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Just another observation of M109

Dob Observing Report
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#1 azarquiel.2001

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Posted 12 August 2022 - 05:50 PM

A new object report from summer nights. If you prefer to read it in PDF format with the support of some images that helps me to explain better myself you can check it in the web:

 

https://theferretofc...essier-catalog/

 

Please take into account those images are pictures not sketches. As you can read in my web they have been gathered from public databases, mainly from telescopes in Palomar Mountain, HST and Calar Alto (Spain). What I have tried (quite successfully, I think) is to reflect how the object shifts with the change of eyepieces. The images can become a composite of several to show a better result. Also I have added a fixed rectangle to show the effect of the apparent field of the eyepiece. I play a little bit with the brightness and contrast to show how your eyepiece field is darker at lower eye pupil, but you lose details in the object. I mean, if you try to find exactly the same picture in the web you are going to fail. It takes a couple of hours (sometimes more) to generate all the pictures to get the better result, plus an extra hour to write down my voice-notes.

 

Nagler 31mm (70x - 1º 10’ - 6.6mm). A small spiral galaxy in a poor star field so it stands out clearly. The galaxy is less than one tenth the size of the eyepiece, so at this magnification, it is quite small in apparent size. What I see is a typical spiral galaxy with a bright nucleus. It does not appear to be fully facing the Earth but slightly tilted, about thirty degrees. Near the nucleus I begin to see a complex structure, like a kind of swirl in the nucleus that may be a reflection of its arms. The arm structure looks to me like a kind of elongated S, but very elongated, typical of barred spiral galaxies, however the magnifications are still low to get good details of the galaxy. Nevertheless at these magnifications I can see few details, just the nucleus stands out as very bright, its oval galaxy shape and inclined view.

 

image.png.cf0438cf3cfbc7d3e5a87508b05bc6

 

Nagler 22mm (98x - 50’ - 4.7mm).  With this eyepiece I get a very beautiful view of the galaxy. I am amazed by the row of stars on which the galaxy seems to be resting, even one of them is very close to the nucleus of the galaxy which makes the whole especially beautiful. I can clearly see a point source of light surrounded by the bright nebulosity of the background galaxy and the nucleus, also very bright, right next to it. This image alone is worth adding more magnification to the telescope. Also now the structure of the arms is more evident, although I still find it difficult to define it properly. I mention in my voice notes: ‘arms look like to rotate on themselves in that kind of whirlpool, but I appreciate it with great difficulty’. The nucleus also does not seem punctual but elongated, typical of barred galaxies. It is tremendously bright compared to the rest of the galaxy. In addition, between the nucleus and the zone of the arms I can see a darker region that gives it more beauty but makes it more complex and difficult to describe. They are a kind of dark patches on the sides of the nucleus, or as a drop in brightness to the right and left of the nucleus. Those patches are more evidences when you see the increase again in brightness by the existence of the arm of the galaxy. These dark patches do not surround the nucleus but are only on the two sides of the nucleus.

 

image.png.e856fcda87031640ad1b7503327262

 

Delos 14mm (154x - 28’ - 3mm). This eyepiece narrows my field a lot but the resolution I observe is very good. First you can see some more stars of our own galaxy, fainter that is within the galaxy itself and that highlights its beauty. The contrast between the nucleus and the area of the arms is spectacular and keeps you with your eyes fixed on the object trying to get more details of that intricate shape that resists me. I perfectly observe the barred shape of the nucleus and the two dark areas on the sides of this bar, the most complicated thing is to identify where the arms of the galaxy end and where they begin and if they are one or more. I get the impression that there is a single arm on both sides of the central bar. One that starts in the right zone and turns around the south of the galaxy passing through the line of stars of our galaxy and ending almost perpendicular to the core bar. And another arm that starts in the left zone of the nucleus and turns north to end at 15 o'clock.

