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Small Target NV in Sagittarius

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#1 Jeff Morgan

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Posted 19 September 2017 - 02:02 AM

Over the last six months, the scope I have used most heavily for my NV observing is a 180mm f/2.8 Takahashi Epsilon. While the scorching speed provides stunning images with my NV eyepiece, using a fast astrograph does have a catch - image scale. Or rather, lack thereof. For small targets, 19x just isn’t enough. So I forced myself back to my larger Newtonian to reap some details on the targets of southern Sagittarius.

 

Arizona suffers from an annual monsoon rain pattern, which brings frequent cloud cover to the higher elevations. Generally speaking, I lose two solid months of prime-time summer observing. So when it breaks in mid-September, the rush is on for the southern Milky Way.

 

When I had a clear night on the 14th, I was determined to get something done despite my 6AM flight the next morning. Sagittarius was already past the meridian and rapidly sinking towards the horizon at the end of twilight. My list was concentrated on the lower portion of the constellation, time was of the essence. This was more of a recon mission - speed dating if you will. I covered 23 objects in 90 minutes. As such my notes are very short - more impressions than details. Having separated the Wheat from the Chaff, next season I can go back for detailed observations on the top prospects.

 

Observations were made from my backyard 7 miles north of Prescott Arizona under Bortle 5 (yellow zone) skies. As the two softball complexes within two miles of my home were active, this sky rating may have been optimistic. The equipment was a 16” f/7 Newtonian (2800mm focal length), Mod 3c NV eyepiece, and a Leica ASPH (9mm-18mm wide field zoom) for conventional views.

 

IC 4673, Planetary Nebula. Smallish, dim. Very close to a tie between the Leica with a NPB filter and with NV with hydrogen alpha filter. On my 1 to 5 scale, I would score this object a 2 (below average, dim) in either eyepiece.

 

NGC 6565, Planetary Nebula. Small and bright with Leica/NPB or NV w/H-alpha. Score 3 (average).

 

ESO 522-16, Open Cluster. ESO objects are not normally on my observing menu, but AstroPlanner returned this one within my search parameters, so I was curious. It was interesting in that it showed both the encroachment of light pollution into my site, and the relative power of the NV technology. With the Leica eyepiece @ 155x perhaps five or six field stars are easily seen maybe 2 dozen very faint ones near the edge of vision. Keep in mind this cluster is rather centrally located in Sagittarius! With NV stars fill the field. Hundreds. Too many to count. The cluster? Very small and not very impressive with either view. Score 1 - Dim and disappointing.

 

Barnard 291, Dark Nebula. Seen in both eyepieces. Another reminder of the deterioration of my home observing site. Ten years ago I was able to capture 15th magnitude IC 4617 with a 12.5” scope. Those days are long gone!

 

NGC 6522, Globular Cluster. Beautiful spray of stars in NV very well resolved but still small. With the Leica I could get more image scale but it still only looked like a faint patch with little to no resolution Score 4 with NV (Above Average, makes constellation “Best Of” list). Conventional Score 2, Below Average.

 

NGC 6528, Globular Cluster. With the Leica resolution is hinted at as faint mottling. With NV easily 2 dozen stars resolved across a small core despite low target elevation and sky glow. Score 3.

 

HR 6780, Double Star. Not a NV target, this one was for the Leica only. The separation is listed at 4 arc seconds, it was the tightest double I could cleanly resolve with a well collimated 16”. Yes, the seeing was that “good”. A pretty ocher primary and blue secondary. Score 4.

 

NGC 6558, Globular Cluster. A very curious globular cluster. With the conventional eyepiece it was barely there just a glow. With NV it was almost like looking at a rich open cluster the spacing of the members were so wide. The innermost core wasn't dense and tight but the outer core was almost loose in character. Almost like two different objects between the eyepieces. Score 3.

 

NGC 6559, Globular Cluster. At the time of observation only 18° above the horizon. Barely there in the Leica eyepiece, stunning with NV. Score 4.

 

NGC 6624, Globular Cluster. This one had a mottled surface hinting at resolution in the Leica. With the NV the are largely resolved. One pattern is developing: These clusters appear somewhat larger with conventional eyepieces.  I suspect what is causing this is the rich area of the skies they are in. The background and/or foreground stars that are below the visual threshold of conventional viewing are brightened with NV to the extent that it makes the cluster itself blends in and looks smaller. Somewhat similar to the effect you get with open clusters that are not classified as Well Detached. In any event, it was still an Above Average cluster in the Mod 3c at 108x. Score 4.

