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Night vision with a Tec160fl

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#1 Gavster

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Posted 09 June 2019 - 04:53 AM

I realised I have been neglecting my Tec160fl. I’ve either been using my c11 for viewing smaller objects or my Tak Epsilon 130 for larger ones. As a refractor man this felt wrong so last night I dusted off my tec and went out for a mixed normal glass and night vision session.

 

First point to note is that I was in London so skies were very lp. Sqm measured 17.9 at start and got to heady heights of 18.3.

 

I used an astro physics 0.75 photo visual reducer and switched between a 55mm plossl (system speed f2.5) and 41mm panoptic (system speed f3.3).

 

The 55mm plossl gave some fairly poor edge stars (linear!) whereas the 41mm pan gave sharp points to the edge (first time I’ve used the pan with the tec).

On nebulae the 55mm was generally better if you ignored the edge stars (which were nullified by the 3nm ha filter to some extent). The North America was rather nice considering the skies- not as in my face as I get at a dark sky but some good detail and nice subtlety. The crescent was a bit disappointing - I have seen much better with the c11 from the same site - maybe transparency wasn’t as good last night, thinking about it I think that was the case.

 

Sagittarius was low down as always in the UK 🙁 about 15 degrees. And the nebulae were disappointing again compared to views I got with the c11 a few weeks ago. The swan was the best of the lot but the c11 gave me real detail previously whereas I just got the broad outline last night. Eagle, trifid and lagoon were basically just disappointing smudges with no detail to make out (I could just make out the lane in the lagoon). Eastern veil was very nice though - some nice detail visible which surprised me.

 

Switching to the 642 astronomik (nice filter even with Lp)

This was more successful. With the less filtered stars, the 55mm edge distortion was really showing up so I used the 41mm panoptic most of the time which gave very aesthetic views across the fov. M13 was lovely as always with the propellor obvious. Even the tiny ngc6229 glob was nice. In fact every glob was good including m92 and several others. M81/m82 as good as normal with the dark lane visible in m82. Oddly I couldn’t see the needle galaxy at all though!! Yes transparency issues again..

I didn’t put the pier extension on so for the high clusters was sitting on the lawn to see through the eyepiece! C11 wins here!!

 

In summary the tec performed very well as expected. With normal glass last night I really enjoyed the 200x lunar views and the double double at 200x and the carbon star t lyrae was a stunning red.

With night vision the tec was nice with the reducer and 41mm panoptic. On reflection, transparency was disappointing I guess so nebulae didn’t really show like I am used to.

 

However, it reinforced my view that the tec sits between two stools - not enough fov for the bigger objects and too much for the smaller ones. If you only have one scope then the tec is a good compromise for nv. But the extra aperture of the c11 really helps on the smaller objects - I think the c11 is noticeably better just because of the aperture and the fact that at low mag the c11 doesn’t need to be fantastic optically to give lovely views. For larger objects my smaller scopes such as the baader 95mm refractor or Tak Epsilon 130 are better since they frame say the veil or the North America nebula much better. The tec just didn’t have enough fov even with the reducer and 55mm plossl (only around 2.5 degrees whereas I get 4 degrees with the other scopes).

 

For nv my preference is definitely the two scope one. One for large objects with a fov of 4 degrees at 10x and one for smaller objects with a fov of 1 degree and mag of 40x.

 

But on the moon with normal glass the Tec160fl is king!!


Edited by Gavster, 09 June 2019 - 04:56 AM.

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#2 Joko

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Posted 09 June 2019 - 05:41 AM

Hi Gavster,

How does NV performs with your Skyvision 16"? It seems you do not use it so much...



#3 Vondragonnoggin

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Posted 09 June 2019 - 06:07 AM

“In summary the tec performed very well as expected.”

 

I almost missed this line in there and it almost read like you thought it disappointing. Maybe the remark on “disappointing smudges”.

 

What do these look like in your 95mm (Eagle, Triffid, Lagoon)?



#4 Gavster

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Posted 09 June 2019 - 06:21 AM

Hi Gavster,

How does NV performs with your Skyvision 16"? It seems you do not use it so much...

