David Geary

M17 The Swan Nebula (In Sagittarius)

Thursday 14th September   8.30 to 9.30pm   No moon

Found the Swan nebula. It’s not visible in the finder scope so I had to sweep the sky looking through the main scope to find it. I didn’t need a filter for this bit – the main body of the swan is visible without one. It could easily be mistaken for a galaxy. Once I’d found it I switched eyepieces giving me slightly higher magnification at 80x. A light pollution filter revealed the neck and part of the head. Not sure whether I prefer the UHC or OIII. It’s right what people say, there is a dark area in front of the swan’s neck – darker than the surrounding sky on all sides.  My star atlas calls M17 the Omega Nebula, which sent me off the trail for a bit. It also suggests the Swan Nebula has a star cluster right on top of it, but I didn’t see any noteworthy stars through the scope.

The Swan Nebula is impressive because of the unusual shape, whereas the Eagle and Lagoon Nebula are impressive because of the combination of a nice star cluster and nebulosity. I recon these three nebulae are about the best in this section of the Milky Way.  After scanning the surrounding sky quite thoroughly using a light pollution filter I couldn’t see anything else glowing, save perhaps a very slight smudge that I suspect was the Trifid Nebula.  Thanks to Nick in one of his posts for putting me on to the Swan Nebula, I may have overlooked it otherwise.

David Geary

The Lagoon Nebula

Saturday 9th September   9.30pm   Coalville   Streetlights nearby

No moon   Visibility clear but not brilliant

Another nebula that could easily be overlooked as you can’t observe it unless you have a clear horizon to the south.  I preferred the view with the UHC – the stars were brighter.  The OIII did however show a bit more nebulosity amidst the star cluster on the right.  This nebula is worth a look.  It’s visible from July to September so you’ll have to be quick if you want to see it this year.

David Geary

Globular star clusters close to the horizon plus the Eagle Nubula

Saturday 12th August 2017 10.30 to 11.30pm
Moon approaching last quarter and rose shortly after my observing session.
Observing with my f5 16 inch Dob.

I set my scope up in my Dad’s front garden this evening because it has a clear view to the south. The aim being to observe some new globular star clusters close to the horizon. To be honest, it was starting to get a bit boring observing the same stuff over and over again, and the only ways to observe new stuff are to go to a much darker site, go on holiday to Australia, or explore a lower patch of sky that’s previously been blocked by trees.

I soon discovered that nothing was visible in the finder scope this low down. The sky is lighter closer to the horizon and didn’t provide enough contrast. Instead, I used the Telrad to point the scope in roughly the right direction, then used my widest field eyepiece to scan for what I was looking for.

M22 proved reasonably easy to find, and reasonably impressive. It seemed to be quite spread out for a globular star cluster, lacking the usual concentrated core. It looked best in my Meade Super plossl, giving 80x magnification, rather than the 155x I normally use for globular clusters. I was denied a view of another globular cluster, M4, by a tree halfway down the street – which tells you how low it was.

I also managed to see M12 and M10 for the first time. (Also globular clusters.) They’d eluded me on previous occasions. Both were smaller and fainter, and needed 155x before I could see any individual stars.

A bonus was the Eagle Nebula. This looked best through an OIII filter at 60x. There are three bright stars at one end, and a cluster of about a dozen stars at the other end, with some cloudiness in-between. A UHC filter showed the nebulosity as well, but it wasn’t so pronounced. Without a filter, the cloudiness wasn’t visible at all. The fact that the Eagle Nebula is located by some prominent stars is handy, which should make it easy to point out to beginners. I can well imagine this nebula is a main attraction in more southern countries where it’s higher in the sky. If it’s clearly visible this low down it must be really impressive elsewhere.

I also showed my girlfriend Saturn, which she’d never seen before. It wasn’t a bad view for how low it was.  So there we are. It’s not every night I can say I’ve seen four new objects. Plus I saw the brightest meteor I’ve ever seen. If you want to see these globular clusters for yourself, and the Eagle Nebula, now is the right time of year.

David Geary

Sketches of Jupiter

 

Here are a couple of sketches of Jupiter I did last month.  I thought they might demonstrate the kind of views you can get of planets with a large Dob.  The first was made on Saturday 1st April at 2am, and the second was on Saturday 8th April at 11.30pm.  The scope was a 16 inch f 5 Dobsonian with a 1/10th wave primary mirror and a good quality unspecified secondary.  If I remember correctly, I worked out that the secondary mirror covers 21% of the area of the primary.  (Anything less than 20% is supposed to be good for planets.)  Teeters Telescopes in the US do a 16 inch f 5 Dob Planet Killer, so they must think it’s a good spec scope for planets.  I realise you’d get better views with a 6 inch apochromatic refractor.  I brought my scope for deep sky objects, but was pleasantly surprised by what I could see on Jupiter.