 

Messier 69, Globular Cluster. The first globular cluster of the night that I could resolve with the Leica. Very nice. With NV was amazing. Score 3 with the Leica, Score 4 with the Mod 3c.

 

NGC 6652, Globular Cluster. NV only observation very small with bright core. Score 3.

 

Messier 70, Globular Cluster. For a Messier cluster I was expecting something larger. Fairly small cluster but very bright well resolved. An interesting Little Dipper like asterism of field stars lays almost on top of it. Score 4.

 

IC 4776, Planetary Nebula. Score 3. Easily picked up with Leica or Mod 3c not much difference between the two. I seem to get a better view in NV when using the 12nm H-Alpha vs. the 640 long-pass.

 

Messier 54, Globular Cluster. At this point I have all but quit using the Leica. In this regime, it can’t keep up. In the Mod 3c appears somewhat larger than most of the other globular's in Sagittarius. Perhaps it is or perhaps being further off Milky Way the outer stars are not blending into a background? Very rich and well resolved outstanding. Score 5.

 

NGC 6723, Globular Cluster. Appears larger and looser than the other globular's I have looked at tonight. Almost like a very rich open cluster. Score 5.

 

Messier 55, Globular Cluster. Looks like a rich open cluster to me. Very large and loose. Score 5.

 

IC 4391, Elliptical Galaxy. Extremely faint, Score 1.

 

IC 4946, Spiral Galaxy. Extremely faint, Score 1.

 

NGC 6902, Spiral Galaxy. Extremely faint, Score 1.

 

At the end of working an observing list, I like to treat myself to a few Eye Candy objects to end the night:

 

M27, Planetary Nebula.  A very nice view with the 640 long-pass, the dumbbell shape was sharply defined. However after viewing so many emission nebula, I was expecting it to be brighter, especially in a 16” aperture. I had observed M27 with my 8” f/9 Newtonian back in April, but did not recall which filter I used. I tried going filterless, and the view was actually better! Then I put in a 12nm H-Alpha filter and was absolutely amazed. In addition to the Dumbbell shape, extensions were seen in the hollow area. I was shaped like a football (American football) and oriented at a right angle to, and larger in size than, the dumbbell structure. Doing a search for images of M27 the next day, I found that it even some CCD images don’t show this as well as the unfilmed L3 tube does!

 

M57, Planetary Nebula. Hot on the success of M27 I went for the ring nebula. As with the Dumbbell, 640 long-pass was not the best filter choice. Unfiltered or 12nm H-Alpha were better. In all cases, the central star was obvious. I’m not sure, but I thought I saw a second star. Next session I will make a more concerted effort to see if a second central star is visible. M57 was very nice, but not near the detail of M27.

 

M13, Globular Cluster. The NV view is absolutely amazing. Best I have ever seen. As an interesting aside, my old friend 15th magnitude IC 4617 was an easy catch next to the cluster. Sure is a lot better to be pointing the scope away from the Prescott light dome!

 

Some Thoughts on the Night

 

In the July 2017 Sky & Telescope article by Ed Mihelich (CN member Chemisted) he claimed impressive magnitude gains on globular clusters. At first read, I thought he was overstating things just a bit. However after this night I had a large enough sample base to say Ed was right on the money. The pattern emerged right away of large gains. As with emission nebula, globular clusters are the strong suite of NV eyepieces. So much so that using conventional eyepieces on these targets is largely a waste of time.

 

OTOH, NV could not rescue dark nebula from the light dome to my immediate south. The combination of sky brightness and low elevation is too much. I either need to wait for local conditions to improve after 11pm, or go to a darker site to complete my survey of DN’s in the far south.

 

I was also surprised that planetary nebula seem to react so well to H-Alpha filters.

 

It was nice to get some image scale (compared to the 500mm Epsilon) to break these clusters open. But even with a large focal length scope (2800mm), the NV eyepiece is barely a medium powered affair at only 108x. After some experimentation and looking at the math (aperture vs. speed) I am not a big fan of barlows with my astrograph. It’s just not very efficient. There is certainly some convenience there as logistically it is much easier to pack a barlow than a second telescope! Nevertheless, I have just been marking targets for later return with a larger scope rather than barlow the Epsilon.

