6 May - Big Dob tackles Leo Galaxies with Photonis Night Vision

[alanjgreen]

Date: Sun 6th May 2250 - 0315am       

Scope: 20” f3.6 Lukehurst Dob with Paracorr (fl = 2089mm & f4.1). Night Vision: PVS-14 with Photonis 4g INTENS.

Eyepieces: 55mm (f2 x38), 35mm (f3 x60), 27mm (f4 x77), 18.2mm (f5.8 x115). Filters: Astronomik CLS (Visual IR pass), Baader 610nm Red.

 

Galaxies and Night Vision

While Night Vision is a “game changer” for visual observers on Nebula targets WITH Ha CCD filters, the increased brightness potential for galaxies is on a “smaller” (but well worthwhile) scale and so far a “magic” filter has not been identified.

Having just got my PVS-14 Night Vision device while galaxy season is still in play, I am making the most of these clear nights to try to get an understanding of the best combination of eyepiece and filters for seeing galaxies with my Night Vision (NV).

 

Choosing Galaxies in Leo for experimentation with Photonis 4g INTENS Night Vision

On the two nights out with NV so far, I have focused on Ursa Major so last night’s plan was to get into Leo and see what I can find using a 55mm Plossl (f2 x38) & CLS visual filter. Here are my descriptions of the “best” that I found. This list of galaxies will be revisited whenever I can get out this week but using a different eyepiece/filter combo.

NGC3628 - The galaxy was big and bright (even at x38) and showed a lovely black lane running through the centre.

M66 - The straight central bar was clear. A distinct “S” shape of arms came and went in the view. I played with the “gain” but could not tune the arms “in”. They came and went as I watched with averted vision.

M65 – Revealed a nice bright halo with a black edge to the lower side.

Copeland's Septet (Hickson 57) – At x38 I saw “two lines” of galaxies in the fov. One of the lines was the Septet which showed as three tiny thin lines. The other line of galaxies was made up of “other NGCs” nearby.

Markarians chain – The chain was easy to follow with all the galaxies showing bright cores. Some longer edge-on galaxies were also seen in the fov as I nudged along. The experience was more like I remember in my 11” SCT and it was nice to find it so easy to move through the chain. (With big dob and x200-x250 there are just too many small galaxies in the fov that the chain is hard to follow, you get distracted and wonder off target!)

NGC4535 – Showed as a large ghostly haze. No arms visible.

M58 – Bright core & halo. No arms.

M88 – Bright core & halo. Some arm detail seen with averted vision.

M91 – Bright core and clear central bar. No clear arms.

M100 – Spiral arms seen with averted vision, coming & going.

M99 – One clear arm “up” and multiple arms hinted “below”. Had to check the Sky Safari image and it was pretty close. The “below” arms needed averted and came & went. The “up” arm was more frequently seen but averted needed.  

M51 – Arms lovely and clear. Whole bridge seen with some averted trying. The companion core has the black area missing where the arms meet.

M101 – A disaster. Just a core and nothing else. Don’t know what happened here as I was picking arms out with relative ease last time out.

Early results compared to "Conventional"

As you can see above, several Messiers in Leo were showing arms with averted vision. Thats a step forward for Big Dob! Any galaxy with a thick dark lanes should be a winner with NV.

 

Onto some Globulars

With my limited experience so far, its clear that NV makes “big improvements” to Globular clusters. They “all” resolve to the core, whether they be bright Messiers or faint NGCs. The NV has no problem seeing all their stars as crisp well defined dots.

M53 – 55mm, x38. Resolved to the core.

M13 – 55mm. Nice and bright “space invader”. Propeller clear. Resolved to core.

M13 – 27mm. Much bigger and now with a “bulging centre section” (That’s more like it). Great!

M13 – 18.2mm. Bigger and more detailed. Propeller lost in the view. Less central bulge than the 27mm (more resolved stars?).

M92 – 18.2mm. Very nice. Much better than I remember with a “conventional” view.

NGC6229 – small & bright. Resolved to the core.

Then onto best ever & memorable views of M12, M10 & M14, all resolved to lovely bright shapes of stars.

NGC6366 – 27mm. Big, spread out & faint. But fully resolved field of stars.

M5 - 27mm. Terrific view of M5. I don't get to see enough of this Globular and I forgot how great it is!

 

Some low power x1, PVS-14 direct to the sky to finish!

The Milky Way was clear naked eye above me. I disconnected the NV from the eyepiece and held it to my eye pointing to Cygnus. Wow! The Milky Way was wonderful right down to the horizon, revealing two “white” arms with clear black lane separating our galaxies beautiful arms overhead. As I get higher into Cygnus then the individual nebulas appeared (unfiltered) and on into Cassiopeia. The Double Cluster was really well resolved and Andromeda – Wow! So big and clear (at x1 !) – It stood out “like a sore thumb”.

Spent a bit of time watching my cats playing in my garden then decided to head inside as the Devils Orb was now clear of the Pennines and my brain was tired.

 

Hope the Weather Gods are in my Favour.

Now I have a “list” of targets with arms, I shall endeavour to revisit at the earliest opportunity for further testing and comparisons…

Clear Skies,

Alan

[wookie1965]

Great write up and objects there many I cannot get to see but so nice someone else writing about them.

[cloudsweeper]

Most interesting Alan!  I wonder if you could kindly explain to those like me who have absolutely no knowledge of NV technology just what the two devices you mention are/do?  How do you use them with a 'scope and EP?  And do they function real time, or use some means of integrating several images gathered over a short interval?

The benefit of your experience will be much appreciated!

Doug.

[alanjgreen]

4 minutes ago, cloudsweeper said:

Most interesting Alan!  I wonder if you could kindly explain to those like me who have absolutely no knowledge of NV technology just what the two devices you mention are/do?  How do you use them with a 'scope and EP?  And do they function real time, or use some means of integrating several images gathered over a short interval?

The benefit of your experience will be much appreciated!

Doug.

I am using military night vision connected to an eyepiece via a special connector. This is called an "afocal" implementation.

the focal length of the eyepiece determines the focal ratio for the view (longer fl eyepiece equals faster focal ratio). Night vision runs at f1.2 so the faster you can make the system, the more light goes into the device for brighter image. Changing eyepiece changes the effective focal ratio of the system.

the night vision has a 20mm entry pupil so you can throw way more light at it than the human eye. A 55mm eyepiece in an f4 system, gives a 13mm exit pupil, too much for a human an eye but easily consumed by the night vision device.

the image is viewed directly at the eyepiece by looking into the night vision device directly. The device has manual gain control so you can dial more or less contrast and increase the sensitivity of the system.

Here are some posts to read up on...

HTH,

Alan