I’ve used the skyvision 16 inch a handful of times now. At the moment, I regret purchasing it. It’s bulky, heavy and not straightforward to set up compared to my c11 on the panther mount which I do find straightforward. If I could leave the dob setup and then just wheel it out with the wheelbarrow handles then I think I’d like it more but that’s just not feasible for the foreseeable future.
On top of that that the difference in views between the sky vision and c11 when using night vision is just not that much in my opinion. I observe at around 40x with both so the dob is a bit brighter due to the faster speed (f2.8 vs f3.3) but the image scale is the same and the c11 edge gives a level of detail and star shape quality that I haven’t managed to get with the sky vision (even though I am using a coma corrector in the sky vision). I like pretty views...

Another factor is that a lot of the objects I want to observe are fairly low in the south in the UK and with the c11 mounted up higher I can observe these objects whereas the dob is lower down and the views are cut off. Something I didn’t consider when I bought the skyvision.

The skyvision has certainly cured any aperture fever I had. In retrospect, I would have been quite happy just staying at 11 inches with the c11 - with night vision the c11 obviously acts as a much bigger scope and gives me huge satisfaction with the views I get of galaxies, globs and smaller nebulae. But I guess I would have always wondered about what a big dob would be with nv so at least I know now!


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#5 bobhen

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Posted 09 June 2019 - 07:24 AM

I have a Mewlon 210 for the small stuff and a 102mm F5 refractor for the big stuff. Both can be reduced.

 

I also have a scope that falls between the two. In my case, it’s a Tak TSA 120.

 

However, I really like using that scope because it gives me more detail on objects than the 102mm and more field than the Mewlon.

 

For example: The Rosetta Nebula fits entirely in the Tak TSA 120’s field and shows more nebula detail than the 102mm refractor’s wider field view. The Mewlon will show even more "close-up" detail but the aesthetic quality view of the complete nebula floating in space is sacrificed.

 

The bottom line is, the universe is filled with varying size targets. I have yet to use any optical aid or telescope of any size or any focal length that does not deliver a smile when used with Night Vision.

 

Bob


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#6 Gavster

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Posted 09 June 2019 - 07:37 AM

“In summary the tec performed very well as expected.”

 

I almost missed this line in there and it almost read like you thought it disappointing. Maybe the remark on “disappointing smudges”.

 

What do these look like in your 95mm (Eagle, Triffid, Lagoon)?

 

Yes this comment of mine doesn’t make a lot of sense smile.gif

 

I was referring to the normal glass views that I got with it last night that were really nice.

On nv it performed as expected I guess but I was surprised how much I preferred the image scale given by my c11. The tec also didn’t frame the larger objects well. Given the extra effort of using the panther mount I think I’ll just go for the c11 in future for nv on smaller objects. For planetary and lunar I’ll of course use the Tec160fl. 

 

Lagoon, trifid etc would have been even worse in the 95mm due to the low height and heavy lp.


Edited by Gavster, 09 June 2019 - 07:39 AM.


#7 Gavster

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Posted 09 June 2019 - 07:40 AM

I have a Mewlon 210 for the small stuff and a 102mm F5 refractor for the big stuff. Both can be reduced.

 

I also have a scope that falls between the two. In my case, it’s a Tak TSA 120.

 

However, I really like using that scope because it gives me more detail on objects than the 102mm and more field than the Mewlon.

 

For example: The Rosetta Nebula fits entirely in the Tak TSA 120’s field and shows more nebula detail than the 102mm refractor’s wider field view. The Mewlon will show even more "close-up" detail but the aesthetic quality view of the complete nebula floating in space is sacrificed.

 

The bottom line is, the universe is filled with varying size targets. I have yet to use any optical aid or telescope of any size or any focal length that does not deliver a smile when used with Night Vision.

 

Bob

For my personal preference the 102 and 120 scopes would be too close in aperture. I like bigger jumps for nv.



#8 chemisted

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Posted 09 June 2019 - 07:52 AM

Gavin,

 

When looking at globs with my 140mm refractor I always use Powermates to get improved image scale and this can make an incredible difference in detail that is presented to the eye.  Most interesting (to me at least) was going from f/12.5 to f/20 (2.5X to 4X Powermates) on the showpiece globulars.  This transformed the views by pulling apart the heart of the clusters into innumerable pinpoint stars.  If you have a chance, try it some time and let me know if you have the same experience.  I realize you will need to do this with other eyepieces afocally but I think it could be worth the effort.  I am a huge fan of afocal as it gives me a fantastic range of magnifications with my OGS RC-10.

 

Ed


Edited by chemisted, 09 June 2019 - 08:48 AM.

