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Paul_R
Carpal Tunnel
Reged: 04/05/05
Posts: 1648
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Tried finding this the other night. It's an object in the Orion Deep Map 600. Was using DSCs, which were spot on for nearby objects. Ended up in what should have been the right field. Had no luck seeing it with different powers and an O-III filter.
I was ready to abandon the Deep Map 600 list as having impossible oddballs, especially after I read somewhere that 6905 is a 12th magnitude object!
Today, in web browsing and reading CN posts, discovered that it's supposed to be a ghostlike, faint blob... I was looking for the more classic blue-green star that would become bigger with higher magnification. Which I didn't see.
Haven't tried again, but the question is whether it is even visible in a 6-8" dob from a semi light polluted site with, say, limiting magnitude 4.5 on a really good night, Milky Way faintly visible. I'll star hop the next time to be sure I'm in the right place, but is it even worth going after? Will I even see anything? 
I might have a more enjoyable experience spending more time with the close by M27 (Dumbbell Nebula) and M71. I really haven't pushed the magnification on M27 or explored filters to tease out details. I also want to revisit 6934, the bright concentrated globular. And it'd be fun to catch a few of the neighboring colorful doubles, too.
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Tony Flanders
Carpal Tunnel
Reged: 05/18/06
Posts: 2096
Loc: Cambridge, MA, USA
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Quote:
The question is whether NGC 6905 is even visible in a 6-8" dob from a semi light polluted site with, say, limiting magnitude 4.5 on a really good night, Milky Way faintly visible.
I haven't tried it yet in the suburbs, but I bet it's not too hard. My notes through my 7-incher under darkish skies record it first as "bluish pale 1' circle evenly bright nestled in leg of equilaterial star triangle." Then another time as "Small, bright, easy @105X, <1' circle, surrounded by 3 stars at edge of disk. UHC filter makes it brighter but not clearer."
The combination of being kinda small and kinda faint makes a lot of planetary nebulae a little tough to spot. Trying "blinking" with one of your filters.
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Tony Flanders
eyeglasses
6x15 and 8x32 monoculars
8x25, 7x35, 10x30 IS, 10x50, and 15x70 binoculars
70mm and 100mm achromatic refractors
4.5", 7", and 12.5" Dobs
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Achernar
Post Laureate
Reged: 02/25/06
Posts: 3720
Loc: Alabama, USA
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I have seen this nebula with my 6-inch, but it was not easy at all from the sites I usually use to the north and west of town. It looks like a faint gray disk almost lost among the stars in the field of view, of which there are plenty. It certainly not bluish and there are more interesting planetary nebulae in the area to look at as well.
Taras
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10-inch F/4.5 Discovery Dob
6-inch F/8 Homebuilt Dob
4 1/4-inch F/4 Homebuilt reflector
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Never
super member
Reged: 11/22/05
Posts: 109
Loc: Finland
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I have to say if the Milky way is even faintly visible, the limiting magnitude is surely above 4.5. Thru my own eyes when the MW is faintly visible, the limiting magnitude is at least close to 5.5.
Is it worth going after at all? How many objects really are from a light polluted skies? I suspect you can spot it but I'd use a filter such as O-III.
From a darker site, an 8" should show the nice double-shell structure. Can't say I remember seeing color.
/Jake
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Jaakko Saloranta - Some basic sketches.../
8" Orion DSE
4" Sky-Watcher
3" Konus RFT
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ngc4565adam
member
Reged: 05/04/08
Posts: 22
Loc: Lat. +46°25', Hungary
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I was able to glimpse NGC6905 under an 5.8 magnitude sky with my 114/900 Newton, more than 1 1/2 years ago. It wasn't easy at all with that scope.
I'll target again with my 6" Newton.
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Celestron Omni 150 XLT (f/5) Newton
Celestron SkyMaster 15×70 bino
wide angle (66 deg FoV) EP's: 20,15,9mm
Unioptik FSS (UHC-like) filter
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Olivier Biot
Amused
Reged: 04/25/05
Posts: 14328
Loc: 51°N (Belgium)
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A happy birthday Ádám!
Since I observe most of the time in severely lit urban skies I increasingly see the benefit of a GoTo system when searching for targets when you see only one star every 10 degrees, rendering star hopping very hard.
But you should be able to pull the planetary from the light polluted skies with either an UHC or an OIII filter, and sufficient magnification.
