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Evaluating a Large Maksutov in the Field

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#151 Asbytec

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Posted 10 October 2014 - 07:35 PM

Eric, gotta dust of the memory of that test, but I believe it will show the diameter of the obstruction if projected onto a wall. Measure the shadow of the obstruction compared with the illuminated diameter of the effective aperture. If you got 33%, that would be interesting and pleasing. That might actually be evidence of the divergent ray effect Don mentioned, maybe the effect is greater than I imagine it would be. Dunno. 



#152 Eric63

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Posted 10 October 2014 - 08:05 PM

When I did the test I got 48mm as the CO, which is 37%.  But then make that a 118mm diameter and it becomes 40% .  I'm just hoping that the divergent ray factor shows this to be wrong.  But regardless of theory, contrast is pretty awesome in this little scope  :grin:



#153 Asbytec

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Posted 10 October 2014 - 08:41 PM

Yea, I agree, the Mak is a nice design. There is just something awesome about them, crisp high power images speak volumes. Not that other scopes cannot do it, but the Mak certainly can. If you ever figure it out, let me know. :)

 

There is some divergence, surely, just not sure how much of a reduction in effective CO there is. If Don is right about another maker joining the market, my next purchase will probably be an 8" Mak depending on the value of quality and price.



#154 hardwarezone

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Posted 10 October 2014 - 11:58 PM

When I did the test I got 48mm as the CO, which is 37%.  But then make that a 118mm diameter and it becomes 40% .  I'm just hoping that the divergent ray factor shows this to be wrong.  But regardless of theory, contrast is pretty awesome in this little scope  :grin:

 

I did physical measurement of the baffle when I did the internal flocking. The baffle cone's widest point is 51.5mm



#155 A6Q6

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Posted 11 October 2014 - 06:35 AM

Here are two links I posted today on the Cats & Casses forum from 2004 on a CN  review of the old Meade 7" Mak vs the C9.25 and C11. http://www.google.co...0,d.aWw&cad=rja 7" Meade Mak vs C11 http://www.google.co...0,d.aWw&cad=rja


Edited by A6Q6, 11 October 2014 - 06:52 AM.


#156 Procyon

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Posted 11 October 2014 - 07:42 AM

Here are two links I posted today on the Cats & Casses forum from 2004 on a CN review of the old Meade 7" Mak vs the C9.25 and C11. http://www.google.co...0,d.aWw&cad=rja 7" Meade Mak vs C11 http://www.google.co...0,d.aWw&cad=rja


Very nice. The 9.25 CAT bullied the little 7" MAK. Good info on the coatings conparison Would have been good to compare the c8 vs the mak. So who finally won between the 6" refractor and 9.25?

#157 A6Q6

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Posted 11 October 2014 - 08:48 AM

 

Here are two links I posted today on the Cats & Casses forum from 2004 on a CN review of the old Meade 7" Mak vs the C9.25 and C11. http://www.google.co...0,d.aWw&cad=rja 7" Meade Mak vs C11 http://www.google.co...0,d.aWw&cad=rja


Very nice. The 9.25 CAT bullied the little 7" MAK. Good info on the coatings conparison Would have been good to compare the c8 vs the mak. So who finally won between the 6" refractor and 9.25?

 

I don't know if Daniel Mounsey ever got around to the comparison to post a review on the 6" AP155 EDF refractor vs C9.25. But because of cool down the 7" Mak did very well against the C11. I think the oversize tube of the Meade Mak may have helped even if the big counter weight was still there.


Edited by A6Q6, 11 October 2014 - 08:59 AM.


#158 Procyon

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Posted 11 October 2014 - 09:06 AM

To the guy that was going to throw the Meade he had just ordered in the garbage a few posts ago, maybe you should keep it after all? LOL

#159 LAF

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Posted 11 October 2014 - 04:20 PM

To the guy that was going to throw the Meade he had just ordered in the garbage a few posts ago, maybe you should keep it after all? LOL

I just received it yesterday. Haven't put it through it's paces yet. Looked at a few doubles and the moon.

 

I think it will be a keeper.

 

Larry



#160 ehallspqr

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Posted 11 October 2014 - 04:46 PM

Always go for the best broadband coatings if given the choice, pay the difference. I know the gain is very apparent with the Questars. Maks are dark scopes to begin with.

 

An 8" mct would be an interesting comparison to a C-9.25 with the added light grasp and gain in acuity.



#161 A6Q6

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Posted 13 October 2014 - 09:42 AM

Always go for the best broadband coatings if given the choice, pay the difference. I know the gain is very apparent with the Questars. Maks are dark scopes to begin with.

 

An 8" mct would be an interesting comparison to a C-9.25 with the added light grasp and gain in acuity.

When I bought my Quantum 6 Mak years ago I was told that if I got the enhanced silver coating on the 6" Mak it would have the light throughput of a 7" with the standard aluminum coatings. This was with the understanding that the Resolving power would still be that of a 6" scope with a CO. :thinking:


Edited by A6Q6, 13 October 2014 - 10:01 AM.


#162 astroneil

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Posted 13 October 2014 - 05:15 PM

Thank you all for your enthusiastic posts. All very interesting!

