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Old 22-09-2007, 08:32 PM
§AB
Its only a column of dust

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Obs report Sat 22/9

What's this? a clear night? Well I never!

Clear, cold and dryer than normal out tonight. Hauled my 10" dob outside just before sundown and checked both primary and secondary collimation. Secondary looked good and I gave the primary a quick tweak using a cheshire. Switched on the cooling fan for about 40 minutes, then switched it off and left the scope to cool for another 10 or 15 while I watched "Deadliest catch".

Telescope: 250mm (10") Newtonian
Seeing: 5-7/10
Transparency: 4/5

Checked collimation again, and it seemed to have shifted a bit as the mirror cooled (I always thought that was a myth and didn't believe the guys on Cloudy Nights lol). A quick turn of the screw and I'm set. During an earlier session I noticed the scope had a bit of astigmatism, so before tonight's session I loosened the primary mirror clips so they sit a paper's width above the mirror. I decided to check on this and glad I did, as two of the clips were quite firmly clamped down.

Observing Jupiter at 138x, I believe I could see an improvement in image quality! I had a clean, sharply defined disk. Seeing was good but not great and often would blur the whole image. At 138x, the rift in the SEB was most obvious, infact the SEB appears as two narrow brownish belts entirely seperated by the much wider rift. The South Temperate Belt was obvious, as was the North Temperate belt in good seeing. The NEB appeared to have a narrow, white rift running about 1/3 of the way across the diameter of the planet.This was intriguing as it was the first time I saw this. I could hint at streamers in the EQ zone and ruffling in the NEB during moments of good seeing. During rare very moments of excellent seeing, more belts would pop into view as would a couple of ovals in the SEB and other white features nestled beneath the NEB. Now, Jupiter was only about 10º above my rooftop so the average seeing was probably confined entirely within my backyard!!

Pumping it up to 166x, which is about as high as I like to go on Jupiter, (on my 4.5", 121x was the clincher ) the image held up quite well, with everything that was evident at 138x visible. But ofcourse, I had to be more patient with the seeing! At 227x, Jupiter's disk started to go a bit 'soft' but seemed cleaner than before my mirror clip adjustment. By now, it was 8.30pm and Jupiter was flirting with my TV antenna. In very good seeing, I reckon I could get decent views at 227x, and definately great views with my 166x and 208x eyepieces.

I then aimed for the moon. At 166x, 4 craters in Plato were resolved, including the "double craterlet".

Next, I went for the globular M4. At 83x, despite moonlight, it was well resolved with the central bar a collection of stars, unlike the "pricks in haze" effect in my 4.5". I upped it to 227x and the 60º field of the plossl nicely took in what was now an intergalactic swarm of bees! Nice! The bar was now well and truly resolved. Until now I could never fully appreciate the spectacularity of a globular cluster hence I always went for galaxies, Nebulae and Open clusters instead with my 4.5". The 4.5" did do justice on the larger globulars but the 10" cleans the smaller scope up in everyway! Can't wait for the day when Omega Centauri is straddling the zenith....

Just for kicks, I then tried the Double Double in Lyra. At perhaps barely 10º altitude, the star images at 166x were completed mangled. Plus I think my garden fence was in the way as I was seeing 6 diffraction spikes instead of 4! Despite this, I could see that each star was decidedly elongated even though it was flaring and jumping in the seeing and it was obvious that there was *something there*.

It's cold out so I came in while I wait for 47 TUC to rise Hope my scope is still dry and hasn't been pissed on by the dog or cat like before lmao

Now when in storage, I lean small bits of carpet against the sides of the base so when Mr Kitty decides to go on a territory marking rampage, it's the carpet that takes it head-on!
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Old 22-09-2007, 11:47 PM
§AB
Its only a column of dust

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ok now for the second part of the evening...

with the moon glow, DSO hunting was out of the question so I concentrated on the Tarantula Nebula and 47 Tuc, 'coz at this time of year at this time of night, those are the only two objects I can find without an atlas In other words....most of the fun is below the horizon!

Without realising it, I actually spent almost 3 hours staring at both the Tarantula and 47tuc in this friggin cold.