 

But when you are talking about your largest telescope and you are still only getting 108x, there is no recourse but a barlow. I did attempt to use a 2.4x Dakin on a few of the targets that night,  but was not pleased with the results. I believe it outstripped the seeing, especially at the low elevations I was working.

 

The field of NV astronomy is still relatively new, and I am still feeling my way around. At this point it appears the path forward will be a two scope solution. Modify the large scope to use focal reducer(s) to bridge the gap between it and the Epsilon as best I can. I hope to avoid having a third scope. For more scale on the big scope I will be in the market for a barlow in the 1.5x to 1.8x range.


Edited by Jeff Morgan, 19 September 2017 - 02:07 AM.

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#2 Eddgie

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Posted 19 September 2017 - 08:52 AM

An excellent report, and yes, Globulars are outstanding in NV.   With my 12" dob (f/4.9) I can resolve globulars that were just barely discernible as a pale glow in my C14.   I can easily resolve triple the number of globulars and I can see so very many more in the 6" but as we both know, in the 6" you can only resolve around the edges because the cores just become to compressed to resolve further.

 

One of the reasons I love a filter wheel is because as you have found, sometimes you get a better view unfiltered than using a long pass.   I keep making the point that long pass filters take a toll of their own, and more and now I try ever target unfiltered.   Sometimes the very best view is unfiltered.   I think at the focal ratio you were working, a milder filter wold be better than something like a 650nm pass.   You might want to try a simpler cheap dark read planetary filter.

 

If you mod the scope for a reducer, make sure you leave room for a filter wheel.

 

Excellent observations. I enjoyed them very much.  Some targets I did not know and will put them on my list!



#3 Jeff Morgan

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Posted 19 September 2017 - 09:24 AM

Last night I was out at my primary dark site, about 10 miles south of Ash Fork, AZ. This is a legitimate Bortle 2 site, and with the exception of the H-a stuff, ran unfiltered almost all night long and it was wonderful.

 

I see what you say about the long-pass - definitely a city-observing tool. And even then, sometimes better without. So I need to get busy on that quick-change filter capability after a busy summer. Although not quite as slick as a wheel, I'm thinking one of the filter drawer products might work better with my scopes:

 

http://www.teleskop-...ngth-15-mm.html

 

http://www.baader-pl...filter-chamber/



#4 Doug Culbertson

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Posted 19 September 2017 - 09:34 AM

Outstanding report! I can feel your pain regarding the monsoon season in AZ, as I haven't had a clear night since April.

 

I am printing out your report just in case I get a clear night while Sagittarius is still up. Like Eddgie, some of those targets I was completely unaware of until I read this.

 

As to barlows, I was never much of a fan of them when using conventional eyepieces, but I now have two barlows since getting into NV. I use an ES 2x focal extender and a TV 3x barlow for getting a bit of image scale with planetary nebula. The Eskimo and Cat's Eye responded very well to barlowed NV, and for the first time I was actually able to make out the face and the fringe on the Eskimo this way.

 

Good luck with your decision on the perfect set of telescopes for this new way of observing. Eddgie and I have been discussing this, and I have been in such a state of analysis paralysis that I need to just stop thinking about it for a bit. Part of me thinks that a 10" f/4.5ish dob with a focal reducer, a very fast 5"ish reflector, and something long like a Mewlon or even a SCT for small targets might be perfect, then I switch gears again. Like you, I would rather keep it to two scopes if possible. I look forward to hearing your solution to the dilemma.



#5 Eddgie

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Posted 19 September 2017 - 10:12 AM

Last night I was out at my primary dark site, about 10 miles south of Ash Fork, AZ. This is a legitimate Bortle 2 site, and with the exception of the H-a stuff, ran unfiltered almost all night long and it was wonderful.

