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Equipment Discussions >> Refractors

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Sky Muse
sage


Reged: 10/26/12

Loc: De Soto County, MS
Re: 15inch dob needs a friend new [Re: Jon Isaacs]
      #5542733 - 11/27/12 08:02 PM

"Motorized tracking is nice..."

Obviously, and the CG-5 equatorial has the GOTO enhancement as well, though I enjoy the hunt myself. I suppose the GOTO would come in handy when ushering the curious into our hallowed hobby.

"...but not necessary."

Only bread and water are necessary...and Twinkies.

"...a 4 inch telescope is just not sufficient aperture to 'seriously study' the planets..."

"For serious lunar, planetary, globular cluster, and binary star observing – as well as for surprisingly good views of the brighter Messier, NGC, and IC catalog objects– many amateur astronomers prefer the crisp, high-contrast, diffraction-free images of a good refractor. Under average seeing conditions, a useful rule of thumb in astronomy is that a good 3" to 4" refractor will usually outperform an average 6" to 8" reflector or Schmidt-Cassegrain for seeing details on the Moon and planets, splitting binary stars, and resolving globular clusters." -Astronomics

Given the funds then allocated, what would you have suggested, this...

http://big-deals.fr/product.php?id_product=37

...?

"That's how it works around here...

'nuff said"

'fraid not.

Cheers,

Alan


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BDS316
Carpal Tunnel


Reged: 09/16/09

Loc: Sol 3
Re: 15inch dob needs a friend new [Re: Sky Muse]
      #5542896 - 11/27/12 09:44 PM

" Under average seeing conditions, a useful rule of thumb in astronomy is that a good 3" to 4" refractor will usually outperform an average 6" to 8" reflector or Schmidt-Cassegrain for seeing details on the Moon and planets, splitting binary stars, and resolving globular clusters." "

Just. Not. True.

My XT8, when properly collimated and cooled down, blows away four inch apo refractors and can go toe to toe against a 5 inch AstroPhysics Starfire. In fact, it even impressed the heck out of the owner of a SIX INCH AstroPhysics Starfire.

I have a nice 80mm refractor and access to several other nicer, larger refractors, SC's and Dobs. Each type of scope has pros and cons.

Aperture rules. At your last star party, how many big Dobs were used with off axis aperture masks?

Edited by BDS316 (11/27/12 10:26 PM)


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Sky Muse
sage


Reged: 10/26/12

Loc: De Soto County, MS
Re: 15inch dob needs a friend new [Re: BDS316]
      #5542970 - 11/27/12 10:23 PM

When I quoted that, I didn't consider it as an absolute, for there are, apparently, exceptions. I've known of a few testimonials to the same effect, of which I've no real reason to doubt. To wit, it's my actual understanding that a four-inch refractor and a six-inch reflector are demonstrably equal, in general at least, save the virtue of direct observance.

Frankly, I was surprised at the quality of the parabola and flat within my own Orion 6" f/5 Newtonian, however nowhere near the equal of my four-inch apochromat.

"At your last star party, how many big Dobs were used with off axis aperture masks?"

...at my star parties? None at all, for it's just me, myself and I...and my telescopes.

Regards,

Alan


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Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: 15inch dob needs a friend new [Re: Sky Muse]
      #5543104 - 11/28/12 12:03 AM

Quote:

Under average seeing conditions, a useful rule of thumb in astronomy is that a good 3" to 4" refractor will usually outperform an average 6" to 8" reflector or Schmidt-Cassegrain for seeing details on the Moon and planets, splitting binary stars, and resolving globular clusters."




Well, you can't always believe what your read. I have several 3 and 4 inch refractors including one of each that I consider excellent. They are no match for my pedestrian 8 inch F/5 Synta reflector on the planets, globulars etc..

If your average seeing conditions are so poor that a 4 inch outperforms an 8 inch, you have my sympathies and I am glad that rarely is the seeing that bad around here.