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#9 Vondragonnoggin

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Posted 09 June 2019 - 09:40 AM

I’m in heavy lp as well - red/white zone - Bortle 7 

 

Some dslr pics I took with an entry level Nikon D3300 coupled by relay lens to a Litton M942 Monocular with an Omni IV mx10160 tube. This was done on my manual mount so I had to take sub 1 second exposure at 800 iso because everything blurred and stars trailed if any longer because of no tracking - you can see the stars starting to trail in the pics and lack of hard edges on nebula because of blur with no tracking. These were done with a 120ST. I’ve seen the length of exposure you give on your C11 to match the actual live view and in some cases up to 30 seconds. I wasn’t able to match the live view with a manual mount and sub 1 second exposures. Live view much much better and more detail. These are crops.

 

Swan 

 

6B195964-9FFC-496A-B8CC-F51C35BAC259_zps

 

Lagoon (some dark neb risers just visible)

 

07817A8B-F0FF-492D-8214-824A8EB0B51C_zps

 

Eagle (you can just barely spot central pillar in this pic)

 

5989DAEC-B1F0-44DB-8FBF-F23E4D5C5432_zps

 

Triffid

 

8EF7A18C-37A2-47FB-9326-55B68D32DA78_zps

 

Its hard to imagine ever describing the Lagoon views as a “disappointing smudge”. It’s an apparent mag 6 nebula. It’s pretty bright. Is transparency really that terrible there for these to appear as disappointing smudges in a 160 and even worse in a 95mm?

 

Trying to figure out why that 160 didn’t have incredible views of those nebulae.

 

If I had a tracking mount I could lower the iso and extend exposure and match a live view, but I don’t want any tracking mounts yet. I like my alt-az manual mounts. These were taken just to experiment. I prefer just viewing.

 

 



#10 bobhen

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Posted 09 June 2019 - 10:25 AM

For my personal preference the 102 and 120 scopes would be too close in aperture. I like bigger jumps for nv.

I get where you are coming from but...

 

For "me" in the 4" to around 10" size, it's more about FL, as the Image Intensifier makes up for aperture. Of course when there are realy big differences like 4" and 20" that's a different story. But then you lose portability, which is one of the advantages of using an intensifier, rather than going to a larger mirror for light gathering capability.

 

Here are the scopes I use and their FLs.

 

My 50mm guide scope has a FL of about 175mm

 

The 102 F5 can be reduced to 350mm FL
The 102’s native FL is 500mm

 

The Tak 120’s native FL is 900mm

 

The Mewlon 210 can be reduced to 1,700mm
The Mewlon’s native FL is 2,400mm

 

All can also be used with a 2.5 Powermate and come to focus

 

So mostly double the FL between scopes, which gives a worthwhile image scale bump between scopes.

 

Bob


Edited by bobhen, 09 June 2019 - 10:27 AM.


#11 Gavster

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Posted 09 June 2019 - 01:45 PM

 

Its hard to imagine ever describing the Lagoon views as a “disappointing smudge”. It’s an apparent mag 6 nebula. It’s pretty bright. Is transparency really that terrible there for these to appear as disappointing smudges in a 160 and even worse in a 95mm?

 

Trying to figure out why that 160 didn’t have incredible views of those nebulae.

 

Yes I was struggling to explain why they were so bad last night given the views I’ve had in the past. They are very low in my skies and it was pretty murky in that direction so I think probably transparency was just really poor. 


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#12 Gavster

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Posted 09 June 2019 - 02:05 PM

I get where you are coming from but...

 

For "me" in the 4" to around 10" size, it's more about FL, as the Image Intensifier makes up for aperture. Of course when there are realy big differences like 4" and 20" that's a different story. But then you lose portability, which is one of the advantages of using an intensifier, rather than going to a larger mirror for light gathering capability.

 

Here are the scopes I use and their FLs.

 

My 50mm guide scope has a FL of about 175mm

 

The 102 F5 can be reduced to 350mm FL
The 102’s native FL is 500mm

 

The Tak 120’s native FL is 900mm

 

The Mewlon 210 can be reduced to 1,700mm
The Mewlon’s native FL is 2,400mm

 

All can also be used with a 2.5 Powermate and come to focus

 

So mostly double the FL between scopes, which gives a worthwhile image scale bump between scopes.

 

Bob

Bob,

I think you raise quite an important point here. As you say, the image scale is determined by the focal length. But I’m always very focused on the f ratio of the setup I am using with night vision. From my experiences, particularly in light polluted sites,I virtually always find faster is better.

