Author Topic: thinking of getting a refractor...  (Read 1061 times)

Steven Morrison

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thinking of getting a refractor...
« on: December 29, 2017, 05:04:51 AM »
I've been gazing longingly at the AT72mm ED f/6 refractor, even though they're not in stock. I know it is more typical to go aperture crazy, but 8" is a reasonable size for me so I'm sticking with the XT8 as my main, "large" scope. The refractor would be used for quick looks after work and for easily moving around the yard and for travel, and would be used for looking at solar system stuff and open clusters.

Concerning accessories, Astronomics suggests the AT 2" dielectric mirror diagonal, but is that the best in that price range? They also suggest the AT Voyager2 alt-az mount. I'm guessing these are both fine choices for the scope, just wondering if there are other suggestions.

Another question: would the use of a 2"diagonal with 2" eyepieces necessitate counterweight measures? I'm trying to keep this set up as simple as possible.

Finally, I have a red-dot finder I'm not using that came with the XT8; can it be mounted on this scope?

Thanks!



Gregory Station

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Re: thinking of getting a refractor...
« Reply #1 on: December 30, 2017, 06:59:11 PM »
I expect there's every reason to think the AT72ED will be as well conceived and executed as the AT115EDT I recently got. The AT 2" diagonal is very likely the same one that came on my scope. I have considered getting that trick silver Baader but then I look through my stock scope and abandon such plans. The AT diagonal is likely a real best buy item. Weights shouldn't be required if there's a dovetail involved in the (alt/az) mounting scenario - just slide the scope along to balance. Astronomics should be able to answer your RDF mounting Q. If they say it won't fit, you may want to check to see if Scopestuff.com offers an adapter that'll make it work.
My heavier scope required a more robust mount and I went with a UniStar Deluxe. Universal Astronomics makes lighter mounts too. Desert Sky Astro is also very good. Both are alt/az and manual with custom options galore and both get @ 5 of 10 stars for communication. But their mounts are very good.

ocgisfulctel

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Re: thinking of getting a refractor...
« Reply #2 on: December 31, 2017, 12:46:38 AM »
For $180 more you can get the 80mm Explore Scientific Essentials APO refractor that comes with a decent 2" diagonal. It will give you an extra 8mm of aperture and a true APO instead of a ED Doublet. It is 2 lbs heavier but well made and comes with a lifetime transferable warranty as well as the ES legendary customer service.

You can put a RDF on there but the field is so wide with this size scope you don't really need to.

John Daniels

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Re: thinking of getting a refractor...
« Reply #3 on: January 01, 2018, 12:43:10 AM »
If you get rid of the solar system stuff, AR102 on a Twilight 1

Scott Bentley

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Re: thinking of getting a refractor...
« Reply #4 on: January 01, 2018, 08:18:47 AM »
Something to consider with the AT diagonal:
I have an AT 2" quartz dielectric diagonal.  The barrel of it that goes into the visual back of my refractor has a taper.  My visual back uses a compression ring to hold the diagonal.  But, the taper on the diagonal doesn't work well with the compression ring.  Had to take the ring out and just use the screws.  I believe the back on the AT72 does use a compression ring.  But you can take the ring out, as I did.  Or you can get a GSO diagonal that has a smooth barrel without the taper that will be compatable. The taper will tend to contort a compression ring.  I saw evidence of it after I took mine out.  I wish everything just had smooth barrels.  Sometimes undercuts will also not catch right on a compression ring.  Otherwise, the AT diagonal is great.

Greg Quevedo

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Re: thinking of getting a refractor...
« Reply #5 on: January 10, 2018, 12:23:48 AM »
Deb:

You have carefully considered this scope and mount and you have lots of good questions. I have an AT72ED as well as a couple of 80 mm ED/apos and AR-102 and a 4 inch TeleVue.  I also have the Vixen Portamount and the ES Twilight 1.

- A -3 inch ED/apo and an 8 inch Dob are a perfect combo, they compliment each other very nicely.

- I like the AT-72 because it is so compact and handy but the 80 mms are enough more capable that I would prefer the 80 mm if I only had a single smaller refractor.

- The Voyager and the Was Twilight 1 both have levers to adjust the friction so there is no need for a counterbalance when using heavier eyepieces, just increase the friction.  Both mounts are fine with an 80 mm, pushing things with a 4 inch.