Jon


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coutleef
Post Laureate
*****

Reged: 02/21/08

Loc: Saint-Donat, Québec, Canada
Re: 15inch dob needs a friend new [Re: Jon Isaacs]
      #5543350 - 11/28/12 07:34 AM

Quote:

Quote:

Under average seeing conditions, a useful rule of thumb in astronomy is that a good 3" to 4" refractor will usually outperform an average 6" to 8" reflector or Schmidt-Cassegrain for seeing details on the Moon and planets, splitting binary stars, and resolving globular clusters."




Well, you can't always believe what your read. I have several 3 and 4 inch refractors including one of each that I consider excellent. They are no match for my pedestrian 8 inch F/5 Synta reflector on the planets, globulars etc..

If your average seeing conditions are so poor that a 4 inch outperforms an 8 inch, you have my sympathies and I am glad that rarely is the seeing that bad around here.

Jon




I agree with Jon. I have had a 3 inch and now have a 4 inch ED refractor with excellent star tests and the are not a match on planets or the moon to my 8 inch SCT. They beat my sct for ease of use and wide fields but the 8 inch scope has more resolving power that can not be matched by the smaller scopes even when the seeing is below average.

When the seeing is that poor, i usually stay indoors


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sniperpride
super member


Reged: 01/04/12

Re: 15inch dob needs a friend new [Re: coutleef]
      #5543454 - 11/28/12 09:21 AM

My only refractor I have ever owned was a 50mm toy. So this should be quite a learning and enjoyable experience.
Also, what really made me want to get a refractor aside from refractors being awesome, was the book starlight nights. One of the best books I have ever read.


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csrlice12
Postmaster
*****

Reged: 05/22/12

Loc: Denver, CO
Re: 15inch dob needs a friend new [Re: sniperpride]
      #5543510 - 11/28/12 09:55 AM

"Only bread and water are necessary...and Twinkies."

Hey man, wanna buy a collector Twinkie.......they're becoming rare you know.....


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Sky Muse
sage


Reged: 10/26/12

Loc: De Soto County, MS
Re: 15inch dob needs a friend new [Re: Jon Isaacs]
      #5543562 - 11/28/12 10:26 AM

"Well, you can't always believe what your read."

Your beef is not with me, on that at least, but with our host, Astronomics, rather.

Perhaps you might correct them.

Cheers,

Alan


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Sky Muse
sage


Reged: 10/26/12

Loc: De Soto County, MS
Re: 15inch dob needs a friend new [Re: sniperpride]
      #5543570 - 11/28/12 10:29 AM

Yeah, buddy! That Stellarvue's gonna make you forget that 50mm forever!

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Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: 15inch dob needs a friend new [Re: sniperpride]
      #5543957 - 11/28/12 02:11 PM

Quote:

My only refractor I have ever owned was a 50mm toy. So this should be quite a learning and enjoyable experience.
Also, what really made me want to get a refractor aside from refractors being awesome, was the book starlight nights. One of the best books I have ever read.




A 4 inch refractor and 15 inch Dob is about as perfect a match as there is... You are in for some real treats.

And if you are not using a Paracorr and the good eyepieces in your Dob, you might be in for another treat.

Jon


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Sky Muse
sage


Reged: 10/26/12

Loc: De Soto County, MS
Re: 15inch dob needs a friend new [Re: Jon Isaacs]
      #5544032 - 11/28/12 02:57 PM

"And if you are not using a Paracorr and the good eyepieces in your Dob, you might be in for another treat."

I'd bypass extras for the old scope and focus on the new toy, the refractor instead, like a pier to clear the tripod which will allow for more comfortable, direct, straight-through observing, if so inclined, in addition to extra two-inch oculars, if lacking.

Refractors do not require coma-corrective devices.

Cheers,

Alan


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Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: 15inch dob needs a friend new [Re: Sky Muse]
      #5544358 - 11/28/12 06:32 PM

Quote:

"And if you are not using a Paracorr and the good eyepieces in your Dob, you might be in for another treat."

