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Orion AstroView 120ST Or The 100ST ?

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#1 mekaone

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Posted 16 February 2012 - 01:56 AM

Hi All.
I am about to purchase one of two scopes that I have been looking at and I have a question I need help with please.
I am looking between the Orion AstroView 120ST Equatorial Refractor Telescope and the Orion AstroView 100ST Equatorial Refractor Telescope.
The 100ST is $399.99 and the 120ST is $499.99.
What my question is, is the extra seven-tenths of a inch worth the extra $100.00 bucks?
Also what do you all think of these scopes?
Thanks for your time. 73 :grin:

mekaone

#2 SeptemberEquinox

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Posted 16 February 2012 - 02:49 AM

Ha I was going through a same phase. 100st or 120st.. I said skip it and spent more. 100st was 349.99 about two weeks ago.

I just looked at telescope.com to see if clearance sale was still there for 120st, but it looks like it's all gone. They had one for 449.99.

May I ask why you want these refractors? You got a good dobsonian.

http://www.telescope...thumbnail2level

#3 Jon Isaacs

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Posted 16 February 2012 - 09:22 AM

Hi All.
I am about to purchase one of two scopes that I have been looking at and I have a question I need help with please.
I am looking between the Orion AstroView 120ST Equatorial Refractor Telescope and the Orion AstroView 100ST Equatorial Refractor Telescope.
The 100ST is $399.99 and the 120ST is $499.99.
What my question is, is the extra seven-tenths of a inch worth the extra $100.00 bucks?
Also what do you all think of these scopes?
Thanks for your time. 73 :grin:

mekaone


Mekaone:

What are you hoping to do with the telescope? Here's a few thoughts:

- I recently purchased a used Astroview 100mm F/6 OTA thinking I might use it as a finder scope. I also had one several years ago. It is a reasonable low power widefield telescope that shows a considerable amount of false color when used for viewing the planets and double stars. I would not recommend either one if your goals include a significant amount of planetary/double star viewing.

- One issue is that the Synta rack and pinion focusers are somewhat problematic. From the factory they use heavy grease and they are adjusted on the loose side so generally there is some rock in the draw tube and they are not smooth and easy. Over the years, I have reworked quite a few of both the 1.25 inch and 2 inch Synta/Orion/Celestron rack and pinion focusers. This last AstroView 100mm F/6 came out very nicely, once I cleaned it, replaced the lower guide strips with Teflon and adjusted it, it is really quite a nice focuser. 10 years ago, Crayfords were expensive and rare and focusers like these were the standard. The world has changed.

- Since these scopes are best suited for widefield and medium power DSO observing, a 2 inch diagonal is very desirable, it lets the scope do what they do best, either one is capable of a 4 degree TFoV with the right eyepiece.

- EQ mounts have their place but for the things that these scopes are best suited for, I prefer a ALT-AZ mount...

If you are looking for a quick look scope that excels at the widefield stuff, one of these could be just ticket but if you are thinking of spending much time viewing the planets with it, I would look elsewhere.

Jon

#4 Bob Griffiths

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Posted 16 February 2012 - 09:48 AM

I too have a f/6 100 mm Orion and I too reworked the focus mechanism and added a 2 inch Diagonal just like Mr Issacs ..UNFORTUNATELY I have not yet replaced the EQ mount with an Alt/Azm mount BUT that does not stop me from using the EQ in alt/azm mode.. only took a little modification with a grinder to allow the astroview mount to be set up taht way...

I use this scope ONLY for viewing open clusters for the most part...NEVER on the MOON or any other bright object ..the CA is horrible

Bob G.

#5 Locoman

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Posted 16 February 2012 - 11:17 AM

If you just want the 100mm OTA you can get it here!