 

 image.png.6f957b4ae09567a30686af512325d8

 

Ethos 10mm (216x - 27’ - 2.1mm). With the 100º apparent field from the Ethos I again enjoy a much wider view of the galaxy and the black background. It becomes more evident the spiral shape of the galaxy and the vision of some arms in the outermost and faintest part of the galaxy, however I can not identify any new detail, but it is a beautiful view. The row of stars in our galaxy, the very bright nucleus, the barred zone that extends the central part of the nucleus, the arms that show beyond this dark zone. It is a real marvel to observe this galaxy in peace and quiet.

 

image.png.7aa22e790d816ea18ce2bac58a3255

 

Ethos 8mm (270x -  22’ - 1.7mm). This is the best view I get on the details of the galaxy. First I am very struck by the area near the nucleus. The spiral arms arise, not from the nucleus itself, but from a darker area that I define as a band of dust that ‘surrounds’ (it is rather to the right and left but it is difficult to determine its limit) the halo of the nucleus. It is from this not very bright area that a pair of arms emerge and wrap around the galaxy giving it that beautiful swirling shape. To try to explain it a little better, looking at the galaxy from the outside to the inside I see in its southern zone, the first dimly bright arm, then a slightly less bright area that shows that it is an arm and then three stars of our galaxy forming a line on which M109 rests. It follows a slightly darker zone and then again a not very bright zone, to, suddenly, fall in brightness (this is the dark zone or the band of dust that surrounds the nucleus), and above it, a very bright halo containing the elongated nucleus of the barred galaxies. I don't know if I have been able to explain it well, but the galaxy is not very wide because it is tilted with respect to us and everything is compressed. Anyway, a very beautiful view at good magnification and with a good sky. A delightful pleasure. Sincerely the best view of the galaxy.

 

image.png.a4189c4c307e3a741bfce8b12d8adf

 

Delos 4.5mm (480x - 9’ - 1mm). I can't see the galaxy clearly, I think that the fatigue of the day has taken its toll on me, a pity, and I can't focus properly. I have also lost a lot of brightness and I have lost the area of the arms, seeing practically only the nucleus of the galaxy, now clearly elongated (barred galaxy). If anything I see some remains of these arms as arcs surrounding the galaxy. Too bad I am tired from this day of observation.

 

image.png.bd75c70e4dbe0368affd97abcfff2d

 

Clear and dark skies, Israel


  • Bob Campbell, Illinois, ifly and 3 others like this

#2 Astro-Master

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Posted 13 August 2022 - 01:14 AM

I think your last statement using the Delos 4.5mm about not seeing the galaxy clearly, and I can't focus properly have more to do with too much power for the seeing conditions. than fatigue, IMHO.

 

Going from 270x to 480x is a big jump in power, if you have a good 2x barlow you might try it on the 14 Delos for a power of 309x and a 1.48mm exit pupil.

 

On my 18" Dob, I like to use exit pupils between 1.7mm (270x) to 1.29mm (354x) on the larger galaxies for observing fine details if the seeing conditions will allow.  Powers of 400x to 500x or more on most nights is best used on the small 15th and 16th mag. galaxy clusters that look like faint fuzzy stars.


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#3 azarquiel.2001

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Posted 13 August 2022 - 01:28 AM

I think your last statement using the Delos 4.5mm about not seeing the galaxy clearly, and I can't focus properly have more to do with too much power for the seeing conditions. than fatigue, IMHO.

 

Going from 270x to 480x is a big jump in power, if you have a good 2x barlow you might try it on the 14 Delos for a power of 309x and a 1.48mm exit pupil.

 

On my 18" Dob, I like to use exit pupils between 1.7mm (270x) to 1.29mm (354x) on the larger galaxies for observing fine details if the seeing conditions will allow.  Powers of 400x to 500x or more on most nights is best used on the small 15th and 16th mag. galaxy clusters that look like faint fuzzy stars.

Hi!

