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Old 23-05-2010, 01:23 PM
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Observing Report 23/5 - Planetaries in Sag. and Aquila

Went to bed at 6pm the yesterday night due to a combo of no sleep on Friday night and a few drinks with mates yesterday, with a possibility of clear skies this morning and my tired state in mind. Woke up just beofore 1am this morning and debated whether or not to go out. I was tired, but it was the second clear sky in a row. A new record for Melbourne. And with a forecast of nothing but the usual ra ra routine clouds and rain for the next googleplex centuries, I decided to suck it up and grab the scope.

One thing that used to put me off early morning sessions was a lack of fans on the scope. It would *never* cool down. But that problem is history

After about an hour I started. Somehow, it just didn't feel "natural". It felt different to my usual sessions. Transparency appeared a bit off, the backyard was brighter than usual. Maybe I'm just not used to 2am starts. It was once again very dewy and really cold, infact the minimum temp on the scope was 0.6C just before sunrise! I was delighted to find the collimation practically dead on, all it took was 5 seconds to align the secondary using the laser and by what was probably good karma, the primary was dead on. A good omen for the night ahead. Call me superstitious but I was always believer in that whenever something starts off well, the rest of it will go well.

Time: 2:45am - 8am
Scope: 12" F4.4 truss dob
Seeing: 7/10
Transparency: 3/5
Dew: Severe
Temp: 1C

NGC 6818
PNe, Sagittarius, RA 19 43 58, Dec -14 09 11 , Size = 22x15" , Mag V = 9.4

A bright, bluish egg shaped gem at low powers, with very high sfc brightness. At 267x and OIII I could see annularity, not particularly obvious though, with a slight N-S elongation. E edge appeared brighter relative to the rest of the cloud. Now, seeing was evidently great, as a magnification of 534x provided nice tight images of the 3 nearby 13.5 mag stars framing the nebula. The nebula at this mag without OIII (I hate using filters at high power - you just cant se anything and get real disoriented) was clearly annular. However, the annularity is not even, with the northern end "missing" giving a horseshoe like appearence. Increasing mag to 762x I could see what appeared to be a small faint knot at in the annulus at the NW edge, and a faint outer halo which stretches out perpendicular to the neb's major axis, but only by a very small amount.

NGC 6751
PNe, Sagittarius, RA 19 05 56, Dec -5 59 32, Size = 21x21" , Mag V = 11.5

Located along a chain of 4 mag 12-14 stars, of which the planetary's 14th mag central star makes up one. Circular at 267x, with the central star easily seen despite being mag 14.5. Increasing magnification to 381x and OIII filter offered only modest improvement, however I suspected slight E-W elongation, andthe very central regions of the neb seemed to have lower sfc brightness than the surrounding areas. At 762x - Slight, very slight E-W elongation, somewhat uneven sfc brightness and the central region immediately in the vicinity of the central star appeared obviously darker than the remainder of the cloud.

NGC 6578
PNe, Sagittarius, RA 18 16 17, Dec -20 27 02, Size = 8.5" , Mag V = 12.6

Easy to see this tiny PN at 166x as a fuzzy "star" in a rich starfield. Located 21" NW of a mag 11 star. Suspected very slight elongation at 534x in NW-SE direction. Appears to have uneven sfc brightness, with the central regions "condensed", visually at the eyepiece looks much like an elliptical galaxy. A faint star was seen just off the E edge.

NGC 6778
PNe, Aquila, RA 19 18 25, Dec -01 35 47, Size = 25x19" , Mag V = 12.1

Small at 267x, elongated NE-SW. No real improvement at 381x but at 534x the surface brightness seemed uneven with an irregular shape. Slightly brighter towards the centre.

NGC 6886

PNe, Sagitta, RA 20 12 43, Dec +19 59 22, Size = 9" , Mag V = 11.4

Easily found by starhopping from the "point" of Sagitta. Forms a triangle with a mag 10 star 1.5' E and mag 11 star 1' SSE. Visible at low power, but almost indistiguishable from the star field. Can be seen as a fuzzy "star" at 267x. At 534x it presented a tiny round disk with a high sfc brightness. No other details seen.

