Am I seeing what I should be seeing?

darkskybondi · #1 06-01-2009, 05:26 AM

Hi all,

I've been quite patient with my new 10" truss skywatcher (focal length 1200mm), taking it out almost every night with very low expectations. I've observed Saturn, the moon, Orion nebula, Omega Centauri (globular), a few other objects that I have largely forgotten, and the Leo Trio.

Now I have marvelled at each of these. However, this is a 10 inch scope. I am surprised at the dimness of most of these objects. Omega Centauri was nice but for such a bright object I would have expected something significantly brighter at the eyepiece. Orion nebula is pretty but certainly not the showcase that all the posts and the books I've read have said it should be; it is clearly visible but not what I would call a bright object. The Leo Trio (M65, M66 and NGC 3628) was particularly dim; I starhopped there and saw but the faintest of tiny fuzzies.

Even with my reasonable expectations, I expected to see far more; Philips' Deep Sky Objects guide has a sketch done of the Leo Trio as seen in an 80mm refractor and even that sketch is far, far more detailed than anything I could even see with all of the following: averted vision, good dark adaptation, reasonably dark skies (I'm on the coast), hours learning to laser collimate the instrument (which included battleship tightening the locking screws since I thought they were the adjusting screws... worried I buggered the mirror cell casting)... etc.

And I should mention that the moon IS bright through the scope - it's bright through my binoculars, for heaven's sake! - but not the blinding sight I imagined it would be through a 10" scope. Maybe I was wrong, but I can comfortably view the moon which is currently waxing gibbous at around 65% for plenty long.

As I mentioned, the skies are as dark as can be expected anywhere near the city; I'm on the coast and the eastern skies are quite dark indeed compared to the light-polluted washout to the west.

What could I be doing wrong? Or am I on the right track here?

Cheers!
DSB

astronut (John) · #2 06-01-2009, 08:39 AM

DSB,
If you're observing from the Eastern Suburbs of Sydney, this is your problem!!
Your observing area is surrounded by the biggest light dome in Australia!!
Once you join M.A.s out in a truly dark sky, you'll see the capabilities of your scope greatly improve.

Cheers, John.

erick (Eric) · #3 06-01-2009, 09:26 AM

I can only agree with John, DSB. I used to try observing from suburban Melbourne but soon gave up. Anywhere less that one hour's drive from the outskirts is a poor substitute for darker skies. Sydney is much worse. I was out Mittagong way last week and the Leo triplet (in the direction of Sydney skyglow) was disappointing.

Pack it up next new Moon weekend and check those targets again from well outside Sydney - then you'll have a better assessment of how it is performing.

From the depths of the city, I suggest you get interested in stars - coloured, doubles, triples, eg: http://scp3.org/blogs/blog5.php/crux/

Coen · #4 06-01-2009, 10:14 AM

Another thing to note is that if you wish to see detail etc is the factor of training. Whether you do that training in Sydney or out the back of Birdsville you still need it. The viewing will be better from back of Birdsville regardless but if you have not practiced and gained experience you may not maximise the time you do get at a wonderfully dark site with perfect seeing.

Deep Sky Objects are called faint fuzzies and there is a reason for it: they are faint and they are fuzzy. Not to be flippant but that is the way of it.

The sketchers that sketch and have them published have been observing for many years and sketching also for a long time, they know what they can and can not see and how to bring that out. They also know that their sketches are often composites (as are photographs) that are built up over time spent observing the object at the eyepiece, adding this detail here, another there. Many sketches are labours that range from a quick scribble through to a number of hours of effort. When you spend considerable time on an object you begin to learn its character and what subtlties you can then see. Go to any sketch artists web site and most will tell you it takes time, patience, practice and training to begin to see more than a distant ball of gray wispy cotton wool for many of the DSOs. They will also tell you to not give up.

There is something rewarding about beginning to see some detail and then comparing to sketches or photographs and checking what you saw. Or maybe I need to book an appoint with a physc to see how well adjusted I am ;-)

There is no substitute for time at the eyepiece and good on you for getting out and doing so. Regarding detail, you'll get there.

Regarding the Orion Nebula, if you concentrate around the Trap you'll see detail associated with the fish-mouth (dark structure near the trap) and some of the fainter variable stars that are embedded in the nebula as they struggle to get their light out. There is also the extent to which the nebulae goes, try determining its boundary and the nature of its shape. Can you see any colour at all - some folk report blue-green (faint) around the brighter parts. I have seen it with an 8" when I was younger. My daughter claims to see it with my 70mm refractor (I can't but then my eyes are older) when I asked can she see any colour or is it all gray (with no other prompting than that) her response I see bluey-green, <sigh> to have young eyes again. View is from northern suburbs of Adelaide.

You can also try your hand at the Eta Carina Nebula which is beginning to make an appearance again and NGC2070, the Tarantula has detail worth a look. NGC 253, an almost edge on galaxy in the sculptor region is also rewarding for a bit of time viewing. There is also nearby NGC 55 and perhaps NGC 300. M77 might be worth a crack too.

ngcles · #5 06-01-2009, 07:05 PM

Hi DSB,

John & Eric are spot-on !!

