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Equipment Discussions >> Refractors

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Eddgie
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Reged: 02/01/06

Re: SW 100: Will I notice Difference? new [Re: Eddgie]
      #6172668 - 11/02/13 09:54 PM

I said CG4 in my previous post, but there are other inexpensive GEMs if money is tight. You can get used CG5 type mounts for less than $300 too.

A really decent Alt Az is going to cost double this by the time you stick a good tripod on it.

I am running my new 110ED (14 lbs with binoviewer and eyepiece) on a humble Polaris mount (though it does have a HAL 110 tripod).

Sure it shakes a little when I touch it, but once I let go it settle down.

And planetary observing is about waiting a lot of times.

You pick the power that you think will give you the best result for the best moments of seeing that are occurring, plug it in, sit, and wait.

Most people make the mistake of using a power that gives the best overall view for the average of the seeing, but I always select the power that is right for the few moments of more stable seeing that always occur.

It is during these fleeting seconds that you get your most challenging detail.

And if you are fussing with eyepieces or with re-positioning the mount, you miss it.

This is the key to getting the most out of your telescope for planetary observing. Push the power a little big over what seeing seems to limit you to, sit, and wait for it.

It almost always comes.

Big scopes are not supposed to do well in most seeing, but all of my best observations were done in less than excellent seeing using the above method.

Edited by Eddgie (11/02/13 09:55 PM)


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BillP
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Reged: 11/26/06

Loc: Vienna, VA
Re: SW 100: Will I notice Difference? new [Re: saemark30]
      #6173840 - 11/03/13 02:20 PM Attachment (40 downloads)

Quote:

I would wait for the 120ED, the 100ED is too small for detailed planetary views.
There are also 6" achromats to consider.




IMO there is a bulk/mount consideration when moving between a 4" to 5" class instrument that is not trivial. As far as details comparitively in a 100 vs 120 I'm not so sure I would chanracterize it as so dramatic for planetary. It's a 20% gain in resolution, which is about the same as going from an 85mm to a 102mm. So if the OP wants to get a flavor of a difference in details between a 100 and 120, all they have to do is make an 85mm mask for thair Celestron 102, point it at Jupiter, and observe with and without the mask to get an idea of the relative difference in resolution.

And as far as details, a 4" can see quite a bit. Below is what I see *typically" on average with Jupiter - boundry details are etched when viewing, my sketching skills not good enough to represent this well however. Last week at about 4:30am I got a peek of Jupiter that was far better than this in my 4" APO as the atmosphere was very clear and stable. This is a binoviewer sketch and the 4" APO was mounted on a simple Vixen PORTA II. Eyepieces and bino were not exotic either.

Edited by BillP (11/03/13 02:32 PM)


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Eddgie
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Re: SW 100: Will I notice Difference? new [Re: BillP]
      #6174104 - 11/03/13 05:10 PM

Well, you may have addressed your post to saemark30, but perhaps you were responding to something I said.

And if that is the case, you have put a word in my mouth that I sure did not use.


seamark30 did not use the word "Dramatic" either.

Here is what I said:

Quote:

If you really want a meaningful improvement, this is the way you should get it.




The move from a 4" f/10 achomat to a 4" APO is going to yield perhaps a rather subtle improvement, but the move to a 120ED will yield an improvement that is much easier to see.

Dramatic is words I would use if he were gong to a 7" APO or a C14, or a 10" MCT or something.

Below that it is just a few small steps in meaningful improvement.

Once you get past 6", it gets big, or it gets expensive to get a "Dramatic" improvement.

So, just wanted to keep the record straight. I don't think I said "Dramatic" and I don't think saemark30 did either.


And I really could care less what the OP gets, but the proven road to better planetary performance is more and more good quality clear aperture.

Mounts, portability, seeing, cooling, and all that other stuff is secondary potential to the full potential of instrument you use.

If you start with a scope with limited capabilities you can never rise past those capabilities, and diffraction of the aperture is the ultimate limit.

Someone on another thread just chided me for the fact that my new 110ED was not going to be as good as his super apo 4" whatever for planets.

Yeah, right. Of course.

But that is why I have a 6" APO if I want to look at planets.

