SW 100: Will I notice Difference?
Posted 02 November 2013 - 12:23 PM
This past summer I jumped on the refractor bandwagon big time and I have been very happy with the Celestron ED80 and that super deal many of us got from OPT on the Celestron 102.
With holiday sales starting, the Skywatcher 100ED has dropped in price to $649, and I'm wondering the following:
Will I notice a difference in my planetary and lunar observing between the 100ED and the two scopes I already have, or
Should I just wait until the day I can add a 120ED? Unfortunately, with the SW120 ED comes the necessity of a new mount, and the SW100ED would probably work fine on my Polaris.
So, your opinions, please: enough of a difference in the 100ED to be noticeable, or simply an improvement in build (nicer focuser, etc.)
Posted 02 November 2013 - 12:39 PM
Posted 02 November 2013 - 12:41 PM
Posted 02 November 2013 - 12:44 PM
Posted 02 November 2013 - 01:20 PM
Posted 02 November 2013 - 02:15 PM
Good luck Thom
Posted 02 November 2013 - 03:21 PM
Posted 02 November 2013 - 03:24 PM
Posted 02 November 2013 - 03:30 PM
Thank you. What do you usually observe? DSO or lunar/planetary? What changed for you with the new scope?
I observe open clusters, globs, and dso's most, then planetary, and doubles least. There is a definite improvement in all of the above. I couldnt make out the adjoining galaxies to adromeda with the 102gt and i can with the ed100. Best analogy would be going from a lcd tv, to a top of the line 4k led tv. Same size, just a ton clearer.
Posted 02 November 2013 - 04:30 PM
Will it be worth $650?
Maybe, maybe not.
My advice? Save your money.
Sell all of these other scopes and stuff.
And go bigger.
Consider a 120ED type scope. If you really want a meaningful improvement, this is the way you should get it.
Changing from an f/10 achomat will of course make an improvement.
But here is the thing. Apeture gives you exit pupil.
A 100mm achromat is going to give you a dim image at 150x.
And guess what. So will a 100mm f/9 ED scope.
And exit pupil and image scale are your friends for planetary observing.
If you really want to improve your planetary observing, but retain all of the virtues of the refracting design (wide fields, no coma) then again, sell all your stuff and buy a telescope that is not only better, but is also bigger.
I know, the price is really nice, but I don't think you are going to pee your pants at the difference.
A 120ED scope though? Now you are talking.
Past this and it gets expensive fast, but the 120ED scopes were a tremendous value. They are still light and have a short enough package that they are not demanding to mount, and they will be much more capable planetary performers than a 100ED.
Do yourself a faver and take a step and a half ahead rather than a half step sideways.
And if you can't afford it now, then live with what you have until you can.
Posted 02 November 2013 - 04:37 PM
Posted 02 November 2013 - 05:11 PM
Look at #7 - Link.
Posted 02 November 2013 - 05:25 PM
Very wise & good thinking in my humble opinion.
8"f/6 OOUK Newt
Posted 02 November 2013 - 06:18 PM
There are also 6" achromats to consider.
Posted 02 November 2013 - 06:59 PM
What would you use to mount. I prefer alt az and that's really what I'd want. The 120 is lighter than most, so the least hefty I can get away with.
Posted 02 November 2013 - 08:42 PM
I do not for the life of me understand how people can use an alt az mount for planetary observing.
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.
For the highest resolution observing, it is really best to have the target at or near the center of the field.
And for planets, where you want to use high power, keeping the target centered is really important.
This allows you to relax and concentrate on the target.
Even today, using only 75x on my 110ED for solar white light, it was driving me mad to track (my motor drive is down for repair).
Just as I would get a few moments of steady seeing, I would be interrupted to re-center the target area. Seeing was coming and going and here I was taking my eye off the ball.
To me, if you are really serious about planets, you need a tracking mount.
You can get the CG4 for $275 brand new and shipped to your door.
This is not the most sturdy mount on the planet but is is not really much worse than a lot of Alt-Az mounts that cost $300.
I really mean this. For planets, I would rather have a mount that shakes when I focus it but has tracking than have a solid alt-az mount.
But that is me. I think I have done some really amazing planetary viewing, and I simply can't comprehend how people can eek the most challenging detail out of their scopes by being interrupted to move it every 30 seconds.
So, that is my take.
Sure, if you can afford a Cadillac mount like the GM-8, then that is great.
But my own advice is that if you really want to get the most detail out of a scope that is aimed at a planet, you need a good, comfortable observers chair and a tracking mount.
I think you can do some pretty good planetary observing with a good 120mm ED refractor (and I would not get the Vixen 120. It is not going to be in the same class as the 120ED scope).
But when you study optics, you quickly realize that most telescopes will perform at there very best when the target is kept very close to the center of the field.
And don't be fooled. Most refractors do defocus at the edge of the field, but as long as the star does not swell up to more than about 3 arc minutes of apparent field, we can't really tell that easily because in a coma free refractor, it remains a small dot.
But the planet will go out of focus and you can easily see it.
Sorry for the rant, but if you get a great planetary scope, get the most out of it with a tracking mount.
And later, get a good pair of binoviewers.
I have come to consider Binoviewers as far more important than the eyepieces you put in them.
These are all the opinions of an old man, but I have been doing serious planetary observing for a very long time now, and have had very great success I think.
And how people do serious planetary observing with an un-driven mount is beyond me.
Today, doing the sun without my motor was maddening. Every time I seemed to get a moment of perfect seeing, the detail seemed to be drifting close to the defocus point of the diffraction limited field of my scope. Maddening.
How do people do it???
Posted 02 November 2013 - 08:54 PM
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.
Posted 03 November 2013 - 02:20 PM
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.
Posted 03 November 2013 - 05:10 PM
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:
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.
Posted 03 November 2013 - 06:02 PM
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
Posted 03 November 2013 - 06:38 PM