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Why would you want a 6 inch Achromat?

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#1 Dave Ponder

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Posted 06 January 2018 - 12:22 PM

I only have a Celestron AVX mount so maybe a scope like the ES 152 AR would be too much for visual use.  I am sure the CA would be there.  Probably takes a while for a big chunk of glass like that to acclimate, but I am thinking of getting one. Why did you get yours? Would you use it on the AVX? If you had it to do over, would you still get one?  Appreciate your input.

Thanks,

Dave

 



#2 Augustus

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Posted 06 January 2018 - 12:28 PM

I suppose the coma-free low-power views would be nice.


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#3 mdowns

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Posted 06 January 2018 - 12:32 PM

Dave,

 I had a 6" f8 achro for 3 years or so and frankly loved it. I might worry about the avx though I'm pretty certain it would do fair to midland with it.I had mine on a g11 and both seemed made for the other. I've almost always had multiple scopes at a time and I enjoy them all but the 6" achro was a fun scope with wonderful star fields and when coupled with an old style long fl barlow (made in japan) it would put up excellent lunar and planetary views. With the good seeing of our area I often could use 400x on the moon and 300x+ on the planets with mine.I hope to someday add another. I have an unused atlas in the garage waiting for another ota.BTW,I forgot to mention that a 2 spd crayford is a easy,much appreciated improvement that anybody can add to a 6"f8 (mine was the celestron 6r).


Edited by mdowns, 06 January 2018 - 12:34 PM.

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#4 Paul Skee

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Posted 06 January 2018 - 12:44 PM

I have the Celestron Evolution 9.25 but love deep sky wide field viewing. I got a Celestron Omni XLT 150 R, (f/5 achromat). I put it on an AVX. The views are breathtaking. The telescope optical tube is listed @ 16 lbs, I think. I've added a 2" diagonal and used a Luminos 31mm. The AVX seems to handle it very well. (I'm visual only). The chromatic abberation is not an issue on the targets I use it for. Love the Double Cluster with the 23mm Luminos. Just got an UHC/LPR 2" filter, can't wait to try it. The AVX is rated for 30 lbs. I'm probably pushing 20 with the diagonal and heavy eyepieces. As I say, the mount handles it very well. If you like deep sky, go for it.


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#5 Jeff B

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Posted 06 January 2018 - 12:45 PM

I suppose the coma-free low-power views would be nice.

No, they can be really nice.  Just get a good one.


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#6 Taosmath

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Posted 06 January 2018 - 12:51 PM

 

I suppose the coma-free low-power views would be nice.

No, they can be really nice.  Just get a good one.

 

Which ones can you recommend ?



#7 Gofr

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Posted 06 January 2018 - 12:54 PM

If I were to go with a short FL 6 inch achro for widefield views, I'd get the Bresser F5. It's a petzval, meaning nicer flatter fields and bonus CA reduction more roughly equal to that of the F8 scopes vs. an actual F5. Plus, it comes with the nice 2.5 inch hexafoc focuser.....heck I kinda want one now too. Lol

Edited by Gofr, 06 January 2018 - 12:56 PM.

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#8 The Ardent

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Posted 06 January 2018 - 12:59 PM

My criteria for a 6" achro is that it's made in the USA.

 

I used to have a D&G and now have a Jaegers 6" f/5.  The D&G was excellent on Jupiter. The Jaegers is excellent for deep sky wide field. 


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#9 coopman

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Posted 06 January 2018 - 01:02 PM

Found this review:
https://onetreeobser...fractor-review/

#10 glend

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Posted 06 January 2018 - 01:03 PM

If I were to go with a short FL 6 inch achro for widefield views, I'd get the Bresser F5. It's a petzval, meaning nicer flatter fields and bonus CA reduction more roughly equal to that of the F8 scopes vs. an actual F5. Plus, it comes with the nice 2.5 inch hexafoc focuser.....heck I kinda want one now too. Lol

For several years I owned the Bresser f5 with the Petzval corrector, it was a very nice, low cost, narrowband imaging scope. I bought it just for that purpose, and the strong focuser. Highly recommended. I wish i had not sold it.


