best 540/50 = 11 inches. But that probably wishful thinking.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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Starstuffed
super member
Reged: 10/15/03
Posts: 101
Loc: Northwest United States
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This is a tough object. I may have seen it with my 12.5 inch scope but, as EdZ has previously pointed out, it is small. . .almost stellar. This coupled with the faintness of the object has made it undiscernible from the myriad of surrounding stars of the globular cluster.
One decides what is worth the effort to spend time attempting to catch. For me, this little planetary will probably stay on my list of things not worth the effort. The only reason I would have for continuing the effort to "run it down" would be to convince myself that my 52 year old eyes are still "maximally capable."
They aren't! 
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Anonymous
Unregistered
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Edz,
Thanks for your lucid explanation. Indeed, the planetary in question, upon further research seems to be out of the reach of most all amateur telescopes - Starstuffed, don't feel too bad it's not your 52yr old eyes. I eagerly wait publication of your next article. Thanks.
Sam
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Anonymous
Unregistered
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I was fortunate to have bagged it last year (in November I think). It was not easy and required >450x while blinking with my OIII filter. I used the charts at Doug Snyder's Pease 1 observations site. Also, I was using a 17.5" scope. Good seeing is imperative, as well as being able to see at high power, for this booger. I posted my observation at his website.
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Anonymous
Unregistered
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Sam,
If you are still interested, try this link:
http://www.blackskies.com/pease_obs.htm
It is within reach of amateur scopes.
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matt
Vendor (Scopemania)
Reged: 07/28/03
Posts: 10022
Loc: Chaville, France
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OK. So it's ~25" north-east of M15's core.
But if it's almost stellar, and the only way to tell it from another star is to use an OIII filter, why did you need to push magnification du 450x?
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Matt
CI700 mount with various scopes on top.
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matt
Vendor (Scopemania)
Reged: 07/28/03
Posts: 10022
Loc: Chaville, France
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Dang! Just check out your link Charles, and one finder chart gives about 25", while another text (the one about the PN in M22) says Pease 1 is "several arcmin" away from M15's core. So who's right?
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Matt
CI700 mount with various scopes on top.
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Anonymous
Unregistered
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Quote:
But if it's almost stellar, and the only way to tell it from another star is to use an OIII filter, why did you need to push magnification du 450x?
Well Matt,
Think about it. You are looking for something that is ~1" of arc in apparent diameter in a swarm of hundreds (thousands) of stars. Higher magnification is necessary to distinguish those points. With the OIII you have to look for the "star" which appears brighter with the the filter in place...The charts on his site are very accurate. Distinguishing the asterizms was the hard part for me.
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Anonymous
Unregistered
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Quote:
Dang! Just check out your link Charles, and one finder chart gives about 25", while another text (the one about the PN in M22) says Pease 1 is "several arcmin" away from M15's core. So who's right?
Based on the charts, and what I saw, I'd say that 25" is more accurate. Several arc minutes is way off. I could not find that information you refer to though. Just use his three charts.
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