 

 

Date: 11.10.14
Time: 19:45h
Ambient: 8C, 1010mB, rising, humidity 97%, ~20 per cent cloud cover, no ground wind. Little or no scintillation in the stars overhead, bringing with it the promise of a good evening.
After a long journey north for our family vacation, the large Maksutov travelled well with absolutely no issues. A cursory examination of the nearby trees on Friday evening served up crisp and clear images at all magnifications indicating that the collimation was still spot on. The instrument was stored on its mount (a Vixen SkyTee II altazimuth) in the accompanying garage (unheated), where it was stored until ready to use. Last night was clouded out, but we enjoyed a clearing at sunset which left behind a lovely, dark sky.  After showing my boys the glories of the Perseus Double Cluster half way up the eastern sky and the fabulous Ring Nebula in Lyra high overhead with my 32mm Plossl (delivering near on a half degree field), I continued my high resolution tests.

I first examined Delta Cygni and was excited to see that it presented a text book perfect image, hardly a quiver, even at 340x! Next, I ventured across to Lambda Cygni and was delighted to see that the sub-arcsecond (0.9”) companion was plain to see and faithfully held in view for most of the time the system drifted across the field from east to west. From there, I swung the telescope over to Iota Cassiopieae and beheld the comely trio, beautifully sharp and stable at 340x. After that, I moved to Psi Cassiopeaie (also discussed previously). The darker sky and excellent transparency allowed me to see the faint close A/B pair better than I have observed at home.

Then I got more ambitious. Using my finder and panning my way up onwards towards the border with Cepheus at 113x, I narrowed in on the seventh magnitude triple system, O Sigma 507 (RA 23h 49 min, Dec +64 degrees 54 min) . The A/C components (mag 6.8/8.6), separated by about a Jupiter diameter and arranged roughly north-south, were easy pickings at low power but I was more interested to see what happened to the primary as I cranked up the magnification to 340x. So I swung the system to the east end of the field and let the vibrations settle down. To my sheer amazement, I glimpsed (often for several moments at a time) the secondary (A/B; mag 6.8/7.8) just (and only just) touching the primary, and extending away to the northwest! I repeated this several times within a few minutes to make sure I wasn’t seeing a diffraction artefact. As I have described elsewhere in my double star surveys, it looked for all the world like a “a tiny little snowman in the sky” morphed time and again by the vagaries of the atmosphere. Now, my records show that A/B is currently of the order of 0.7 arc seconds apart! This is truly an extraordinary result, as the components were not merely elongated but very nearly separated to my average eye. Clearly, the Maksutov was operating real close to its theoretical limits (so far as is known conventionally).

This is a new ‘personal best’ for me. If anything, it shows that I can go beyond the 0.9 arc second barrier under the best conditions which were clearly on offer at this location on this evening. That said, my notes show that I already enjoyed excellent seeing here before, albeit using smaller instruments.
This economical Maksutov, acquired for just a few hundred pounds, is turning out to be one of the most exciting telescopes I have had the pleasure of using in quite a few years. Cornelia; my portable powerhouse!

23:30h: After going indoors for the next few hours, I popped my head out of doors and noticed more clouds had rolled in from the North Sea and although the waning gibbous had now reached a decent height, the seeing had degraded noticeably as evidenced by the return of scintillation of the brighter stars overhead. This was confirmed by a quick examination of Delta Cygni, which was now poorly resolved at all powers. No craterlets were seen on the floor of Plato; only whitish spots hinting at their loci. Temperature was then recorded at 4C, with absolutely no signs of thermal stress in the optical train.

What a difference a few hours makes!

I am very much looking forward to the up-and-coming Jovian encounter later in the season, but now I have my sights set firmly on the glittering stellar jewels and nebulae of Orion.

Thanks,

 

Neil. ;)

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#163 Procyon

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Posted 13 October 2014 - 05:55 PM

I am just curious and for the records, :) based on this map, what color zone would you say you are observing from?

 

http://darksitefinde...aps/europe.html

 

Great report, thank you!


Edited by NorthWolf, 13 October 2014 - 06:48 PM.


#164 astroneil

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Posted 13 October 2014 - 06:25 PM

Hello Northwolf,

 

Thanks for the thumbs up!

 

It was conducted from the outskirts of the village ofTorphins (featured on the map of North East Scotland) on the edge of a blue/green zone.

 

Goodnight.

 

Neil. ;)



#165 Procyon

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Posted 13 October 2014 - 06:43 PM

Awesome! Enjoy, have a good time and clear skies!


Edited by NorthWolf, 13 October 2014 - 06:43 PM.


