Which newton scope for observatory

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Newton 250 F4 or Newton 300 F4
Single choice poll 32 votes
6% (2 votes)
94% (30 votes)
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Vandewattyne avatar
This year I will do an upgrade from a newton 200 F5.
I'm hesitating between a 250 F4 or a 300 F4 with a 3" 1.14 coma corrector.
The mount can handle the weight and its inside an observatory.

Thx for the feedback smile
Dan_I avatar
I don't see any reason not to choose the 300 f/4 assuming there are of equal quality. 1368mm focal length is rather ideal with current sensors for high-resolution work while keeping a large FOV.

What's most important is the quality of the design and execution, both optical and mechanical.  Which particular scopes do you have in mind?
Well Written Concise
Médéric Hébert avatar
As a rule of thumb, aperture is king.
Vandewattyne avatar
The one I have in mind is the Artec 250 or 300. Working with 1m of FL I see there is still a little room for more resolution. But its hard to tell what the max resolution is under my sky.
David Zimák avatar
If your mount is cabable enough, don´t wast your money for 250…go straight to 300 aperture. There is not big diffrent between 200 and 250 in case of resolution so…

David
Vandewattyne avatar
The mount is a GM2000. No problem to handle it.
David Zimák avatar
Then do not hesitate for a moment… 300 it is smile
Dan_I avatar
Vandewattyne:
The one I have in mind is the Artec 250 or 300. Working with 1m of FL I see there is still a little room for more resolution. But its hard to tell what the max resolution is under my sky.

The ARTEC astrographs look good on paper. What bothers me is that they don't mention the origin of the optics. Personnaly in this price range I would not accept mass-produced optics from China or Taiwan. 

 In case the focal length is a bit too much for you seeing, you could trade the 1.14 corrector for a corrector with no magnification (or with slight reduction). In any case you'd benefit from the extra light gathering ability of the 300 over the 250.
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Oscar avatar
In case the focal length is a bit too much for you seeing, you could trade the 1.14 corrector for a corrector with no magnification (or with slight reduction).


or bin, or use another camera with bigger pixels
Vandewattyne avatar
The ARTEC astrographs look good on paper. What bothers me is that they don't mention the origin of the optics. Personnaly in this price range I would not accept mass-produced optics from China or Taiwan.

They told the next batch of scopes will have a Ronchi and Fringe Test report but no details about the origin of the mirrors. Also some details about the mirror cell would be nice.
andrea tasselli avatar
David Zimák avatar
Or if I may suggest, you can get also very reliable f4 Newton from Lacerta Austria . I have their 200/800 (now 200/600 with Nexus coma corrector) and cannot complain anything at all.
Only problem will be maybe waiting time, this you would have to check with them.

You can look on my profile and find many pictures I did with this scope.

https://lacerta-optics.com/FN30012c-new#m

Just my five cents..

David
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andrea tasselli avatar
Lacertas are pretty darn good, if only you'd get hold of one.
Dan_I avatar
Vandewattyne:
The ARTEC astrographs look good on paper. What bothers me is that they don't mention the origin of the optics. Personnaly in this price range I would not accept mass-produced optics from China or Taiwan.

They told the next batch of scopes will have a Ronchi and Fringe Test report but no details about the origin of the mirrors. Also some details about the mirror cell would be nice.

If they don't say we understand what it means. At this price point I'd like optics from reputable mirror makers in Europe like Romano Zen, Fausto Giacometti, Franck Grière (Mirrosphere) or Michel Bonin (Skyvision) to name a few.

While the overall shape of industrial-made mirrors can be OK, their polish is typically rather rough and they often have edge problems.

I'm working with an 8" f/4 with Romano Zen optics and get results like this:
https://www.astrobin.com/k4joar/

and a 10" f/4.8 with Franck Grière optics which gives me this:
https://www.astrobin.com/31x2yd/G/
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John Stone avatar
andrea tasselli:
Those Artesky are too expensive for what they do. Get a TS ONTC at 1/3 of the price:
https://www.teleskop-express.de/en/ts-teleskope-143/unc-ontc-high-end-newtonians-from-germany-312/ts-optics-ontc-250-mm-f-4-carbon-photo-newtonian-with-conical-primary-mirror-and-2-inch-rap-focuser-lightweight-construction-17697

To that ONTC be sure to add the cost of a 3" focuser, 3" Paracorr, and a 3" Pegasus electronic focuser, and a tip/tilt system.

I think you'll see things begin to equalize.
Tony Gondola avatar
300 for sure, not even a question in my mind given your constraints or lack thereof.
andrea tasselli avatar
John Stone:
To that ONTC be sure to add the cost of a 3" focuser, 3" Paracorr, and a 3" Pegasus electronic focuser, and a tip/tilt system.

I think you'll see things begin to equalize.


Why would you? There is no reason to go 3" unless you're going full frame and then some. Besides, that's up to the buyer to decide how the thing is spec'd. The other one is fixed.
Vandewattyne avatar
Thx for everyone input.

After adding all the extra's on the TS-Optics Astrograph 12" I'm getting close to the price of the ARTEC 300. 
(2x long dovertail, Pegasus focuser & baseplate, internal flocking of the tube, main mirror ring, rigid spider, stainless steel end ring, covering the  back of the tube end, check of the optics on the bench). In the worst case the optics need to be redone also.

About the one from Lacerta you get a better deal but they dont want to change the focuser to something else like an ESATTO 2. The holes of the octoplus plate don't fit for a Esatto. 

There is indeed no origin of the ARTEC optics. 

In these 3 case it can be a good enough optics or just not good enough optics.

Another option is a scope from Axis instruments with a craftman mirror. The price is a bit more but you get a full option quality scope.
andrea tasselli avatar
I'm somewhat hesitant about giving this advice but I'd check the CT line from Orion Optics UK.

CT SERIES - Orion Optics

I can't fault the quality of their mirrors and they have most of the features you'd want and are most accommodating about any special requirement, such as a custom base for your focuser of choice ( I had mine from MoonLite back then).
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