Good quality clear aperture is what you need for planets and the more, the better.

If one is worried about how big it is, then one has to be willing to settle for less.

Even Roland Christen uses a big MCT for planets.

Edited by Eddgie (11/03/13 05:38 PM)


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BillP
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Reged: 11/26/06

Loc: Vienna, VA
Re: SW 100: Will I notice Difference? new [Re: Eddgie]
      #6174186 - 11/03/13 06:02 PM

I don't think we need to get wrapped up with individual words. That's just my interpretation of things. So simply replace dramatic with one you think correct. My post where I quoted Seamark30 was in response to 2 things, one being that a "100ED is too small for detailed planetary". So by inference from that quote, which is quite proper, if a 100 is too small and a 120 is fine, I would personally chanracterize the difference between going from too small to acceptable as a dramatic one relatively. So that is where dramatic comes from, all contained within interpretation of what I quoted. So if that particular word is bothering, then my apologies and simply put in another word you want that charaterizes a situation where one aperture is inadequate by being too small and the other aperture of 120 is adequate. I will keep that relative difference as being dramatic for my perspective on things.

But again, let's not get wrapped up in the single word. My inclusion of the sketch is to indicate that 100 is indeed not too small at all, not by a long shot And going larger means lots of things, like beefier mounts and more effor and longer cool downs and of course much more money. I am trying to keep my responses atuned to the spirit of the OPs starting post. Talking all those other larger aperture instruments is way afield I think since the OP is asking about 100 vs 120 differences. I, btw, do care what the OP gets as they are asking advice afterall specific to a narrow request of 100mm vs 120mm.

As far as starting with "limited" capabilities, well all scopes have limited abilities and larger ones certainly limit lots of abilities relative to readiness. Heck, I've had SCTs that were never ready for planetary all evening long! Just one of their limitations in certain environmental scenarios. As far as MCTs, well I would expect RC to use that and tout it because he makes them, it is marketing afterall!

Anyway, none of these are chides, just another opinion for the OPs to consider. I personally don't think 100mm is too small and find it rewarding as my sketch shows. Larger is always better in *some* terms, but always has its downsides as well. The magic is in striking the balance that best meets individual goals


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jag767
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Reged: 06/20/13

Loc: Massapequa, NY
Re: SW 100: Will I notice Difference? new [Re: BillP]
      #6174252 - 11/03/13 06:38 PM

I think for many ignorance is bliss. I love my ed100 and find it great for planetary viewing. That being said I have no viewing time through a larger refractor to compare it to.

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pdxmoon
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Reged: 06/27/13

Loc: Oregon
Re: SW 100: Will I notice Difference? new [Re: BillP]
      #6174253 - 11/03/13 06:38 PM

I appreciate both points of view, Ed's and Bill's. Ed obviously feels strongly about EQ mounts,etc., and his words have a lot of wisdom to them, and I am grateful he "ranted", as he said :-)

I also appreciate Bill's comments, and there's wisdom there too. Particularly the issues with mounting, and frankly, the way I prefer to observe--which is alt az. I like doing it that way. I find it relaxing to track the moon by hand.

I am also an incremental kind of guy. I like moving up slowly in the food chain, and not moving too quickly. It's just how I roll.

So, I believe it's very likely that both the mechanical aspects of the 100ED (i.e., the improved focus mechanism, better build) and the improvement in viewing--even if subtle, and the fact that I already have mounting I can use and that is easy for me to use, may win the day.

I'm still not entirely sure I'll do this, but I believe the chances are good I'd enjoy the 100ED if I did.

Thank you, everyone, for your thoughts.

T


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BillP
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Reged: 11/26/06

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Re: SW 100: Will I notice Difference? new [Re: pdxmoon]
      #6174316 - 11/03/13 07:16 PM

One of the things I enhoy about a smaller scope is the ability to move it between multiple less expensive mount plantforms. So the 102mm APO I have gets rotated around depending on my seasonal mood So I have an iOptron Minitower Pro for tracking, a Porta II Alt-Az for a light and easy solution, and also a CG4 for equatorial needs. I've had the 102 on the iOptron for the past few months and have just recently switched it to the Alt-Az to enjoy more rapid excursion capability, so basically a zero setup and work on this and light as a feather while still being stable enough.