#6 Binojunky

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Posted 16 February 2012 - 12:34 PM

I bought the 120ST OTA, the stock focuser on mine was very good, maybe I got lucky?, however as I had a almost new single speed GSO crayford that was purchased for a Stellarvue scope I used to own I purchased the adaptor and swapped it over, as said earlier a 2" diagonal is needed to bring out this scopes best, though usable on planets and the moon its real strength is star clusters etc.
Note that ther are other choices out there, Antares do a 105mm F6.6, Explore scientific offer a similar instrument in an OTA as well, Dave.

#7 mekaone

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Posted 16 February 2012 - 12:41 PM

Thanks all.
A few weeks back I went to a wedding and dusted off my old 35mm Pantax SLR camera and it made me think about astrophotography. I was hoping that the 120ST or 100ST may be a good basic setup for someone who was starting to take photos and also be good for looking at other stuff as long as they were not to bright. I was reading some reviews where some did talk about the CA but they stated that the CA was not that bad and others did say to replace or rework the focuser. I was thinking about a Crayford style focuser. I also was planning on using 2" EP's and a 2" diagonal.
With this scope though I just didn't know if paying $100.00 more was worth it for going from a 4" tube to a 4.7" tube?
Would that .7" be that much more noticeable?
I am mad that I missed that sale on these scopes. $50 dollars off would have been nice :-)

mekaone

#8 Eddgie

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Posted 16 February 2012 - 01:08 PM

This is just an opinion of course...

Neither of these scopes would be a good choice for astrophotograpy. Booth will have pretty noticeble field curvature and both will have a lot of chromatic abberation.

And by the time you thow away a lot of money upgading it, why not just start with a better telescope?

Again, just my opinion, but I have seen people by telescopes that were not well suited for what they envisioned themselves doing with them, then thowing good money into them to "Upgrade" and wind up with an expensive scope of somewhat limited appeal on the used market when they eventuallf figured out that they needed a different telescope.

My own advice would be to just start with a better telescope. I have owned several fast achromats and they were among the least satisfying telescopes I have ever owned.

I am sure you will find champions for just about anything you might ask about on these forums though, and I am sure these scopes have their advocates. In my own opinion though, you can do better. It might cost you a bit more, but once you factor in the money you are going to dump on one of these scopes to upgrade it, the difference may not be all that much.

#9 Jon Isaacs

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Posted 16 February 2012 - 01:12 PM

I was hoping that the 120ST or 100ST may be a good basic setup for someone who was starting to take photos and also be good for looking at other stuff as long as they were not to bright.



I would not recommend one of these for astrophotography. The chromatic aberration is quite apparent visually and cameras have capture a significantly wider spectrum so good color correction is important. These mounts are not well suited to Astrophotography either. A-P starts with a stable mount.

Probably the least expensive really capable AP rig is a used ED-80 on a used CG-5 ASGT...

Jon

#10 mekaone

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Posted 16 February 2012 - 02:28 PM

Thanks all.
That is why I ask first :-)
I'll start looking for something else.
This setup was attractive because of the price and that it was a all in one setup. I guess I'll have to pay a lot more to get what I want. I was just looking for a cheep way there :-)
I'll have a look at the ED-80 and look through the used equipment to see what is out there. 73

mekaone

#11 Jon Isaacs

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Posted 16 February 2012 - 02:34 PM

Thanks all.
That is why I ask first :-)
I'll start looking for something else.
This setup was attractive because of the price and that it was a all in one setup. I guess I'll have to pay a lot more to get what I want. I was just looking for a cheep way there :-)
I'll have a look at the ED-80 and look through the used equipment to see what is out there. 73

mekaone


I often see used ED-80s on Astromart for around $300. It was an ED-80 that caused me to part with my first 100mm F/6...

