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"A scope under 7 inches aperture is of no use observing planets"

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#26 mikemarotta

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Posted 19 November 2020 - 12:38 AM

A 1-inch telescope can show Jupiter's four largest moons, the planet's South Equatorial Belt and hint at the existence of a North Equatorial Belt:

A 1-inch telescope can show that Saturn is different and has "ears", or "handles", or a ring, or whatever:

A 1-inch telescope can show that Venus undergoes phases along with corresponding changes in its apparent diameter:

Thanks for the pictures, Sketcher. Clearly, I agree with you. That being so, please do not disparage the blind. We have a topic here about Astronomy for the Blind. They use sound to transduce the data, just like in Carl Sagan's science fiction story, Contact.

 

The late Jean Texereau (1919-2014) was not just some guy with an opinion. 

https://skyandtelesc...aster-optician/

Clearly, I disagree that "science" cannot be done with less than 150 mm or 1500 mm or whatever.

 

Our local club is having Tom Field (Field Tested Systems https://www.fieldtestedsystems.com) speak (via Zoom) on spectroscopy. He said to me via email that perhaps 80% of the work in astronomy is done with spectroscopy. On that basis, why bother with optical observation at all? The answer is that when we engage as scientists, it is the method, not the tools, that defines what we do. Publishing your work is the last step. The discovery of truth is a personal quest. Tonight, I split eta Cassiopeia for the first time with my 102 mm refractor. I noted the time and the instrumentation and sketched my observation. I verified for myself what I read in an authoritative publication. To me, that is the practice of science.


Edited by mikemarotta, 19 November 2020 - 12:40 AM.

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#27 BillP

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Posted 19 November 2020 - 04:28 PM

FWIW, I've seen users of 10 and 12" scopes at star parties ooo-ing and ahh-ing over the views of Jupiter they were getting from their scope, and when I looked in their scopes I just politely said yes that was nice knowing full well my 4" would have eaten how their scope was performing at the time for lunch.  My point is not that aperture doesn't make a difference but that many times observers just do not know what a "good" planetary view looks like with whatever aperture they are wielding!  Larger aperture only gets you a more detailed view when a host of other conditions are properly attended.  And if you've never seen that, then you just don't know.


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#28 Sheol

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Posted 19 November 2020 - 07:47 PM

         My old 6 inch Criterion would have politely have disagreed with above comment. Back in the 50s & 60s, most Planetary viewing was done by 6 to 8 inch reflectors or 4 inch refractors..

 

 

    Clear Skies,

       Matt.



#29 wonderbass

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Posted 19 November 2020 - 09:38 PM

I took this picture 2003 with an Astro Physics 155 EDF Starfire from the light and smog polluted skies of North Hollywood,

Los Angeles California using a cheap ToUcam.

Whoever said anything under 7" of aperture is useless for planetary work is an idiot..

Yup I said that..

Mars 7.25.03

Edited by wonderbass, 19 November 2020 - 09:39 PM.

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#30 E_Look

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Posted 19 November 2020 - 11:16 PM

Thanks for the pictures, Sketcher. Clearly, I agree with you. That being so, please do not disparage the blind. We have a topic here about Astronomy for the Blind. They use sound to transduce the data, just like in Carl Sagan's science fiction story, Contact.

 

The late Jean Texereau (1919-2014) was not just some guy with an opinion. 

https://skyandtelesc...aster-optician/

Clearly, I disagree that "science" cannot be done with less than 150 mm or 1500 mm or whatever.

 

Our local club is having Tom Field (Field Tested Systems https://www.fieldtestedsystems.com) speak (via Zoom) on spectroscopy. He said to me via email that perhaps 80% of the work in astronomy is done with spectroscopy. On that basis, why bother with optical observation at all? The answer is that when we engage as scientists, it is the method, not the tools, that defines what we do. Publishing your work is the last step. The discovery of truth is a personal quest. Tonight, I split eta Cassiopeia for the first time with my 102 mm refractor. I noted the time and the instrumentation and sketched my observation. I verified for myself what I read in an authoritative publication. To me, that is the practice of science.

Mike, don't get me wrong, I like and agree for the most part with your post.

Just to split hairs, the practice of science, yes, is not the publication of your article in a world-class journal, it is that you grabbed your scope, went out, thought hard and did hard work observing and took data and in this case, communicating via your sketches.  The verification often comes because some other guy wants to start a fight with you, so checks your data.  Um, also, this is partly tongue-in-cheek.


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#31 E_Look

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Posted 19 November 2020 - 11:26 PM

FWIW, I've seen users of 10 and 12" scopes at star parties ooo-ing and ahh-ing over the views of Jupiter they were getting from their scope, and when I looked in their scopes I just politely said yes that was nice knowing full well my 4" would have eaten how their scope was performing at the time for lunch.  My point is not that aperture doesn't make a difference but that many times observers just do not know what a "good" planetary view looks like with whatever aperture they are wielding!  Larger aperture only gets you a more detailed view when a host of other conditions are properly attended.  And if you've never seen that, then you just don't know.