 

I see what you say about the long-pass - definitely a city-observing tool. And even then, sometimes better without. So I need to get busy on that quick-change filter capability after a busy summer. Although not quite as slick as a wheel, I'm thinking one of the filter drawer products might work better with my scopes:

 

http://www.teleskop-...ngth-15-mm.html

 

http://www.baader-pl...filter-chamber/

The filter drawer is a great solution if you need to control light path.  Telescope Express sells a nice one with 15mm path length.  It is T2 male on the eyepeiece side so you can use a T2 to C mount adatpter to connect to the NVD.   This would give a total path of about 33mm, so a lot of dobs would reach focus this way.

 

Yeah, when the skies get even to mag 4.5, except for H-a, I run unfiltered.   Even under mag 3 skies, I find the filters of less value with slower scopes, and I step down to the 610nm a lot of times.  The brightening of the field gives the illusion that the light pollution is affecting the image, but limiting magnitude comparisons and nebula or galaxy extension comparisons in the filter wheel quickly showed me that the very agressive long pass filters were doing more damage than they were helping.  The view looked more aesthetic because the background was darker, but the targets themselves were likewise affected. 

 

This is why I practically beg people to get a filter wheel.   It makes a quick A/B comparison possible, and often, the very best result on galaxies and globulars will be with no filter or with a milder filter than many are using.

 

It was a great report though and it is through reports like these that we learn more and more about getting the best views possible for different conditions and different target types.

 

Thanks for posting it!



#6 Solar storm

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Posted 19 September 2017 - 04:34 PM

I have had similar experiences using my Comet Catcher and my 11" dob.  I kind if use my Comet Catcher as my grab and go for NV.  But, I like using my dob more for scale.  And since my focal reducer works so well, I tend to use the dob more. And now that I have an awesome dolly for my dob, it is honestly just as fast to set up the dob.  I am able to use my filter slide for both with has been rockin.  Ed is definitely right about that!  

 

As as far as scopes go,  in my future I see a 20" f3ish.  Aperture +speed+NV = happiness.  That will give great scale.  And I am pretty sure I can still use the reducer with NV with hardly any ill effects.  That New Moon hybrid looks sweet, but I will need to beg my wife.



#7 GeezerGazer

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Posted 19 September 2017 - 11:18 PM

Thanks Jeff for taking time to post your results, and especially your target list.  Globs are definitely better with NV than glass eyepieces in my scope.  I have not found an exception to that finding.  Filtered H-a targets are a close second.  Galaxies seem to be in a distant 3rd place... improved with NV for sure, but not the way globulars are improved.  

 

I too use an inexpensive 2x barlow for image scale with NV on small targets with excellent results in my TEC 140.  It puts me in the medium power range, but it seems adequate for most targets.  Like Doug, I've never been fond of barlows, but they are very helpful with NV.  But barlows do have limitations as with your Epsilon. 

 

I'm still in the process of cobbling a small, 60mm achro/finder specifically for H-a, using a diagonal, a filter wheel, and possibly a reducer.  At native f:3.8, I'm not sure the reducer is needed.  I'll post when it's finished and I've had time to thoroughly test it.  It MAY provide an inexpensive means for a dedicated H-a scope.  Jim Henson at ScopeStuff has been very helpful in my effort to find the optimum spacing for a generic reducer.  I should have all my parts soon.  I purchased two different 1.25" reducers specifically for a TV-60, so I'm hoping one will work satisfactorily... if I can find the correct spacing. 

 

I am headed to Australia and New Zealand soon... sadly, my Mod 3 must remain at home!  I am looking forward to seeing those targets in southern Sagittarius.  Thanks again Jeff.



#8 chemisted

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Posted 20 September 2017 - 08:13 AM

Jeff,  This is an awesome observing report! I have left the Colorado rockies as the sky conditions just got worse and worse over the years.  Night vision was a real savior as poor seeing did not seem to matter much and I was blessed on those infrequent clear nights with excellent transparency.  Thank you for the honest appraisal of my article.  I first made those views on two nights of perfect conditions back in July of 2010 and did not write the article until I could replicate them in subsequent years.  One summer was lost entirely to forest fires in California; the particulates in the air absolutely destroyed the views.

 

I am now using my new (to me) NVD Micro with my TV-140 and Powermate 2.5X and 4X "Barlows".  Amazingly, this smaller scope at f/20 (F=2800mm) with the Micro is giving me the same views of globulars that my OGS RC-10 did with the Collins I3.  My new observing location is at 3000 ft in the mountains in western NC.  On clear nights I am getting both excellent seeing and transparency.