Jon

#12 David Knisely

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Posted 16 February 2012 - 02:58 PM

Well, to put a broader perspective in, these scopes are basically wide-field instruments not designed for optimal high-power use. That having been said, they will work at least somewhat for viewing the moon and planets, especially if a proper minus-violet filter is used. Indeed, I have used my 100mm f/6 refractor at powers up to nearly 200x on the moon, and while there is a lot of secondary color visible in the image, filters can tame it to some degree. My 100mm f/6 will easily show Cassini's division and the bands on Saturn, as well as the polar caps and a little of the dark markings on Mars (again, using filters). Where the scope really shines though is with its wide-field capability. With 2" eyepieces, you can get up to a 4.39 degree true field of view, which is great for scanning the Milky Way. Indeed, I have even viewed a number of difficult large deep-sky objects with the scope (including viewing the Horsehead using the H-Beta filter), although a larger aperture might serve better here. These short refractors aren't optimized for lunar and planetary use, but they do work pretty darn well at low to moderate powers. Clear skies to you.

#13 Jon Isaacs

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Posted 16 February 2012 - 03:26 PM

These short refractors aren't optimized for lunar and planetary use, but they do work pretty darn well at low to moderate powers. Clear skies to you.



:waytogo:

For deepsky stuff, these scopes are about as good as any 4 inch and quite affordable too. I bought mine used on Astromart for $125 shipped, it included a finder and mounting rings.

One interesting thing about these scopes is that both David and Tony Flanders own one and both are well know deep sky observers. It is true that there are other 4 inch scopes that are considerably better for high power work but no matter how good a 4 inch scope is at high magnifications, it is still only 4 inches.

So... the thing that a 4 inch refractor does best, that is lower magnification, widefield views, these scopes do about as well as much more expensive scopes. The things that a 4 inch refractor does not do so well, these don't do so well...

Jon

#14 mekaone

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Posted 17 February 2012 - 04:00 AM

Thanks for all the very good advice everyone but I may just get the Orion AstroView 100mm Equatorial Refractor Telescope after all. I just found a complete package used for $250.00 shipped to my location and it also has the travel bag with it too. For $250.00 in my opinion I think it may just be worth it. At the very least it would give me something good to experiment on and it is at about half the price I was willing to spend. If anything, If I don't like it I could always resell it and get my money back. I think when I get it the first thing I'll do is check the focuser and mount to see if it is clean and working OK. As others have stated, sometimes the focuser needs to be reworked. As for the CA I guess I can try some filters if I don't like what I see. Any tips about this scope and mount would be welcome. 73

mekaone

#15 helpwanted

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Posted 17 February 2012 - 08:30 PM

I have had both, liked the 120 better, you could see the difference in the extra light, but I never saw a problem with the focusers.

#16 Astroforecast

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Posted 18 February 2012 - 10:12 PM

Thanks for all the very good advice everyone but I may just get the Orion AstroView 100mm Equatorial Refractor Telescope after all. I just found a complete package used for $250.00 shipped to my location and it also has the travel bag with it too. For $250.00 in my opinion I think it may just be worth it. At the very least it would give me something good to experiment on and it is at about half the price I was willing to spend. If anything, If I don't like it I could always resell it and get my money back. I think when I get it the first thing I'll do is check the focuser and mount to see if it is clean and working OK. As others have stated, sometimes the focuser needs to be reworked. As for the CA I guess I can try some filters if I don't like what I see. Any tips about this scope and mount would be welcome. 73

mekaone


I started out doing astrophotography with a 120ST on an Astroview mount, with E200 film which required tracking/guiding accurately for 20 minutes or more.

You probably won't be happy with the purple halos around stars in photos with either of those scopes. You will be happy with the speed at f/5 (f/4 with a ff/fr). Its a good scope for learning astrophotography on a budget and you'll capture a lot of nebulosity in just a single one-minute DSLR exposure from a dark site.

The 120ST surprisingly turned out to be the favorite scope I've owned although I eventually sold it (and since owned an ED80, a Megrez II 80ED triplet, ZS 66SD, ES152 and 110ED) but I'll be looking to re-aquire one on the used market. For that aperture size its relatively light and portable for traveling to my dark site and the wide field views are great. But for AP it only got me through the beginner phase then I wanted something with less CA.


Edit: I found a couple of photos taken with the 120ST on film. At the time (2004) I was just getting started and happy with this result on a budget. But you can clearly see the CA even on low-brightness stars plus the field curvature.

