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Anyone familiar with Orion 120 ST Refractor?

Started by Guest_**DONOTDELETE**_* , Nov 03 2003 08:50 PM
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21 replies to this topic

#1 Guest_**DONOTDELETE**_*

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Posted 03 November 2003 - 08:50 PM

Just purchased this scope and am not happy with it.
Just wondering if I am expecting too much, or maybe scope has bad optics. Lots of problems focusing on Mars and other planets. So much so that I am wondering whether to return it. Dan

#2 Guest_**DONOTDELETE**_*

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Posted 03 November 2003 - 09:48 PM

I'd like to be familiar with it! ;) It is next in line behind the 100mm on the Pro mount for me...

#3 Blair

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Posted 03 November 2003 - 09:51 PM

Being an f/5 scope it will not perform well on the planets. It is a rich field scope which means it is for low power, wide field views. It performs very well on Galaxies and nebulas for it size of aperature. A decent 90mm f/11 or so refractor will out perform it on Jupiter, for instance. Hope this helps.

#4 Guest_**DONOTDELETE**_*

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Posted 03 November 2003 - 11:46 PM

What size eyepieces were you using?

#5 litespeed

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Posted 04 November 2003 - 04:10 PM

Check this out if you havent already:

http://www.cloudynig...stroview120.htm

AJ

#6 Guest_**DONOTDELETE**_*

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Posted 04 November 2003 - 05:54 PM

Thanks...I tried a 32 mm Celestron Plossel, a Meade 26mm, a Celestron 20 and 10mm. I would have thought that at the lower powers, I could get some focus on planets, but the chromatic abberation is pronounced with all eyepieces. There is a fuzzy, off-color double image at all magnifications except on stars, which will focus, but not to pinpoint. Help. Dan

#7 Guest_**DONOTDELETE**_*

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Posted 04 November 2003 - 06:00 PM

Hi..thanks for the info. I did read the article and it was one of the reasons I bought the scope. But mine won't be pushed even up to 60x on anything except the moon. Even with a 26mm Meade Plossel, the chromatic abberation is horrible. I get two images, one approximately the right color, and another off to the left edge , usually a bright purple. I cannot get them to come together, even with the Orion v block, which is supposed to stop this abbertion problem. I think it actually adds to the problem. I am becoming convinced that I need to return this scope and hope for a better sample, since I understand that optics quality varies greatly from scope to scope in this model. any ideas?

#8 Guest_**DONOTDELETE**_*

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Posted 04 November 2003 - 06:05 PM

Hi and Thanks...
You are right on the money. The scope is designed for views of neblua and clusters, ect. But, I am surprised that it seems to be totally useless for anything else. I would expect some common (cheap) refractor problems, but not so pronounced that nothing else can be viewed. Another point...I set it up beside my ETX 125 a few nights ago..
Even with much lower powers, the Orion wouldn't deliver imagaes as bright and clear as the Meade. The only thing it seems to excell at is bright star clusters . That's a little too specialized for my tastes. Dan

#9 Guest_**DONOTDELETE**_*

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Posted 04 November 2003 - 06:43 PM

Sounds like you have a serious problem with it, time to return it! They should make it right.

#10 Blair

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Posted 04 November 2003 - 06:54 PM

I agree return it as the one I owned performed much better. It is not unusual for one of the objectives to be put in backwards but I wouldn't try to fix it yourself; it also sounds as if it could be really badly misaligned. If you call Orion they may pay for the shipping charges back; they did for me once when I received a bad product. I'd call them regardless. Sorry for your misfortune.

#11 Jacques

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Posted 04 November 2003 - 07:00 PM

This may sound stupid, but you don't use an amici prism by any chance? Sounds like there's something really wrong though. Good luck.

#12 Guest_**DONOTDELETE**_*

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Posted 04 November 2003 - 07:31 PM

O.k...I think everyone agrees that something is wrong with this scope...
Now is get a chance to let everyone know that I am new to the hobby and am trying to learn more about it. That's part of the fun, learning new things. So here goes...
Tonight...I put on the lens cover, removed the small stop-down lid on the front and aimed the scope at the moon. Instant contrast with a 26mm. I put in a 2x Barlow. Same results. Then a 10mm, a 10mm with the Barlow and the v block filter. 120 x and crystal clear. Now I am confused.
First...does this tell me anything about the scope? Or is this normal when you stop down the scope? Help. Dan

#13 Stelios

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Posted 04 November 2003 - 09:58 PM

Well, seems to me that by stopping down the scope so much you raised the f/ratio enormously, as f/ratio = focal length/diameter of objective, you didn't change the focal length but you reduced the diameter of the objective by what? 3-1?