 

I think you are totally right. Go to Delos 4.5mm was a painful challenge this time. I have a Powermate 2x so on the next new moon I'll use it with 14 Delos as you are telling me. Very good advice, thank you so much Astro-Master


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#4 russell23

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Posted 13 August 2022 - 08:58 PM

M109 is the galaxy that probably most resembles the mapping of the Milky Way.  It is a multi-arm barred spiral classified as an SBbc I-II which is the likely classification of the Milky Way.  


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#5 David Knisely

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Posted 13 August 2022 - 10:21 PM

While the galaxy itself wasn't all that hard, I remember just seeing hints of the central bar of M109 in my 8 inch f/7 with some hints of the outer spiral structure in my 10 inch f/5.6 Newtonian.  My last view of it was in my 14 inch f/4.6 Dobsonian a couple of months ago from my dark sky site (ZLM 6.6), where I wrote:

 

"Moderate-sized oval diffuse fuzzy patch with brighter slightly elongated core (52x).  157x shows central bar with star-like nucleus and 14th magnitude star just north of nucleus.  Two tightly-wound spiral arms off east and west ends of bar, faint but visible in diffuse outer haze.   UGC 6923 is 14' to S.S.W."

 

Clear skies to you.


Edited by David Knisely, 14 August 2022 - 12:05 AM.


#6 azarquiel.2001

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Posted 15 August 2022 - 02:54 PM

Hi!

 

@Russell, thank you for your information I did not know that galaxy was the one most similar to the Milky Way. Amazing.

 

@David, have you tried to go far in magnifications? In my notes I see a significant difference when reaching 270x. (or maybe it is related to the exit pupil, I have the impression around 1.7mm is a very good value for galaxies, but I do not have any theory to support that impression, only my personal experience). With 154x I was not able to define properly the arms of the galaxy, only a vague view of them, but with 270x I was able to see the point in which starts the arms of the galaxy. I am eager to see if another colleague has experienced the same when adding magnification to this galaxy. Please give me your opinion regarding that point.

 

Clear and dark skies, Israel



#7 David Knisely

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Posted 15 August 2022 - 03:23 PM

Hi!

 

@Russell, thank you for your information I did not know that galaxy was the one most similar to the Milky Way. Amazing.

 

@David, have you tried to go far in magnifications? In my notes I see a significant difference when reaching 270x. (or maybe it is related to the exit pupil, I have the impression around 1.7mm is a very good value for galaxies, but I do not have any theory to support that impression, only my personal experience). With 154x I was not able to define properly the arms of the galaxy, only a vague view of them, but with 270x I was able to see the point in which starts the arms of the galaxy. I am eager to see if another colleague has experienced the same when adding magnification to this galaxy. Please give me your opinion regarding that point.

 

Clear and dark skies, Israel

It varies a bit depending on the galaxy.  I generally start at a "finding" magnification of around 5x to 6x per inch of aperture (5 mm to 4 mm exit pupil) but for picking up finer detail, I will begin with around 9x per inch of aperture (2.8 mm exit pupil) and go up from there.  To pick out things like star-like nucleii or central dust lanes, I will sometimes go to as high a power as the seeing will allow.  A few months back, I studied M82 at length at around 384x in my 14 inch (27x per inch of aperture or a 0.9 mm exit pupil), so sometimes on some objects, I can go pretty high, although usually, I work around half of that level of magnification.  Clear skies to you.   


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#8 Starman1

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Posted 16 August 2022 - 06:20 PM

M109 is the galaxy that probably most resembles the mapping of the Milky Way.  It is a multi-arm barred spiral classified as an SBbc I-II which is the likely classification of the Milky Way.  

 

MW map:

https://sci.esa.int/...f-the-milky-way

M109 pic:

https://freestarcharts.com/messier-109

Uncanny similarity.


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#9 azarquiel.2001

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Posted 17 August 2022 - 05:08 AM

Thank you @David and @Don Pensack, very useful information. Thank you so much




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