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15inch dob needs a friend

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#1 sniperpride

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Posted 25 November 2012 - 04:13 PM

My 15inch obsession is very lonely, and needs a companion. I have roughly 2500 to spend on scope, and mount. This will be for visual use only, and I would like a goto mount. Uses will be for planetary, doubles, star clusters.
Help me find him a new friend :confused:
Im leaning towards a few scopes but all of them are either backordered or out of stock. I would like to spend as little as possible. But I love quality, and it comes at a cost, we all know this ;)

#2 Erik Bakker

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Posted 25 November 2012 - 04:36 PM

My 15inch obsession is very lonely, and needs a companion. Uses will be for planetary, doubles, star clusters.


You should be able to find the intended subjects without goto, that should free-up some cash :)

Spend 1/4 on the alt-az mount and the rest on the OTA. That should get you a very nice APO, especially on the used market. For performance, a 4" is great. For portability, a 3"-3 1/2" is a better choice.

#3 maknewtnut

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Posted 25 November 2012 - 05:21 PM

IMO, a Petzval or MakNewt is excellent in this role. Why? Because the smaller scope will often be used to present wide fields. There's no better widefield scope than one that presents a wide, flat field.

#4 sniperpride

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Posted 25 November 2012 - 06:00 PM

I had been interested in the AT-111 apo, but these have been out of stock everywhere for a long time. Stellarvue 105 is a possibility. I guess i would like to stay between 90-115mm, but I dont know how much aperture I truly need because its big brother will be next to it.

As far as sturdy manual control eq mounts go, what are my options?

#5 Jon Isaacs

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Posted 25 November 2012 - 08:36 PM

IMO, a Petzval or MakNewt is excellent in this role. Why? Because the smaller scope will often be used to present wide fields. There's no better widefield scope than one that presents a wide, flat field.


There is nothing quite like an NP-101 for a companion to a larger Newtonian... It only weighs about 10 lbs and with it's 540mm focal length and Petzval flat field, it is amazing at low magnifications. And it's a performer at high magnifications too...

Jon

#6 johnnyha

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Posted 25 November 2012 - 08:44 PM

Another great companion is the Takahashi FS102, just a flat-out beautiful image and no thermal issues. And it should fit your budget.

#7 sniperpride

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Posted 25 November 2012 - 09:17 PM

I would have to find both of those scopes used to fit my budget, and have barely if any left over for a mount, mainly with the NP101

#8 rockethead26

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Posted 25 November 2012 - 09:47 PM

To accompany my 14.5 dob, I recently acquired an EON 120ED on a CG-5. With a diagonal and finder this great combo is under your budget. EONs are now only available used, and there were two on a-mart a week or so ago. The Skywatcher version which is available new contains the same fine optics. Highly recommended!

#9 gillmj24

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Posted 25 November 2012 - 10:27 PM

If you have limited funds for the mount I would say the orion Atlas gives the most for your money. It will be rock solid on any 120mm or smaller apo. You can find a used goto one for under 1000. Maybe closer to 800. It is heavy but if you can manage it, it will be much more solid than the cg5.

#10 Rob E

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Posted 25 November 2012 - 10:42 PM

I found a Skywatcher Synscan GOTO for a good price here in the S&S.
I've paired it regularly with an Orion ST120 & Stellarvue ST 80ED. I really enjoy both tubes.

#11 Jon Isaacs

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Posted 26 November 2012 - 12:13 AM

If you have limited funds for the mount I would say the orion Atlas gives the most for your money. It will be rock solid on any 120mm or smaller apo. You can find a used goto one for under 1000. Maybe closer to 800. It is heavy but if you can manage it, it will be much more solid than the cg5.


In my view, the difficulty with a 120mm scope on an Atlas or CG-5 is that it takes a fair amount of effort to get it up and running, probably about the same effort as a 15 inch Dob that is stored fully assembled.

To compliment a larger Dobsonian, something that is easily portable, provides the widest fields possible and doubles as a terrestrial scope is what I find the most useful.

YMMV

Jon

#12 Sky Muse

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Posted 26 November 2012 - 06:34 AM

Per the title, I thought you were selling, or even giving it away in the spirit of Christmas. :jump:

"Uses will be for planetary, doubles, star clusters."