Started off with 47 tuc as it was quite high. At 83x, it was a gorgous (sic) sight. It was well resolved, right down to the core infact which quite surprised me at this modest magnification. In my 4.5", only the outer third is resolved, the rest is granular. But now, I am seeing something resembling a pile of glitter. Increasing it to 138x, the cluster as better resolved, the haze of the core littered with tiny pin pricks. Further increasing the magnification to 227x, the view was even better, the stars of the cluster overwhelming the field of view. The core, a large area of haze was covered with specks of light and using averted vision really bought out the best of the cluster. Using 416x, the view was similar but the cluster appeared spectaculary large with the outer 2/3rds completely resolved while the central regions remained a delicate haze littered with stars. My mum was particulary impressed with the 416x view

The Tarantula Nebula was a decent sight despite the overpowering moonglow. At 83x, it was easy to pick out and it exhibited considerable filamentary detail. At 227x, the view was far better, with two looping filaments easy to pick out - the features which give the nebula its name and it does indeed look like a spider. One loop is the head, complete with stars as the "eyes", while the other loop could be interpreted as the abdomen. Some outlying nebulosity was also visible at this magnification which was quite impressive considering the intense moonglow. Sweeping the area, several little knots could be seen littered everywhere. Surprisingly, I had my best view of the Tarantula at 416x, there was simply better contrast between the nebula and the background sky. The surrounding swaths of faint nebulosity were indeed easier to pick out than at 227x. Sweeping the general area at 416x I could pick out absolute scores of little fuzzies everywhere. I can see myself having fun in the LMC with the 10" on a moonless night

Can't wait for the moon to disappear - then we'll be in business

after sitting inside for almost an hour now, parts of the scope are still covered in dew...

Last edited by §AB; 22-09-2007 at 11:58 PM.
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Old 23-09-2007, 07:29 AM
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davidpretorius
lots of eyes on you!

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you write excellent obs reports and i can here the excitement in your writings.

top stuff
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Old 23-09-2007, 11:28 AM
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erick (Eric)
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A fun night in Berwick! Excellent report!!
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Old 24-09-2007, 01:13 PM
DougAdams
Lord Lissie

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Man, you're pulling 416x with a 10" scope! How did you find the hand tracking? I tried all sorts of mods with my 12" but never got it satisfactorily smooth - never made it as far as Ebony Star though

Four craterlets in Plato is great too!
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Old 24-09-2007, 02:19 PM
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ngcles
The Observologist

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Hi §AB & All,

Great report mate -- much enjoyed. I too used to observe the Tarantula Nebula (NGC 2070) at moderate/high magnifications (x160, x181 & x276) in my old 25cm and x184, x266 in the 31cm.

It really benefits from the extra magnification (narrowing of the exit-pupil) to darken the sky background. I nowadays commonly use x185 x209 and x247 in the 46cm on the Tarantula. Even after all these years, it is still one of my most treasured favourites.

You said: "I can see myself having fun in the LMC with the 10" on a moonless night" -- Amen! There is heaps to see.

As David said, I too can hear the excitement in your writiings!

Best,


Les Dalrymple
Contributing Editor
AS&T
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Old 24-09-2007, 02:43 PM
§AB
Its only a column of dust

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Quote:
Originally Posted by DougAdams View Post
Man, you're pulling 416x with a 10" scope! How did you find the hand tracking? I tried all sorts of mods with my 12" but never got it satisfactorily smooth - never made it as far as Ebony Star though

Four craterlets in Plato is great too!
Yep 416x on the Tarantula was the clincher! The stars didn't appear as sharp as at 166x for example, but near the limit of the theoretical magnification limit for a 10" scope and with 5-6/10 seeing that was to be expected, but I tell ya, at 416x, the Nebula itself was far superior to the 166x view. I could trace swaths of nebulosity well beyond the main filaments - in bright moonlight

As for as tracking goes, the Alt motion is smooth and free from jerkiness, but the Az seems a bit stiff but this being my first large Dob I have nothing to compare it to thus I can't really jump to conclusions.

The Plato craterlets were remarkably easy at 166x. I could resolve the double craterlet without even trying . At 227x, during breaks in the seeing the craterlets were even easier. In my 4.5", I don't think I've ever resolved it even in good seeing it and in that scope the view goes soft over about 200x.

Well, tonight looks semi-prommising, will make a sketch of Jupiter. Early morning tomorrow should be clear so I'll be tracking down M42 with the narrowband
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Old 24-09-2007, 03:37 PM
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taminga16 (Greg)
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Sab, Thank you for another wonderful report, your enthusiasm shines.
Best Wishes to you and your Mother, Regards Greg.
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