Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

NV Initial Impressions with Filters

NV
  • Please log in to reply
5 replies to this topic

#1 john hraba

john hraba

    Lift Off

  • *****
  • topic starter
  • Posts: 5
  • Joined: 19 Oct 2010
  • Loc: Madison, Alabama

Posted 22 January 2020 - 04:49 PM

Two of the last three nights at my location, here in northern Alabama, were cloud free and clear as only dry north winds produce in this area.  My zenith measured SQM-L reading was 19.1 to 19.2.  Temperatures were in the upper 20’s with a dew point in the lower 20’s.  The stars were not twinkling.  By the way, I live in a very well lighted subdivision in a red-orange zone.

 

With these conditions I ventured out into my back yard at about 6:30 pm central to try to find a little shelter from the streetlights and my neighbors outdoor lights.  My goal was to see what objects I could see using my MOD3-C filtered at 1X with an Envis f/1.2 lens.  All filters used were 2” and attach to the front of the Envis with step-up rings.  The first filter I tried was a 7nm Baader H-alpha narrow band filter.  I started viewing toward the north west and to my surprise I saw the outline of the North American nebula with the Pelican nebula next to it.  Under these conditions I frankly did not expect to see anything this near the horizon under my conditions.  As it turns out I was able to clearly see the North American nebula set over my neighbors house 200’ away an hour and a half later.

 

As I scanned toward the zenith I also saw the Elephant Trunk, Pac man, Heart and Soul nebulae.  The last 2 showed some internal detail.  Again at 1X I did not expect this.  I continued my sweep and saw the Flaming Star nebula and the California nebula.  The California showed structure and spanned at least 5 degrees of sky, perhaps more.

I continued scanning eastward and saw the Cone and the Rosette nebula.  A little detail was visible in the Rosette.  While I had seen the cluster NGC 2244 in the center of the Rosette with a telescope I had never seen the nebula from this location.  Next up was Orion with Barnard’s Loop clearly visible forming a half circle.  Near Alnitak the Flame and IC434 were visible but my tired old eyes could not see the  Horse Head.  Magnification is needed for me.  The Orion nebula was of course spectacular and many more nebula were visible but I did not try to identify them all at this time.  Switching to a Astronomk 12nm H-alpha narrow band filter the nebula were all still visible but substantially less bright.

 

Also tried were three long pass filters,  640nm Lumicon, 685nm Baader and a 742nm Astronomik.  I initially tried the sky unfiltered and the only nebula visible, the Orion nebula, was also visible in the 640.  I used Andromeda to try to get a relative comparison of filter performance. Unfiltered Andromeda appeared as a 1/2 degree ellipse.  The 642 produced an ellipse about 1 degree in extent. Through the 742 it appeared to subtend about 1.5 degrees through the 685 it appeared to be about 2 degrees in extent.  I could not see any divisions or detail with any of the three filters.  Perhaps a little more magnification will help. The 685 and 742 seemed to yield the most stars that is the background looked like a starry carpet with these filters.

 

Since I have not given the as built specifications in the past for my MOD3-C they are listed below.  Values for my MOD3-C are from the inspection report which came with it.

 

Tube:  L3, filmless, white phosphor
PR: 2200
EBI: 0.2
Gain: 66,462
SNR: 33.7
Resolution: 72
Halo: 0.7
FOM: 2426
Dark & Bright Spots: none


  • Jeff Morgan, GeezerGazer, eros312 and 1 other like this

#2 Eddgie

Eddgie

    ISS

  • *****
  • Posts: 25,607
  • Joined: 01 Feb 2006

Posted 22 January 2020 - 05:22 PM

A great report!   Yeah, North America, as nebula go, is quite bright, so I think most people using NV would have told you that you could expect to see it.   

 

California is huge.  I had posted over the weekend that in the 3x, it was far bigger than the catalogs list it.

Many of these nebula will be much better when you can apply some amplification and a great way to do that is with SLR lenses.  80mm to 105mm is probably going to be great for California. You can pick up nice f/2.8 lenses in this range for reasonable prices and I highly recommend picking up something in the the 200mm range.  Now it is not great for nebula, though OK for bright nebula, but one of my favorite all-round lenses is an inexpensive Vivitar 80mm to 210mm Zoom.  While it is "only" f/4.5, f/4.5 in a lens is faster than f/4.5 in a telescope.  Better transmission. It will work OK for brighter nebula, but not the best choice for dim stuff.  Still, for $20, you get 3x to about 7x and that is a great range for general observing with a lot of very large clusters and star clouds to cruise through in the summer.  

 

While the Cone and Rosette are more easily visible, careful study will show you that they are practically joined together by very faint nebula.   Seeing these big, bright subject is easy, but careful examination of the sky between them will reveal a lot of very faint nebulosity. 

 

Now the one thing you did not share with us in your report was how you felt about it !!!! 

 

Sounds like you have a great night though!  So happy that you took the time to post!