 

Just one question on your report.  NGC 6559 is not a globular.  Did you mean 6553?

 

Ed



#9 Doug Culbertson

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Posted 20 September 2017 - 09:44 AM

Jeff,  This is an awesome observing report! I have left the Colorado rockies as the sky conditions just got worse and worse over the years.  Night vision was a real savior as poor seeing did not seem to matter much and I was blessed on those infrequent clear nights with excellent transparency.  Thank you for the honest appraisal of my article.  I first made those views on two nights of perfect conditions back in July of 2010 and did not write the article until I could replicate them in subsequent years.  One summer was lost entirely to forest fires in California; the particulates in the air absolutely destroyed the views.

 

I am now using my new (to me) NVD Micro with my TV-140 and Powermate 2.5X and 4X "Barlows".  Amazingly, this smaller scope at f/20 (F=2800mm) with the Micro is giving me the same views of globulars that my OGS RC-10 did with the Collins I3.  My new observing location is at 3000 ft in the mountains in western NC.  On clear nights I am getting both excellent seeing and transparency.

 

Just one question on your report.  NGC 6559 is not a globular.  Did you mean 6553?

 

Ed

 

Ed, Just a bit OT for this thread, but where in NC are you? We are thinking of retiring to the Spruce Pine area in a couple of years, as we used to spend a lot of time up there.

 

Getting back on topic, I was just thinking recently that there has been a lack of NV observing reports around here lately. In my case it's because of the worst summer that I can remember. At any rate, it's nice to see such an in depth, well written observing report again.



#10 Eddgie

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Posted 20 September 2017 - 09:56 AM

I have been hampered by a vacation and by limited transparency.  

 

I am hoping to get out to Mansfield in the next couple of nights and will hopefully have a report then.

 

There is nothing like darker skies though, but I need to find a new place east of the city.  The amount of low level dust at Perdenales Falls State Park is mind boggling.   A high intensity LED flashlight shows a column of dust so dense that the reflecting light blinds me.   Even though it is much darker than Austin, it there are still transparency issues, and I have come to realize that it is mostly in the 300 feet just above the surface.   

 

Have to find a new place, but for now, I will just go back to Mansfield Dam, probably tomorrow night.  

 

Peter, when am I going to get to look though your new PVS-7???



#11 chemisted

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Posted 20 September 2017 - 10:16 AM

 

Jeff,  This is an awesome observing report! I have left the Colorado rockies as the sky conditions just got worse and worse over the years.  Night vision was a real savior as poor seeing did not seem to matter much and I was blessed on those infrequent clear nights with excellent transparency.  Thank you for the honest appraisal of my article.  I first made those views on two nights of perfect conditions back in July of 2010 and did not write the article until I could replicate them in subsequent years.  One summer was lost entirely to forest fires in California; the particulates in the air absolutely destroyed the views.

 

I am now using my new (to me) NVD Micro with my TV-140 and Powermate 2.5X and 4X "Barlows".  Amazingly, this smaller scope at f/20 (F=2800mm) with the Micro is giving me the same views of globulars that my OGS RC-10 did with the Collins I3.  My new observing location is at 3000 ft in the mountains in western NC.  On clear nights I am getting both excellent seeing and transparency.

 

Just one question on your report.  NGC 6559 is not a globular.  Did you mean 6553?

 

Ed

 

Ed, Just a bit OT for this thread, but where in NC are you? We are thinking of retiring to the Spruce Pine area in a couple of years, as we used to spend a lot of time up there.

 

Getting back on topic, I was just thinking recently that there has been a lack of NV observing reports around here lately. In my case it's because of the worst summer that I can remember. At any rate, it's nice to see such an in depth, well written observing report again.

 

We are down south of Brevard almost to the South Carolina line.  Last summer was unusually dry and this summer has been just the opposite.  We did get to see the eclipse viewing from the comforts of home!


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#12 Jim4321

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Posted 20 September 2017 - 10:20 AM

Jeff, great report!  I'm still mostly at the ~1X  'Oh, wow!' stage due to too many cloudy nights, but you've given me something to shoot for in the future.