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#17 mekaone

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Posted 19 February 2012 - 04:49 AM

Hey all.
You know I have not pulled the trigger just yet on the 100ST.
I started to look at some of the online pics from both the 120ST and the ED80 to compair. It does seem that the CA in most of the pics on the 120 has a effect of making the pic look almost out of focus.
It would also seem that most of the pics from the ED80 look very sharp. Is this generally true? This is kind of swaying my mind a bit on spending a bit extra.
QUESTION?
Does anyone know what a "2nd" from Orion is and would you trust it?

#18 Jon Isaacs

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Posted 19 February 2012 - 06:03 AM

Hey all.
You know I have not pulled the trigger just yet on the 100ST.
I started to look at some of the online pics from both the 120ST and the ED80 to compair. It does seem that the CA in most of the pics on the 120 has a effect of making the pic look almost out of focus.
It would also seem that most of the pics from the ED80 look very sharp. Is this generally true? This is kind of swaying my mind a bit on spending a bit extra.
QUESTION?
Does anyone know what a "2nd" from Orion is and would you trust it?


Hi

It looks out of focus because it is out of focus. In an achromat, the ends of the spectrum, the red and blue, are out of focus when the center of the the spectrum is in focus. The eye is more sensitive to the center colors, green and yellow which are in focus so chromatic aberration is only visible at higher magnifications.

Cameras however are sensitive to a broader range so the defocused light is much more apparent. For photography, an apochromat or "apo" is the ticket. It was not all that long ago that 80mm apos cost in the thousands of dollars but the ed80 changed all that.

Used ED80s are commonly available on Astromart for around $300, often with rings and even upgrades like after market focusers.

Jon

#19 gmartin02

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Posted 19 February 2012 - 07:49 PM

This is an image of NGC188 I took with my ST120 - before doing a bunch of hue/saturation adjustments in Photoshop in the blue and violet channels, the chromatic aberration around the bright stars was unacceptable. It cleaned up OK after heavy processing in Photoshop, but I'm saving my pennies to get an ED or APO refractor instead, so I don't have to fight with the CA just to get a decent image. I was using a field flattener so I didn't have a problem with field curvature.

Greg

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#20 mekaone

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Posted 19 February 2012 - 09:31 PM

BIG THANKS to Greg and everyone else that has helped me.
My mind is made up on the ED80. I always thought aperture was king but it would seem clarity in my eyes wins out. I wish I had more money to spend to get a even better APO scope with more aperture but the ED80 seems to have a very good following and I am happy to get it with all of your help :-)
Now on to my last question.
Would you trust a "2nd" from Orion?
I tried calling but they aren't open till Tuesday and the sale is over today at midnight so I have to make a last minute decision without asking Orion why it is a "2nd" or what is wrong with it. Thanks all. 73

mekaone

#21 JIMZ7

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Posted 19 February 2012 - 09:44 PM

I was going to say also that I had both the Orion 100mm f/6 and Antares 105mm f/6.3 refractors. With a 2" diagonal and a 32mm 2" wide angle eyepiece they were stunning on star clusters and star fields. But if you wanted more power the CA on both scopes made me wish for a longer 4" scope which I did do.

Jim :refractor:

#22 Jon Isaacs

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Posted 20 February 2012 - 03:27 AM

My mind is made up on the ED80. I always thought aperture was king but it would seem clarity in my eyes wins out. I wish I had more money to spend to get a even better APO scope with more aperture but the ED80 seems to have a very good following and I am happy to get it with all of your help :-)



For astrophotography, the mount is king. Accurate tracking is where it begins. Smaller telescopes with shorter focal lengths are easier on the mount for two reasons. First, the shorter focal length means they are less sensitive to tracking errors. Second, they are lighter, shorter and so the mount is not loaded as much, the vibration and stability problems are reduced.

A CG-5 class mount with an 80mm apo is a good way to start.

Jon






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