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Nippon
scholastic sledgehammer
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Reged: 10/22/09

Loc: Central Florida
Re: SW 100: Will I notice Difference? new [Re: pdxmoon]
      #6174327 - 11/03/13 07:23 PM

I think the Celestron 8SE is at a $200 rebate. The mount is a little shaky but the gotos are accurate and it tracks. The 8" optics will crush the SW 100ed on planets and go much deeper for deep sky. Later you can buy a mount such as the Celestron AVX and have a solid set up for planetary viewing. I love my Vixen ED 103 S but it simply can't compete with my NexStar 8SE tube on anything but wide field. I used the 8 SE tube on it's goto alt/az for three years before I bought the AVX mount and it is a very competent set up. The AVX just added more stability and increased goto accuaracy.

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timps
sage


Reged: 02/24/13

Re: SW 100: Will I notice Difference? new [Re: BillP]
      #6174347 - 11/03/13 07:38 PM

Quote:

Quote:

I would wait for the 120ED, the 100ED is too small for detailed planetary views.
There are also 6" achromats to consider.




IMO there is a bulk/mount consideration when moving between a 4" to 5" class instrument that is not trivial. As far as details comparitively in a 100 vs 120 I'm not so sure I would chanracterize it as so dramatic for planetary. It's a 20% gain in resolution, which is about the same as going from an 85mm to a 102mm. So if the OP wants to get a flavor of a difference in details between a 100 and 120, all they have to do is make an 85mm mask for thair Celestron 102, point it at Jupiter, and observe with and without the mask to get an idea of the relative difference in resolution.

And as far as details, a 4" can see quite a bit. Below is what I see *typically" on average with Jupiter - boundry details are etched when viewing, my sketching skills not good enough to represent this well however. Last week at about 4:30am I got a peek of Jupiter that was far better than this in my 4" APO as the atmosphere was very clear and stable. This is a binoviewer sketch and the 4" APO was mounted on a simple Vixen PORTA II. Eyepieces and bino were not exotic either.




I am waiting for delivery of my TSA102 and am certainly not expecting to see Jupiter like that. I haven't even seen that much detail on Jupiter with a TOA130!


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BKBrown
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Reged: 08/23/09

Loc: Northern Virginia, USA
Re: SW 100: Will I notice Difference? new [Re: timps]
      #6174586 - 11/03/13 10:08 PM

Quote:

I am waiting for delivery of my TSA102 and am certainly not expecting to see Jupiter like that. I haven't even seen that much detail on Jupiter with a TOA130!




And yet the detail is there to see if you have the skill set down. I agree with BillP that a 4" ED/Apo is a very capable instrument for planetary viewing, my SW100ED has given me many splendid, memorable views of Jupiter, Saturn, and the Moon. What is more problematic is having the time, patience, and willingness to become a skilled planetary observer...that doesn't happen overnight, you have to work for it

Clear Skies,
Brian


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Eddgie
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Reged: 02/01/06

Re: SW 100: Will I notice Difference? new [Re: pdxmoon]
      #6174721 - 11/04/13 12:06 AM

Enjoy your new scope. I am sure it will be excellent.

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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: SW 100: Will I notice Difference? new [Re: Eddgie]
      #6174893 - 11/04/13 05:39 AM

Quote:

Almost all scopes only perform at their full potential when the target is within a few arc minutes of the center of the field.

For reflectors, coma is the contrast killer if you let the planet get out of the center of the field by more than 5 or 6 arc minutes for a typical reflector. Beyond this and the image is no longer diffraction limited.

For refractors, it is field curvature. Once you let the target drift about 5 or 10 arc minutes out of the center of the field it is no longer at best focus.




This is why people use coma correctors like the Paracorr when viewing with a Newtonian and realize that even at 100x, the field curvature of a 100mm F/9 is miniscule.

You know how to do the math... The depth of focus at F/9 is 0.0070 inches, the field curvature across a 12mm field of view (0.76 degrees = 45 arc-minutes) is only 0.0023 inches... the depth of focus is three times the field curvature across a field greater than the size of the moon.