 

Doug, we get  lot of clouds here in WNC, at least around Asheville.  But Mayland CC & the Blue Ridge Astronomy Group in the Spruce Pine / Burnsville area are nearly finished with a big RoR observatory that houses a 34" Dob. I was up there a few weeks back.  I think the main thing they lack is  bit of earthmoving & landscaping to be open to the public. 

 

Jim H.



#13 Doug Culbertson

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Posted 20 September 2017 - 10:25 AM

Jeff, great report!  I'm still mostly at the ~1X  'Oh, wow!' stage due to too many cloudy nights, but you've given me something to shoot for in the future.

 

Doug, we get  lot of clouds here in WNC, at least around Asheville.  But Mayland CC & the Blue Ridge Astronomy Group in the Spruce Pine / Burnsville area are nearly finished with a big RoR observatory that houses a 34" Dob. I was up there a few weeks back.  I think the main thing they lack is  bit of earthmoving & landscaping to be open to the public. 

 

Jim H.

 

Thanks Jim. I'm familiar with the clouds, as my late father had a house up between Spruce Pine and Little Switzerland and we spent a lot of time up there, but when it is clear, it's really nice! I'm ready for a change of seasons anyway, rather than the 9 months of summer here in Florida. I had heard about the Blue Ridge Astronomy Group's observatory, but I've never been. I look forward to a few more visits up there before we make up our minds about moving.



#14 Jeff Morgan

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Posted 20 September 2017 - 03:03 PM

Jeff,  This is an awesome observing report! I have left the Colorado rockies as the sky conditions just got worse and worse over the years.  Night vision was a real savior as poor seeing did not seem to matter much and I was blessed on those infrequent clear nights with excellent transparency.  Thank you for the honest appraisal of my article.  I first made those views on two nights of perfect conditions back in July of 2010 and did not write the article until I could replicate them in subsequent years.  One summer was lost entirely to forest fires in California; the particulates in the air absolutely destroyed the views.

 

I am now using my new (to me) NVD Micro with my TV-140 and Powermate 2.5X and 4X "Barlows".  Amazingly, this smaller scope at f/20 (F=2800mm) with the Micro is giving me the same views of globulars that my OGS RC-10 did with the Collins I3.  My new observing location is at 3000 ft in the mountains in western NC.  On clear nights I am getting both excellent seeing and transparency.

 

Just one question on your report.  NGC 6559 is not a globular.  Did you mean 6553?

 

I have also noted that clusters don't suffer too badly from the reduced focal ratios that barlows provide, especially when the yardstick is a conventional eyepiece:

 

https://www.cloudyni...long/?p=7736060

 

 

Good catch on NGC 6559. A typo, that should be NGC 6569.

 

When I checked my observing notes, I found a possible bug in SkySafari with respect to object logging. My practice is to break large constellations down manageable "suspect lists". When objects are determined to be "above average", I migrate them from their respective suspect list (such as "Sagittarius A", "Sagittarius B", etc.) to my Sagittarius Best Of list.

 

Unfortunately, when you add an object (with observing notes) from one observing list to another observing list, the previous notes don't seem to survive the trip to the new observing list!

 

I'll post this to the Software forum later today.



#15 pwang99

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Posted 20 September 2017 - 10:20 PM

I have been hampered by a vacation and by limited transparency.  

I am hoping to get out to Mansfield in the next couple of nights and will hopefully have a report then.

 

There is nothing like darker skies though, but I need to find a new place east of the city.  The amount of low level dust at Perdenales Falls State Park is mind boggling.   A high intensity LED flashlight shows a column of dust so dense that the reflecting light blinds me.   Even though it is much darker than Austin, it there are still transparency issues, and I have come to realize that it is mostly in the 300 feet just above the surface.   

 

Have to find a new place, but for now, I will just go back to Mansfield Dam, probably tomorrow night.  

 

Peter, when am I going to get to look though your new PVS-7???

 

Yeah we gotta get together soon.  Maybe this weekend?  I'm traveling now and am traveling again next week, so this weekend might be it for a while.

 

I (once again) sent off my green PVS-7 and my Mod3 to Okie-Tex, and hopefully Mike Lockwood will induct a few more people into the legion of the NV faithful.  But I kept my WP Mod3 at home.

 

Also, exciting news - I'm going to be getting a 16" f/4.  Not sure when I'm going to be able to look through the darn thing with all my travel this fall, but maybe second or third week of October.  I should be taking delivery of it this weekend, whenever my friend gets back from Okie-Tex with it.



