Blue Planetary

[PSALM19.1]

Hi all...had two cracker nights of seeing last week - probably some of the best ever...so I thought why not have a crack at the Blue Planetary Nebula...had my star chart and mobile observatory app and was real excited...nah, couldn't see it! I sware I was in the right spot, just to the right of the southern cross...took my time too, but it still eludes me...:sadeyes:

[raymo]

Your equipment is not shown, so what were you using to try and see it?
It is small[12" diam] and bright blue/green. When you are certain that you are in the right area you will have to increase the magnification in order to pick it out from field.
raymo

[PSALM19.1]

Thanks Raymo...using an 8" Dob with a 9mm ep...

[glend]

It can be easy to mistake it for a star.

[PSALM19.1]

A star...yeah, I was looking for more of a fuzzy blue blob, that might help next time :thumbsup:

[raymo]

Its not in the least fuzzy, its sharp and bright, but very small. A 9mm EP
will make it larger, and hence easier to spot, but will obviously give you
a smaller field of view with a correspondingly higher chance of it being
outside of that field of view. Perhaps a 12mm to 15mm would give you a
better chance of locating it, and then up the power when you find it.
raymo

[PSALM19.1]

Great, thanks guys! So when I finally zero in on it, does it look like a star or different to that?On a good night would it be worth using a 6mm ep?

[barx1963]

One of the best tools for locating planetary nebula is an OIII filter.
One like this will work very well, what you do is hold it and with an eyepiece with decent eye relief move it in front of your eye and back a few times. This is known as blinking. Normal stars will dim very noticeably, but the PN will not.
If only using for locating an inexpensive OIII filter will do. Bintel used to do a rebadged GSO one, shop around and you may still find one somewhere.

Malcolm

[PSALM19.1]

Thanks Malcolm...is that anything like the greenie filter I have that makes Eta Carinae and the Orion nebulas stand out? (That is a super helpful filter!)

[barx1963]

Maybe. Does the filter have anything written on it? Most likely would be UHC or OIII but it may be something else.

If it is not an OIII filter (BTW OIII means "O3", meaning doubly ionised oxygen. It isolated a very narrow band of light emitted by ionised oxygen which is commonly found in the light from Planetary nebula) it will not be able to be used for this blinking procedure.

Malcolm

[mental4astro]

One thing needs to added to using a filter to suss out planetaries. Most planetary nebulae are tiny. Even the Blue Planetary, though it is actually quite bright, its angular size is actually very small. This is part of the reason that it is bright is that it is so small. If it were larger in diameter, it would appear dimmer as its light would be spread out over a larger area.

Anyway, PN's are not always immediately obvious, be it for their size, brightness, location, etc. And while an OIII filter is invaluable in identifying them, unless you know what to look for, or the PN is very obvious, in most instances an OIII filter won't help. The Blue Planetary is an example where it really requires a lot of magnification to bring out its disc size. So unless you were anticipating this, you'll run right over, even with your OIII filter.

One brilliantly easy tool you can make that is fantastic to chase out PN's is a blinking paddle. This paddle holds a 1.25" OIII filter that you then flick between your eye and the eyepiece. If there is a PN in the field of view (FOV), the filter will make the PN literally "POP" out from the background. Once you've identified where the PN is, you can either put the filter in an EP or filter slide, or whatever, and further your examination of it. The Blue Planetary is one PN that really benefits from 'blinking' it out first if you are not to confident in identifying it.

In other instances, blinking out a PN is the only way to identify it from its surroundings. The giant open cluster M7 holds no less than 6 planetary nebulae within its boundaries (not all associated with the cluster, if any). But because M7 lies in within a rich area of the Milky Way, and the PN's are so tiny, blinking them out initially is the only way to isolate them. And it staggers me just how much these PN's leap out by blinking, and impossible to identify without doing so. Even large PN's benefit from blinking as they can have a low surface brightness, and blinking will just help identify their location.

For what it's worth, also within the celestial boundary of M7 are four other open clusters and at least one globular cluster, none of which are associated with M7, and all are just a line of sight coincidence.

Pluto was similarly first discovered by blinking, though for Pluto the blinking was done between two photographs, and the 'moving star' that was how Pluto was noticed.

