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Posts Made By: Inge Skauvik

July 30, 2002 10:28 PM Forum: Deep Sky Observing

Where did the noctilucent clouds go?

Posted By Inge Skauvik

Here, in the sub-arctic zone, the stars are beginning to re-appear. We have a 6 - 7 long period between sunset and sunrise, but unfortunately the sun does not dive far enough below the horizon to give conditions for deep-sky observation. The northern sky glows brightly, adorned by Capella which always keeps well off the horizon.

At this time of the year, we often see noctilucent clouds in the north from my location. Capella is a useful guide to these clouds, they have about the same distance from the northern horizon. Often, noctilucent clouds have an appearance almost like sunlit cirrus clouds. However, cirrus clouds always will appear dark when Capella is visible. The glow of noctilucent clouds also is peculiar, with a phosphorescent appearance, but not iridiscent (like mother-of-pearl clouds seen in winter). Sometimes very bright, lens-shaped clouds may appear.

The altitude of noctilucent clouds is several times greater than that of cirrus clouds, and they do not seem to be associated with weather. A few years ago, we could see these clouds almost every clear night, but this year I have not seen a single one.

Do you see such clouds from lower latitudes, or is this a pehnomenon associated with our long periods of twilight conditions?

Inge, 59.5 deg N

August 1, 2002 04:45 AM Forum: Equipment Talk

12-inch premium Dob

Posted By Inge Skauvik

I have used an 8-inch Portaball for two years, and I'm highly satisfied with it. However, there's always a desire to go deeper in limiting magnitude and increase resolving power, and I'm seriously considering to upgrade to the 12.5-inch PB. Before making my final decision, however, I thought it would make sense to look at other alternatives. There are very few Portaballs available on the second-hand market, but occasionally I see other fine Dobs in the 11 - 14-inch range for sale. The 11-inch Starmasters look very nice to me, and I'm open to other alternatives with fine optics.

What bothers me a bit, however, is portability, set-up time, and general ease of operation. I'm also concerned about ergonomics, after two years with the Portaball, I'm spoiled. How does e.g. the 11-inch Starmaster EL compare with the 12.5-inch Portaball in these respects? Are there other alternatives around? Any comments are welcome.

August 15, 2002 05:31 AM Forum: Equipment Talk

Anyone ever consider a tilted Dob?

Posted By Inge Skauvik

By tilting a Dob arrangement with the correct angle, it would be possible to make an equatorial out of it. There are some problems associated with this, particularly lateral load on the vertical (if tilted, the polar) axis, a problem which would be less serious at higher latitudes. At the north pole any Dob (except the Portaball) would work as a perfect equatorial.

Advantages would be easier navigation for manual/visual use, and benefits for persons considering astrophotography. And the "difficult zone" would be moved from zenith to the less interesting polar region.

Has anybody made or considered to make such an arrangement with a Dob? Any problems? (I do not think about older fork mounted Newtonians - there were a few of those, very heavy and expensive telescopes.)

August 26, 2002 03:08 AM Forum: Deep Sky Observing

What does it take to see IC1396 visually?

Posted By Inge Skauvik

IC 1396 is a large gaseous nebula in Cepheus, associated with a large, loose cluster of stars. I have been observing a couple of double stars in it, the quadruplet (triplet in small scopes)Struve 2816 being located in the very centre of the nebula.

However, I can not see any sign of nebulosity there with my 8-inch f/6. O-III does not help, and since I have no UHC-filter I can't tell if this will make the nebula visible.

I suspect that the ideal for this object is a smaller widefield scope (4-inch f/5 ???). Have anyone ever seen this nebula? Will UHC help? How do large Dobs perform?

September 3, 2002 10:37 PM Forum: Deep Sky Observing

Time to hunt for IC342

Posted By Inge Skauvik

IC342 in Camelopardalis is an extremely difficult face-on spiral galaxy. The integrated magnitude is relatively high, but it is large, and is considered to be at least as difficult as NGC147 in Cassiopeia, but detectable in an 8-inch. I have never seen it, but never made an attempt either. Now, however, is the right time, I will have it at a convenient altitude when it gets dark at night. I just have to wait for clear sky.

Anyone else taking the challenge?

September 6, 2002 05:16 AM Forum: Equipment Talk

What is the technology behind?

Posted By Inge Skauvik

Is there anybody knowing the technology behind the Collins image intensifying eyepiece. I have never seen one, and can hardly be considered a potential buyer, but I'm curious about how it works.

I'm also interested in the principles behind image stabilised binoculars.

Comments from owners of Collins pieces as well as image stabilised binoculars also welcome. Are you satisfied? Is it something every amateur astronomer should own?

September 13, 2002 05:15 AM Forum: Deep Sky Observing

Dark site observation???

Posted By Inge Skauvik

Wednesday night a few of the members of our local astronomy club went out observing. Conditions seemed very promising, no wind, transparent air, no moon interfering and end of twilight about 22:15 p.m. We had three scopes available, my 8-inch PB, a home-made 6-inch F/10 dob with Lichtenknecker optics and a short-tube 80mm refractor which was not used very much. There was some stray light from the town 10 - 15 km away, and some auroral glow in the north, and during the time needed for dark-adaptation we observed double stars.