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#11 Planethunter80

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Posted 06 January 2018 - 01:06 PM

I have an AVX that I haven't even had a chance to use yet(Thanks to the coldest week in over a century here)I also have a 120mm achromat refractor that I plan on using with the AVX mount.

I would love to move to a 150mm achro refractor before Mars reaches opposition.

 

So regardless of any(and all)negatives I feel a 6 inch achromat would be an incredible choice for Lunar and Planetary observation. I would want to go with the longest focal length the mount could handle(but you and I have and share many similarities with our goals).



#12 jgraham

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Posted 06 January 2018 - 01:15 PM

I have a 6" f/8 achro and I just love it! When paired with the right eyepiece a short focal length is not needed and the reduced CA of the longer focal length is a bonus. With a refractor you can max-out the exit pupil without worrying about the shadow of a secondary. Coming from an olde ATM background where I made several RFTs, I was surprised at how my biggo refractor quickly became my favorite richest field telescope. And no, the 6" object does not take very long to acclimate sitting out at the end of the tube exposed to the night air.

 

There's just something magical about using a large refractor, the fact that it is also very practical is a bonus!


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#13 Gofr

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Posted 06 January 2018 - 01:42 PM

I kinda want one for solar work someday. Both white light (with a solar continuum filter) and H-alpha are perfectly fine on an achro as they are narrow band anyway. One day....until then my smaller 90mm will have to do. =)

#14 Steve Cox

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Posted 06 January 2018 - 02:14 PM

I've had my C6R for going on 6-7 years now, and like mentioned above, the unobstructed coma free views are something to treasure.  As for acclimating, it's not that bad; true, it's slower than the 10-15 minutes of my older 4" refractor, but still much quicker than comparable glass in a dob (8" or higher).  And a 2 element lens is far quicker cooldown than a triplet.

 

As for views, on DSO's a 6" is a wonderful piece of gear giving splendid views, even an achromat.  But if you're bothered by CA, then plan to get another scope for planets and very bright stars.


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#15 Crow Haven

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Posted 06 January 2018 - 02:51 PM

I have the Celestron Omni XLT 6" f/5 (and also the CR6 f/8 currently stored away) and love it for the wide-field low mag. views.  At 16 lbs.+whatever accessories you choose it's not a big deal to mount.  I prefer using it on my Twilight II alt/az mt. either alone with a counterweight on the other saddle or use another ota -- even a 6 to 7" Mak for planetary or other apo refractor at the same observing session.  Works for me! grin.gif  YMMV.


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#16 Don W

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Posted 06 January 2018 - 04:51 PM

I have used a 6" f/8 on a Super Polaris mount which is the ancestor of the AVX. It was a bit wobbly, but not that bad. Great wide field views, but plenty of color around bright stars, planets and moon.


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#17 Jeff B

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Posted 06 January 2018 - 05:22 PM

 

 

I suppose the coma-free low-power views would be nice.

No, they can be really nice.  Just get a good one.

 

Which ones can you recommend ?

 

I'd start with the Celestron version with a collimate-able lens cell.  I say "start" because it took me a few samples to find one with pretty good optical correction (no astigmatism, sharp & even lit diffraction rings close to focus, no coma) during high power star testing with a green filter.  I'm picky, but there are plenty out there to choose from and they are cheap really.

 

Good hunting and enjoy.

 

Jeff



#18 Steve Cox

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Posted 06 January 2018 - 05:24 PM

Quite right Jeff, and like a dob, they make a great inexpensive platform for mods and additions without worrying too much about cost.



#19 Edwin

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Posted 06 January 2018 - 06:26 PM

I use my 152 F5.9 achro mainly for clusters, extended nebula and the brightest galaxies. With a Panoptic 35 in the diagonal (26x, 2.5 degrees FOV) it is a perfect tool for low power milky way sweeping. Those pinpoint, sparkling stars across the whole FOV make you smile and then that contrast! M42 for example is really wonderfull with a lot of nebulosity in more then 50 shades of grey and 6 pinpoint trapezium stars in the centre. Point at any open cluster and you know why you should get or bought an 6" achro. An 6" APO is even better, but at a cost. For the mentioned targets, an achro is more then OK.