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Also had a look at Jupiter. By the time it rose high enough, seeing was starting to go although I could still get good viewing at 267x, and at 381x on occasion. Quite strange seeing it missing the South eq belt. Numerious belts, ruffling and ovals could be seen in the southern temperate regions at 381x, and a large white rift was present in the NEB, splitting it in half for about 1/3 of the diameter of the disk. Continued viewing until after sunrise, the view in daylight isn't too bad at all, the larger features were still visible.
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Old 23-05-2010, 08:59 PM
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Another very impressive report, Sab. I'm going to have to arrange some way of getting to those high mags you're using. I was very interested in Dave's response to your other post about the duration of the session increasing the chance of good viewing. I got up about 4.30 this morning to have a look at Jupiter, but the seeing was just awful in that part of the sky. I suspect some of this is the scope coming out of the shed into very cold air, but it wasn't bad after a while when going for the higher altitudes, so some of it must have been atmosphere. Still, I could see that there was no southern equatorial band. Did look bit odd.

Anyway, congratulations on another good night with your regenerated scope and thanks for some more targets to look for.
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Old 24-05-2010, 08:02 AM
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*adds those objects to his next observation list*

I've had those feelings some sessions, like it just doesn't seem to fall into place.
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Old 24-05-2010, 05:47 PM
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Quote:
Originally Posted by kustard View Post
*adds those objects to his next observation list*

I've had those feelings some sessions, like it just doesn't seem to fall into place.
Make no mistake, it fell right into place this time, with the great seeing, collimation perfect and all that
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Old 24-05-2010, 05:52 PM
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Quote:
Originally Posted by Paddy View Post
Another very impressive report, Sab. I'm going to have to arrange some way of getting to those high mags you're using. I was very interested in Dave's response to your other post about the duration of the session increasing the chance of good viewing. I got up about 4.30 this morning to have a look at Jupiter, but the seeing was just awful in that part of the sky. I suspect some of this is the scope coming out of the shed into very cold air, but it wasn't bad after a while when going for the higher altitudes, so some of it must have been atmosphere. Still, I could see that there was no southern equatorial band. Did look bit odd.

Anyway, congratulations on another good night with your regenerated scope and thanks for some more targets to look for.
Thanks Paddy. All you need is good seeing! These magnifications are a rare exception.....usually I don't go above 400x, even on small compact DSOs as I don't find mush visually appealing Infact the 150-300x is my most used range. But this was a rare exception when faint stars come to a nice tight focus even at 762x. I've noticed that seeing becomes quite poor just before dawn, when it has been great only minutes before, not sure why this is but I theorize that the first rays of sun could be hitting the upper atmosphere and starting to excite the gases/air molecules. Something like that. David is right though, in the evenings everything is cooling off so seeing won't be as good, even if the air above is perfectly still. That's something I've always though about.

Do you have a fan on your scope?
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Old 24-05-2010, 08:30 PM
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I do have a fan and thanks to the set up of the rocker box, the airflow is directed across the face of the mirror, so it works as a boundary layer scrubber and cools the front of the primary fairly quickly. I also use mainly 175 - 250X but can go to 500X with a barlow, which I've been able to do on rare occasions.
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Old 25-05-2010, 08:12 AM
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Originally Posted by Paddy View Post
I do have a fan and thanks to the set up of the rocker box, the airflow is directed across the face of the mirror, so it works as a boundary layer scrubber and cools the front of the primary fairly quickly. I also use mainly 175 - 250X but can go to 500X with a barlow, which I've been able to do on rare occasions.
Thats good. I've only now realised the importance of fans. There's 3 on my scope, and the mirror cools 15C in an hour or less. Without fans, i'd never reach eqilibrium, and with the old scope that was always noticable.
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