Cheers,
Olivier
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Tal-200K (#199) with JMI NGF-Mini2M focuser on GEM3 • Astro-Tech AT80ED on Orion Sirius EQ-G with EQDIR & home made wireless EQDIRECT • Celestron Regal LX 8x42 & 10x42 • Helios 15x70
ATM 14" f/5 (designing mirror cell and filter wheel/focuser) • ATM 10" f/6 Portable Truss (polishing) • ATM 10" f/25 Dall-Kirkham (primary: polishing, secondary: #120 grit)
AstroForecast
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Paul_R
Carpal Tunnel
Reged: 04/05/05
Posts: 1648
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Tony, thanks! Your notes give me optimism that I will be able to see it. I've never had much luck with the hold the filter over the eyepiece routine, but I can certainly try it again. I'm usually better off shuffling the eyepiece out and putting an O-III on it-- or simply ramping up the magnification and see which bluish-greenish star becomes bloated. But it seems the BF is a different kind of animal.
How would you all say it compares with the Blinking Planetary? From what I dug up on the web, the Blue Flash is supposed to be substantially larger, right? 40" or some such vs. 25" or so for the Blinker. But BF is much, much fainter. BP is easy to view and fun to track down and see.
Thanks to everyone for their observations--it sounds elusive, but at least I have a better idea of what to look for. I will search with an Ultrablock or O-III the next time.
Do have a question about limiting magnitude... I've never systematically checked it... just checked some stars in the area where I'm looking. The Milky Way shows up faintly... the Scutum Star Cloud, perhaps some haziness in Cygnus, etc. I know what I'm looking for, but I'm not sure it would be that obvious to, say, a novice. So, can that be squared with 4.5? Or would it have to be 5.5? If so, then my eyesight's not very good for seeing individual fainter stars. Could that be the case? Seeing the MW but not 5-5.5 mag stars?
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nytecam
Post Laureate
Reged: 08/20/05
Posts: 4812
Loc: London UK
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Hi Paul - your post prompted me to image the PNe field last night for the first time and you may find my degree wide field of NGC 6905 pic helpful in finding it 
Much smaller and near stellar PNe like NGC 6886 and NGC 6790 in the general area maybe of interest too 
Last night's whole DSO 'bag' here.
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Nytecam 51N 0.1W
Meade 30cm LX200+ETX-70+DS-2090+C8+Ha+CaK PSTs SBIG SGS+homebuilt spectrographs
Starlight SXVF_M9/Lodestar/Canon 300D DSLR/Fuji E550
My observatory build-ETX-70 imaging-spectro page
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LumpyDarkness
sage
Reged: 08/06/07
Posts: 311
Loc: San Francisco bay area
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Quote:
Do have a question about limiting magnitude... I've never systematically checked it... just checked some stars in the area where I'm looking. The Milky Way shows up faintly... the Scutum Star Cloud, perhaps some haziness in Cygnus, etc. I know what I'm looking for, but I'm not sure it would be that obvious to, say, a novice. So, can that be squared with 4.5? Or would it have to be 5.5? If so, then my eyesight's not very good for seeing individual fainter stars. Could that be the case? Seeing the MW but not 5-5.5 mag stars?
You may want to try determining your limiting magnitude by star counting. The Finnish Triangles are one good method.
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Mark Wagner
18" f/4.5 Dob
The Astronomy Connection: Observing Reports - updated 12/1/08
Adventures In Deep Space: updated 12/1/08
Join us in June at California's Golden State Star Party
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Fiske
Carpal Tunnel
Reged: 03/14/04
Posts: 2057
Loc: Missouri / United States
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Quote:
Tried finding this the other night. It's an object in the Orion Deep Map 600.
Paul:
If you can faintly see the Milky Way from your yard, you should be able to observe this PN. I have observed it easily with a C11 from midtown KC, where the Milky Way hasn't been seen (even faintly) for decades. 
The problem is that the Deep Map 6 doesn't provide enough detail to pin-point the object's location and it is dim enough you won't be able to sweep it up. A better approach would be to create a custom star chart using something like Cartes du Ciel (free online) adjusted for a wide-field eyepiece on your scope. It's also a good idea to determine the limiting magnitude for your eyepiece and scope under typical sky conditions for your site, and then limit the chart magnitude to match.