 

Would I buy one again? Yup, but not an F5, because it has too much CA. I got one but sold it quickly because of the amount of CA and poor optical quality. Tried a 6" newton, but sold it quickly because of the amount of coma. After that, tried a 6" mak, but sold it (not so quickly this time) because of the cooling down time and restricted FOV. Finally I bought my current 6" achro and I'm very happy with it.

 

I use mine (20 lbs) sometimes on a Orion Sirius but mostly a Giro II. A longer 6" might be challenging for an AVX, a F6 will be OK but is at the max for an AVX, a F5 is no problem.

 


Edited by Edwin, 06 January 2018 - 06:48 PM.

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#20 tomwall

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Posted 06 January 2018 - 07:05 PM

I have an ES152 that I run on an AVX. It works just fine for visual. If that's what you want, don't worry, it will work just fine.

 

Tom


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#21 coopman

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Posted 06 January 2018 - 07:29 PM

I had an AR152 for about a month & used it 2 or 3 times.  It was just too heavy for me to handle and install on the mount safely (I was 62 at the time and have a bad lower back).  If you're not old and/or physically limited like me, I say go for it.  I don't remember very much about its optical performance at night.  I do remember looking at some distant trees during the daytime and the CA was horrible.  Everything had purple edges. 



#22 Dave Ponder

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Posted 06 January 2018 - 10:52 PM

I have an ES152 that I run on an AVX. It works just fine for visual. If that's what you want, don't worry, it will work just fine.

 

Tom

 

Tom,

That is very encouraging!  How do you like the ES 152?

Thanks,

Dave



#23 MrJones

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Posted 07 January 2018 - 10:16 AM

I more or less traded in a very nice 107/700 triplet for a f/5.9 152mm achro. Probably one of the versions of what Edwin has. It was for a few reasons including the 107 was really too big for the quick grab and go I wanted it for and that aperture is fairly small if you like DSOs. I thought the 6" still had enough FOV for me and I planned to use it with nebula filters a lot also. The 6" is obviously not grab and go but works well on an AVX and is less cumbersome than a f/8. In reviews and IMO the higher quality f/5.9 (Starwave) actually has less CA than the f/8s also. I'm sure an f/8 one will work on an AVX but the extra length would be an annoyance for me.

 

It's been great and I used it as much as my other scopes in 2017. CA is exactly what I expected, even lower really, and I rarely go over 150x with it. Like Edwin my most used EPs with it are 40mm and 34mm 68 degree and it has nebula filters in it half the time.

 

As much as I like it I still kind of want a smaller lighter wider FOV refractor for various purposes including easy planetary so might add a 4" something that is lighter than the 107/700.


Edited by MrJones, 07 January 2018 - 11:34 AM.


#24 Jason B

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Posted 07 January 2018 - 10:20 AM

I had an ES152 for a while on a AS-GT mount. I thought it was a very good deep sky scope and mount combo. The big clear 6" of apertures on deep sky is hard to beat. I didn't use it much on planets or the moon as I have better choices for that but for deep sky, it was used often. The mount held it just fine though it did put the eyepiece pretty low when looking overheard. Only reason I let it go is that darn imaging bug keeps biting harder and harder!


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#25 Steve Cox

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Posted 07 January 2018 - 10:23 AM

I have the Celestron Omni XLT 6" f/5 (and also the CR6 f/8 currently stored away) and love it for the wide-field low mag. views.  At 16 lbs.+whatever accessories you choose it's not a big deal to mount.  I prefer using it on my Twilight II alt/az mt. either alone with a counterweight on the other saddle or use another ota -- even a 6 to 7" Mak for planetary or other apo refractor at the same observing session.  Works for me! grin.gif  YMMV.

If you don't mind me asking, have you ever mounted or run the 6" f/8 on your Twilight II?  If so, how well does the mount perform on high power planetary viewing, and also on changing eyepieces from heavy to light?  I've often considered moving my 6" to a Twilight II and mounting an Orion 180 Mak-Cass on the other side for planetary viewing.


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