In truth, there is little hope of any dark sky at Bondi. You are much more likely to find hen's teeth and/or "bargain-basement" rents there. I know the sky might look okay to you out to the east but from Bondi, mate the light pollution there in any direction is a choice between bad, awful and horrific -- and then there is the amount of moisture in the air ...

It is unrealistic to expect good deep-sky views of non-stellar objects from Bondi -- apart from the very brightest.

I'm pretty sure there is nothing much wrong with the 'scope and I don't think your eyes are making as much of a difference as you think.

What you need is a darker background against which to see those faint fuzzies -- simple as. Most beginners have little idea of the difference a dark sky can make to the way their 'scope performs. In addition to the darker background you will actually become dark-adapted in a way not possible at Bondi.

To quote Darth:

"You don't know the power of the dark-side"

Oh and BTW -- read Coen's post well -- much, much truth there young padawan ...

Best,

Les D

darkskybondi · #6 07-01-2009, 05:19 AM

Guys,

Thank you very much! It sounds as if most DSOs are being washed out by Sydney skyglow, even though I'm literally about 20 metres from the cliffs. This is a relief!

The other suggestions/reasons you listed are a relief, too. What concerned me was that something as bright as the Orion nebula was so underwhelming - not that I wasn't awed to see it (I was! for real!) but I did expect it to be somewhat brighter. Omega Centauri cluster was similarly awe-inspiring - phenomenal - but I expected more brightness. It sounds as if Sydney skyglow is the main culprit for some of this.

Coen and astronut - excellent suggestions - I will persist with observing from here on the coast until the various observing sessions in a couple of weeks in dark sky sites around Sydney. Looks like I'll be heading mostly south. Very keen to accompany you, Les, because you've been particularly attentive!

Les - regarding the scope: as long as I didn't stuff the mirror cell casing by battleship tightening the screws last week, I'm happy. That is, if some more experienced astronomer looks at my scope and says, yeah, your instrument looks fine, and the views through it are what's expected for the aperture, then great! I'll wait till an observing session for that.

Having said that, I am enjoying my time at the eyepiece. Waiting till I see Les and other astronomers at an observing session before I buy Barlow or more EPs. I'll start logging my observations now, too.

Erick - will definitely start getting into doubles and triples now that you've suggested it.

Mostly I think the best thing about being out there and trying to observe particular objects is that you get the opportunity to learn the constellations - obviously the most important starting point if you want to avoid lugging a laptop around everywhere. So far, Orion, Crux and Leo are my skymarks. Will proceed from there. To illustrate how addictive astronomy has been: I bought a Playstation 3 today, and a few hours later I'm back on iceinspace and into the astro books!

Warm regards all, and clear skies
- DSB

erick (Eric) · #7 07-01-2009, 10:19 AM

Quote:

Originally Posted by darkskybondi

Erick - will definitely start getting into doubles and triples now that you've suggested it.

I see you have Albireo (Beta Cygni) listed as favourite star. There is an equally spectacular double in the southern skies - in Vela - not far from the Eta Carina nebula. X Velorum!

http://www.iceinspace.com.au/index.p...69,198,0,0,1,0

http://www.iceinspace.com.au/forum/s...ead.php?t=1941

At the moment you probably need to wait until some time after sunset for it to have risen high enough.

Coen · #8 07-01-2009, 11:37 AM

I have been using doubles as a way of touring a constellation, specifically the fainter ones. There are some really nice ones out there and there are plenty of lists to get started on. I am building a bit of my own list.

Multiple stars are something to enjoy regardless of Moon (well, not quite as splitting tight high magnitude difference ones, all help is useful). It also fun stumbling across a few.

I recommend Taki's double star atlas (down to magnitude 8.5) with its associated MS Excel spreadsheets (1000s of doubles listed). I also use CNebulaX to compile a bit of list, it displays graphically the relative magnitude difference and separation plus what a certain magnification might expect - it does not do colours. There are other bits and pieces of software out there to help.

The big Washington Double Star database (WDS), in MS Access format with search queries or as a text file, is a fantastic resource that does take a little effort - it is about 25MB in size and regularly updated. The MS Access database allows for searching by a number of criteria including constellation, magnitude difference, separation, limiting magnitude etc. A short search with limiting magnitude of 11.5, minimum separation of 1.5" and no constraint on magnitude difference returns over 550 pages of double stars. More than enough to keep busy for a while. I understand that the WDS custodians welcome corrections etc.

There are also sites that give orbits of pairs and their relative positions as time goes on. There are a number of stars within reach of your telescope that you can watch change over a period of a few years. They might not be massive changes but still...Also there are some stars that are openning up that can become visible or others that you can watch as they can not be split.

I have watched off and on Alpha Cent over the last 25 or so years and been interested to watch its changing separation as it progresses along its nearly 80 year orbit. Have not bothered with Proxima yet.

Another option you might consider besides planets and the Moon are perhaps tracking minor planets or comets?

Coen · #9 07-01-2009, 11:51 AM

I found this on another astronomy board (moderators: if it is not appropriate to post such a cross link, please forgive and delete as needed).