#3 john hraba

john hraba

    Lift Off

  • *****
  • topic starter
  • Posts: 5
  • Joined: 19 Oct 2010
  • Loc: Madison, Alabama

Posted 23 January 2020 - 02:52 PM

A great report!   Yeah, North America, as nebula go, is quite bright, so I think most people using NV would have told you that you could expect to see it.   

 

California is huge.  I had posted over the weekend that in the 3x, it was far bigger than the catalogs list it.

Many of these nebula will be much better when you can apply some amplification and a great way to do that is with SLR lenses.  80mm to 105mm is probably going to be great for California. You can pick up nice f/2.8 lenses in this range for reasonable prices and I highly recommend picking up something in the the 200mm range.  Now it is not great for nebula, though OK for bright nebula, but one of my favorite all-round lenses is an inexpensive Vivitar 80mm to 210mm Zoom.  While it is "only" f/4.5, f/4.5 in a lens is faster than f/4.5 in a telescope.  Better transmission. It will work OK for brighter nebula, but not the best choice for dim stuff.  Still, for $20, you get 3x to about 7x and that is a great range for general observing with a lot of very large clusters and star clouds to cruise through in the summer.  

 

While the Cone and Rosette are more easily visible, careful study will show you that they are practically joined together by very faint nebula.   Seeing these big, bright subject is easy, but careful examination of the sky between them will reveal a lot of very faint nebulosity. 

 

Now the one thing you did not share with us in your report was how you felt about it !!!! 

 

Sounds like you have a great night though!  So happy that you took the time to post!

My feelings as I was observing the wonders I described above were of wonder and awe.  As I was making the observations I kept saying wow to myself over and over again. I was seeing the sky as I had never seen it from my home either with or without a telescope.  The MOD3-C is allowing me to almost see the sky as I have only seen it when observing above 10,000 feet far removed from city lights.  I say almost see because of the lack of star colors in the MOD3-C.

 

Upon reflection I am saddened by what we have done to our night sky that makes it necessary to go to such extraordinary measures to see the wonders of the night sky.  Yes, I am a member of the International Dark Sky Association for that reason.

 

You mention camera lenses and magnification.  My intention is to use my old Nikon 35mm camera lenses with the  Nikon to c-mount adapter I bought as well as an adapter to use my 2" filters on the front of those lenses.  Since the lenses largely have 52mm front threads my light loss should be minimal.  I also bought the c-mount to 1 1/4" adapter to allow me to use the MOD3-C with some of my telescopes.  So I think I am ready for some magnification.



#4 GOLGO13

GOLGO13

    Aurora

  • *****
  • Posts: 4,839
  • Joined: 05 Nov 2005
  • Loc: West Virginia

Posted 23 January 2020 - 03:21 PM

 

Tube:  L3, filmless, white phosphor
PR: 2200
EBI: 0.2
Gain: 66,462
SNR: 33.7
Resolution: 72
Halo: 0.7
FOM: 2426
Dark & Bright Spots: none

Your specs are very similar to mine. You have a bit more gain and resolution. Would be very interesting to compare them. Unfortunately I am far from Alabama.

 

 Snr: 33.7
Ebi: 0.2
Blems: 0
Res: 64

​Gain: 61093
Pc sensitivity: 2194
Halo: 0.7



#5 john hraba

john hraba

    Lift Off

  • *****
  • topic starter
  • Posts: 5
  • Joined: 19 Oct 2010
  • Loc: Madison, Alabama

Posted 25 January 2020 - 05:48 PM

Your specs are very similar to mine. You have a bit more gain and resolution. Would be very interesting to compare them. Unfortunately I am far from Alabama.

 

 Snr: 33.7
Ebi: 0.2
Blems: 0
Res: 64

​Gain: 61093
Pc sensitivity: 2194
Halo: 0.7

I agree, it would be interesting to compare the devices but I am not sure if the difference that we observed would be due to the difference in specs or the difference in how the internal gain is set on the individual devices.  Yes, if we set-up a resolution chart we should be able to see the difference between 64 and 72 line pairs resolution with the units.  However since these units are auto-gated they have an internal auto gain circuit that has been factory set and it is unlikely they were set exactly the same.  So not only is there the external gain setting there is the automatic internal circuitry operating in the background.  Perhaps someone, like Eddgie might have an idea of the probable observed difference between our units but I do not.  

 

As you point out we live a long distance apart so are unlikely to ever get together to make the comparison.  This is one reason we should be grateful to people like Eddgie who have multiple devices with specs on multiple tubes and are willing to share the results of their comparisons and their expertise.


  • GOLGO13 likes this

#6 GOLGO13

GOLGO13

    Aurora

  • *****
  • Posts: 4,839
  • Joined: 05 Nov 2005
  • Loc: West Virginia

Posted 25 January 2020 - 07:43 PM

Exactly...Not many of us can get multiple units. Either way I think you will be very happy with it!




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics





Also tagged with one or more of these keywords: NV



Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics