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Old 03-04-2014, 10:10 PM
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barx1963 (Malcolm)
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One of the greatest joys of owning a reflector is collimating it. I just feel a great sense of grounding when my mirrors come together in perfect harmony = beautiful experience.
Actually, that is true! I get a lot of satisfaction from getting my dobs just right. Knowing I have contributed even in a small way to the superb image in the eyepiece is a pleasure in itself. And doubly so with my little 8" where I designed and built the collimation system myself.

Cheers

Malcolm
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  #22  
Old 03-04-2014, 10:20 PM
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Varangian (John)
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Actually, that is true! I get a lot of satisfaction from getting my dobs just right. Knowing I have contributed even in a small way to the superb image in the eyepiece is a pleasure in itself. And doubly so with my little 8" where I designed and built the collimation system myself.

Cheers

Malcolm
Yes indeed! I use a film cannister with a little hole in it and then do a star test. Loads of fun.
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  #23  
Old 03-04-2014, 10:31 PM
ausastronomer (John Bambury)
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Originally Posted by Larryp View Post
I'm afraid I'm a refractor man through and through. Only high quality ones, though.
The views that knocked my socks off in over 30 years in this hobby have always been through a high end APO, like an Astro-Physics, Tak, or Televue.
I have never looked through any Newtonian that I subsequently wanted to own-apologies to the dob owners, but that's how I feel!
Then you've never looked through a good newtonian that's been properly cooled and collimated. I have used some of the best refractors on the planet, including a Tak TOA 130, a Tak TOA 150, an AP 160, a Televue NP 127 and a 15"/f12 D & G, just to name a few. Just this past week I have had a few views through a Tak TSA 120 at Coonabarabran. All of these scopes have provided excellent views. None of these views have convinced me I should swap one of these scopes for one of my 3 newtonians, all of which are premium scopes.

Not even a close contest really. When both scopes are properly set up and cooled a larger aperture high grade newtonian is going to beat a smaller aperture high grade refractor every time. When one considers cost, a high grade 10" newtonian will cost a lot less money than a high grade 6" refractor and easily outperform it.

Cheers
John B
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  #24  
Old 03-04-2014, 10:51 PM
Renato1 (Renato)
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Hmm ..as the owner of three refractors and two reflectors I would have to say in my experience this is not true unless you frequent Newts with poorly cooled , poorly collimated optics of dubious quality . I'm afraid my Newts trounce the refractors on every task I can offer and I would expect them too .

If I want to see perfect mathematic stars on any night I can put a small aperture stop on the Newts to cripple their ability to resolve the atmospheric turbulence ( and any other target for that matter ) and I can drop the magnification down to mimic that in the smaller refractor. Win - pinpoint stars . It is a `myth ' that a smaller aperture scope will show _more_ than a lerger one at any time ...all the detail will be there at least as much as the smaller aperture and maybe not as clean but it will be there.

You can't beat the portability , freedom from collimation responsubility and dust seal of a smaller refractor but that comes at a big cost considering you can buy a good 8" dob for $399 which will probably be superior for most tasks .

I don't feel threatened in these discussions because I own them all but I don't like to see Newts maligned as they are so effective at such a lower cost .
I dont like to see refractor owners over aggrandizing the capability of their instruments. Refractors work so well for some people but please don't peddle nonsense about Newtonians .
The spider vanes - if one has the standard four ones - limit the size of the clear aperture of the stopped down reflector. And it is still affected by tube currents some of the time. And one optical expert did tell me that there was some deviation from using the stopped down mirror, which made the result slightly different in the reflector from using an APO refractor (can't remember exactly what it was).

And on the few occasions I tried using an aperture mask on my 14.5" dob, I was unable to split Antares - but that is nothing conclusive, as I could only achieve splitting Antares with a 4" APO refractor on every 2nd or third night's attempt (the sky had to be really steady). Have you managed to cleanly split it with your dob and aperture mask?

That said, the best views I've ever had of Jupiter and Saturn were through a club member's 10" Dob which he had built himself with the best possible parts, and a Panoptic and Powermate. He had a Parks mirror in it, and the tube was made of octaganol wood. I was in astonishment as he pulled it out of the back of his station wagon, set it up on the ashphalt and aimed over various school buildings at Jupiter and Saturn - no cooling down time required - to deliver the sharpest most detailed images imagineable. But then again, his mirror alone cost more than my entire 14.5" dob.

You are very right though about people putting down reflectors unreasonably. My very first telescope was a 4.5" Focal reflector from Kmart, and it still delivers better images than my 4" and 6" Maks do - which I am still struggling to collimate each correctly to give me a view of planets akin to those of that reflector.
Regards,
Renato
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Old 03-04-2014, 11:01 PM
clive milne
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The attainment of perfect collimation in a Newtonian is an ideal... but it is not necessarily a prerequisite for an an excellent visual experience. All it means is that the diffraction limited portion of the view is centred in the eyepiece field stop. You can be slightly off and still see a perfectly sharp image in the eyepiece (albeit with the sweet-spot de-centred). Refractors are different in that the magnitude of off axis aberrations are generally better controlled (mostly a function of the focal ratio) and the mechanical requirements of lens assembly necessitate an ota that stays orthogonal. If you were to throw $10k at a 6" newtonian you could also make it impervious to collimation errors.
To reiterate... the primary advantage that refractors have over any other optical format is that they scatter slightly less light across the image rendering what can be perceived as a slightly more 'pure' view.
However, I disagree with the maxim that implies that the merit function of refractors is intrinsically superior to reflecting telescopes as a priori. It simply doesn't stand up in the real world .... at all.
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  #26  
Old 04-04-2014, 03:00 AM
ausastronomer (John Bambury)
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Originally Posted by Renato1 View Post
I suspect you would have a hard time splitting the tiny companion star from Antares with the big dob.

Regards,
Renato
That is simply not true. I have cleanly split Antares on hundreds of occasions in newtonians from 6" to 25", which is the sizes I have tried on it. The mirror needs to be cool, the telescope needs to be collimated, the optics need to be decent, the seeing needs to be decent and Antares needs to have reasonable elevation, to achieve a clean split. I have also split it in high quality APO refractors down to 4". The smallest being a Takahashi FS 102. The same type of conditions apply when splitting it in a refractor.

Two nights ago at Coonabarabran under reasonably good seeing we split Sirius at 300x in my 18" Obsession and Antares at 200x in my 14" SDM. These were at different times. Had I swapped the scopes around the 14" would have split Sirius easily and the 18" would have split Antares. My 10" SDM has split them both under favourable conditions on many occasions.

I first split Sirius many years ago, when it was infinitely harder due to the closer separation, in my 18" Obsession, under excellent conditions at 1050x (5mm Pentax XW + 2.5x TV powermate).

You should try 1050x in a refractor, (I am sure a 6" APO can pull 175x per inch of aperture) , it does an excellent job of showing extended detail in targets like the homonculus and planetary nebula like the Ghost of Jupiter (NGC 3242).

Cheers
John B
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  #27  
Old 04-04-2014, 06:02 AM
astro744
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Originally Posted by Renato1 View Post
Different telescopes for different uses. I suspect you would have a hard time splitting the tiny companion star from Antares with the big dob.
10.1" F6.4 Suchting Mirror, Clave Plossl eyepieces, evening twilight; piece of cake!

This was the first time I ever split Antares and was surprised how easy it was. A good mirror and eyepieces help but I think it was the twilight that made the task easier.

I have Newtonians, Refractors & and SCT. I have looked through both 7"/f9 & 6"/f12 Starfire, 9"/f15. At one point I was convinced the 7"/f9 was simply the best ever telescope. It was mounted on top of a 16"/f5 Newt/Cass that simply never produced images worth looking at mainly due to local atmospheric disturbances and city light.

I love the pin point stars and and flat field of my 2.4" & 4" refractors and the fact that I can get well over 4 degrees of stunning star fields. Planets are very sharp and contrasty but I often want a brighter image as I simply run out of exit pupil diameter; that's how much I can push the refractor.

I love my 9.25" SCT because it is compact and yet has ample light gathering and good focal length. Higher powers with bigger eyepieces is nice.

I love my short 6" Newt when combined with Paracorr delivers a near 3 degree field of pinpoint stars that rivals that of the 4" refractor. One day I'll do a side by side comparison.

I love my 10.1" Newtonian because it is the largest aperture I own and gives me the brightest images of deep sky objects and also gives me plenty of light when pushing up the power on planets. The mirror can certainly take it. This telescope is also a great galaxy buster not because it is a big Dob but because it has a great mirror that gives me excellent contrast and lets me pick up very faint galaxies.

I have seen Jupiter in a 16"/f5 Suchting mirror that was better than any view I had ever seen of any planet in any of the above mentioned telescopes including that of the 9"/f15 refractor. However the big refractor had tracking and a good long focal length and looking at a 'big' image of a planet for extended periods without having to nudge the telescope has considerable advantage.

