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6" f/5 Achro Refractors

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#1 clusterbuster

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Posted 12 March 2019 - 08:09 PM

Hi All,

 I am getting a Celestron 150mm f/5 Omni XLT Refractor,

The threads about these and other 6" f/5 Achros, seem to focus on things like LOTS of CA, Mounting Concerns,.. and there seems to be more negative than positive.. I really enjoy my Orion ST120 and the widefield views that it produces.. I have read articles about the 150 f/5 that had phrases like, THE DOUBLE CLUSTER presented glistening stars , many with color, and bright GLOBULARS resolved to the core, Bright galaxies showing some detail... I have always had a Big Dob among my Scopes , and one particular night I went to our dark sky site with just an 80mm Televue Nighthawk,  and the views were just Awesome..

I would love to hear some feedback from some of you that have these, and like the views, knowing that these excel at low power, we all know that these are not intended to be Planet Killers, I leave that up to my Discovery 10., so if any of you guys could describe some of the views that YOU have seen with these Telescopes, showing the strengths of these, I would surely appreciate it,

Thanks

Mark


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#2 Astro-Master

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Posted 12 March 2019 - 08:36 PM

 Years ago I bought an Orion 120mm F5 refractor for wide field DSO's,  The problem was if I wanted to resolve a globular cluster at 100x to 150x the image would not come to a sharp focus, too much chromatic aberration.  It did a nice job on the double cluster at 43x.

I think if I bought the F8 model it might have been better.



#3 Loren Toole

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Posted 12 March 2019 - 08:48 PM

I've owned two of the 150mm f5 Omni's since 2015, the first was used and the second new.

 

I sold the first due to a grossly overcorrected lens, I did respace the lens and improved its correction somewhat. The second was better corrected, and I still own it but I'm struggling with the focuser. I've been through several focuser change outs on this scope, however the images are actually usable up to about 120x with filtering. In general you'll use less than magnification anyway for most deep-sky observing. One feature I do like: the tube is fairly well balanced and easy to mount on CG5-class mounts, it's very compact given 6" aperture.

 

I've seen more color in nebula and stars using these scopes than others I own (including larger reflectors) of course you might suspect false color is the cause. M42 revealed a beautiful red-green coloration several winters ago. Last summer I also experimented with planetary imaging, using dense color filters, see attached photo of Jupiter. While seeing in this case was worse than average, you can see some potential.

 

Loren

Attached Thumbnails

  • Jup_211730_castr 2.jpg

Edited by Loren Toole, 13 March 2019 - 06:48 AM.

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#4 Vondragonnoggin

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Posted 12 March 2019 - 08:52 PM

To the OP - Did you find a new one that was old stock or bought used? 

 

I have an AT152 at F/5.9 and 25lbs for the OTA. Would actually prefer the F/5 and 16lb OTA of the Omni XLT for both mounting and my use of low power Night Vision eyepieces with it.


Edited by Vondragonnoggin, 12 March 2019 - 08:53 PM.


#5 coopman

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Posted 12 March 2019 - 08:58 PM

You might find this site interesting:
http://affordable-as...el150/page1.htm

#6 clusterbuster

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Posted 12 March 2019 - 09:04 PM

To the OP - Did you find a new one that was old stock or bought used? 

 

I have an AT152 at F/5.9 and 25lbs for the OTA. Would actually prefer the F/5 and 16lb OTA of the Omni XLT for both mounting and my use of low power Night Vision eyepieces with it.

I found it used.

Mark

I have been looking for one for a long time.....


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#7 otocycle

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Posted 12 March 2019 - 09:06 PM

Hi - I bought a used Celestron 150mm f/5 refractor back in 2012, having already owned and used two other Synta made 150mm f/8 refractors.   I specifically wanted a shorter wide field version in an achromat knowing full well that it would have more CA, to be used for visual and imaging, ultimately just narrowband imaging in Ha.

 

The original owner had replaced the 2" Synta focuser with the usual GSO two speed Crayford, but I preferred the original (included) R+P single speed focuser for heavier eyepiece and imaging loads, which I re-installed.

 

The scope is easy to mount for alt-az or EQ, but balance can be tricky using just the rings because the tube is so short...so a long dovetail bar helps.

 

Optically it does have lots of CA on bright objects, but it is still a big refractor with sharp, unobstructed views of globulars, emission nebula, and galaxies at low and medium power.   There is also some field curvature evident with very low power sweepers.

 

These are not planetary scopes by any means, but they still perform OK, especially on the very forgiving Saturn.

 

Mine is a keeper !


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#8 clusterbuster

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Posted 12 March 2019 - 09:06 PM

You might find this site interesting:
http://affordable-as...el150/page1.htm

Thank You Coopman,

 actually I have seen this in all of my querys on this telescope.