With a custom chart, you should be able to identify the object's location, and then use a higher magnification eyepiece to pull it in if you can't actually see it at lower power. Your OIII filter would probably help too, only, as the eyepiece magnication is increased, the advantage of your filter will decrease.
Good luck!
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Fiske Miles
Nikon 8x42 LX / 12x50 SE Binos
Mini Borg 60ED, TV-101, AT80Ach, XT-8, C11/CI-700, 22-Inch Dob
Way too many Nagler eyepieces
http://www.fiskemiles.blogspot.com/
www.fiskemiles.com
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Never
super member
Reged: 11/22/05
Posts: 109
Loc: Finland
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Quote:
Do have a question about limiting magnitude... I've never systematically checked it... just checked some stars in the area where I'm looking. The Milky Way shows up faintly... the Scutum Star Cloud, perhaps some haziness in Cygnus, etc. I know what I'm looking for, but I'm not sure it would be that obvious to, say, a novice. So, can that be squared with 4.5? Or would it have to be 5.5? If so, then my eyesight's not very good for seeing individual fainter stars. Could that be the case? Seeing the MW but not 5-5.5 mag stars?
Having bad eyesight affects naked eye limiting magnitude - yes of course.
I've personally always though the limiting magnitude as one of the most important aspects of observing. If you measure most of the things properly (seeing, transparency, background brightness...) and keep good notes, it makes doing it again and noting the little differences in the sky easier. Also, when you compare notes/sketches with others, the LM comes an issue. Usually people have far too low limiting magnitudes, for example the old myth that mag 6.5 is the limit for the human vision, so people just put in 6.5 and say they have dark skies. So summa summarum, try to measure the limiting magnitude always as accurately as you can, this is how I play it.
There is of course a big difference between magnitude 4.5 skies and magnitude 5.5 skies. For example, from my old observing site in the suburbs, only a few times did I witness limiting magnitude below 5.2 even with the moon up. With a regular 5.2 (winter, hazy, snow-covered ground skies) the Milky way is invisible in Cassiopeia and Cygnus. In August, the same region shows the Milky Way clearly even with the background still being fairly bright.
Measuring the limiting magnitude. How I do it is by look at certain stars in a certain region and depending on those, see what was the faintest star I could detect at that particular night. There are several older threads about this in the forums. Being more dependent on background brightness is of course trying to see deep sky objects with the naked eye such as:
M44 (visible at around 5.2 magnitude)
M35 (visible at around 5.8 magnitude)
M34 (visible at around 6.0 magnitude)
M15 (visible at around 6.5 magnitude)
M67 (visible at around 6.8 magnitude)
M81 (visible at around 7.0 magnitude)
And so and so on...
Summer Milky way visible = Lim. Mag. >5.6 (Perseus, Cassiopeia, Cygnus-region)
Winter Milky way visible = Lim. Mag. >6.0 (Auriga-Monoceros-Canis Major-region)
Of course, in the end you can play with the idea that you should measure the limiting magnitude every time after an observation is made and from as close as to the object in question as possible but who has the time for it!
Those triangle-things are good if you like that stuff. I prefer looking at just a single star, not trying to count 50 stars from Pegasus without getting a nervous breakdown.
/Jake
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Jaakko Saloranta - Some basic sketches.../
8" Orion DSE
4" Sky-Watcher
3" Konus RFT
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Paul_R
Carpal Tunnel
Reged: 04/05/05
Posts: 1648
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Well, dug up some old notes of mine... discovered that I had seen 6905 from my backyard in my 12.5" scope a couple of years back! I wrote "hazy blob--neat!". So it clearly is doable from my semi light polluted skies... but I wonder if a 6-8" dob can pick it up as easily. I'll find out at some point. (That photo will help me know I'm in the right location!)
(That 12.5" also showed me the Crescent Nebula, NGC 6888, quite clearly.)
Thanks all on the limiting magnitude biz... I haven't checked that in several years and so should. My technique is to pick a constellation, e.g. Hercules, and then try to find successively fainter stars. Or to sketch the main stars and then try filling in an area with the fainter stars and double-checking which magnitudes they were.
It must be easier to see the Milky Way than an individual faint mag 5 star.
By the way, I'm not using the Deep Map 600 to find objects (that would be hard!), but rather found a web site that lists the objects on line. Then I can use Argo Navis or Planetarium to get to them.
