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Old 24-02-2014, 06:14 PM
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What Would You Put on an MEII?

OK, my MEII will arrive any day now and naturally I will set it up with my TEC140. Someday, perhaps sooner than later I want to put a larger scope on this mount. But what if say the budget is around 15-18K? New, used?

I have to say that I currently favour galaxy imaging, but I also love the wide field views that I see in Mike's images. He seems to get the best of both words with his AG12. I would consider the AG16 but I have some concerns about the stability of the focusing system even with the additional ring support and my other concern is the somewhat limited back focus. For example it would be impossible to use an ONAG. And then my current cameras are not great choices for very long FL (a Trius and G2-8300).

So, what else should I ponder that would be faster than F7 and perhaps not as fast as F3.8, has good back focus, perhaps not over 2000 mm fl, and that I could enjoy for a while without buying another camera and Atlas focuser, and is of course great optically. Ha ha, this is probably impossible!!! But Thanks.

Peter
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Old 24-02-2014, 08:30 PM
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No brainer.

Ceravolo 300mm with all the options. Problem is, it doesn't fit in your budget.

But...if you really want a corrected Newt...get an ASA...the images Stu's machine are producing are sublime.
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Old 24-02-2014, 08:41 PM
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I have always wondered how the orion optics ODK scopes perform. They are f 6.8 though. The 12 inch would be at your maximum FL of 2000.
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Old 24-02-2014, 09:13 PM
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Peter,

Thanks for the suggestions. The Cerevolo looks fantastic. I should start saving up! Only negative I can see is the very limited back focus in the fast configuration. Read one review that said it wasn't possible to guide off axis unless at slower F setup due to back focus limitations. I'm thinking that with an MEII I ought to be able to go unguided with a scope like that one.

The ASA scopes also look interesting. I was surprised, however, to see that the back focus on the 16" model was even smaller than the Orion Optics offering. But, certainly worth considering. Not exactly inexpensive either!

Peter
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Old 24-02-2014, 09:35 PM
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Originally Posted by PRejto View Post
Peter,
...........

The ASA scopes also look interesting. I was surprised, however, to see that the back focus on the 16" model was even smaller than the Orion Optics offering. But, certainly worth considering. Not exactly inexpensive either!

Peter
Problem is the internet can be a cesspool of misinformation, with bias for one reason or another to promote various manufacturers.

I quite happily admit my devotion to SBIG, Astro-Physics and Ferrari

I've known Peter Ceravolo for a long time, and know any optic from him will be superb...sure... I can source his optics...but I'd recommend them regardless of who they are obtained from.

Frankly I've been a little nonplussed by the results from Orion scopes... I've long thought the ASA's corrected Newts in skilled hands have produced images with more snap... (also had a Pommy car...one was enough ) suggest you Google images from all of the above and draw your own conclusions.
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Old 24-02-2014, 09:40 PM
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The Cerevolo looks fantastic. I should start saving up! Only negative I can see is the very limited back focus in the fast configuration. Read one review that said it wasn't possible to guide off axis unless at slower F setup due to back focus limitations.
Atlas focuser
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Old 24-02-2014, 09:50 PM
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Atlas focuser
Ditto.
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Old 25-02-2014, 12:42 AM
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The new CDK14 would have to be high on the list. You can mate it with an AP reducer or perhaps even the APM reducer to get it around 2 metres.

I am imaging at 2 metres with the reducer and liking that setup.

It would be a good galaxy imaging setup. The other cheaper choice would be a GSO RC. They are now selling carbon fibre trusses and bringing out a 16 inch.

Replace the focuser with an Atlas and it may be quite good. Time will tell. Perhaps wait for Paul Haeses to show some images to see if they are good enough or not. The 10 inch seems to produce some very nice images.

Keep the TEC140 for widefield. I like my AP140 for widefield. 140mm is a good focal length for that. There is also the APM reducer which is supposed to work on a TEC140 if you want an even wider field.