I just thought that there should be more OBSREVING REPORTS with these Telescopes,

Mark



#9 coopman

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Posted 12 March 2019 - 09:26 PM

I found some comments on them here by searching "Omni XLT 150R".
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#10 F.Meiresonne

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Posted 13 March 2019 - 02:04 AM

A scope like that is for wide views. i have an 120 mm F/5 skywather.

CA? On some objects like terrestrial objecst (leaves on trees on a sunny day) is horrible yes, then again that is the worst, al the rest is not that bad at al. On airplanes even in sunny skies CA is hardly seen and the view is bright and sharp.

 

The scope indeed is not for high magnifications. You see this on the moon, where the yellow or violet rim is quite visible and you cannot  really get a tack sharp view at say 100x.

But on low powers it is exquisite. Pleiades are tack sharp ,best view i ever had. I use glasses that correct my astigmatism (and only that, i had it special made by my local opticien) to view with a 35 pan or 28 ES eyepiece..

 

So for me you will hear no complaint about that kind of scopes, you just have to know how to use them at best.

I did not pick the 150 mm , because indeed the load is much more then the 120 mm scope. The 120 mm is easier to handle

This said i have obtained recently a 70 mm F/6  ED glass scope. CA hardly seen and you can boost the magnification with that one,120x on the moon is a sharp image, even at 200x it was still a rather good image, not the best but doable.

Those kind of things you can not try with an achro F/5.


Edited by F.Meiresonne, 13 March 2019 - 02:08 AM.

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#11 Marcsabb

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Posted 13 March 2019 - 02:14 AM

I own a Skywatcher Startravel 150, which is the same as the Omni 150R. It's very short and stubby but still unbalanced towards the front, like many big refractors. The dew shield is also quite heavy, so most of the time I don't use it, to improve the balance. Despite the size, on the whole, it's only 6.8Kg so it can be employed also on medium mounts, if properly balanced.

 

The CA is visible at all magnifications, during daytime, above 30x but on celestial objects it looks more prominent on the yellow part of the spectrum, so I find it less distracting that the classical purple violet halo. All bright stars look like shining diamonds when there is a slight turbolence. Kids love that effect a lot wink.gif

 

I've read a lot of conflicting opinions about the quality of its optics. Some say it's garbage, other say that they're actually very good; I've a second hand specimen whose former owner raved about the quality of its lens. With a green filter, I found they are indeed well figured around that wavelength. With a solar screen and a proper set of narrowband filters it could a be worthwhile instrument for observing our star.

 

If you want to employ this scope for the occasional moon and planet sighting, get the Baader Contrast Booster. Forget about the Fringe Killer or Semi-Apo: Contrast Booster is THE filter to have, as it is most effective in suppressing CA in the blue, red and yellow portion of the spectrum. And if you really like the scope for what it is and decide it's a keeper, maybe it would be wise to invest in a new focuser. The stock one is functional but rather crude. If I remember correctly, it has a 96mm flange so a focuser like this should work: https://www.teleskop...6mm-flange.html You will also gain a few centimeters of backfocus, good for binoviewers. Last, a handle could also be a useful accessory.


Edited by Marcsabb, 13 March 2019 - 02:43 AM.

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#12 otocycle

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Posted 13 March 2019 - 02:40 AM

Here is a photo of my Celestron Omni XLT150 refractor to show just how compact it is.   All metal and glass except for the dew shade cover and focuser knob grips.   At some point I changed out the Vixen dovetail bar to a longer Losmandy style 'D' plate to better support this rather stout OTA.

 

 

Celestron_XLT150A.jpg


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#13 Edwin

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Posted 13 March 2019 - 05:24 AM

I've read a lot of conflicting opinions about the quality of its optics. Some say it's garbage, other say that they're actually very good;

It is a Chinese made telescope so optical quality may vary per sample and you have to have some luck to get a good one. I didn’t have that luck so got a lemon SKywatcher 150 F5 which basically is the same telescope as the Celestron. Mine got a lot of CA, wasn’t very sharp above 80x and the lightgathering power was not that what you could expect from 150 mm of unobstructed glass. It was said that the focusser tube from these SW’s was too long and cut into the (relatively steep) lightcone thereby reducing the effective aperture to about 120-130 mm, what matched with my observations. I don’t know if Celestron has adjusted the focusser for their Omni XLT, you might want to check that out. If you have an optical good sample my tip is to replace the stock focusser for a double speed 2.5” one.

 

In the end I sold the SW and now have a Kunming United Optics (Tecnosky-labelled) 152 F5.9 achro with a 3” focusser that performs much and much better: a lot less CA, sharp till 180x and brighter images.


