#981  
Old 26-01-2010, 03:47 PM
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iceman (Mike)
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Hi Dave
to IIS and thanks for a great introduction!
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  #982  
Old 26-01-2010, 06:45 PM
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barx1963 (Malcolm)
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Dave
Good to see another 12" dob on the way. Look forward to hearing how you go with. What charts etc have you ordered?
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  #983  
Old 30-01-2010, 09:17 PM
Bern
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ATM-optics query

Hello everyone, this is my first post, and I am impressed by the amount of information and knowledge available here. Do people still hand grind their own mirrors, or is this a dying art? My late father made several telescopes in the 1960s and '70s, mainly Newtonians and a casegrain. The primary mirrors varied in size from 4.5 inches to 8 inches. In the final stages of polishing he would assess the accuracy of the optics and focal length using various methods, such as straight-edge and grid tests, I think. He used different hand-polishing manoeuvres to correct optical deficiencies. I recall him referring to turned-down edges and turned-up edges among other things. He never had much time for commercially made or machine-ground mirrors because he felt they weren't up to standard or were just too expensive because of the enormous amount of labour required to make them. So how does the optical quality of current commercially made mirrors compare with hand-made ones? I would imagine mirror manufacturing technology has improved vastly since my father's time, but is a good hand-grind-polish job still regarded as superior to a commercial job? If not, how do you independently assess optical flaws in a commercial mirror before purchasing it? Also is there much optical variation within identical telescope models? Thanks for taking the time to read the post.

Bern
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  #984  
Old 01-02-2010, 11:53 PM
Dave88 (Dave)
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Originally Posted by barx1963 View Post
Dave
Good to see another 12" dob on the way. Look forward to hearing how you go with. What charts etc have you ordered?
Hi Malcolm,

I've ordered the Herald Bobroff Astro Atlas, Astronomy 2010 and picked up a copy of 'Astronomica' for $20 from a book sale - I'm really enjoying reading it and would recomend it to anyone


Dave
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  #985  
Old 02-02-2010, 12:03 AM
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barx1963 (Malcolm)
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Dave
Haven't used the Bobroff atlas, but have heard good things about it. Astronomy 2010 has some good basic info.
Please post your impressions when the dob arrives!

Malcolm
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  #986  
Old 02-02-2010, 11:55 AM
bgrif (Brad)
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Herald Bobroff Available Again?

Is the HB Astro Atlas available again? If so, would you post the contact information? Many thanks from the cloudy midwest USA.

Quote:
Originally Posted by Dave88 View Post
Hi Malcolm,

I've ordered the Herald Bobroff Astro Atlas, Astronomy 2010 and picked up a copy of 'Astronomica' for $20 from a book sale - I'm really enjoying reading it and would recomend it to anyone


Dave
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  #987  
Old 02-02-2010, 01:02 PM
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mental4astro (Alexander)
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I used this list to guide my observing tonight. Thanks for the suggestions Malcolm.

I had limited success but the ones I could find were quite spectacular.

I couldn't quite catch Eta Carina Nebula but did manage to get NGC 3532. 47 Tuc is one of my favourites at the moment so I'm pretty good at finding it.

Couldn't find NGC 362 but the sky in that area was pretty light polluted so will try again another night from elsewhere. Also couldn't find the Tarantula Nebula - there's quite a bit happening around there so it was hard to locate for me.

The Jewell Box (NGC 4755) was amazing. I thought I found it the other night and tonight confirmed it. The longer I spent on it, the more I managed to see. Caught a glimpse of a couple red stars (red giants?)

Omega Centauri is up too late for me!

So, mixed results tonight but worth finding a few new sights. If it wasn't for the nicotine addicted neighbour who had to to have a fag in full light every 30 minutes, I may have been a little more successful (and patient!)

Cheers,
Af.

Hi Af,

If you are using charts to find stuff, and are having trouble doing so, you might like to make this little gizzmo to use with your charts and finder scope:

http://www.iceinspace.com.au/forum/s...ad.php?t=53378

I use it from both my home site (inner city Sydney), and also from dark sites.

Binoculars are also a big, big help with observing done from a light polluted site as they show stars otherwise washed out by the light pollution, making star hoping much, much easier. These I always use at home. They donot need to be expensive, or overly big. Anything with an objective lens over 25mm will reveal most stars plotted in charts, with 7X50 binoculars being the "standard" astro size.
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  #988  
Old 02-02-2010, 01:42 PM
Afro Boy (Carl)
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Quote:
Originally Posted by mental4astro View Post
If you are using charts to find stuff, and are having trouble doing so, you might like to make this little gizzmo to use with your charts and finder scope:
That's a great idea. I'm not using printed charts but may be at some time soon. Getting a bit tired of dragging out the laptop each clear night!