 

As an example, the focal length of my Altair 72mm refractor is 430mm, the same as my Tak Epsilon 130.

However, using my 41mm panoptic (giving about 10x in each case) means the Epsilon is running at f2.1 whereas the Altair is running at f3.8, so I get much brighter, more detailed views in the Epsilon.

 

Because I use afocal only I’m quite used to reducing the f ratio to low amounts. If I was using a tsa120 which is f7.5, I’d want to reduce it to say around f2.7 by using a 0.75x reducer with a 55mm plossl giving a mag of 12x. With a 102 f5, using a 0.75x reducer and 41mm panoptic I get to a similar f ratio of f2.4 but the mag is 9x.

ie little change in mag.

 

In order to keep the f ratio fast but get bigger image scale, the only option I have is to increase aperture. A fast setup is critical for me to get nice nebulae views given the heavy filtering used. What has surprised me is that I also much prefer retaining a fast setup for observing globs by increasing aperture etc rather than running a slower setup to get more image scale, but less detail etc.


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#13 Gavster

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Posted 09 June 2019 - 02:14 PM

Gavin,

 

When looking at globs with my 140mm refractor I always use Powermates to get improved image scale and this can make an incredible difference in detail that is presented to the eye.  Most interesting (to me at least) was going from f/12.5 to f/20 (2.5X to 4X Powermates) on the showpiece globulars.  This transformed the views by pulling apart the heart of the clusters into innumerable pinpoint stars.  If you have a chance, try it some time and let me know if you have the same experience.  I realize you will need to do this with other eyepieces afocally but I think it could be worth the effort.  I am a huge fan of afocal as it gives me a fantastic range of magnifications with my OGS RC-10.

 

Ed

Ed, I’m struggling to get my head round running such slow setups as f20 with nv even on globs. Was this at a dark site?

From an sqm 19 site earlier this week, I used my c11 (with 0.7x reducer) with a 55mm plossl and 41mm pan on m13. I preferred the views with the plossl - more definition to the cluster even though it was smaller. This was a setup of f3.3 vs f4.4 so much faster than what you are mentioning here.



#14 bobhen

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Posted 09 June 2019 - 02:34 PM

Bob,

I think you raise quite an important point here. As you say, the image scale is determined by the focal length. But I’m always very focused on the f ratio of the setup I am using with night vision. From my experiences, particularly in light polluted sites,I virtually always find faster is better.

 

As an example, the focal length of my Altair 72mm refractor is 430mm, the same as my Tak Epsilon 130.

However, using my 41mm panoptic (giving about 10x in each case) means the Epsilon is running at f2.1 whereas the Altair is running at f3.8, so I get much brighter, more detailed views in the Epsilon.

 

Because I use afocal only I’m quite used to reducing the f ratio to low amounts. If I was using a tsa120 which is f7.5, I’d want to reduce it to say around f2.7 by using a 0.75x reducer with a 55mm plossl giving a mag of 12x. With a 102 f5, using a 0.75x reducer and 41mm panoptic I get to a similar f ratio of f2.4 but the mag is 9x.

ie little change in mag.

 

In order to keep the f ratio fast but get bigger image scale, the only option I have is to increase aperture. A fast setup is critical for me to get nice nebulae views given the heavy filtering used. What has surprised me is that I also much prefer retaining a fast setup for observing globs by increasing aperture etc rather than running a slower setup to get more image scale, but less detail etc.

Everyone says faster is better but I have yet to see it be “so much” better than to negate “any” of the advantages of larger image scale.

 

I’ll take my F11, 2,400mm FL Mewlon view of globular clusters (large and resolved to the core) in my heavily light polluted location any day to something faster but with a much smaller view of that globular, unless of course it’s a 20” f5 or something. The core of the Orion Nebula in the slower Mewlon is also unmatched by any of my faster telescopes. I’d also really rather have the portability of my Mewlon 210 than deal with that larger/faster Dobsonian in order to get the same image scale.

 

Bob


Edited by bobhen, 09 June 2019 - 02:53 PM.


#15 chemisted

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Posted 09 June 2019 - 02:47 PM

I have used my RC-10 setup on globulars at its native focal length (2383 mm) looking over very light polluted skies of a large midwestern city and have had spectacular views so I don't believe dark skies are important at all.  This includes faint NGC clusters as well as the bright ones. Also, that was with the Collins I3 which has poorer SN and PR than current devices (although the EBI is phenomenal).  I am very surprised to hear of your reticence.  Have you tried the C-11 at f/10 on a variety of globulars?  