Edited by Edwin, 13 March 2019 - 05:32 AM.

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#14 Marcsabb

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Posted 13 March 2019 - 06:11 AM

It is a Chinese made telescope so optical quality may vary per sample and you have to have some luck to get a good one. I didn’t have that luck so got a lemon SKywatcher 150 F5 which basically is the same telescope as the Celestron. Mine got a lot of CA, wasn’t very sharp above 80x and the lightgathering power was not that what you could expect from 150 mm of unobstructed glass. It was said that the focusser tube from these SW’s was too long and cut into the (relatively steep) lightcone thereby reducing the effective aperture to about 120-130 mm, what matched with my observations. I don’t know if Celestron has adjusted the focusser for their Omni XLT, you might want to check that out. If you have an optical good sample my tip is to replace the stock focusser for a double speed 2.5” one.

 

In the end I sold the SW and now have a Kunming United Optics (Tecnosky-labelled) 152 F5.9 achro with a 3” focusser that performs much and much better: a lot less CA, sharp till 180x and brighter images.

CA is very prominent but this is something to be expected: the ratio to diameter is 0.85; not even a fluorite doublet would be 'color free' ! Reagrding the focuser, I've noticed it has a somewhat limited excursion, so possibly Syntha did reduce the drawtube length to avoid obstructing the light path. 



#15 DeanD

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Posted 13 March 2019 - 06:30 AM

Hi Mark,

 

You inspired me to have a play with my Celestron Omni 150 f5 tonight, and I thought you might like some comments. (I have had it for a while, but haven't had much opportunuity to put it through its paces.) 

 

I bought mine (used) to use mainly as an outreach scope (the punters love a "real" looking telescope!), but like you I had been looking for one for quite a while (who doesn't want a 6" refractor!). I have a Tak TSA102, so I am quite used to near-perfect views; but even so I have been impressed with the Omni. Yes it has CA, but not as much as I feared. On bright objects like the Moon it is hard to get the focus just right because the red and blue are at different points; but like the referenced review I find that a Baader "Fringe Killer" filter helps to get a sharp focus, even if it does turn the Moon yellow... I don't generally use the filter with DSO's though. (I would like to have a try with the "Contrast Booster" filter as Marksabb mentioned above, but I don't have one...)

 

Looking at M42 tonight I was impressed by how much nebulosity I could see, even though the Moon was not that far away (sitting in the Hyades as I write), and I am looking through a suburban sky. At 100x (with a Tak LE 7.5 eyepiece) the "wings" of the main nebula filled the field, with M43 clearly visible with direct vision. What amazed me though was that not only was the Trapezium clear and sharp, but I could also make out the E and F stars. These were even more apparent at 125x. The seeing was a bit wobbly, but I increased the power to 250x and the stars remained pretty much "textbook" for an achromat.

 

I swung around to Eta Carina just for fun (I am at 35 degrees South). The "Keyhole" was nicely visible, and again from 100x I could make out the double-lobed shape of the "homunculus" around Eta. This was clearly a red colour: this is the first time I have really noticed this colour, and I have looked at this through a 24" dob...

 

Down to the "Jewel Box", and again the view was excellent, with sharp stars and lots of colour.

 

No planets just at the moment, but I think it will do surprisingly well when Jupiter and Saturn again appear at civilised hours. It can cope with 250x on a good night, as it did tonight even though the seeing wasn't good!

 

This scope is a keeper, and I am looking forward to taking it to a dark sky in 6 weeks or so to run it against my 12" dob on some DSO's. 

 

Good luck with yours when it arrives. Make sure you post a "first light" report!

 

All the best,

 

Dean

 

(PS: I was using a home-made alt-az mount tonight, but it sits quite happily on my Stellarvue M2, and tracks happily on my early model iOptron Mini Tower.)


Edited by DeanD, 13 March 2019 - 06:44 AM.

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#16 hoes

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Posted 13 March 2019 - 06:51 AM

Views of the sun with a Daystar Quark are fantastic in this scope.

 

Steve


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#17 Marcsabb

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Posted 13 March 2019 - 07:53 AM

In-depth review with a lot of pictures http://www.astrotest...0-f5-refractor/

 

From the menu on the right, select English for a translation. Oddly enough, towards the end of the article, the reviewer says that he found the Contrast Booster less effective than the Semi-Apo. My own experience was a bit different, but with chromatic aberration there is always a degree of subjectivity involved. Some of the pictures posted in the article are real nice, though.


Edited by Marcsabb, 13 March 2019 - 07:56 AM.

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#18 junomike

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Posted 13 March 2019 - 12:56 PM

I have the SW 120 F5 and SW 150 F5.

Both are excellent at what they were made for (Wide Field).

I rare (If ever) point either at bright objects.