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EJN
super member
Reged: 11/01/05
Posts: 147
Loc: Pluto
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I have seen NGC 6905 from my suburban Chicago location,
with my 8" f/6 dob it's somewhat easy without a nebula
filter. With an OIII filter it's obvious.
From this location I have seen it with an 80mm refractor,
but it was difficult and you have to know exactly
where to look.
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Tony Flanders
Carpal Tunnel
Reged: 05/18/06
Posts: 2096
Loc: Cambridge, MA, USA
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Quote:
Having bad eyesight affects naked eye limiting magnitude - yes of course.
Dramatically so. Moreover, your vision can be perfectly corrected for bright conditions but poorly corrected for night observing, as explained in Josh Roth's groundbreaking article "Spectacles for Spectacular Skies" in the September 2005 issue of Sky & Telescope.
My stargazing glasses are 0.75 diopters stronger than my normal distance glasses. The first time I put them on, I stepped outside, not yet fully dark adapted, looked at the Hyades, and immediately noted stars 0.3 magnitudes fainter than I had ever before seen at that location.
Quote:
I've personally always thought the limiting magnitude as one of the most important aspects of observing.
Which just goes to show how much things vary from one person to another. Granted, Jaakko is a far more experienced observer than I am. But I long ago gave up on limiting-magnitude estimates. It takes me the better part of a half hour to do one -- something I cannot spare out of the few hours per month that I get to spend time under a clear, dark sky. And even with all that time, I think that there's a random fluctuation of at least +-.2 mag in my estimates.
I do find limiting-magnitude estimates of some value in comparing transparency at a single known location from one night to the next for my own personal use.
I find limiting-magnitude estimates nearly useless for comparing my conditions to those of another observer, since there's a variation of at least +-.5 magnitudes among experienced observers working side-by-side under identical skies, and much more than that if you include novices.
I find instrumental measurements, notably the new Sky Quality Meter with Lens (SQM-L) much more useful for comparing sky conditions from one site to another and from one individual to another. And in general, I find that the visibility of fuzzy objects like the Milky Way varies less from one individual to another than the visibility of stars does. So the fact that you can see the Milky Way tells me a lot more than any limiting-magnitude estimate could.
For reference, when I can see mag 5.0 stars, then there's a good chance that I can see the summer Milky Way too -- though I sometimes fail. But if I can see mag 5.5 stars, then the summer Milky Way is genuinely obvious as long as it's reasonably high in the sky.
I do agree with Jaakko on one thing, though. If you can see the Milky Way reasonably easily, and if you can't see stars fainter than mag 4.5, it's probably either because you're not trying very hard or because your eyes are quite poorly corrected for nighttime conditions.
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Tony Flanders
eyeglasses
6x15 and 8x32 monoculars
8x25, 7x35, 10x30 IS, 10x50, and 15x70 binoculars
70mm and 100mm achromatic refractors
4.5", 7", and 12.5" Dobs
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Paul_R
Carpal Tunnel
Reged: 04/05/05
Posts: 1648
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EJN, that's helpful info! I'll have to try it in my "smaller" dob and see how it comes out.
Tony, thanks for a thoughtful post as usual. I'm due for some new eyeglasses later in the summer and I think I'll get a second pair made up for astro, night time viewing with the diopter push. I know that the last time I pressed them to really investigate & correct my astigmatism, that the resulting prescription showed me the Pleiades in a way I had never seen before, i.e., resolving the main stars clearly. So I imagine that pushing this with the diopter upping will yield some good results.
Does anyone know if the optometrist(s), lens makers that were offering those lens kits for testing (increments of 1/4 or 1/2 or some such added diopters) are still around? Or how to get in touch with them? To do this right, I really should experiment at night myself and then tell the eyeglass people what I need.