I'd bypass extras for the old scope and focus on the new toy, the refractor instead, like a pier to clear the tripod which will allow for more comfortable, direct, straight-through observing, if so inclined, in addition to extra two-inch oculars, if lacking.

Refractors do not require coma-corrective devices.

Cheers,

Alan





Alan:

I know you don't seem to appreciate the capabilities of a large Newtonian but the refractor is a companion to that Newtonian and both can benefit from high quality eyepieces. The combination of high quality eyepieces plus a Paracorr in a 15 inch Newtonian can provide those nice pinpoint stars all the way across the field of view, the difference being that they can be about 3 magnitudes dimmer and still be seen.

And it is true, faster refractors do not require coma correctors but they do require correctors for field curvature if sharp to the edge views are to be obtained...



Jon


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sniperpride
super member


Reged: 01/04/12

Re: 15inch dob needs a friend new [Re: Jon Isaacs]
      #5544366 - 11/28/12 06:38 PM

Using Delos eyepieces at the moment, and looking at getting a 3-6 TV zoom for the refractor.
Also, since this is my first venture into refractors, Is there more to dew control that I should be concerned about than just using the "dew shield"
Should I invest in those heating strap thingies
I go out in the winter and such living in MN, not sure how dew will affect this new scope.

Edited by sniperpride (11/28/12 06:40 PM)


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Sky Muse
sage


Reged: 10/26/12

Loc: De Soto County, MS
Re: 15inch dob needs a friend new [Re: sniperpride]
      #5544656 - 11/28/12 10:02 PM

The integrated dew shield will delay dew formation for only a short time. There used to be foam-lined dew shield extensions offered, I've forgotten the brand, but AstroZap currently offers a felt-lined shield which slips over the end of the scope's shield and would help extend observing time. I've been looking at the electric dew controllers, and they're the best, particularly if you observe for several hours, with heating straps for the objective, eyepiece, etc. I haven't decided which method to choose myself...probably the electric system.

Cheers,

Alan


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Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: 15inch dob needs a friend new [Re: Sky Muse]
      #5544693 - 11/28/12 10:21 PM

Quote:

The integrated dew shield will delay dew formation for only a short time. There used to be foam-lined dew shield extensions offered, I've forgotten the brand, but AstroZap currently offers a felt-lined shield which slips over the end of the scope's shield and would help extend observing time. I've been looking at the electric dew controllers, and they're the best, particularly if you observe for several hours, with heating straps for the objective, eyepiece, etc. I haven't decided which method to choose myself...probably the electric system.

Cheers,

Alan




There are a number of options. What I find works best is to live in a dry climate...

Jon


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Sky Muse
sage


Reged: 10/26/12

Loc: De Soto County, MS
Re: 15inch dob needs a friend new [Re: Jon Isaacs]
      #5544728 - 11/28/12 10:38 PM

"There are a number of options. What I find works best is to live in a dry climate..."

Wouldn't we all, but I'm thankful for a relatively dark sky right outside my front door. Unfortunately, my lifelong love of trees has hampered my view.

Cheers,

Alan


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csrlice12
Postmaster
*****

Reged: 05/22/12

Loc: Denver, CO
Re: 15inch dob needs a friend new [Re: Sky Muse]
      #5545117 - 11/29/12 08:51 AM

Northern Minnisota in the dead of winter--probably a touch cold with dry air so dew would probably not be a problem...wanting to be out in that cold, dry air is another story.......

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sniperpride
super member


Reged: 01/04/12

Re: 15inch dob needs a friend new [Re: csrlice12]
      #5602580 - 01/03/13 09:18 AM

I changed my order from the Stellarvue 105mm to 115mm. Havent even looked through it yet and my aperture fever kicked in.

Edited by sniperpride (01/03/13 09:18 AM)


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johnnyha
Postmaster
*****

Reged: 11/12/06

Loc: Sherman Oaks, CA
Re: 15inch dob needs a friend [Re: sniperpride]
      #5603316 - 01/03/13 04:24 PM

Smart move.

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