Greg.
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Old 25-02-2014, 06:26 AM
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Hi Pete

Great times ahead for you

Problem on this forum is that you will get plenty of misinformation and biased opinions based on interpretations, prejudice, ignorance and plain ill will, for example... all ASA Newt astrograph mirror sets are actually made by Orion Optics UK and the Orion Optimised Wynn Corrector is a 4 element design

On the up side it will be a fun journey and I wish you well, if money was no option then the Cerevolo would be very nice, even if only 12"...but 16" sounds attractive for much less cost huh? and don't forget aperture and speeeeeed - being able to reduce that exposure time makes for more productive imaging.....how about a 20" F3.8

Mike
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Old 25-02-2014, 07:05 AM
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I appreciate all the info, even if it isn't all in agreement. It provides a great deal of food for throught. And, with such large sums involved it pays to be prudent before mortgaging one's life away! (I always thought it's interesting that the word "mortgage" contains the word death!) Anyway, I digress.

Am I wrong to think that every fast scope will have rather limited back focus? Should I worry that in some of these scopes it isn't possible to use both an Atlas + MMOG? I know that Mike uses the SX OAG but that is with a small camera. Just how feasable is it to guide through a guide scope at 1300-1500 mm? Reasonable? Then I may not need to guide if the MEII lives up to expectations....

I'm very intrigued by those designs that allow the scope to fuction both as fast and at longer FL too.

Peter
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Old 25-02-2014, 07:30 AM
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strongmanmike (Michael)
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Am I wrong to think that every fast scope will have rather limited back focus? Should I worry that in some of these scopes it isn't possible to use both an Atlas + MMOG? I know that Mike uses the SX OAG but that is with a small camera. Just how feasable is it to guide through a guide scope at 1300-1500 mm? Reasonable? Then I may not need to guide if the MEII lives up to expectations....
Yes, going down a Starlightxpress with OAG outfit route you should be fine, I think the only configuration that you may have to confirm is the big ProLine/MicroLine or STX + filter wheel working with an MMOAG...I believe it is doable but it would be very tight - talk with the manufacturer.

Re piggy back guiding with a fast Newt - the three biggies are

1) Make sure the primary mirror is perfectly held within the main mirror holder so it can't move and without imparting any stress forces on the glass - an easy adjustment.
2) Make sure the OTA support rings are as far apart as possible - you can customise the mounting plate length or make it adjustable OO will provide any length you desire with multiple hole attachment points for the rings so you can space the rings as you like
3) Use a small light guide scope and guide camera (the Loadstar is excellent) that are both rigidly attached to the system and preferably to the OTA

It is the differential flexure that you want to minimise but if you do these three things and you should be fine

Quote:
I'm very intrigued by those designs that allow the scope to fuction both as fast and at longer FL too.
Yes - an awesome capability for sure

Peter

Last edited by strongmanmike; 25-02-2014 at 07:40 AM.
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Old 25-02-2014, 08:38 AM
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Originally Posted by strongmanmike View Post
Hi Pete

Great times ahead for you

Problem on this forum is that you will get plenty of misinformation and biased opinions based on interpretations, prejudice, ignorance and plain ill will, for example... all ASA Newt astrograph mirror sets are actually made by Orion Optics UK .......
So the ASA web site, stating they use Lomo optics specified by Phil Keller is incorrect or misleading?
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Old 25-02-2014, 09:06 AM
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So the ASA web site, stating they use Lomo optics specified by Phil Keller is incorrect or misleading?
Wrong page link for the corrected Newts

Here is the correct link (bottom paragraph) ...just so people are not mislead (again)
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Old 25-02-2014, 09:55 AM
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Wrong page link for the corrected Newts

Here is the correct link (bottom paragraph) ...just so people are not mislead (again)
OK...so you go there and download the .pdf, and that says:

"All ASA astrographs are manufactured from superior
Suprax glass material and polished to an accuracy
of P/V = 1/7 lambda etc.. ..................... on
request, premium Astro-Sital ceramics polished by
LOMO optics can be ordered"

Suprax as far as I can tell is a Schott borosilicate glass similar to pyrex.

Assuming Orion are supplying their pyrex optics one wonders why ASA don't mention this fact and continue to refer to LOMO

..anyhow, it seems pretty clear if you want zero-expansion optics, then they come from LOMO, not Orion.
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Old 25-02-2014, 10:08 AM
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Assuming Orion are supplying their pyrex optics one wonders why ASA don't mention this fact and continue to refer to LOMO
Pride..?