Get a German equatorial and a motor-drive set, and to accomplish higher mangnifications. An average alt-az mount will disappoint. I ordered a Celestron CG-4 and the dual-axis motor drives, the mount to arrive later today. That would allow for a plethora of moderate focal-lengthed achromats from which to choose, and per your quoted observing interests. Then there's this, and highly rated...

http://www.telescope...ronc6rgtrefr...

The possibilities are almost endless given the budget.

Cheers,

Alan

#13 Jon Isaacs

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Posted 26 November 2012 - 07:01 AM


Get a German equatorial and a motor-drive set, and to accomplish higher mangnifications. An average alt-az mount will disappoint.



This is a personal choice. High magnification duties are going to disappoint when compared to a decent 15 inch Dob. High magnifications require a stable mount and good optics... 300x in a 4 inch is easily done with an alt-az mount..

For me, refractors represent a balance, a companion to a larger reflector. They are small, agile and when the skies are dark and clear, provide the widefield, low magnification views that are beyond the capabilities of a larger scope. An Equatorial mount is more cumbersome and less agile, less intuitive than an alt-az mount.

Me, I have a variety of mounts, GEMS and otherwise but to go along with my bigger scopes, refractors sit on appropriate alt-az mounts.

That's my two cents...

Jon Isaacs

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#14 Sky Muse

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Posted 26 November 2012 - 11:16 AM

In addition, with an alt-az, one would be forever having to manually move the refractor up and down, left and right to find something, and then tapping it up and down, left and right just to keep the object almost centered in the eyepiece. The finest alt-az mounts, for me, are of the yoke type, yet will take away a larger portion of the budget from the refractor.

An alt-az is best for viewing wildlife and distant vistas, and if at a dark site, for a quick look-see just prior to night falling.

With a motorised equatorial mounting, and it doesn't have to be a beast, one centers the object of choice, and they're done, as it will track the object for hours on end, perhaps only requiring very fine adjustments in declination once in awhile.

True, there is the portability factor to consider, and a modest equatorial can be just that, however if you're fortunate to live in area that is reasonably free of light pollution, it remains the best of the two.

Cheers,

Alan

#15 jrbarnett

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Posted 26 November 2012 - 11:24 AM

$2500 for the OTA and mount, in refractorland, where you want top quality, will not go very far. Buying used is probably your best bet given your quality requirements and budget.

Regards,

Jim

#16 Jon Isaacs

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Posted 26 November 2012 - 01:06 PM

In addition, with an alt-az, one would be forever having to manually move the refractor up and down, left and right to find something, and then tapping it up and down, left and right just to keep the object almost centered in the eyepiece.



A few thoughts, comments:

- This scope is a companion to a 15 inch Obsession, Sniperpride almost certainly is familiar and skilled at manual tracking, probably at much higher magnifications than one could ever achieve with a refractor.

- In my experience, the manual best alt-az mounts for a refractor are the balanced mounts with slow motion controls. The main advantage of these mounts is that they can be used "point and shoot dob style" for low power scanning and observing and yet at the high magnifications, the geared slow motion controls allow for easy, accurate, vibration free tracking, tapping and such is simply not necessary. (As an aside, I must admit, I have never used a mount that required tapping to track.) These mounts are simple, compact and easy to setup and require no electronics to make them work...

The Vixen Portamount was the first affordable balanced alt-az mount with slow motion controls and it is still reasonable choice for a 3 inch or relatively light 4 inch, particularly with an upgrade to a wooden tripod. I frequently mount my NP-101 on an upgraded Portamount and operate it up to about 300x.

The Astro-Tech Voyager is similar in cost and capacity. Currently there are quite a number of balanced alt-az mounts equipped with slow motion controls. I also have a StellarVue MG2, I have used it with an 8 inch F/5 Newtonian with good success.

There is no doubt that there good quality alt-az mounts out there, no need to compromise. If tracking is desired and one is willing to pay the price in setup time and awkwardness, a GEM is a reasonable solution. I have a CG-5 but only use it for astrophotography...