The link: http://www.cloudynights.com/ubbthrea.../1#Post2847793

It shows via a sketch the impact of light polllution on a view of the Orion Nebula. Note that the view is from the North Western United States.

Screwdriverone (Chris) · #10 07-01-2009, 04:22 PM

Hey DSB,

My suggestion: Pack that gorgeous collapsible metallic black scope in the car on the next clear observing night [17th January] (or perhaps PM me and we can organise a non observing night attendance) at Linden which is about 80kms WEST of you in the Blue Mountains and the home of the Western Sydney Amateur Astronomy Group (WSAAG) dark sky site.

I live in Kellyville which is not too bad for Skyglow, but the difference I get by driving about 60km west to Linden and the hour it takes to get there is WELL worth it.

I can see a lot of DSO's including the Andromeda Galaxy with the naked eye from up there and the band of the Milky Way overhead is awe inspiring to say the least.

Well worth the trip, even if its only so I can show you the ropes re collimation and working your way around the skies on the "classics" Such as LMC, SMC, Orion, 47Tuc and Omega etc etc.

PLUS, I may get a squiz through that sexy new scope of yours......hee heee heee

Cheers

Chris.

darkskybondi · #11 13-01-2009, 11:17 AM

Hi all,

Wish I could have replied sooner but have been a little busy.

Meanwhile, thanks Erick, Coen, and Screwdriver - all excellent suggestions. Particularly interesting were the suggestions about observing double stars, the link about how Orion looks in light-polluted skies (amazing link, Coen!) and Chris' consequent suggestion that I should get out to some dark skies.

I have to say that I am amazed at how true Les' comment about light pollution on the coast must be. The skies seem inky black off the east coast, and yet Orion looks like the washed-out image in the sketch on cloudynights (see coen's post below).

The only thing I remain concerned about is the adjusting knobs on my scope. I know I keep rabbiting on about it, but one of the knobs has to be completely loose in order to get the laser dot in the right place on my collimator. I suspect something is wrong; either in what I am doing, or the scope's mirror cell mechanism.

In any case, I'll be taking all of your advice, and today I shall begin making arrangements for getting out to dark skies this week and next for the various clubs' observing nights that are planned. Very exciting to finally be getting out to dark skies with the scope!

Thanks again!
- DSB

erick (Eric) · #12 13-01-2009, 11:23 AM

Quote:

Originally Posted by darkskybondi

The only thing I remain concerned about is the adjusting knobs on my scope. I know I keep rabbiting on about it, but one of the knobs has to be completely loose in order to get the laser dot in the right place on my collimator. I suspect something is wrong; either in what I am doing, or the scope's mirror cell mechanism.

Just checking I understand - you mean one of the three collimating knobs at the primary mirror end?

darkskybondi · #13 13-01-2009, 12:57 PM

Quote:

Originally Posted by erick

Just checking I understand - you mean one of the three collimating knobs at the primary mirror end?

Yep. Almost completely loose, while the other two are relatively tight. I've been doing all of this at the suggestion of the vendor, and he gave me some information that wasn't quite right - initially he told me that "one of the knobs tightens and the other loosens". An innocent mistake but as I said, I ended up battleship tightening one of the locking screws to collimate the primary.

I have suspected that this might have stuffed the mirror cell mechanism. Or that it came that way.

- DSB

erick (Eric) · #14 13-01-2009, 01:14 PM

Yes, sounds a bit odd. However, since it is a strut style, you should be able to get a good look at what is going on from top and bottom? I don't know the exact model, so I'm only guessing.

Here's the theory, to my mind, of how it should work. Once the three collimation locking screws (the smaller ones?) are screwed well back out of the way, you can see what is going on. As each of the three collimation screws are turned clockwise, they should pull their corner of the mirror cell and the mirror follows!) down towards the bottom end of the scope tube - and the primary mirror tilts accordingly. They should pull against spring pressure so it may get a bit firmer as the springs gets more compressed. As you turn them counter clockwise, the opposite occurs, that corner of the mirror cell moves upward, assisted by the spring. Now, is it possible to screw this so far that the screw comes out of the mirror cell and turns freely - well maybe, depending on the design. Could one completely strip the thread so the screw turns freely? Hopefully not by hand? Did you put the pipewrench and a six foot piece of water pipe on the wrench to get some action! I doubt it. So a visual inspection from above and below may show what is happening. Perhaps you can post some photos so we can see.

Before you do all this twiddling, you have an ideal opportunity to understand what is happening. Being a strut, you can stand behind and see the laser spots on the secondary mirror. The approximately centred spot is the one coming out of the laser. If the Primary is roughly right, the other spot will be the laser returning after bouncing off the primary. If way off, the spot will be missing the secondary. Just search for it with a sheet of paper over the open end of the scope. You can look at that spot and adjust each of the primary collimating screws in turn and see if the spot moves exactly as you would anticipate from my description above. If it doesn't, time to stop and examine carefully to see what is happening mechanically - something is wrong and it shouldn't be to hard to pinpoint and repair.

Sydney is full of IceInSpacers! Is it time to offer the coffee/tea/beer/view of Bondi Beach etc. to entice some experienced over to help you?

Eric