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#19 nirvanix

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Posted 13 March 2019 - 03:12 PM

Good review of this scope:

 

https://astromart.co...n-omni-xlt-150r

 

Also, you can scroll through here were they have tested many of the 5" and 6" short achros (Skywatcher "Startravel" branded):

 

http://teleskop-spez...-teleskope.html

 

In general they seem to test well for what they are.


Edited by nirvanix, 13 March 2019 - 03:27 PM.

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#20 Sketcher

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Posted 13 March 2019 - 03:39 PM

It's possible you're already aware of all this; but just in case:

 

Have you determined what eyepiece you'll need to get the true FOV that you want, taking into account your dark-adapted pupil size and the telescope system's exit-pupil?  If the exit-pupil is too large, you'll not be utilizing the full aperture of the telescope.  In order to get the widest true field while utilizing the full aperture, you may or may not have to resort to a more expensive eyepiece than originally planned for (depends on your own dark-adapted eye's pupil diameter).

 

For some people, a 6-inch f/6.5 might be a better choice -- usable with potentially less expensive eyepieces, potential for slightly better control of CA, potentially sharper image closer to the field edge, and a little more potential as an all-around telescope -- at the cost of a somewhat narrower (about 2.6* maximum) true FOV and a somewhat longer and heavier OTA.

 

I read some of the stuff from one of the links that was posted.  I noticed that a 40mm eyepiece was used at times.  With a 6-inch f/5 telescope, that eyepiece would provide an 8mm exit pupil.  Few of us have eyes that can provide a dark-adapted pupil that large.  For most of us, that eyepiece, used with that telescope, would be equivalent to observing with a smaller aperture refractor.  Furthermore, I had to wonder a little about the quality (and collimation) of the SCT that was used for comparisons purposes . . .

 

Globulars tend to suffer a bit in large, fast achromats (many faint stars bathed in the cumulative CA of a multitude of brighter nearby stars).  But most other DSOs (as well as stars and star colors) can be quite nice.  Large, fast achromats can be fun to use and are capable of providing some very beautiful views -- as long as one's expectations remain realistic.

 

Sky darkness and transparency may need to be taken into account when reading the descriptions of various DSOs as provided by various individuals.  Equal telescopes/eyepieces used on the same objects by different people under different skies can result in very different views.

 

I have a reasonable amount of experience with a 6-inch f/6.5 achromat; but not with an f/5.  My other telescopes include a 5-inch apochromat and a 12-inch Newtonian, along with (too many) others.


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#21 F.Meiresonne

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Posted 13 March 2019 - 03:57 PM

My remark about the SW focusser: it works yes ,not that bad but i find a dual speed focusser is preferable. At F/5 you easily overshoot the sweet spot .

 

The one on my 70 mm would be nice for it. On that one there is a really nice focusser, dual speed, no play , if drawn out completely with pan 35 and 2 inch diagonal. Off course it would  bump up the price...

Honestly especially the F/5 120 mm is at a very low price...the 150 mm about the double here in Europe..


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#22 AstroRed

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Posted 14 March 2019 - 03:15 PM

My 150mm f5 hasn't been getting much love in the 10 years since I bought my ED120. I really should dust it off and give it a go a lot more often


Edited by AstroRed, 14 March 2019 - 05:41 PM.

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#23 F.Meiresonne

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Posted 14 March 2019 - 04:46 PM

My 150mm f5 hasn't been getting much love in the 10 years since I bought my ED120. I really should dust it off and give it to a lot more often

I you own a 120 ED , i can understand ...smirk.gif


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#24 Jeff B

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Posted 14 March 2019 - 05:48 PM

I have a 6" F5 Jaegers ATM build that I did.  It is bino-friendly but, as everybody has said, it is not a high power scope.  For me it does excellently what I designed it to do, wide field low power viewing, and at that, it is a whole bunch of fun.

 

Remember, these are aplanats, meaning coma free, so in mono-vision,they work splendidly with eyepieces like the TV Pans and Naglers.  For example, the 35mm Pan will give you a 2.9 degree TFOV but a 7mm exit pupil too, while the 31mm Nagler 5 is 3.2 degrees TFOV with a more friendly (to me anyway) exit pupil of 6.2mm.

 

Jeff



#25 Awesomelenny

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Posted 14 March 2019 - 06:05 PM

I too have my venerable Jaegers 6" f/5 home built telescope.  I fitted it with a nice AP 2.7" focuser too and that is one sweet telescope. Definitely an awesome wide field RFT for low power sweeping and viewing of any deep sky object.  If you're not looking at some 1st magnitude star, the CA is not even noticeable. I even took pictures using my Astrodon H-alpha filter and they come out super nice.  See this one below.

 

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