[PSALM19.1]

Awesome info again guys! My filter is a UTC so might have to grab me an O3...little wonder I couldn't find the Blue...:(

[JoeBlow]

I'm not sure what a UTC filter is? but if it's similar to a UHC filter than there is no need for an O3. In fact if you were to have only one filter, than a UHC filter would be it. A UHC filter does everything that an O3 does but allows for a few extra wave lengths of light through, which makes it useful for a broader range of nebulas. Astronomiks makes a nice UHC filter that I like.

Once you do find the Blue planetary, don't be afraid to pump up the magnification as far as you can go. It handles magnification very well and starts to show some structure at high magnification. Also at high magnifications you are probably better off removing the filter. High magnification alone boosts contrast and a filter will probably make things too dark.

Cheers,

Joe

[bojan]

I think for NGC3918 there is no need for any filters to see it, you simply can't miss it - it looks like Uranus with it's green colour.
See here, from light poluted Melbourne and no filters:
http://www.astrobin.com/174748/

[JoeBlow]

At low magnification in a small telescope you can easily mistake it for a star. But at high magnification you can also miss it if you're not looking in the exact location.

[PSALM19.1]

See, that's why Ice in Space is so cool...and yes, typo...UHC filter! Mate, I wouldn't say "you can't miss it"...I sure did :P Will keep looking...!

[raymo]

Joe, I would agree that a UHC would be better to have than an OIII if only
having one filter, but a UHC does not do everything that an OIII does. There
are numerous nebulae that respond better to an OIII than a UHC, as a
glance at any of the published comparative lists will verify.
raymo

[Greenswale]

The Blue Planetary is one of my favourite things. As a newbie, finding it by star hopping was initially quite difficult, but with patience and a reasonable star chart it does appear.

I got onto it originally with a 6" SCT and have never used filters, so you should be able to get it, using good logic (your eyepiece image may be upside down or back to front or when compared to your star chart!), and above all, patience!

Yep, it is worth it!

[JoeBlow]

I probably worded that a bit badly.. What I mean is that a UHC passes the same lines as an O3 plus a few others. However like you said some objects, often planetary nebula, respond better to the more restrictive O3, but a good UHC will still provide a good boost to the same objects. Overall a UHC filter is more versatile, but if you can afford it get both.

[JoeBlow]

Regarding the Blue Planetary, once you find it, it's bright enough for a good look without a filter.

[raymo]

I don't think anyone mentioned using a filter for viewing 3918, its just that
Alexander pointed out that an OIII would be useful for locating it.
raymo

[JoeBlow]

True. Though it should be noted the blinking technique should also work in Shaun's UHC, so no need to buy an OIII.

[PSALM19.1]

Bojan, what scope were you using for that awesome photo?

[bojan]

I am glad you like it :)
It was Rubinar 10/1000 with Zenit MC TKA-2 tele-extender, camera was Canon 60D.

[raymo]

I hope Bojan doesn't mind, but I thought this was a great chance to
demonstrate to any newbies following this thread, just what is out there. Bojan has shown you what 3918 looks like through a long lens; This is what it looks like through an 8" Newt at f/10 and cropped and considerably enlarged.
raymo

[PSALM19.1]

Wow Raymo :eyepop: cool pic! Looks like part of our immune system (I'm a Nutritionist by qualification) :lol: now I definitely have to spot it...my scope is F6ish but same aperture...thanks mate!

[raymo]

I neglected to mention that to view it at the right size click on the
paperclip, not on the image itself.
raymo

[JoeBlow]

Nice pics, you can see similar structure visually with high magnification but at the cost of losing colour.

[PSALM19.1]

Spent a bit of time Saturday night...still no BP...maybe it doesn't like Shellharbour :sadeyes: Did, however, get to look at a fair bit of other DSO's...so was a good session...:)

[Saturnine]

Hi all
Have been following this thread with some curiosity and on the weekend, being that the skies were clear, put the 150mm refractor on the EQ6 and hunted down the Blue Planetary. Hadn't observed it for a year or two but still remembered the field stars around it, only took a few minutes to find it. A filter is really not necessary for it as it has a reasonably high surface brightness but it is small so about 100X mag, plus, is needed to help show it as a disc.
if you're still having trouble finding it and next Sat. evening is clear, come out with my fellow club members to our observing site out west of Kiama and I'd be happy to guide you to it. It is a lovely little pale blue planetary neb, can see it easily from the Gongs' northern suburbs with mag. 4 naked eye skies in the 150 mm scope.

Jeff

[PSALM19.1]

Thanks for that Jeff! Will keep that in mind...I found the Sombraro last year quicker than this...once I hit on it, I'll never forget where it is! :)