There is no one perfect telescope and after 30 Years I have acquired a few different types. I'm yet to own a large reflector but I am having so much fun with my TV-60 that I don't think I really want and definitely do not need one.
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  #28  
Old 04-04-2014, 06:35 AM
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Larryp (Laurie)
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Then you've never looked through a good newtonian that's been properly cooled and collimated. I have used some of the best refractors on the planet, including a Tak TOA 130, a Tak TOA 150, an AP 160, a Televue NP 127 and a 15"/f12 D & G, just to name a few. Just this past week I have had a few views through a Tak TSA 120 at Coonabarabran. All of these scopes have provided excellent views. None of these views have convinced me I should swap one of these scopes for one of my 3 newtonians, all of which are premium scopes.

Not even a close contest really. When both scopes are properly set up and cooled a larger aperture high grade newtonian is going to beat a smaller aperture high grade refractor every time. When one considers cost, a high grade 10" newtonian will cost a lot less money than a high grade 6" refractor and easily outperform it.

Cheers
John B
To me, visual astronomy is all about aesthetics, and as I said, the views that have knocked my socks off over the years have all come from APO refractors.
You like reflectors and I like refractors-its as simple as that! I get a bit tired of this "mine's bigger than yours" argument
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  #29  
Old 04-04-2014, 06:46 AM
N1 (Mirko)
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Yes, the discussion has reached a point where even this argument would seem valid:

KECK TRUMPS DOB

where does that leave us?
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  #30  
Old 04-04-2014, 11:39 AM
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cometcatcher (Kevin)
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Yes, the discussion has reached a point where even this argument would seem valid:

KECK TRUMPS DOB

where does that leave us?
Hubble trumps Keck.
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  #31  
Old 04-04-2014, 11:47 AM
julianh72 (Julian)
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Hubble trumps Keck.
James Webb trumps Hubble
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  #32  
Old 04-04-2014, 11:54 AM
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barx1963 (Malcolm)
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James Webb trumps Hubble
Not yet it doesn't!!
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  #33  
Old 04-04-2014, 11:56 AM
N1 (Mirko)
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:l ol:
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  #34  
Old 04-04-2014, 12:08 PM
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sn1987a (Barry)
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My Suchting, Zambuto and Kennedy stand ready to meet and take on any puny Refractor
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  #35  
Old 04-04-2014, 12:16 PM
Renato1 (Renato)
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Originally Posted by ausastronomer View Post
That is simply not true. I have cleanly split Antares on hundreds of occasions in newtonians from 6" to 25", which is the sizes I have tried on it. The mirror needs to be cool, the telescope needs to be collimated, the optics need to be decent, the seeing needs to be decent and Antares needs to have reasonable elevation, to achieve a clean split. I have also split it in high quality APO refractors down to 4". The smallest being a Takahashi FS 102. The same type of conditions apply when splitting it in a refractor.

Two nights ago at Coonabarabran under reasonably good seeing we split Sirius at 300x in my 18" Obsession and Antares at 200x in my 14" SDM. These were at different times. Had I swapped the scopes around the 14" would have split Sirius easily and the 18" would have split Antares. My 10" SDM has split them both under favourable conditions on many occasions.

I first split Sirius many years ago, when it was infinitely harder due to the closer separation, in my 18" Obsession, under excellent conditions at 1050x (5mm Pentax XW + 2.5x TV powermate).

You should try 1050x in a refractor, (I am sure a 6" APO can pull 175x per inch of aperture) , it does an excellent job of showing extended detail in targets like the homonculus and planetary nebula like the Ghost of Jupiter (NGC 3242).

Cheers
John B
Thanks John, I did say "suspect" and am happy to be corrected. The best views of Jupiter I've ever had with any of my telescopes is through my 14.5" dob, but that's only been on a couple of occasions at the end of a four or five hour observing session, and in the middle of rural fields. Unfortunately, I can't do those sessions any more, and have never been able to get anything sharp from my old suburban backyard or current semi-suburban backyard. Even my C8 struggles where I now live - after six weeks of lousy views of Jupiter, Mars and Saturn, I had a friend pop in who I showed them to, and magically, the C8 worked perfectly for a change.

I'll try 175X per inch in my 4" APO when I remount it in a few weeks, though given seeing conditions here, I'm not optimistic.
Regards,
Renato
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  #36  
Old 04-04-2014, 12:57 PM
Renato1 (Renato)
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Originally Posted by astro744 View Post
10.1" F6.4 Suchting Mirror, Clave Plossl eyepieces, evening twilight; piece of cake!

