A "12 Inch Footprint"...

[ChristianR]

Minkowski 1-92, also known as Minkowski's Footprint, is a proto-planetary nebula in the constellation Cygnus. The bipolar nebula has a special shape in the form of two lobes that are formed by material emitted from the central star. It is bright but very small, means that high magnification needs to be used. It doesn't respond to filters since not an emission but a reflection nebula. Because a star spends only a few thousand years in this phase, these type of objects are rather rare.

Minkowski_92.jpg
Hubble Picture

I've observed M 1-92 using a 12 inch dobson.

My experiences with this object go from
• did not even find it,
• seen something causing me to have severe doubts about the quality of my mirror up to
• having really great fun

The key for a successful observation is the seeing and a properly collimated scope.

This August I was able to "separate" the two lobes with my 12" dobson having good seeing conditions. The observation was confirmed by a second observer.

The sketch together with more data related to the observation.
Minkowski_92_comp700.jpg
Observing Location: Sudelfeld, Bavarian Alps, Germany
Date: 08/02/2013, 1am
Conditions: SQML = 21,5 mag/arcsec*2, rel. humidity = 50%, 18 GradC, seeing good
Scope: Dobson Hofheim Instruments 300mm / F5
Power: 500x (Nagler Zoom 3mm)


My questions are:
• What are your experiences with this object?
• What is the smallest aperture to separate the two lobes?
• What aperture is needed to see the central star?

I would appreciate to read about your experiences with minko 1-92, whatever aperture used.

[Jim Chandler]

Hi Christian,

I have two log entries for M 1-92, as follows:

30" f/4.5
TeleVue Nagler Type 6 5mm, 769x
TeleVue Nagler Type 6 3.5mm, 1099x

Minkowski's Footprint. At 769x, the "toe" resolved into a lopsided diamond shape.
At 1099x, the "heel" resolved from amorphous nebulosity into a small disk.


82" f/13.7
TeleVue Panoptic 41mm, 696x
TeleVue Nagler Type 5 26mm, 1097x

Asymmetrical bi-polar pn. One part is larger and roughly diamond-shaped, the other is smaller and circular, together forming an image reminiscent of the footprint of a high-heeled shoe.


As you have noted, the two lobes can be split in a fairly small aperture. Discerning the asymmetrical nature of the lobes requires both good conditions and substantial aperture.

Jim

[Astrojensen]

I can see it in my 63mm Zeiss as a fuzzy star, using high magnifications, but that is about it. In my 12", with its poor optics, the two lobes are hinted at at 340x.


Clear skies!
Thomas, Denmark

[ChristianR]

Hi Jim, Thomas,

thanks for your feedback and notes.

The aperture range goes from 63mm up to 82" so far.
I'm pretty sure, that further log entries will be taken with apertures somewhere in between...

82" f/13,7!
Is it the Otto Struve Telescope at McDonald Observatory?
When I remember it right, Jimi Lowery mentioned, that it is possible to use this mirror visually.
Amazing.

Christian

[Uwe Glahn]

Hi Christian,

great that I could share your observation and I think it is an outstanding observation to separate the two lobes with a 12". It bring me to mind why so many observers miss the object or could not separate the knots. I was also amazed how fainter the second knot is, this is not so apparent with bigger aperture.

My experience with the separation:
With 16" and 600x I could barely separate the knots. It was not easy but obvious to see. I never tried the object in smaller aperture. (sketch with 16")

My experience to see the CS:
Since I observe with my 27" I tried several times to see the CS. The Seeing was always good. The last observation in high Alpine place (9500 ft) was successful. With an incredible Seeing of around 0,3" (meteorological calculation) I could split the CS from the brighter loop with a power of 1465x. (sketch with 27") The "second CS" was visible with direct vision and was much easier than the CS itself. Also new for me the structure within the Proto PN. The fainter lob was visible as a triangle with a parallel curvature to the brighter lob. The brighter lob shows a very bright edge and a black hole behind it. The longer brighter lob shows a diffuse end to the W end. All in all very spectacular but I believe the 27" is the minimum aperture to separate the CS. But I would also be interested if anyone else could separate the CS...Jimi?

[Jim Chandler]

82" f/13,7!
Is it the Otto Struve Telescope at McDonald Observatory?
When I remember it right, Jimi Lowery mentioned, that it is possible to use this mirror visually.
Amazing.

Yes, I was referring to the Otto Struve. One of its possible configurations is with a secondary mirror and a visual back with a 2" focuser. And, yes, it is an amazing visual scope. Those of us fortunate enough to have had access to it over the years have had some incredible views.

Jim
Christian[/QUOTE]

[reiner]

Hi Christian,

great observation of the heel of the footstep with your "little" 12". Even with my 22" I find it often very difficult to separate the two lobes.

[ChristianR]

Hi Uwe, Hi Reiner,

thanks for the feedback first of all. After some disappointing trials it was really great to see both lobes.

#Uwe
Your sketch taken with 16" and my one match pretty well, there is one faint star near the larger lobe I didn't see. The "27inch footprint" is simply marvellously.

[Atlas]

Hi Christian,

congratulations on seeing both lobes with only 12"!
I have observed Mink 1-92 several times this year. I could always perceive both lobes with my 25", but the amount of details visible depends very much on the seeing conditions. Under good conditions I could see the outlines of the object very clearly - the droplike forefoot including the toes, and the fainter heel with the knot of light in it. However I could never seperate the central star from the bright edge of the forefoot. I assume this requires excellent seeing conditions.
Uwe, obviously you have had these conditions. I know that you have been hunting for the central star for a while. Congratulations on your final success.

Johannes

[ChristianR]

Hi Johannes,

thanks for the Information. Tt seems, that with apertures above 20 inch details start to become visible within the lobes.
However, the object is interesting and fun with really different scopes.

[Jimi Lowrey]

I tried the footprint last night to see if as Uwe suggested if I could separate the central star from the brighter lobe. Both of the bipolar lobes were split and on the faint triangle shaped lobe I could see a brighting or bright bar near the center of the lobe. The seeing was average or a little below average. I used 375X up to 1627X and could not separate the star this night. Uwe's drawing is very realistic as the high power views I saw. I think it will take a night of excellent seeing to split the central star. I will try it again on a better night and report back my results.

[Don Pensack]

I viewed this in my 12.5" one night, when it was near the zenith, at 608X. At that magnification, it was viewed as a small faint oval with
and smaller, fainter, oval immediately adjacent. I did not note a central star, but did note that it was definitely a double object. No color whatsoever.
Transparency was also good--both "handles" of M76 were visible (I liken it to a two-handled beer stein). In my modest aperture, dark skies and good seeing are essential. otherwise, forget it.


[Aside: on that same night, I noted NGC1514 in Taurus looked like a pansy and had "purple tints" in the nebula. It still remains one of the very few I've ever seen a purple color in.]

[hajuem]

Hi Christian

Super Observation with 12 Inch and great sketch!!
My Observation and drawing with 16 Inch are similar to you!!
Min 1-92 700pneg.jpg
Observation Location: Edelweißspitze
Fst: 7m+

CS Hajü
www.astromerk.de