Jon

Nong Inthisorn

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Re: thinking of getting a refractor...
« Reply #6 on: January 11, 2018, 07:28:11 AM »
I agree with what Jon said. The 80mm refractors are very capable for visual, especially the ED doublets in the f/6 to f/7 range for a compact and easy to use package. Doublets are less expensive than comparable triplets, and are also lighter and acclimate faster. On something like a Twilight I mount they are very grab and go, making them easy to move around the yard, etc. If you can swing the extra cost for a good 80mm ED you may want to consider getting one. Some come with a mounting foot, like the AT72ED, and some are meant to be used with rings. Rings with a dovetail bar can give you more versatility in balancing the scope on the mount, but you can also install a longer dovetail bar on the mounting foot.

I have owned an AT72ED for several years and love it. It was my second scope, which I bought to compliment a 6" Dob. I mount the AT on a Twilight I and it is a super package that is light and easy to move around. As with any scope, learning how to use it within its capabilities will let you get the most from it. I attached pics showing the longer dovetail bar I installed. You can see for yourself how easy it is to balance the scope with 2" accessories using the dovetail bar.

Ed D

lorndwatassi

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Re: thinking of getting a refractor...
« Reply #7 on: January 13, 2018, 01:46:14 PM »
I would get the 2" diagonal because you may want 2" EPs in the future,
with with the 2-1 1/4 adapter, smaller EPs will work for now.

I believe everyone needs a grab and go scope, to compliment the bigger optics.

edj

Ryan Miller

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Re: thinking of getting a refractor...
« Reply #8 on: January 13, 2018, 11:17:49 PM »
I like to keep my 70mm scope as light as possible. Use it in 1.25" mode.
 My red dot finder is attached to the saddle not the scope, no balance issues. An erecting diagonal and 15mm 60ยบ eyepiece make up my terrestrial kit. Easy to swing around and rack the focuser in and out when following birds.
At night it is the 32mm plossl, 11mmT6 and a 2x barlow.
When using anything with a taper I just rotate the compression ring until the gap is over the set screw. This way the groove  is still filled and not as likely to catch any edge.
Dereck

redoroto

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Re: thinking of getting a refractor...
« Reply #9 on: January 14, 2018, 12:05:36 AM »
Quote
I would get the 2" diagonal because you may want 2" EPs in the future,
with with the 2-1 1/4 adapter, smaller EPs will work for now.

I believe everyone needs a grab and go scope, to compliment the bigger optics.

edj

DebhasanES 34mm 68degree. WithanAT-72, that's atotallyamazing 5.1degreeTFoV..Whenyouuse ascopelikethiswith 1.25incheyepieces,youcanstillachieve awide fieldbutnotthoseextraspecialviewspossiblewith 2incheyepieces..

Jon

erenlinra

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Re: thinking of getting a refractor...
« Reply #10 on: January 16, 2018, 12:33:39 AM »
Quote
I've been gazing longingly at the AT72mm ED f/6 refractor, even though they're not in stock. I know it is more typical to go aperture crazy, but 8" is a reasonable size for me so I'm sticking with the XT8 as my main, "large" scope. The refractor would be used for quick looks after work and for easily moving around the yard and for travel, and would be used for looking at solar system stuff and open clusters.

Concerning accessories, Astronomics suggests the AT 2" dielectric mirror diagonal, but is that the best in that price range? They also suggest the AT Voyager2 alt-az mount. I'm guessing these are both fine choices for the scope, just wondering if there are other suggestions.

Another question: would the use of a 2"diagonal with 2" eyepieces necessitate counterweight measures? I'm trying to keep this set up as simple as possible.

Finally, I have a red-dot finder I'm not using that came with the XT8; can it be mounted on this scope?

Thanks!

Should you opt for the AT72 and if your red dot finder comes with the Synta style dovetail stalk you can get a base from Scopestuff ( I believe that RDPZ is the correct model)or Agena Astro ( MFURB I believe). The holes for mounting are 5mm on the AT72.
Astronomics carries a different style base for use with their multi reticle finder.
Adding a short dovetailas Ed Dshowedreally helps with mounting optionswhen using 2" eyepieces.I added one to mine because I switch between a Microstar on a Bogen tripodand a Portamount..
I share the frustration expressed by RussL regarding tapered or somesafety cut 2"diagonals. They do not play well with compression rings. I had to pop out my ring to use my GSO 2" diagonal.

Ricky Mondal

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Re: thinking of getting a refractor...
« Reply #11 on: January 16, 2018, 02:45:48 AM »
Quote
Deb:

You have carefully considered this scope and mount and you have lots of good questions. I have an AT72ED as well as a couple of 80 mm ED/apos and AR-102 and a 4 inch TeleVue.  I also have the Vixen Portamount and the ES Twilight 1.