So instead of an f/6 you now have an f/18 or so -- that should be pretty color free! I used to have a 80mm f/15 scope and there was never any color issues with it although it was only a doublet.

I am not an optics expert and am more than willing to be corrected by the more knowledgeable. :bow:

#14 Guest_**DONOTDELETE**_*

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Posted 05 November 2003 - 12:57 PM

Ive got a 5" doublet at f9.3, any idea what the ideal aperature stop would be for this size lens before aperature got too small and dimmed the views? Id like to try this myself as ive never seen it done but heard about it, Id love to be able to raise the fl to about 15-20 maybe for the moon & planets. Any ideas out there or should I just start cutting black paper rings and change at 1/2" increments? Dave

#15 SAL

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Posted 05 November 2003 - 06:45 PM

Dan: Please see my post in the refractor forum called “Optics Problems With New Scope?” I had similar problems (worse than average false color, color spiking, and optical distortions) with my second Orion 120mm f8.3 refractor, and it turned out to be a bad focuser unit. Orion was great about fast turn around time on my scope. They gave me the option to either replace it or repair it. Orion repair indicated Ronchi and star tests demonstrated my OTA had above average optics, so I elected to have my original OTA focuser repaired instead of exchanging my OTA for a new one. I’m extremely happy with the performance now. Assuming your objective lens is collimated correctly sounds like there must be problems with the scope. Orion will make it right. They told me that if a product is defective they would pay the return shipping as well… (Scott)

#16 Guest_**DONOTDELETE**_*

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Posted 06 November 2003 - 09:49 PM

I would check the focuser alignment and also didn't read about what diagnal if any you used.


What do defocused stars look like in the ep?

Does the objective lens appear to be set roughly square in the tube?




#17 Guest_**DONOTDELETE**_*

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Posted 07 November 2003 - 05:59 PM

Thanks, I use the diagonal that came with the unit. I have suspected it might be the problem, since I now have a new unit that isn't any better than the first one. I did not replace the diagonal, only the ota. Also, stars are not quite pinpoint, spikes run north and south more than east-west. The focuser seems to be well centered. Go Figure.

#18 Guest_**DONOTDELETE**_*

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Posted 07 November 2003 - 06:41 PM

Use the scope with no dia first, if prob still persists then rack the focuser to midway, shine a light down the oblective and look to see if the focuser is concentric with the tube baffles. If it is concentric then your mainlens is bad or out of collimation, if however the focuser tube looks cocked to one side your in luck, just loosen the screws holding the focuser to the tube OTA , adjust straight, then add washers under the screws, tighten and use. Good luck, Dave

#19 Guest_**DONOTDELETE**_*

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Posted 08 November 2003 - 02:00 AM

I had that problem you’re describing, or something very similar.
Is this scope made by Synta, and has your focuser got any slack in the draw-tube?
Mine had, but I fixed it by adjusting the two small Allan bolts (1.5mm) next to the focus lock knob. Both of these tiny bolts only needed turning a small amount and this improved my views significantly. Now the tube is rock steady and not too stiff :)
Now I only need to wait for a clear night to try midwestman’s fix.
I had to disassemble the focuser to discover that these bolts were there.
Didn’t get a manual with my scope :(

Check the star image either side of focus and tell us what you see.

Steve
BTW Does anyone know what type of grease to lube these focusers with?

#20 Guest_**DONOTDELETE**_*

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Posted 08 November 2003 - 10:03 AM

Steve,
Ive been using hi temp thin lithium grease on my parts. It dosent get thick when subjected to extreme cold.
Lithium brake grease is about the same stuff at any auto parts store too. Dave

#21 Guest_**DONOTDELETE**_*

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Posted 08 November 2003 - 09:41 PM

Dave.
Thanks for the info on the grease, I’ll go hunting some.
Since I’m new at this I never even thought about the cold effecting the grease.

Cheers
Steve.

#22 StarWars

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Posted 26 November 2003 - 03:36 AM

Hi Dmvguy...


A Refractor Designed for Deep-Sky Exploration!

Orion AstroView™ 120ST EQ Rich-Field Refractor


This telescope was not designed for high-power examination of planetary or lunar surface detail; for that we recommend the AstroView 120, with its longer focal length. Rather, the 120ST excels for breathtaking, wide-field images of deep-space delectables set against their stellar backdrops. A new refractor with a new purpose—that’s the Orion AstroView 120ST EQ!
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