I have found, the very few times I was fortunate enough to look through a scope bigger than the 8-inch gun sitting in my battlesh, uh, house, even moderately far planets (for reference, I think Neptune is far for my scope) look too bright to be able to glean serious surface detail.  This was true for me of Jupiter and of Saturn.  My 8" Newt most often (as late as several days ago) shows Saturn to be a golden orange color.  In a 16" beast I looked through, it was just shining white; and the banding and other details on Jupiter were more washed out.  Perhaps they should have put in a shorter focal length eyepiece, magnify the picture, which necessarily dims it some.  Maybe filters, as two guys I know of were recently discussing.  But wow, I have to now openly admit to recalling a bit of disappointment the first couple of times I looked at Jupiter and Saturn in a big scope.  (Oh boy, if I had a big scope like that, I'd constantly be trying to get crazy high powers on even fuzzy targets; I found Neptune hard to focus in the big scope at powers over 700x.)


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#32 kb58

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Posted 20 November 2020 - 01:16 PM

For the first time, I found Uranus and Neptune in my 16", and though both resolved into discs, I was surprised how small they were at x300. At least right now in their orbit, and with the seeing I had, cranking the magnification up only resulting in more blurriness.

 

To get back on topic, I'm having an ongoing argument with myself on whether to build an 8" Chief. While it's unobstructed, the smaller aperture will provide less detail. Whether one makes up for the other, it's unclear whether it would be "better" than the 16" for planetary viewing. The 16" can also be masked down to 6" unobstructed, making the decision even more muddled!


Edited by kb58, 20 November 2020 - 02:16 PM.


#33 lee14

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Posted 20 November 2020 - 01:44 PM

When the aperture exceeds a few inches, seeing becomes the single most significant factor in revealing planetary surface detail. Experience with reflectors and SCT's aside, I've observed planets with everything from the 60mm Tasco I had as a kid, to the 24 inch Clark at Lowell, and quite a few in between. Aperture is king, but only when the seeing cooperates. I've had better views of Saturn in a 4 inch Unitron in great seeing than the Clarke in poor. Excellent seeing, unless you're in a uniquely great location is rare. 

 

Lee


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#34 icomet

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Posted 20 November 2020 - 02:30 PM

I read an article about a well known astronomer, a double star observer, and other things probably, and how he said the art of "seeing" at the eyepiece was necessary to master to see the hard stuff like sub-arc splits, or probably anything astronomical.

 

He uses a very unique design of scope, all be it, 12.5" of aperture, and said it took him 20 years of observing, and probably constantly in his case, to get "seeing" down at the eyepiece.

 

Practice, practice, practice; provided the weather conditions hold out.

 

That being said, here is a scope that I built to master my "seeing" with.  It's a fun scope. That helps, too.

 

Clear Skies

 

6" f/9.92 Ed Beck mirror

Moonlite focuser

Antares secondary

Astrosystems secondary holder/spider

Cave Astrola primary mirror cell

Cave Astrola rotating rings

fans for cooling/mirror boundary air removal

CG-5 ASGT mount (resurrected)

 

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#35 E_Look

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Posted 20 November 2020 - 07:54 PM

I think that astronomer uses the word, "seeing" to mean what Asbytec, a sharp-eyed observer here on CN, means by "more than just taking in the image", while "seeing" means something else to the rest of us!

But yeah, I know what you/he mean(s).  I swear, I had some nights of pretty good seeing (atmospheric stillness) when I first started out, but looking back, I don't think I knew what to make of the images my eyepiece was presenting to me.  I'd love to have some nights like that again nowadays.  Who knows, maybe soon!


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#36 luxo II

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Posted 21 November 2020 - 08:21 AM

Icomet, your photo shows a modest 6” in the foreground.

But there’s something rather larger lurking under the tarp in the background. Time to ‘fess up, I suggest, that’s got to be a 12” or more hiding in there !

Edited by luxo II, 21 November 2020 - 08:21 AM.

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#37 Sheol

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Posted 25 November 2020 - 07:23 PM

       Yes, what scope is that under the blue tarp? Oh, actually, I see you have 2 more scopes aside from that 6 inch reflector. Well. a 6 inch reflector was my first SERIOUS astronomical 'scope. Quite a step up from a 70mm Jason Refractor with a built in Zoom ( which I used for years btw.). You made that one for practice I think you said. So how much work does it get, Icomet?

 

   Clear Skies,

      Matt.



#38 mikemarotta

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Posted 26 November 2020 - 05:06 AM

Mike, don't get me wrong, I like and agree for the most part with your post.

Just to split hairs, the practice of science, yes, is not the publication of your article in a world-class journal, ...  The verification often comes because some other guy wants to start a fight with you, so checks your data.