Quote:
Binoculars are also a big, big help with observing done from a light polluted site as they show stars otherwise washed out by the light pollution, making star hoping much, much easier.
Another great idea. Never thought of using binos to help with star hopping. Will have to put that on my shopping list.

Thanks for the help/advice.

Cheers,
Af.
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  #989  
Old 02-02-2010, 02:14 PM
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mental4astro (Alexander)
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Here is a link to a sticky in the Beginners forum to two excellent charts you can print yourself, and a DIY planisphere:

http://www.iceinspace.com.au/forum/s...73&postcount=1

The first one is great to start out with, with a limiting magnitude of 6.5. If you have access to an A3 printer, better still. Enough stuff on it to keep you happy for years. Also better suited to observing from light polluted areas.

The second is much more detailed, and a finer scale, going down to magnitude 8.5 for stars plotted.

I use both these charts.

This thread also has plans for making you own planisphere which you use to familiarize yourself with the sky, and plan your sessions too, for what ever time of year you want. I still use mine, 25 years on. I can't be bothered with lappies. Red cellofane over a head-mounted torch and the charts is all I use. Have left behind one or the other, or both, at different times, .
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  #990  
Old 02-02-2010, 03:34 PM
malmac (Mal)
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Quote:
Originally Posted by Bern View Post
Hello everyone, this is my first post, and I am impressed by the amount of information and knowledge available here. Do people still hand grind their own mirrors, or is this a dying art? My late father made several telescopes in the 1960s and '70s, mainly Newtonians and a casegrain. The primary mirrors varied in size from 4.5 inches to 8 inches. In the final stages of polishing he would assess the accuracy of the optics and focal length using various methods, such as straight-edge and grid tests, I think. He used different hand-polishing manoeuvres to correct optical deficiencies. I recall him referring to turned-down edges and turned-up edges among other things. He never had much time for commercially made or machine-ground mirrors because he felt they weren't up to standard or were just too expensive because of the enormous amount of labour required to make them. So how does the optical quality of current commercially made mirrors compare with hand-made ones? I would imagine mirror manufacturing technology has improved vastly since my father's time, but is a good hand-grind-polish job still regarded as superior to a commercial job? If not, how do you independently assess optical flaws in a commercial mirror before purchasing it? Also is there much optical variation within identical telescope models? Thanks for taking the time to read the post.

Bern
This is my first post. I have started to grind my first mirror (8 inch F 7 to 8). This will be a prolonged project as I am about to relocate from Dongara W.A. to Geraldton W.A. and have packed everything away for the move.
I am keen to hear the opinions of others regarding "bought" vs "handmade" mirrors. My understanding is that few people in Australia grind mirrors now. It is still popular in America and Europe though.

I will look at any responses with interest.

Cheers for now...............Mal
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  #991  
Old 03-02-2010, 10:24 PM
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alistairsam
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Quote:
Originally Posted by barx1963 View Post
The 8" is an excellent instrument for viewing DSO's, there are hundreds within reach of your scope. Use the 26mm eyepiece first, and I would suggest you get a medium power eyepice say 15mm or their abouts, if you can offord it get a wide field one rather than a plossl.

Mars is not easy at the moment, very low, you have to wait for moments of good seeing to pick up much detail, but you should be able to see the polar cap.

Good objects in the Southern part of the sky are

Eta Carina Nebula
NGC 3532 which is close to Eta Car
47 Tucanae, NGC 104
NGC 362 close to 47 Tuc
Tarantula Nebula
The Jewell Box NGC4755
Omega Centauri (it rises late best after 1am)

All these will look great in an 8" and several (Omega Cent, Eta Car, NGC 3532) are naked eye and all are locatable in a finder

In the northern sky you can try for

M67 Open cluster in Cancer
M43 just near M42
Rigels companion star

Anyway thats just some starters of the top of my head, see how you go.

Thanks to this, I was able to see most of the above and quite a few open clusters that showed up in stellarium.
I increased the light pollution to match what the sky from my site looks like.

any suggestions for galaxies that can be seen from an 8" reflector.

I came across a list in a thread here, but most were mag 10 and above.
any idea on what the limiting magnitude would be for an 8" reflector.

I bought a digital angle meter to measure alt.
just need to find an accurate compass as well.

almost finished with my fork mount. just waiting on the bearings and slr.
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  #992  
Old 03-02-2010, 10:48 PM
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barx1963 (Malcolm)
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Hey Alistairsam, glad you liked the list! And even gladder it was some help. There are plenty of galaxies to check with and 8" BUIT you will need reasonably dark skies.
Suggest you start on the messier galaxies, as all of these are within an 8" capability, although some (M74 being the obvious example) will need very dark skies.

