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niallk

To Laugh or Cry...

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I've started reading the rather excellent looking 'The Dobsonian Telescope' by Kriege and Berry, and came across this sentence when they describe Parson's Leviathan:

"Poor seeing ... and the terrible weather of central Ireland severely limited its use"

It seems conditions haven't changed much in nearly 200yrs so...! ?

IMG_20170420_072153663.thumb.jpg.e78ae673ab589d74d97f43743ebe1bdd.jpg 

 

Edited by niallk
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Mmph

saying that, there were a couple of days last week where seeing and transparency were excellent. Lovely detail on an Io transit with shadow with GRS and great detail in the bands. Hope it's great for Skellig. Are you going this year Niall?

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Laughing is usually preferable to crying. You could do both of course! ???

Newton, a great british scientist, designed and created the Newtonian reflector, and James Nasmyth a great british astronomer, designed a superb altazimuth mount. Dobson, an american, invented half a box! If only Nasmyth had been called Dobson! :hiding:

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9 minutes ago, mikeDnight said:

Laughing is usually preferable to crying. You could do both of course! ???

Newton, a great british scientist, designed and created the Newtonian reflector, and James Nasmyth a great british astronomer, designed a superb altazimuth mount. Dobson, an american, invented half a box! If only Nasmyth had been called Dobson! :hiding:

Harsh :)

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1 hour ago, niallk said:

I've started reading the rather excellent looking 'The Dobsonian Telescope' by Kriege and Berry, and came across this sentence when they describe Parson's Leviathan:

"Poor seeing ... and the terrible weather of central Ireland severely limited its use"

It seems conditions haven't changed much in nearly 200yrs so...! ?

IMG_20170420_072153663.thumb.jpg.e78ae673ab589d74d97f43743ebe1bdd.jpg 

 

what a great book :happy11:

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1 hour ago, Bart said:

Mmph

saying that, there were a couple of days last week where seeing and transparency were excellent. Lovely detail on an Io transit with shadow with GRS and great detail in the bands. Hope it's great for Skellig. Are you going this year Niall?

Hi Barry,

Yep - I'm definitely going to Skellig this year :) !  Unfortunately missed it last year.

Yes, very good conditions last week - though I could only get out one night: I had Jupiter sharp at 560x ... the seeing was incredibly steady, even with its lowish altitude, and I was even observing over a rooftop!

-Niall

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29 minutes ago, mikeDnight said:

Laughing is usually preferable to crying. You could do both of course! ???

Newton, a great british scientist, designed and created the Newtonian reflector, and James Nasmyth a great british astronomer, designed a superb altazimuth mount. Dobson, an american, invented half a box! If only Nasmyth had been called Dobson! :hiding:

I don't know if you have read the book, but there's a great opening chapter.  Kriege and Berry give a nice history of Newtonians, and give due credit to many people including Nasmyth in the evolution towards the modern dob.  The guys are very humble about their own contributions - this book does not read like a marketing tool for Obsession telescopes.  In fact, it is quite the opposite: it is instructions (500 pages) as to how to build your own!

In fairness, Dobson was a very clever guy. I'm an electronic engineer, and in my work I'm often struck by how simple and straightforward the most elegant designs are - belying the underlying deep insight and expert execution.

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14 minutes ago, faulksy said:

what a great book :happy11:

Yeah - I'm only starting to read it, but flicking through, I'm very impressed at the depth of detail and analysis.  The writing style seems very engaging too :)

The danger is I might get notions -especially looking at all the beautifully crafted dobs people have created here ;)

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1 hour ago, niallk said:

Yeah - I'm only starting to read it, but flicking through, I'm very impressed at the depth of detail and analysis.  The writing style seems very engaging too :)

The danger is I might get notions -especially looking at all the beautifully crafted dobs people have created here ;)

nothing wrong with that niallk , if you do, go for the later style mirror cell, even though that one still works fine

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Niall

if you were observing detail at x560 there's obviously nothing wrong with your setup! Fair dues. I'm looking forward to looking through yours at skellig, if you'll allow.

we got very lucky there in march for the marathon, hopefully the weather will play ball again in august. 

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2 hours ago, faulksy said:

nothing wrong with that niallk , if you do, go for the later style mirror cell, even though that one still works fine

Yes, I'm delighted with my scope - love it - and I hope to enjoy many years ahead observing with it.  But if I were to alter it, a thinner quartz mirror would be nice I guess, with a modern balanced wiffle tree to support it like the one you did a lovely job crafting.  I'd also welcome the drop down tailgate option - so that I could put the mirror out to cool independently of setting up my scope.

Tbh, the sling appears to work very well with my 2" mirror - I've literally no complaints. I generally give >2hrs cool down if I'm going to be viewing planets/moon.  Less important for DSOs.  I believe I see overcorrection while cooling, and more symmetric diffraction rings either side of focus when closer to fully cooled.

So cooling is my main consideration, not so much weight.  Obviously, the bigger the aperture gets, weight would also be increasingly a concern I imagine :)

Edited by niallk
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3 hours ago, Bart said:

Niall

if you were observing detail at x560 there's obviously nothing wrong with your setup! Fair dues. I'm looking forward to looking through yours at skellig, if you'll allow.

we got very lucky there in march for the marathon, hopefully the weather will play ball again in august. 

I would have loved to make Ballinskelligs for the Messier Marathon - I was away with work. Glad to hear you got good weather - I was keeping an eye on it online to see what I was missing :)

Yeah it would be great to meet up with the scopes - I'd love a look through your big 16"!!

My wife is going to a class on Thursday evenings, so it is just not suiting me to make the monthly club meetings in Youghal at the moment - minding the kids. Still always interested to go along to any group observing sessions etc if there's any going on and I can make it :)

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You probably wouldn't see much of a difference in my 16 compared to your 15 but I'd like to see the improvement your better mirror would make. 

Id like to try out a spot near the Vee if you were interested though in the coming weeks 

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11 hours ago, Bart said:

You probably wouldn't see much of a difference in my 16 compared to your 15 but I'd like to see the improvement your better mirror would make. 

Id like to try out a spot near the Vee if you were interested though in the coming weeks 

Sounds good!! I'd be on for that.  Who knows about mirrors - I've seen Synta mirrors give better strehl numbers & PV than mine on Mr Rohr's website!  To-date I've only ever looked through my own two scopes: I'm almost afraid to look through someone else's - ignorance can be bliss ... I've had great views some nights; frustrating views at other times - hopefully mostly seeing/cooling related.

I've been watching Sat24 and trying to judge if this cloud overhead will pass out to sea in an hour or two, and we might get a bit of clear sky tonight.  The jetstream is way off north too. We might be lucky: car packed, windows down and mirror fan on!  Planning to pop down to the coast after I get chores done and the kids to bed, if the clouds shift :)

EDIT:

This was 'posted' last night Barry, but didn't upload properly; just saw that this morning!

Edited by niallk

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Ha! As I was reading it I was thinking your dedication was definitely better than mine!

last night was pretty good. Great views of jup and got both comets in Hercules amongst a couple of others even thought I could see the dust lane in the sombrero in the 10" at low altitude, but that could have been the couple of beers I had?

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Sounds great Barry : I only saw your note on the comets this morning, and never went looking.  I ended up in my front garden under the glare of several street lights to avoid the sea mist, so I prob wouldn't have had too much luck on fainter stuff ?

Nice catch on the Sombrero at such low alt - have only caught it the once, but a lovely sight to see with your own eyes!  Looks like cloud tonight: I'll be having a few ? tonight!

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