This was the first time I ever split Antares and was surprised how easy it was. A good mirror and eyepieces help but I think it was the twilight that made the task easier.

I have Newtonians, Refractors & and SCT. I have looked through both 7"/f9 & 6"/f12 Starfire, 9"/f15. At one point I was convinced the 7"/f9 was simply the best ever telescope. It was mounted on top of a 16"/f5 Newt/Cass that simply never produced images worth looking at mainly due to local atmospheric disturbances and city light.

I love the pin point stars and and flat field of my 2.4" & 4" refractors and the fact that I can get well over 4 degrees of stunning star fields. Planets are very sharp and contrasty but I often want a brighter image as I simply run out of exit pupil diameter; that's how much I can push the refractor.

I love my 9.25" SCT because it is compact and yet has ample light gathering and good focal length. Higher powers with bigger eyepieces is nice.

I love my short 6" Newt when combined with Paracorr delivers a near 3 degree field of pinpoint stars that rivals that of the 4" refractor. One day I'll do a side by side comparison.

I love my 10.1" Newtonian because it is the largest aperture I own and gives me the brightest images of deep sky objects and also gives me plenty of light when pushing up the power on planets. The mirror can certainly take it. This telescope is also a great galaxy buster not because it is a big Dob but because it has a great mirror that gives me excellent contrast and lets me pick up very faint galaxies.

I have seen Jupiter in a 16"/f5 Suchting mirror that was better than any view I had ever seen of any planet in any of the above mentioned telescopes including that of the 9"/f15 refractor. However the big refractor had tracking and a good long focal length and looking at a 'big' image of a planet for extended periods without having to nudge the telescope has considerable advantage.

There is no one perfect telescope and after 30 Years I have acquired a few different types. I'm yet to own a large reflector but I am having so much fun with my TV-60 that I don't think I really want and definitely do not need one.
Certainly you are a proponent of different telescopes for different purposes. Thanks for sharing your star splitting experience. I'm still fascinated with the concept of the 7" telescope mounted on the 16" one, and the 7" one being the superior performer.

Yes, one can see thousands of galaxies with a 9.25" and 10" telescopes, one of the delights of life. Oddly though, on occasions I was in really dark places in central Victoria for work, I've been quite amazed at the views with the performance of my 25X100 binoculars, where each sweep across Virgo was showing dozens of tiny galaxies that stood out like sore thumbs. I never got that effect with my small travel telescopes.

Fascinating to hear of your enthusiasm for the TV-60. I have a little WO 66mm refractor I bought for camping (when all my wife's stuff left me with no room for my 80mm in the boot), and it was quite a lively telescope out in the country, but I must confess to not having used it at home. You have piqued my interest.
Regards,
Renato
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  #37  
Old 04-04-2014, 01:45 PM
astro744
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I'm still fascinated with the concept of the 7" telescope mounted on the 16" one, and the 7" one being the superior performer.
See at the bottom of http://www.questacon.edu.au/science-...fts-from-japan

The observer is looking through the AP 7"/f9. The orange one on top is a Celestron Comet Catcher. Not the best picture for showing off the refractor but you can just make out the tube assembly.

I worked there for many years many moons ago well before the fire in 2010 which destroyed the observatory & planetarium. I haven't kept in touch and am not really sure if any of the telescopes were saved.
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  #38  
Old 04-04-2014, 04:57 PM
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I just dug out my 40 year old Tasco 80mm F15 refractor for some solar and lunar observing. Not sure why. Think I might be going senile in my middle age. Oh yeah that's what it was, I want prime focus to fit in the field of the APSC sensor without a barlow and for the Sun and Moon I don't need aperture. But man, I forgot how loooong this thing is.
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  #39  
Old 04-04-2014, 07:03 PM
N1 (Mirko)
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Originally Posted by sn1987a View Post
My Suchting, Zambuto and Kennedy stand ready to meet and take on any puny Refractor
Sure?

Here are some candidates:

Suchting:
http://www.cfa.harvard.edu/hco/grref.html

Zambuto:
http://en.wikipedia.org/wiki/File:Wilder.jpg

Kennedy:
http://en.wikipedia.org/wiki/File:Po..._Refractor.jpg



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  #40  
Old 04-04-2014, 07:23 PM
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sn1987a (Barry)
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Ha!, it would be a joy to be smashed by those.
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