We are pretty much on the same page. Posting here is publication. That's the last step in the scientific method. But it can also be publishing in your own records which remain private. That's a small audience; and you can be your own harshest critic. My last class in graduate school was Ethics in Physics. Notorious moral failures appeared in Nature. I also had an undergrad class in research methods in social science, a 200-level course for sophomores. We were to read and critically review two papers each week. After the first class, I went to the professor's office and asked if he thought that undergraduates could critically review articles that had already been peer reviewed. He assured me that we could. "Check the math," he said. So, while my CV does have peer-reviewed publications, I am happy to post here, also. Scientists report their work.


Edited by mikemarotta, 26 November 2020 - 05:07 AM.

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#39 icomet

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Posted 26 November 2020 - 10:48 AM

Icomet, your photo shows a modest 6” in the foreground.

But there’s something rather larger lurking under the tarp in the background. Time to ‘fess up, I suggest, that’s got to be a 12” or more hiding in there !

My 1985 Model 291 Towa/Meade 60mm is.  See it hanging on that scope?

 

Clear Skies.

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#40 luxo II

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Posted 26 November 2020 - 08:28 PM

Oh you are sooo modest...



#41 icomet

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Posted 26 November 2020 - 08:57 PM

       Yes, what scope is that under the blue tarp? Oh, actually, I see you have 2 more scopes aside from that 6 inch reflector. Well. a 6 inch reflector was my first SERIOUS astronomical 'scope. Quite a step up from a 70mm Jason Refractor with a built in Zoom ( which I used for years btw.). You made that one for practice I think you said. So how much work does it get, Icomet?

 

   Clear Skies,

      Matt.

Clear Skies.

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#42 Sheol

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Posted 27 November 2020 - 07:22 PM

     So 6", 8", 10" then? At least that is how that appears to me! Man, just looking at 3 GEQ mounts makes my arthritis scream & my back ache..

 

        Matt.



#43 icomet

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Posted 27 November 2020 - 08:13 PM

12.5" f/7

10" f/7.5

6" f/10

 

Clear Skies.



#44 BlueTrane2028

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Posted 27 November 2020 - 08:33 PM

I'm not a scientist by any stretch... my favorite scope will probably always be my 12" Skywatcher Dob, but I've been spending time on scopes smaller than 6" on purpose lately.  For one, I don't have anything "large" on a GEM, and having spent most of my time with alt-az mounts, this forces me to learn something new.

I can't say I'm getting views that are exactly as good on my 90mm refractor as I get on an 8" f/6 or larger... but they're not bad either.  I'm enjoying it enough that I think I'm going to invest in a decent diagonal and maybe a motor drive or the mount, would be cool to actually have it track.  I'm invested all of $20 in the telescope, why not, haha.



#45 gwlee

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Posted 28 November 2020 - 06:32 PM

In regards to resolution, I’d say about 12% less useful than an 8” and about 16% more useful than a 6”.

#46 Paul Sweeney

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Posted 29 November 2020 - 02:41 AM

I agree that seeing is the most important factor in viewing planets. I live at 50° north in Europe, and we have terrible seeing in the Fall. I have done almost all my planetary viewing with an 80mm f/15 refractor. On occasion I went down to 60mm. Sure, my 12" dob will show much more detail. But viewing with it means 30 seconds of mush, then a millisecond of "wow!", and then more mush. An exercise in frustration. In the small refractors, the image moves around but holds together, with only occasional mushy periods. Here where I live, the refractors show me the most. Back where I used to live in Texas, the 12" dob would be the scope of choice.
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#47 litesong

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Posted 29 November 2020 - 12:17 PM

I don't believe everything I read.

You don’t believe everything I post?..........Good for you!

I live by the motto, “To err is human.....& I am very human”.



#48 luxo II

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Posted 17 December 2020 - 08:21 PM

In regards to resolution, I’d say about 12% less useful than an 8” and about 16% more useful than a 6”.

You wouldn't be an accountant, by any chance ? 


Edited by luxo II, 17 December 2020 - 08:24 PM.


#49 planet earth

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Posted 18 December 2020 - 06:52 AM

You don’t believe everything I post?..........Good for you!

 

That's not exactly what I said.



#50 grif 678

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Posted 21 December 2020 - 03:36 PM

If you came up like I did, raised on a farm, and you had to work for everything you got as a kid, and if you were lucky enough to get a 3 inch scope, I believe you would be very happy with what you can see on the planets. I think most of us are spoiled, we want to see more, and that is not always the answer. I just got a 80mm F15 refractor, and it shows me more detail on Jupiter than a couple C-8's I had years ago. Cloudy Nights is very much fun, very informative, and useful. But I feel like many of us have bought scopes just because of what we have read from other members, only to find out ( I wish I had not of spent that money on that scope, the views are not that much better, and I was happy with what I had)

I have read lately though that a lot of viewers are going back to smaller scopes, especially as age creeps up on us. I had much rather see 3 or 4 bands on Jupiter with a scope that I can handle easily and want to use, than see 6 bands with a scope that I do not want to try to carry out and set up, and wind up using it only once or twice a year.


Edited by grif 678, 21 December 2020 - 09:31 PM.

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