- A -3 inch ED/apo and an 8 inch Dob are a perfect combo, they compliment each other very nicely.

- I like the AT-72 because it is so compact and handy but the 80 mms are enough more capable that I would prefer the 80 mm if I only had a single smaller refractor.

- The Voyager and the Was Twilight 1 both have levers to adjust the friction so there is no need for a counterbalance when using heavier eyepieces, just increase the friction.  Both mounts are fine with an 80 mm, pushing things with a 4 inch.

Jon

Thank you to everyone who has commented on my post -- I appreciate all your feedback! The point that has really resonated with me is the increased capability of 80mm, and I want to take this under serious consideration, though I haven't ruled out the AT72ED. After looking into it a bit, 2 scopes seem decent options, though neither seems "perfect."

1. Sky-Watcher Pro 80mm f/7.5 ED APO -- nice package and very reasonable price. Anyone have experience with this this? I'm guessing the optical quality is quite decent, but will it keep me happy for years? (Yes, I am asking you to read my mind AND the future!)

2. AT 80EDT f/6 -- AT does strike me, and many others it seems, to have hit a really nice balance between better than decent quality and price. It's probably silly, but this would seem the more obvious stand out if it had a case. Also, is this intended more for astrophotography? I don't want to pay for features that won't be apparent with strictly visual use; 2 elements rather than 3 would seem better suited to my purposes.

enmofinwins

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Re: thinking of getting a refractor...
« Reply #12 on: January 16, 2018, 03:15:45 AM »
The Sky-Watcher 80mm f/7.5 would give you a better shot at viewing the Moon and planets up closer, and when using a 2x barlow. The FPL-53 ED element within the doublet is currently the ultimate low-dispersion glass, and to ensure keeping chromatic aberration(false colour) at a minimum. The focal-length, at 600mm, still classifies the refractor as being somewhat fast, and the extra 4" to 5" in overall physical length over an 80mm f/6 is negligible when its other advantages are taken into consideration. There may be many instances in future where you'll want to increase the magnification, and the slightly longer focal-length will make that easier.

Refractor doublets also acclimate to outdoor conditions the quickest, and more than any other telescope design, including all other refractors. Triplets of the same aperture as a doublet will take a little longer to acclimate, are more prone to collimation errors, and are slightly dimmer. For visual use only, doublets are more than capable.

A doublet ED refractor may also be used with a Herschel wedge, which is the ultimate in white-light solar observation, and for observing our nearest star, the Sun...

http://www.highpoint...V6J4aAoqM8P8HAQ
http://www.highpoint...8zZIaAnNT8P8HAQ

The lens or lenses of a triplet refractor have been known to crack when using said wedge, and must never be used with any mirrored telescope, either Newtonians, or Cassegrains(Schmidt and Maksutov, along with the classical types in addition).

Now, I have an 80mm f/6 achromat, with a standard crown-and-flint doublet...
But I look upon it more as a monocular than a telescope; one half of a binocular, in other words, albeit with the ability to alter the magnification with eyepieces.

Indeed, many take it a step further and combine two refractors, and for the ultimate binocular; a binoscope...

http://www.sciencece...op/s100edmt.jpg

Now, Lunt offers an 80mm f/7 ED doublet(not of FPL-53 glass), which is only about 3" longer than an 80mm f/6, and a focal-length of 560mm...

https://www.bhphotov...2,&A=details&Q=

With a 2x barlow, you can still get the focal-length up to 1120mm, and for the higher magnifications, whilst still enjoying the low-power wide-field views. It's like having your cake and eating it, too.

Now, if you feel the slightest inkling that you may want to image in future, you can still do so with either the Sky-Watcher or Lunt ED doublets, but an 80mm f/6 triplet would be the best for that.

migresinli

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Re: thinking of getting a refractor...
« Reply #13 on: January 16, 2018, 10:56:56 PM »
I have an AT72 to compliment my larger 6" sct and also use a longer fl 80mm refractor for when I need to boost magnification. I don't thing you can go wrong with the AT72 especially for wide field g&g scope. Optics are very good and the scope is very portable. Mine rides on a vixen porta II without any issues.

handthedemo

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Re: thinking of getting a refractor...
« Reply #14 on: January 20, 2018, 01:35:52 PM »
Quote
Quote

Deb:

You have carefully considered this scope and mount and you have lots of good questions. .....................

Thank you to everyone who has commented on my post -- ...
After looking into it a bit, 2 scopes seem decent options, though neither seems "perfect."

SADLY, with time we all discover,------- THERE IS NO PERFECT SCOPE

edj