#16 pwang99

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Posted 20 September 2017 - 10:25 PM

Getting back on topic, I was just thinking recently that there has been a lack of NV observing reports around here lately. In my case it's because of the worst summer that I can remember. At any rate, it's nice to see such an in depth, well written observing report again.

 

Yeah, I've been falling down on my side because I've been swamped with real-life work stuff.  Fall is always pretty rough for me because of conference season, and I have 3 international trips this fall so it's really going to put a damper on things.  Weather and seeing have been pretty abysmal in Austin, though.

 

On the plus side, I got to visit Starbase when I was out in Tokyo last week, and lust after a pile of Takahashis... Got to see a couple of Epsilons in real life so I have a sense of what Jeff has been rocking.  The owner of the store was too nice or demure to shoo me away from petting them. :-)



#17 Rickster

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Posted 21 September 2017 - 01:05 AM

Excellent report Jeff.

 

I too have been enjoying a 16" Dob with my NV.  I have had numerous rewarding nights over the last few months. 

 

I have to say that as much as I like the wide view and convenience of NV with smaller scopes, NV with a big scope is a blast.  The most recent highlights were the veil and ring nebulae.  The veil was too big to fit in the FOV, but it was nice to be able to view them in more detail.  The ring nebula was a stunner.  It was bright doughnut, like the rings of Saturn without Saturn.  But I couldn't make out the central star, even at 1800mm.  I haven't tried with a Barlow yet.  If anyone with a big dob and NV gets a chance to try it, I would be curious to know whether or not you can see the central star.

 

My 1800mm focal length plays well with the Canadian Antares .7x reducer threaded onto an old Zummel 2" Barlow body.  This gives me a choice between 1800mm and 1260mm, which is perfect for small and medium sized nebula and clusters.  I piggy back my 6" f4 on the 16".  It also plays well with the Antares .7x and I am able to quickly switch the NV/FR back and forth between the 2 scopes. 

 

Getting the 16" into position has been a challenge.  The best way I have found has been to keep it in the 8'x15' bed of a grain truck.  If you can imagine, it looks a little scary.

 

Locating objects has also been a challenge.  A digital angle finder works well for  altitude.  I got started on making a setting circle for the azimuth, but changed priorities to mounting it on a large equatorial mount that is currently just taking up space.  This mount will make locating objects easier and give me the option to also do camera based EAA.  I intend to build an observatory for them, but I haven't been able to decide between several locations.  One is more convenient, one is darker, one is more hidden from potential vandals, etc.  So I am going to skid mount it and try it at each location before deciding.  The assembly will weigh well over 1000lbs, so moving it will have to be done with a tractor/truck.


Edited by Rickster, 21 September 2017 - 01:08 AM.


#18 The Ardent

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Posted 21 September 2017 - 03:14 AM

About the TS filter drawer: it works, especially is you want to "blink" the filter.

 

Drawback is there is no "out" position. Lift the filter out, let go, and it will fall back in. I have the drawer attached at a 45 degree angle. Pull the drawer out and it rests precariously . A good knock and it falls back in or out on the ground. 

 

Another issue: the open drawer allows stray light to enter the NVD. Not an issue at a dark site, but not good where I have streetlights. 

 

Im going to look at filter wheels next. 



#19 Eddgie

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Posted 21 September 2017 - 07:17 AM

The filter wheel takes more light path; about 25mm if you use a T2 Male to C mount male adapter:

 

https://www.xagylast...productid=16688

 

 

Funny  that I have never heard of the above company but they have an area code that is local to me. 

 

Anyway, this would allow direct connection of the NVD to the top of the T2 filter wheel.  This would mean you needed about 40mm of back focus (with the 15mm of back focus required for the C mount flange to photocathode of the NVD).   Most refractors will have that if you use a 1.25" diagonal but my guess is that many dob's wont (maybe jacking the mirror up a bit would get some there though). 


Edited by Eddgie, 21 September 2017 - 07:27 AM.


#20 The Ardent

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Posted 21 September 2017 - 11:10 PM

This one 

https://www.amazon.c...0?ie=UTF8&psc=1

 

i have a c-to-T mount  adapter already  that connects the TS filter drawer. Will give it a try. 




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