#16 Gavster

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Posted 09 June 2019 - 02:53 PM

I have used my RC-10 setup on globulars at its native focal length (2383 mm) looking over very light polluted skies of a large midwestern city and have had spectacular views so I don't believe dark skies are important at all.  This includes faint NGC clusters as well as the bright ones. Also, that was with the Collins I3 which has poorer SN and PR than current devices (although the EBI is phenomenal).  I am very surprised to hear of your reticence.  Have you tried the C-11 at f/10 on a variety of globulars?  

Looks like I need to give it a go, Ed! I will report back...



#17 Vondragonnoggin

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Posted 09 June 2019 - 03:01 PM

Yes I was struggling to explain why they were so bad last night given the views I’ve had in the past. They are very low in my skies and it was pretty murky in that direction so I think probably transparency was just really poor. 

Thanks for the explanation. I hope you get some better transparency next time you try with the 160. That is a very nice scope. 

 

Thanks for the report also. Really liking all the info for afocal setups. Very easy way to get extreme reduction or more magnification without need for reducers or barlows. I like having a lot of options.

 

cool.gif


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#18 chemisted

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Posted 09 June 2019 - 03:04 PM

I have another thought that I think might be relevant.  I have always been impressed by the fact that light pollution and seeing conditions didn't matter very much with my globular exploits but transparency is a completely different matter.  Good transparency is really, really important.  One summer in Colorado I lost a tremendous number of viewing nights due to particulate matter in the air that blew in from forest fires in California.  So it may be that your best bet will be to try to pick a night of better transparency if you can get one.  Good Luck!


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#19 Eddgie

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Posted 09 June 2019 - 06:57 PM

 so I don't believe dark skies are important at all.  

They are not "important" in the sense that it is no longer necessary to go to dark skies to see a lot of objects that used to require it, but you have to trust me on this>>> Just as with conventional astronomy, there is nothing that makes as much difference as moving your heinie out to dark skies.

 

I have urged over and over that people that started using NV and enjoying things they could not see before even from dark skies still take time to go to dark skies to observe because just like with traditional observing, getting to dark skies greatly expands your reach.

 

I posted on field illumination that long pass filtering rejects energy and for this reason, when you observe from the city using long pass filters, you are throwing out some baby with the bath water.   Gen 3 is not as sensitive to green as it is to red, but it is still pretty sensitive to it (blue is where the dive is).  This means that when you ditch the filter, the sky explodes with stars and galaxies.

 

I remember sweeping the Coma Berenices galaxy region from Bortle 1 skies using an 80mm f/6 refractor and seeing dozens of galaxies in the same field of view.  I can never do that from home.

 

Even with filters though, the view of nebula gets much better. Under dark skies, the extension of most nebula increases substantially.    

 

Andromeda under dark skies is titanic.  Under city skies, I struggle to see a dark lane, and the extension seems only about 2.5 degrees.   Under dark skies, I can see two lanes, and the galaxy extends to well over 4 degrees (and sometimes I think close to 5 degrees.  Far better than in the city).

 

So while people don't fell the need to leave the city anymore, I urge them to make a trip to dark skies now and then.  

 

Seeing the sky in H-alpha from a Bortle 1 or 2 site at 1x or 3x is a profound experience.  You see nebula that you can't imagine. IN a 6" scope, you can see fields with thousands of stars, and in that field, the Ink Spot Nebula totally lives up to its name, becoming a small irregular totally black void at the center of this vast number of star so thick that they almost touch. 

 

While you may not thing dark skies are important, I urge you to do at least one dark sky trip in the summer because it is a surreal experience that everyone using NV should make the effort to see. 

 

I feel like I am in outer space when I go to dark skies.  It is difficult to convey the full impact of observing under dark skies with Night Vision.  Even my best descriptions fall short of the reality of it. 

 

Don't think that it is not important to view from dark skies once you start using NV, because if you do, you are depriving yourself of an off-world like experience.  


Edited by Eddgie, 09 June 2019 - 07:00 PM.

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#20 Jeff Morgan

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Posted 09 June 2019 - 10:52 PM

For nv my preference is definitely the two scope one. One for large objects with a fov of 4 degrees at 10x and one for smaller objects with a fov of 1 degree and mag of 40x.

 

I have been running (generally) two scopes for the last two years, aperture for small targets and speed for big targets. That captures perhaps 95% of the possibilities, with telephotos getting the rest.