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stevek
Pooh-Bah
Reged: 04/16/06
Posts: 1229
Loc: west michigan
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I hit NGC 6905 last night with my 8"DOB from my burb driveway as the moon was coming up- showed up at 92X and was easy when I added the NPB filter. Its a pretty nice one really & takes mag well. Not as bright as the Blinking but surf brightness seemed comparable to the Dumbell. Good luck & clear skies
Steve
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DSO 8" f6 DOB w/ 8x50 RACI & 2"Crayford
1958 Sears Discoverer 76mm Refractor
GSO SV 30mm 2",21mm Hyp,13mm Strat,BO/TMB ver2-6mm & 4mm
1.25"Filters: DGM-NPB, 25%ND
1.25" plossls: 25mm,20mm,15mm,9mm
Orion 2X Shorty Barlow
Garrett Gemini LW 11x56mm binocs
BTG-10 4.0mW green laser pointer
"What is that burning in the sky? Tell me y'all..." Jeff Beck/Jan Hammer
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RRaubach
AstroCowboy
Reged: 01/26/05
Posts: 2173
Loc: Douglas (Converse County),WY
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I observed the "Blue Flash" using my TMB 203 APO. It was an easy catch using the following technique: go to Sagitta and visit M71 and M27 on this quest. Then center eta-Sagittae in an eyepiece of giving 75-100x (I used a Nagler 17T4 and 83x). Stop tracking and time exactly 17.5 minutes, and the "Blue Flash" should be nearly centered. My observing notes from 8/18/2006: "Easy to identify at 83x,; takes magnification well. Pentax 10 XW and 142x good, but better still for aesthetic visual impact at 203x using Pentax 7 XW. No sign of annular structure even at 335x in UWAN 4. No central star seen."
Granted, this was from a very dark observing site, on a night of excellent transparency. Hope this helps!
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Rodger
Meade SN-10 (UHTC) on Tak EM-200 mount/Antares rotating rings. Moonlite focuser.
Parallax 14.5" Newtonian on HD 200 mount (arriving soon!) w/ conical Royce mirror.
TMB 203 f/7 APO refractor on Tak NJP-160 mount.
Discovery 12.5" PDHQ
Schneider 18x80 "Flakfernrohr" binoculars/tripod mounted. Canon 15x50 IS binoculars
Unihedron Sky Quality Meter
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Fiske
Carpal Tunnel
Reged: 03/14/04
Posts: 2057
Loc: Missouri / United States
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Rooting around in my observing logs for some stuff on NGC 7006 for another thread on this forum, I came across an entry for NGC 6905 I had logged on September 3, 2003. I made the observation with a Tele Vue TV101 refractor and 7mm Nagler T6 and 3mm Radian eyepieces (aprox 78 and 182x) from midtown Kansas City.
"I last observed this PN with the C11 from a dark site and I must say it is quite a bit fainter in the 101 than I had anticipated. It's distinct and easy to hold in averted vision, but just at the threshold of visibility in direct. It's quite near a 10th (?) magnitude guide star. I can't make out structure, though it's obviously non-stellar. I can't detect any color. It does seem to flicker or flash a bit in averted vision. SkyMap Pro lists it at 11.9 mag -- it seemed brighter to me. Anyway, a pleasing challenge under urban skies with a 4-inch telescope." (J4-57)
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Fiske Miles
Nikon 8x42 LX / 12x50 SE Binos
Mini Borg 60ED, TV-101, AT80Ach, XT-8, C11/CI-700, 22-Inch Dob
Way too many Nagler eyepieces
http://www.fiskemiles.blogspot.com/
www.fiskemiles.com
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Tony Flanders
Carpal Tunnel
Reged: 05/18/06
Posts: 2096
Loc: Cambridge, MA, USA
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Quote:
Does anyone know if the optometrist(s), lens makers that were offering those lens kits for testing (increments of 1/4 or 1/2 or some such added diopters) are still around?
Apparently so. The URL is www.optego.com. I strongly advise against getting a different prescription without trying it first. Some people find stronger prescriptions useless or counterproductive. Moreover, you may find that the flippers alone are sufficient. Just hold them in front of your regular glasses for moderate-length looks at the night sky.
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Tony Flanders
eyeglasses
6x15 and 8x32 monoculars
8x25, 7x35, 10x30 IS, 10x50, and 15x70 binoculars
70mm and 100mm achromatic refractors
4.5", 7", and 12.5" Dobs
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Paul_R
Carpal Tunnel
Reged: 04/05/05
Posts: 1648
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Appreciate the continuing posts on seeing 6905 from suburbia... all helpful data points!
Tony, thanks for the link and advice. Those look like what many optometrists use. Now a cool version of this would be like those flip sun glasses... attach the diopter flipper and put it up or down depending on what one is viewing!
I'll have to dig up that great S & T article on this and see what increments they recommended getting for the trial runs of this. (Although I just browsed that site more and it seems those flippers can cover a wide range of corrections--and there's even a "night myopia diagnostic" pair. Still, I know how good that article was so I'll find it in my bookshelf!)
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