September 18 - typical Melbourne conditions....

[§AB]

.....which was atrocious seeing and ofcourse the promise of a "clear evening" by the BOM ended up being overcast by 9pm. In other words, clear evening my @$!*&$! @$*.

Took the 10 inch dob out to observe jupiter and the Moon. Ofcourse the clouds were already looming on the horizon at 7pm - classic! I was shocked to discover that one of my cats had marked their territory on the base. :scared:

Telescope: 250mm Newtonian
Seeing: 3/10
Transparency: 2/5

At 104x, Jupiter was pleasingly bright and crisply defined, despite shocking seeing. The rift in the SEB was obvious, the GRS was an easy catch and I could hint at streamers in the EQ zone. The pole areas also exhibited obvious shading. I upped the mag to 166x and a few more belts came into view and the EQ zone streamers became a little more obvious. :thumbsup: Just for kicks, I dropped in a 5.5mm Plossl for 227x but the view went soft. Thanks alot normal Melbourne seeing.

The moon was a delight at 104x, very pure in colour and sharply resolved. Similar a 166x.

I then aimed the scope at Antares and I noticed as I racked thru focus that the out of focus image flipped 90º betraying some astigmatism. Could the mirror clips be too tight? It was getting cloudy now, obviously the BOM was wrong yet again.

After I bought the scope in I decided to check the mirror clips. I was nervous, because this is no 4.5" cell that you can lift with one finger! Anyway, I pulled the cell out, which banged against the tube wall (underestimated the weight-size-inertia of this thing!) and set it down. Two of the clips were fairly tightly screwed on. I loosed all 3 clips so that they just lightly rest on the surface, if not a tiny but above. At this time, one of my cats decides to crawl into the tube :eyepop: "NOOOO get out! I promptly pull him out before any damage could be done to the secondary assembly! I re-attach the mirror cell, once again theres that inevitable bump and bang or two, and re-collimate. Now that I've learnt how to handle the mirrorcell, future adventures in removing it will go smoother :thumbsup: oh and another thing I learnt is close all door so no cats can disturb me!

Now, the weeks forecast is tragic. Melbourne style. Thursday and Saturday nights are the only *remote* chances. Both are in the distant future :(

Now I'm curious to see what degree that astigmatism was removed - if the awful (normal for Melbourne) forecast is anything to go by, I'd say I'll be getting super crisp views of Jupiter at 400x LOL

[DougAdams]

At least you got the scope out! I was walking home at 8pm and could see the moon right by Antares, and was keen to have a peek. By the time I got home at and had cooked dinner, it was almost completely clouded over. And this morning... sheesh, 35 knot northerlies and the rain is smashing against the window.

And don't knock the BoM, I'm one of them :D

[§AB]

^^ what infuriated me was the presence of a very, very rare phrase in a Melbourne forecast, which was "clear evening" but it was overcast before evening twilight even finished :bashcomp: Gotta love Melbourne weather....not!

That's two evenings where unforcasted cloud has ruined my night :cloudy:

Incredible how the second I purchased the Dob, the weather becomes more like something you'd expect in Iceland.

With the mirror clips loosened on my dob, I was eager to see what effect this had so I set the alarm for 2am but low and behold the beautiful sight of overcast cloud greeted me. Took me almost an hour to get back to sleep bcause I was that annoyed! It's been cloudy everyday since Saturday (when I got the dob).

Satellite image shows a clear slot behind this latest round of normal Melbourne rain, cloud and wind but the forecast reads "showers increasing" :family2:

I was hoping to take the scope out after work this evening.

[DougAdams]

This is where I hastily add I'm not a forecaster. I like to watch the MSL prog charts though, and can usually predict what the weather is going to do off them. Of course, new scopes play heck with the local conditions.

[GTB_an_Owl]

Hi Doug

perhaps your BOM forcasters should start ringing round the dealers to see what/how much astro gear has been bought before they issue their forcasts Doug

:lol: :lol: :lol:

geoff

[erick]

I was 60km north of Melbourne. Seeing started quite good, but the wind picked up to a stage where it blew a book off the table and the chairs over, and the bins were hopeless, BUT the 8" scope soldiered on - no shaking or movement of the image, no windmill action on my Ebonystar-enhanced base - I was quite amazed.

[§AB]

^^ that's what I love about Dobs, they stand up to the wind. During the 30 mins I got last night, it was rather breezy but the image stayed rock solid even at moderate powers.

[Scoper]

Hi, relax mate and don't be too hasty to accuse your scope of astigmatism. When checking for astigmatism you need to have the star/planet dead centre in the FOV, if it is slightly off-axis you get a false reading, also use a fairly high power. If after checking it you still get some astigmatism from the primary mirror itself then it must be mild and nothing to worry about because your description of what you could see on Jupiter seems to show that you have a good mirror overall, so sleep easy:thumbsup:. Enjoyed reading your observation notes by the way.

Cheers
Malc

[Scoper]

Sorry, forgot to mention that if the astigmatism is due to pinched optics the stellar image would appear triangular in shape. Once again don't worry too much, just enjoy the views.

Cats love reflecting telescopes, years ago our old cat once slept on the mirror of my old 8inch scope, open tube job. I now own a 10 inch scope, our latest cat hangs around it, loves to rub herself on the Dob mount and climb into the rocker box.

Let's hope the the skies are clear for you tonight.

Malc

[§AB]

After loosing the primary mirror clips, leaving a paper's width gap between the clip and the mirror, the images seemedd to have improved.