 

It is a very good state of affairs.


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#21 chemisted

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Posted 10 June 2019 - 05:16 AM

They are not "important" in the sense that it is no longer necessary to go to dark skies to see a lot of objects that used to require it, but you have to trust me on this>>> Just as with conventional astronomy, there is nothing that makes as much difference as moving your heinie out to dark skies.

 

I have urged over and over that people that started using NV and enjoying things they could not see before even from dark skies still take time to go to dark skies to observe because just like with traditional observing, getting to dark skies greatly expands your reach.

 

I posted on field illumination that long pass filtering rejects energy and for this reason, when you observe from the city using long pass filters, you are throwing out some baby with the bath water.   Gen 3 is not as sensitive to green as it is to red, but it is still pretty sensitive to it (blue is where the dive is).  This means that when you ditch the filter, the sky explodes with stars and galaxies.

 

I remember sweeping the Coma Berenices galaxy region from Bortle 1 skies using an 80mm f/6 refractor and seeing dozens of galaxies in the same field of view.  I can never do that from home.

 

Even with filters though, the view of nebula gets much better. Under dark skies, the extension of most nebula increases substantially.    

 

Andromeda under dark skies is titanic.  Under city skies, I struggle to see a dark lane, and the extension seems only about 2.5 degrees.   Under dark skies, I can see two lanes, and the galaxy extends to well over 4 degrees (and sometimes I think close to 5 degrees.  Far better than in the city).

 

So while people don't fell the need to leave the city anymore, I urge them to make a trip to dark skies now and then.  

 

Seeing the sky in H-alpha from a Bortle 1 or 2 site at 1x or 3x is a profound experience.  You see nebula that you can't imagine. IN a 6" scope, you can see fields with thousands of stars, and in that field, the Ink Spot Nebula totally lives up to its name, becoming a small irregular totally black void at the center of this vast number of star so thick that they almost touch. 

 

While you may not thing dark skies are important, I urge you to do at least one dark sky trip in the summer because it is a surreal experience that everyone using NV should make the effort to see. 

 

I feel like I am in outer space when I go to dark skies.  It is difficult to convey the full impact of observing under dark skies with Night Vision.  Even my best descriptions fall short of the reality of it. 

 

Don't think that it is not important to view from dark skies once you start using NV, because if you do, you are depriving yourself of an off-world like experience.  

I agree with Jeff 100% on this.  My comment was in a paragraph where I was discussing observations of globular clusters where a filter is not used at all. I guess I should have been more specific.  For the record, in my current location I am blessed with very dark skies and do all of my observing from home.



#22 Gavster

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Posted 10 June 2019 - 06:23 AM

I agree with Jeff 100% on this.  My comment was in a paragraph where I was discussing observations of globular clusters where a filter is not used at all. I guess I should have been more specific.  For the record, in my current location I am blessed with very dark skies and do all of my observing from home.

Thanks, that’s helpful. I do the majority of my observing from lp London with heavy filtering. I guess this explains my preference for fast setups. However, next time I am at my dark site I will try my 27mm panoptic and 18mm delite on my c11 afocally and unfiltered on globs to see how they look.



#23 chemisted

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Posted 10 June 2019 - 09:58 AM

Gavin, My recommendation is to still try your C-11 from home on a night of decent transparency with no filter and the 27 Panoptic.  This is specifically for globular clusters.  Start with those big, beautiful and bright ones and if you are impressed with those (which I think you might be) try some fainter ones too.  Ed



#24 bobhen

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Posted 10 June 2019 - 11:30 AM

I use a strong 685 Pass filter to eliminate light pollution from my extremely light polluted home and both bright and faint globulars are still impressive with larger image scale.

 

Light amplification is the reason one gets an intensifier in the first place.The light amplification properties of intensifiers make the difference, as they illuminate the fainter stars in globulars that would go unnoticed using conventional glass, especially in light pollution, and give even the faint globulars individual identities.

 

Bob



#25 Jeff Morgan

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Posted 10 June 2019 - 04:17 PM

Another piece of the puzzle appears to be the diagonal.

 

Dielectrics fall off pretty fast beyond 700nm, while our intensifiers are sensitive down to 900nm. The information published by Collins indicates peak sensitivity of 775nm:

 

http://www.ceoptics....ech_report.html

 

A Baader BBHS is very high on my Buy List.

 

That also begs the question of how much we are losing with the aluminized coatings of our reflectors. Fortunately, the net gain is still substantial.




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