Probably the one to try for at the moment is M104 (the Sombrero) in Virgo. It is well up by midnight at the moment and quite easy to locate. First find Corvus, then locate Eta Corvi and it is about 5.5deg northeast (a smidgen over on finder field away). Its bright enough that sweeping should pick it up.
The other Messiers in Leo and Virgo will very soon become very visible.

Malcolm
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  #993  
Old 21-02-2010, 12:30 PM
smurf (Simon)
Starting with a 12"

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Hi all! Hope I'm posting in the right thread here.

Another beginner in Astronomy here. Looking forward to buying my first scope...

I am sure that I want a dobsonian scope, however what I'm not too sure about is brand - mainly I'm trying to decide between a (12") GSO and a SkyWatcher. Is anyone able to say that one brand would be much better over the other? I am hoping to get a collapsible one, just so that I have something relatively portable. I know that I have seen SkyWatcher collapsible dobsonians, but I'm not sure I've seen GSO ones (GSO has actually been reccommended to me before).

Any help appreciated!

smurf
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  #994  
Old 21-02-2010, 03:19 PM
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barx1963 (Malcolm)
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If concentrating on visual observing, dobsonions are usuaaly the way to go and the bigger the better. There is not much to pick betweeen the Skywatchers and the GSO's. The collapsible Skywatchers certainly save on storage and may be easier to transport in a car, but as I undestand it they are not able to have the OTA disconnected from the base, so you transport it as one unit.
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  #995  
Old 21-02-2010, 03:20 PM
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AG Hybrid (Adrian)
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Quote:
Originally Posted by smurf View Post
Hi all! Hope I'm posting in the right thread here.

Another beginner in Astronomy here. Looking forward to buying my first scope...

I am sure that I want a dobsonian scope, however what I'm not too sure about is brand - mainly I'm trying to decide between a (12") GSO and a SkyWatcher. Is anyone able to say that one brand would be much better over the other? I am hoping to get a collapsible one, just so that I have something relatively portable. I know that I have seen SkyWatcher collapsible dobsonians, but I'm not sure I've seen GSO ones (GSO has actually been reccommended to me before).

Any help appreciated!

smurf

Well, Both the GSO and Skywatcher dobs are pretty good. Optically, they are about the same. They have the same light grasp, assuming its a 12" skywatcher your looking at too. The GSO is solid tube, so it might require some man handling to mount the tube on the base. The skywatcher folds up like an accordian. So portability points goes to the skywatcher. If you get a skywatcher, you might want to buy a light baffle to cover the huge abses of where a solid tube would have covered.
However, they are both excellent value for money. No one here can say that you will go wrong with either.
And btw a 12" is a monster first scope. Thats the size scope Ill be upgrading to let alone starting with haha
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  #996  
Old 21-02-2010, 03:56 PM
smurf (Simon)
Starting with a 12"

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Thanks for the replies guys!

That is one thing I was not aware of, barx1963... Might have to remember that for carrying it in the car.

Yep, AG! That's what I was thinking. Everyone seems to recommend a dobsonian, so why not go for the biggest (whilst still having some portability) I can get!

I think I might keep looking around at pricing/where I can get them for a bit, but that has certainly helped, thanks again!
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  #997  
Old 21-02-2010, 04:47 PM
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barx1963 (Malcolm)
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Simon
Have just re read my post and don't think I was clear. The OTA stays assembled in the SW collapsibles, but you can seperate the OTA and base. The OTA is still relatively bulky compared to the more traditional truss tube designs.
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  #998  
Old 21-02-2010, 05:31 PM
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that_guy (Tony)
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smurf, you could always go for the 12" Light Bridge. Very Portable and not much price differnce.
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  #999  
Old 21-02-2010, 07:37 PM
smurf (Simon)
Starting with a 12"

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Oh, I see what you mean now barx1963. That should be fine though.

Looks like the LightBridge might be a good option too, thanks that_guy!
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  #1000  
Old 05-03-2010, 01:00 AM
Jaybee (John)
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Phew!!

Hi all
I joined this great forum several weeks ago and inquired about some S/H scopes in the for sale section. I have just finished reading this thread from post 1 thru to post 999 and deviating to other threads at the same time. Have picked up a wealth of information, tips, tricks, etc. Thanks to all the members for such an informative and friendly site.
I'm hoping to pick up my 8" LX90 this weekend...and wouldn't you know it...the forecast is....rain... Mind you we have had so little of it here in SA, I'll believe it when I see it.

Thanks again!
John
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