In an 10 inch F/5 Newtonian fitted with a Paracorr, the "coma free field of view" is 0.65 degrees or 36 arc-minutes, again greater than the size of the moon...

As far a 120mm ED on a GEM being a better choice than a 100mm ED on an alt-az mount:

Both a relatively small scopes and the differences in the views, while noticeable, will be much more the same than they are different. That 20% increase in aperture provides somewhat finer contrast but not a great deal. To see a major difference, it takes a major difference in aperture. Either of these scopes can provide meaningful, enjoyable planetary viewing but neither will provide the best possible views that decent seeing will allow.

The major difference between a 120mm F/7.5 on a CG-5 class GEM and a 100mm F/9 (or even better F/7) on an alt-az is the portability, ease of use, ease of setup. The smaller scope qualifies as "grab and go" but the larger scope is no longer so easily managed and setup. In my experience, it takes about the same effort and time to setup a 10 inch Dob as it does a 120mm refractor on a equatorial mount.

This gets to the heart of why I (and maybe others) use hand tracked alt-az mounts. It comes down to getting the best image to the focal plane for the least amount of hassle. A good 10 inch will easily outperform a very good 5 inch..

Some people have more trouble than others hand tracking.. I enjoy it. It's that simple.

The right scope for you, the right scope for me, the other guy, that is what is important. They are all very likely quite different. In the final analysis, it's all about the actual experience. This is just a hobby we enjoy, nothing more..

Jon


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jag767
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Reged: 06/20/13

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Re: SW 100: Will I notice Difference? new [Re: Jon Isaacs]
      #6174900 - 11/04/13 05:53 AM

For me, there have been nights where i am so dead beat tired I just grab my 65mm and go out because I can literally carry my entire setup with one hand with ease. I got a 100ed over a 120 for 2 reasons. First reason was it no longer is a light scope easy to mount for those quick sessions (which most of mine are) to just pop outside on something like a porta II. Second is it would have eaten up too much of my budget right off the bat. In the used market and ed100 f9 can easily be found for 300 plus shipping without accessories, where as a 120 will be at least triple that.

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Eric63
scholastic sledgehammer


Reged: 06/16/12

Loc: Ottawa, Ontario
Re: SW 100: Will I notice Difference? new [Re: pdxmoon]
      #6174987 - 11/04/13 08:25 AM

I think you made a wise choice Thom, I have only heard amazing things about the 100Ed and this way you don't need a new mount. And like Jon said, the difference from 100 to 120 will not be that great, at least not $700 worth . Later on you can decide if you want to venture into the larger SCT or Newtonian world, but keeping aperture fever under control has its own merits too! This is something I keep struggling with. I read some nice threads about amazing views with larger instruments, but then I remember that the simplicity of the hobby is what keeps me observing. Going too large and complicated will just reduce the enjoyment for me.

Eric


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Stephen Strum
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Reged: 04/18/09

Loc: Tulsa, OK
Re: SW 100: Will I notice Difference? new [Re: jag767]
      #6175007 - 11/04/13 08:39 AM

My experiences are similar to the last couple of posts. Probably 90% of my observing sessions are less than 20 minutes long as a result of long work days, family, etc. I generally can't stay out more than that during the week and still get anything remotely close to 6 hours of sleep. So, small scopes, of whatever type, on an alt-az mount that can be taken out in one trip with everything attached make observing frequently a possibility. I can still get a 8" SCT out the door on an alt-az mount in one trip but it is awkward enough that SCTs <=6" get used more, and refractors over 4" exceed that limit quickly, and even 4" can be pushing it. Obviously it is nice to have a large scope available to use when you have the time, but if I was limited to just one scope it would probably be a 3-4" refractor simply because it would be used so much more frequently.

