Planetary Nebula Kohoutek 1-16

[iansmith]

This is my image of K1-16, a planetary nebula in the constellation of Draco, between 5200 to 7000 light years away. I have yet to come across much information about the PNe itself, other than its size which is put at between 1.6’ to 2’ across. It lies in front of a very distant galaxy cluster and to the south (left in my image) there is a bright 14^th mag quasar, HB89 1821+643 which is part of the cluster. The quasar is 3.3 billion light years away but almost as bright as the central star of K1-16 which puts the power of quasars into perspective.

The central star is DS Dra and judging by the number of professional papers it is of great interest to professional astronomers. It is classed as a PG1159 variable star, one of 20 such stars and only one of 7 which are the central star of PNe. These types of stars exhibit a small amount of variability (~±0.01 magnitudes) which comes and goes.

It’s also hydrogen deficient and carbon rich, showing the same kind of spectra as WR stars. WR stars are normally very heavy, but as the central star of a PNe (CSPN), DS Dra must have been below 8 solar masses to start with, which is much lighter than most WR stars. It is thought to have just finished it’s AGB phase and is now transitioning to a white dwarf. There is a suggestion that it underwent a late Helium flash which dredged up and expelled a load of Carbon into the surrounding environment. The current mass is reckoned to be about 0.65 solar, with a surface temperature of 140,000K. This high surface temperature probably explains the high terminal velocity of the winds blown off this star. They have been measured at about 3800km/s. The mass loss rate is now fairly low, estimated at ~10^-8 solar/year. This fits in with the expected behaviour of a post AGB star.

My image was taken between July and September of 2019 using an Edge HD11 at prime focus and a QSI6120 camera, binned 3x3, mounted on a Mesu 200.

NB: 42x600s in Hα, OIII, NII blended as: NII, Hα and OIII for red, green and blue respectively and then spent ages messing about with saturation, hues, etc to try and get a pleasing colour image.

BB: 15x120s in red, green and blue.

The stars were removed from the NB images and the PNe was removed from the RGB images. These two images were processed separately before being combined to create the final picture.

I would welcome any comments or criticisms, especially on how to improve.

Cheers, Ian

[MartinB]

Crikey Ian, you've really pushed the envelope with this one, it is tiny even at this long focal length.  Well done indeed.  I like the colour and the NII shows very nicely.  It inevitably shows some atmosphere induced fuzziness which must be unavoidable really.  The only think that could tighten that up would be adaptive optics I think, but then you would have to find a bright guide star.  Thank you for sharing, it is completely new to me.

[DaveS]

That's a cracking image Ian, huge amount of data, and an absolutely tiney PN. Just seen how many nights of imaging this has taken, a real marathon effort.

 

Interesting to see someone else using [NII] in their imaging. Have you tried it with other PNs, or even other emission nebulae? I found quite a lot in the Rosette Nebula.

[iansmith]

On 12/11/2019 at 12:33, MartinB said:

Crikey Ian, you've really pushed the envelope with this one, it is tiny even at this long focal length.  Well done indeed.  I like the colour and the NII shows very nicely.  It inevitably shows some atmosphere induced fuzziness which must be unavoidable really.  The only think that could tighten that up would be adaptive optics I think, but then you would have to find a bright guide star.  Thank you for sharing, it is completely new to me.

Thanks MartinB. I have thought about adaptive optics, but as you say I’d need to find a bright guide star for it to work on. I have been wondering about if it could work, looking at a star from a larger field of view. In other words, could it work if I had a separate guide scope that was looking in the same direction, but was viewing a square degree of sky and then adjusted based on that. Will have to think more on that. 

Cheers, Ian

[iansmith]

On 12/11/2019 at 12:51, DaveS said:

That's a cracking image Ian, huge amount of data, and an absolutely tiney PN. Just seen how many nights of imaging this has taken, a real marathon effort.

 

Interesting to see someone else using [NII] in their imaging. Have you tried it with other PNs, or even other emission nebulae? I found quite a lot in the Rosette Nebula.

Thanks DaveS.

I like to go deep with these objects to see if there is anything interesting surrounding the PN such as a faint halo or some such.

I have so far only tried N2 on this and NGC 6058, which you can also find in my astrobin page. I’ve not had it very long and with the poor weather we’ve been having I haven’t had much chance to use it. Currently imaging NGC 40 with it, but not enough data yet to present it. 
 

Cheers, Ian

[MartinB]

10 hours ago, iansmith said:

Thanks MartinB. I have thought about adaptive optics, but as you say I’d need to find a bright guide star for it to work on. I have been wondering about if it could work, looking at a star from a larger field of view. In other words, could it work if I had a separate guide scope that was looking in the same direction, but was viewing a square degree of sky and then adjusted based on that. Will have to think more on that. 

Cheers, Ian

I don't think it will work Ian because there would be no movement of the guide star in response to the AO correction.  In fact you wouldn't be able to calibrate the AO.

[iansmith]

10 hours ago, MartinB said:

I don't think it will work Ian because there would be no movement of the guide star in response to the AO correction.  In fact you wouldn't be able to calibrate the AO.

Thanks for the info MartinB.
 

I doubt I will pursue this idea much further. For me there are other issues as well. For example, one reason for using ONAG was to avoid having to fiddle around finding a suitable guide star which I would have to do with an OAG. 

Having said that, does anyone have some real world performance figures with it? My current system gives me ~0.4” to ~0.7” rms  with ~0.7” to ~1.3” peak to peak (depend on seeing conditions). Would an AO unit improve on that? If there was a chance of significant improvement then I would be willing to reconsider an OAG. 

Cheers, Ian. 

[x6gas]

Well Ian that's very nice indeed.  I do love these PNs that look like Star Trek 'energy we've never seen before'.

Is that 7 hours per channel on the narrowband or 7 hours in total?

Anyway, lovely image, thanks for sharing.

[iansmith]

6 hours ago, x6gas said:

Well Ian that's very nice indeed.  I do love these PNs that look like Star Trek 'energy we've never seen before'.

Is that 7 hours per channel on the narrowband or 7 hours in total?

Anyway, lovely image, thanks for sharing.

Thanks x6gas. It’s 7 hours per narrow band channel, so 22.5 hours in total. 
 

Cheers, Ian.