Half the trouble with observing planets with a Newtonian is tube currents.  This isn’t an issue with this scope – because it has no tube.  I usually pull up the shroud on the upper side just above the primary, to let out any warm air.

Obviously the main thing when observing planets is to wait until they’re high in the sky.  The light is then passing through the atmosphere at more of a right angle, meaning the light travels a shorter distance through the air.  This results in less blurring.  I also avoid looking over houses close by, as warm air rises from these too.

David Geary

Report on The Peak District Star Party

Peak District Star Party – Riverdale Campsite

Saturday 25th March 2017  

7pm to 11pm   No moon

M51 (The Whirlpool Galaxy) and NGC 5195  

It’s been my ambition for 20 years to see the spiral arms of a galaxy, and I finally got the opportunity to take my 16 inch Dob to a dark sky site last Saturday.  Shortly after arriving I asked a guy with a big Dob which galaxy is the best bet.  As I suspected, the answer he gave was M51.

I trained my scope on M51, and as usual, I could see this galaxy plus the fainter galaxy, NGC 5195 underneath.  Where I live, in town, I can see the bright core of M51, and the dimmer outer regions, but I can’t see any detail.  I was very much hoping things would be different in the Peak District.

By mid-evening I could see that the outer region definitely looked brighter in some places than in others.  I found that 150x magnification showed more detail than lower magnification.  As I moved away from the core, downwards and to the right, there was quite a dark area, then a brighter area as I moved further way from the core.  But I couldn’t piece the lighter and darker areas into a spiral.  By 10.30, however, I was confident I could see at least a little piece of a spiral.  The most obvious part started on the right of the core then swept down and round to the left underneath the core.  There was also a hint of one on the opposite side.  I decided that if I could work out from my own observations which way the spiral arms went round, then I would conclude I’d really seen them.  After finding some sketches on the internet when I got home I decided that this in fact was the case, so I’m counting the expedition as a success.

Other targets

As you might imagine, most other things looked a little more impressive, particularly M3, the globular star cluster just above Bootes in Canes Venatici.  The most noticeable difference was the Owl Nebula.  In the past I’ve only been able to see this using a light pollution filter, but it was clearly visible through the main scope without a filter in the darker sky.  I still couldn’t see the eyes though.  Unfortunately I could still only see the usual four galaxies in the Virgo Galaxy Cluster, M84, M86, NGC 4338 and 4435.  Maybe I’d have seen more on another night or if I’d stopped latter.

22 inch Dob and 13mm Ethos eyepiece

I had a look at M51 through an 18 inch Dob, and then a 22 inch Dob.  I could see a bit more detail in each, but not masses more.  It’s the same when moving from a 10 inch to a 16 inch.  There’s a worthwhile improvement in what you see, but not as much as you might expect.

Interestingly, both guys were using 13mm Ethos eyepieces, which would give them around 150x magnification.  The opportunity to look through a really big Dob and an Ethos eyepiece made the trip doubly worthwhile.  I have to say though, that I wasn’t sufficiently awed by the 100 degree apparent field of view that I’m going to buy one.  Nor would a larger telescope be practical given how I store and transport my scope.

The one thing missing

The one thing missing from this event was the car loads of locals who’d travelled up to see the wonders of the universe and take advantage of the clear sky and fabulous telescopes.  There weren’t any regular campers who wanted a look either.  I did, however, notice that the campsite bar and café were jam packed with people.  Shame.  At least some people benefitted from the experience.  I enjoyed myself.  Even my girlfriend said she enjoyed the evening.  Praise indeed!

David Geary

Observing NGC 2362, the Porch Light Star Cluster

16th March 2017   No moon   Just after 7pm

NGC 2362   The Porch Light Star Cluster

I found an interesting star cluster I’ve never seen before, probably because it’s so low in the sky.  NGC 2362, the Porch Light, as it’s called, which is so named because it resembles moths round a light.

The star cluster is located just below Sirius (the bright star below and to the left of the constellation Orion).

There’s one bright star visible in the finder scope, which is presumably the light, and a host of smaller stars that can be seen through the main scope.  Four of the brighter stars form an oblong, and midway along one of the longer sides is the bright star.  About 100x magnification is best.

I also found a nice double star in the vicinity whilst I was trying to find the cluster.  It’s a white and yellow combination with two stars of roughly equal brightness.  They looked nice at 100x magnification.  Unfortunately I can’t provide any more detail about its location because it clouded over very quickly.

Next time it’s clear early in the evening I’ll try and spot M79, a globular star cluster just under Orion.  This is another object I’ve overlooked because it’s so low.

David