Quote:
..anyhow, it seems pretty clear if you want zero-expansion optics, then they come from LOMO, not Orion.
Oh reeeally??? well done ...and so does the significant price increase
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Old 25-02-2014, 10:12 AM
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Oh reeeally??? well done ...and so does the significant price increase
I always take home the Scotch I'd rather drink, rather than be reminded on every sip it was cheap.
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Old 25-02-2014, 01:24 PM
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Peter R,

I think a guide scope is somewhat wishful thinking at almost any focal length. PME will not guide without an autoguider and get round stars at regular and long focal lengths. I doubt ME 11 is any different in this regards. Claims Protrack can do long unguided round star images I think are highly spurious. I have a 310 point T-point model and I find Protrack enabled does improve star roundness but not 10 minutes unguided at 2 metres +.

I am currently using a guide scope on my CDK17 and reducer setup because the Planewave reducer whilst a nice unit optically has almost no backfocus and CCD has to be 45mm from the back of it. That does not really allow an OAG. I am considering SX filter wheel with built in OAG or TS OAG 9mm thick as alternatives or even using an AP reducer in place of the Planewave one. Setups often require ongoing tweaking.

I am using a little Vixen 95 VMC scope that is remarkably good for its cost. I get quite round stars with a decent PEC curve (oops shouldn've brought that up eh!!) and Protrack assisted guiding. 10 minute subs are often very round stars and sometimes a tad elongated. That is fairly tweaked and very rigid so must be close to as good as it gets.

So when planning out whatever system you intend I would put either a OAG in the system or consider the self guiding SBIG systems. Starlight Express have OAGs that fit with their cameras. QSI WSG cameras are also good for that. Not sure if they sell a 16803 yet or are about to.

Flexure as Mike can tell you is the enemy of fast systems. So heavy camera/filter wheel combos are somewhat inappropriate. A FLI Microline 16803 is currently the smallest/lightest of the 16803 cameras. But no guiding solution so you have to add in a MMOAG or other OAG to the system.

The Planewave focuser is very very good so that is not a worry. Its built like a tank and the electronic focusing is very accurate and does not slip (its geared). I also think Planewave now have gone through the beta stage (they did not have many bugs to start with, mostly baffle issues and stray light) and is now quite a mature system.

Greg.
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Old 25-02-2014, 01:45 PM
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.......I also think Planewave now have gone through the beta stage (they did not have many bugs to start with, mostly baffle issues and stray light) and is now quite a mature system.

Greg.
Indeed, the Planewave 14 would also be a great choice, and just make the budget
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Old 25-02-2014, 04:04 PM
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+1 for the Planewave 14". I'm sure it incorporates the latest and greatest from their design floor, and builds on their experiences with the 12" which they've retired.
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Old 26-02-2014, 09:58 AM
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Thanks everybody for the great suggestions and information. I'm digesting this and reading, and gathering ideas. I have a few more to add to the mix that have not been mentioned.

1. http://www.agoptical.com/
Received some excellent remarks at Cloudy Nights. 2 models. The 14"
IDK looks interesting and is marginally faster than the CDK. The IHW
line looks good too but is over my budget...quite fast though.

2. http://starizona.com/acb/Telescopes-C787.aspx
The 12.5 & 16" Hyperions from Starizona. I saw these in Tucson
recently. Look well made. Is there one in Australia?

3. http://www.italiantelescopes.net/
Something new coming along. They have an office in Albuquerque, New Mexico.

Anyone have info to share on any of these in relation to those already mentioned?

My tentative conclusion so far: The DK type scopes, especially the fast ones, are a lot more expensive than a fast Newtonian, but they offer greater back focus (in some cases) and a more rigid and convenient camera setup position. Nonetheless, I see some fantastic images posted here from Newtonians, namely those of Mike Sidonio, Ray Shiraz, and Rolf, and Stuart (sorry if I missed somebody!), so I'm beginning to wonder (a lot) if it's really necessary to hock one's soul to the devil to buy a folded system with the camera out the back? And Ray seems to be onto something with a not very expensive scope at all (I noticed also an f4 12" from Skywatcher). Now, I'm not suggesting that a Skywatcher mirror can really compete with others under consideration on a lab bench, but if the sky is the limiting factor for resolution is chasing fabulous numbers on a bench actually worth all that much when not imaging from space (or doing planetary work)?

Peter
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