Zeta Aquarii was very nice in both Dobsonians, and I trained the PB on several closer doubles just to confirm that seeing was sub-arcsecond.

But a really dark sky appears to be difficult to get these days. As our eyes got dark-adapted the auroral activity increased, and although most of the activity was in the north, the light from the aurora became annoying. Of course, the brighter deep-sky objects were nice. We observed M27, M71, M92, M81/M82 and several others with pleasure. Also M33 and M101 were visible, but the views could not be compared with what could be experienced under excellent conditions. The Veil-nebula with an O-III filter was nice, but not outstanding. The Crescent-nebula (NGC 6888) was extremely difficult. The 14.2 mag star near M57 could not be seen (sometimes this is possible from my driveway). NGC7331 was reasonably bright, but Stephan's quintet was a mere smudge even when its position was accurately known. I didn't even bother to look for NGC185, NGC147 and IC342 which actually were on my observing schedule.

Two objects, however, seemed to impress the club members. The two planetaries NGC7027 and NGC7662 impressed both with their surface brightness and their blue colour.

During the session I also observed the two globulars in Delphinus. NGC6934 is the brighter of the two. The 8-inch, in fact, shows several stars in it. It reminds me a bit of M56, although it is a bit fainter. NGC7006 is much fainter due to its location 150.000 light years away from the galactic centre on the far side of the Milky Way. It appears much smaller to me than the "Intergalactic traveller" in Lynx, but the brightness is comparable.

At the end of the session, the auroral display was quite impressive. Certainly it is a beautiful phenomenon, but hopefully the next great display will be an evening when the wind is too strong for telescopic observation. We really need the few clear, dark nights we can get.

September 16, 2002 02:30 AM Forum: Deep Sky Observing

Cool object: IC2149 and two enigmatic clusters

Posted By Inge Skauvik

Saturday night I observed for a couple of hours from a dark site. (No ambient light, no moon, no auroras). As always, I observed a mix of objects, doubles, clusters and nebulae.

It was dark enough to view both NGC185 and NGC147 with ease with the 8-inch Newtonian. However, I did not manage to spot IC342. Possibly this was because I did not know its position exactly, possibly because it is at the very limit of what can be viewed with 8-inches of aperture.

I observed two very interesting, but perhaps not very well known open clusters this evening. Not far from Polaris is NGC188. For astrophysicists this is a famous cluster, being almost as old as a typical globular. Visually it is not exactly easy. It is large and contains only very faint stars. By scrutinising the field, I could see a swarm of 13 - 14 mag. stars superimposed on a background glow. I also observed a cluster in Lyra, NGC6791, which resembles the Cepheus cluster. The Lyra cluster, however, is smaller in extent, and the number of stars visible is smaller. But the background glow indicates that this is an extremely rich open cluster. Both NGC188 and NGC6791 must be magnificient objects in larger scopes.

Near Pi Aurigae (just north of Beta Aurigae - Menkalinan) is a small planetary nebula, IC2149. Its extent is so small that it easily is taken to be a 10'th magnitude star. I had to use the blinking technique with my O-III filter to identify it, but as soon as I found it I realised that it was definitely fuzzy in appearance. Using a power of 240x I had the impression of viewing a miniature version of NGC7662. This nebula is bright enough to be seen in very small scopes, and it is a recommended target for people wanting to see something new.

September 26, 2002 11:06 PM Forum: Deep Sky Observing

"Top ten" list of open clusters

Posted By Inge Skauvik

I enjoy observing open clusters. They come in so many sizes, magnitudes and shapes, and many of them contain both blue-white and orange or red stars. I have my own "top ten" list of open clusters which I find particularly appealing in my 8-inch scope. Owners of scopes with different aperture may have other favourites. My list is also restricted by my high latitude. I have not included objects which can not be seen reasonably well from here.

So here is my list (random order):

NGC6791,Lyra: Only hint of resolution in 8-inch
M67, Cancer: Great swarm of stars
NGC7789,Cassiopeia: Beautiful, rich and large cluster
M11, Scutum: In "difficult" part of the sky
M37, Auriga: Best winter cluster
M46, Puppis: Beautiful, but a bit far south
h & Xi Persei: Double cluster. Large but impressive
NGC188, Cepheus: Faint but very rich
NGC2158, Gemini: Only hint of resolution. Compressed
NGC2420, Gemini: Stands out well. Pretty rich

As you may see I have a preference for highly populous clusters. But I also enjoy more scattered groups if they stand out well against the sky background (e.g. NGC 1502)or clusters containing orange or red stars (e.g. M41)

Other observers' favourites? What about astronomer living "down under"? I know that there are a few gems out of range for me.

October 2, 2002 11:10 PM Forum: Equipment Talk

Risk of getting spoiled

Posted By Inge Skauvik

For a person mostly having access to a small scope, is there a risk of getting spoiled by one-time use of e.g. a big dob (e.g. Obsession, Starmaster in the 15 - 20 inch range)?