Jon Isaacs

#17 csrlice12

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Posted 26 November 2012 - 01:09 PM

$2500...well, there's always a BIGGER brother, who says you gotta so smaller????

#18 Sky Muse

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Posted 26 November 2012 - 01:30 PM

"They are small, agile and when the skies are dark and clear, provide the widefield, low magnification views that are beyond the capabilities of a larger scope."


"I would like a goto mount. Uses will be for planetary, doubles, star clusters."

...hence, an equatorial combined with either a moderate-to-long focal-lengthed achromat or a fast-to-moderate apochromat, like a used Takahashi FS-102, if they haven't been gobbled up. Else, you'd need either an extender, a barlow or both to duplicate the former, and per viewing interests.

...my three cents, and a ball of lint from my pocket for good measure.

Cheers,

Alan

#19 simpleisbetter

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Posted 26 November 2012 - 01:35 PM

In my view, the difficulty with a 120mm scope on an Atlas or CG-5 is that it takes a fair amount of effort to get it up and running, probably about the same effort as a 15 inch Dob that is stored fully assembled.


I wholeheartedly agree with that statement. A well balanced manual alt/az with slow motion is the easiest and the best grab and go mount for the 90-110mm scopes, and the quickest out the door and viewing. I moved "up" to the CG-5 only due to my arthritis in my neck. Even though I really like my mount I knew what I was getting into when I bought it, understanding that I would lose grab and go capability.

Even if I haul the CG-5 and a 4" scope out in one piece, there's still power wires, laptop cables, leveling, alignment, etc. All that can take upwards of 30 minutes or more. My old 4" f/7 on the Voyager was up and running in 5 minutes.

And picking the whole thing up to rapidly relocate for a better vantage point to view a specific area of sky, or to block stray light, is non-existent with the go-to mount (especially an Atlas or greater); even a large dob is easier to relocate and get back up and running.

#20 rockethead26

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Posted 26 November 2012 - 01:49 PM

I don't see where the OP said anything about grab n go being a requirement. If he had, I certainly wouldn't have recommended my rig, but since he didn't...

He even says that he wants GoTo.

#21 Jon Isaacs

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Posted 26 November 2012 - 02:13 PM

"I would like a goto mount. Uses will be for planetary, doubles, star clusters."

...hence, an equatorial combined with either ...



In a later post, Sniperpride also asks this question:

"As far as sturdy manual control eq mounts go, what are my options?"

It seems that GOTO is not a requirement. If one is open to manually tracked mounts, certainly alt-az mounts are worthy of serious consideration.

In any event, the world of alt-az mounts has come some distance from the old yoke mounts...

Jon

#22 simpleisbetter

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Posted 26 November 2012 - 02:14 PM

You might be right Jim, but the reason I said grab and go is because outside of that requirement, for visual use only, I really, honestly, see absolutely no need to have a second scope, except as a grab and go to get out and observe on those nights when you can't get the big scope out. If that's not the case here, then I recommend he save his money and that it be better spent on other accessories.

#23 Sky Muse

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Posted 26 November 2012 - 02:17 PM

"The Astro-Tech Voyager..."

I have said "Voyager", and, putting it mildly, it leaves more to be desired. Also, I've searched the galaxy for a slo-mo cable for the declination, but to no avail. Thirdly, in that dude is wanting a refractor for visual only, like me...

...what "awkwardness"? It's no more awkward than a large Dobson-Newtonian utilised for visual, let alone for snapping photos.

Cheers,

Alan

#24 csrlice12

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Posted 26 November 2012 - 02:35 PM

You can also always lay an EQ mount on it's side and use it as Alt/Az...

#25 cloud_cover

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Posted 26 November 2012 - 02:51 PM

I agree that setting up a GEM is cumbersome. In fact, one fo the reasons why I hardly use my 8" SCT although it performs better overall in my urban skies is the set up time: Its far, far easier to grab the NP-101 and Portamount than to mount the 8" on a Vixen SXD...
Sniperpride: Have you ever thought about mounting the refractor on your Obsession? I seem to recall one Obsession review where the finderscope was an NP-101. Unusual, but effective...






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