Similarly, I sold my only equatorial mount (that offered tracking) because it never got used. Partly because my yard has numerous trees and so observing different objects usually requires picking up and relocating the scope, and doing that frequently with an equatorial mount wasn't as fun. Plus, I also enjoy tracking objects by hand, even planets at high power. Manual tracking with an overloaded alt-az mount is hardly easy or fun, but when matched correctly and well balanced, it is easy to track at well over 200x with a little practice, at least for me. Also, for whatever reason, I prefer to see objects move rather than remain stationary. Now, if I was retired or otherwise had more time, or had a larger property that allowed me to put in a more or less permanent mount, then I would likely observe much differently. Luckily, we all have numerous options available and so with some trial and error most people can find the scope sizes and types and mounts that provide them the most enjoyable experience. Unfortunately, there is really no way to figure that out without actually living with a scope for a while since listening to various opinions and experiences all day long can't replace your own. Even trying a scope out at a star party can't replace actually trying to negotiate your kitchen, back door and steps with the thing. And, those best-for-me combinations will always be changing as your life changes. But, trying new things is half the fun of the hobby.


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Stephen Strum
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Reged: 04/18/09

Loc: Tulsa, OK
Re: SW 100: Will I notice Difference? new [Re: Stephen Strum]
      #6175016 - 11/04/13 08:50 AM

As a follow-up, scope choice I think often depends on whether an observer gets more enjoyment out of being able to see the greatest amount of detail possible when observing (when considering physical and financial constraints on that) or whether the observer simply wants to be able to get out an observe easily and frequently. For me, I'm not usually so concerned about that fact that I could have seen more detail on Jupiter or some other object if I had a scope a little bigger out with me. Most of my enjoyment simply comes from the relaxing experience of being outside observing the sky with whatever instrument I have. Now I suppose that view might change in 30 years after I've observed the same things countless times.

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Eric63
scholastic sledgehammer


Reged: 06/16/12

Loc: Ottawa, Ontario
Re: SW 100: Will I notice Difference? new [Re: Stephen Strum]
      #6175038 - 11/04/13 09:11 AM

I agree with you 100%. That's why I have recently returned to using binoculars. Just yesterday with 0 degree (32F) temperatures, I drove 5 minutes to a dark spot with my 15X70 Binoculars and a photo tripod to simply enjoy Auriga and Orion for only 20 minutes. I just loved how the objects were framed in the sky instead of trying to see the detail within them. A change of perspective is sometimes good

Eric


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pdxmoon
Pooh-Bah
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Reged: 06/27/13

Loc: Oregon
Re: SW 100: Will I notice Difference? new [Re: Eric63]
      #6175226 - 11/04/13 11:05 AM

I do most of my observing in the summer months, because of the weather here in Portland, and because of my work schedule. In the winter I rarely get out, and when I do I have a 60mm Meade right outside my door just waiting for looks at the moon.

My 102GT is covered in the garage, so if the weather is mild and I can spend more than 10 minutes, I can open the garage and lift it into place in about 15 seconds. But mostly, it's the summer.

And here's another thing I've noticed about myself. Because of the deliciousness of the two speed focus on my AT72, I often reached for that, even over the ED80, sometimes. It is just such a pleasure to use. If I go for the ED100, I expect that because of the improvement in build, that alone will add to my pleasure.

I appreciate all your comments and ideas.

Edited by pdxmoon (11/04/13 11:06 AM)


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PeterR280
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Reged: 05/27/13

Re: SW 100: Will I notice Difference? new [Re: pdxmoon]
      #6175325 - 11/04/13 12:09 PM

I find 100mm the best compromise between portability and visual performance for a grab and go setup. For ordinary seeing situations, a magnification of 150x or maybe a little bit higher is about all you can get. The 100mm will do just fine up to about 200X depending on optics. It is also noticably brighter thn an 80mm refractor.

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saemark30
Pooh-Bah


Reged: 02/21/12

Re: SW 100: Will I notice Difference? new [Re: BillP]
      #6175347 - 11/04/13 12:19 PM

BillP,
Can you tell us the details of the drawing such as power, eyepieces, filters if any, and planet apparent size?

Jupiter can vary from 30 to 50 arc sec.
An exquisite Takahashi 4" can show detail on Jupiter.
Typically a 6" is the aperture to notice significant increase in detail as reported in literature from the last 100 yrs and ValeryD suggests 6"-7" apos.

A 5" can show some polar caps and dark regions on Mars at a close opposition.

I am now trying out 6" f/8 achromats. Forget the theory and just view. These scopes are amazingly sharp and contrasty.
When growing owning a 6" refractor was a pipe dream, now they are dead cheap. Right now its my favorite scope.


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