#166 Asbytec

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Posted 13 October 2014 - 08:22 PM

Harper, it's interesting you mentioned enhanced aluminum. I was shocked to read Company 7's specs on the Orion as having enhanced coatings. I like to give Company 7 is due credibility and suspect they might be right. It may be a mistake, but it may not be. Truth is, I don't know and can't tell just by looking at it. But the possibility is pleasing, so no one burst my bubble, please. :)

 

"Mirror Reflective Coatings: Enhanced aluminum, SiO2 overcoated"

 

http://www.company7....f12makcass.html



#167 gene 4181

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Posted 13 October 2014 - 10:33 PM

Harper, it's interesting you mentioned enhanced aluminum. I was shocked to read Company 7's specs on the Orion as having enhanced coatings. I like to give Company 7 is due credibility and suspect they might be right. It may be a mistake, but it may not be. Truth is, I don't know and can't tell just by looking at it. But the possibility is pleasing, so no one burst my bubble, please. :)

 

"Mirror Reflective Coatings: Enhanced aluminum, SiO2 overcoated"

 

http://www.company7....f12makcass.html

they've been putting it on the xt 8's for quite awhile, in a pure logical thought, it wouldn't make sense to coat all the other mirror's in a different facility or even in a different coater with a lesser al coat. pyrex primary, interesting. company 7 knew the previous mirror material for the xt 8's, ultraplex. not even the tech support guys knew this except for marshall who just retired.


Edited by gene 4181, 13 October 2014 - 10:56 PM.


#168 SpooPoker

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Posted 14 October 2014 - 01:45 AM

Any ideas how to get a 2" diagonal on these Maks?  I just received mine through the post and do not like the stock focuser that shifts the mirror or the minature diagonal.  Would rather just do it refractor style if that makes sense - a hefty dual speed R&P focuser and a 2" diagonal.  Would this work?



#169 ehallspqr

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Posted 14 October 2014 - 12:02 PM

Any ideas how to get a 2" diagonal on these Maks?  I just received mine through the post and do not like the stock focuser that shifts the mirror or the minature diagonal.  Would rather just do it refractor style if that makes sense - a hefty dual speed R&P focuser and a 2" diagonal.  Would this work?

Don't know for sure, might these adapters from ScopeStuff work? Like these guys, good prices and selection of widgets.

 

http://www.scopestuff.com/ss_smsa.htm

 

I would be curious to know just what Synta is using for the optics coatings on these Orion and Skywatcher Maks. I would assume they are using some sort of enhanced coatings? Would be nice to find out it was something like Starbright XLT. 



#170 Ed Holland

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Posted 14 October 2014 - 01:22 PM

Since I had a 2" refractor diagonal already, I decided to set up my 127mm Mak with the ability to use it rather than a medium quality (and restricted aperture) erecting prism....

 

I bought a thread adapter ring (Maksutov to SCT - available from a few sources). Then a 2" SCT visual back, or dedicated SCT diagonal will fit directly. I have a refractor diagonal, so chose the visual back.

 

It works well enough, although the additional path length, and the refocusing this requires does add focal length to the system (about 1700mm IIRC from the 1540mm claimed with a 1.25" setup.).



#171 gene 4181

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Posted 14 October 2014 - 03:41 PM

Harper, it's interesting you mentioned enhanced aluminum. I was shocked to read Company 7's specs on the Orion as having enhanced coatings. I like to give Company 7 is due credibility and suspect they might be right. It may be a mistake, but it may not be. Truth is, I don't know and can't tell just by looking at it. But the possibility is pleasing, so no one burst my bubble, please. :)

 

"Mirror Reflective Coatings: Enhanced aluminum, SiO2 overcoated"

 

http://www.company7....f12makcass.html

this link above shows a 150 mak, but the collimation procedure shows the back of the 127. orion is re-doing they're files and they can't find the link to the 150 or 180 mak collimation procedure from their archives, the tech support is working on it



#172 gene 4181

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Posted 14 October 2014 - 03:45 PM

Any ideas how to get a 2" diagonal on these Maks?  I just received mine through the post and do not like the stock focuser that shifts the mirror or the minature diagonal.  Would rather just do it refractor style if that makes sense - a hefty dual speed R&P focuser and a 2" diagonal.  Would this work?

yes, after you add the mak to sct thread adapter, it will add to the focal length of the scope and might reduce the usable aperture. William's made a nice focuser


Edited by gene 4181, 14 October 2014 - 03:49 PM.


#173 astroneil

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Posted 15 October 2014 - 03:36 PM

Oops, my apologies folks. I wrote in my latest report that I was using a "Vixen Skytee II altazimuth mount". :lol:

 

No such thing: for clarity it was a Vixen Porta II.

 

Me dunderheid.

 

Cheers,

 

Nelly. ;)

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#174 astroneil

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Posted 03 November 2014 - 08:30 AM

Just a quick update.

 

I have been continuing my thermal studies of the large Maksutov but the number of suitable nights that have been amenable to study have been few and far between over the last few weeks, owing largely to the movement of the jet stream. I have begun my observations of Orion and Jupiter, but I will refrain from making any specific comments about these targets until further work is completed.

 

Date: 29.10.14

Time 04:20-05:20h

Temperature inside shed; 3C

Temperature outside at end of vigil: -1C

1015mB, rising, 95% humidity

 

Observations compared with a fully acclimated 5" f/12 classical refractor.

 

Still no thermal problems experienced with the Maksutov.

 

One definition of wilful scare mongering:using 'thermal issues' to justify the purchase of a more expensive refractor in comparison with a much more economical catadioptric, as is showcased in this thread.

 

Thanks,

 

Neil. ;)


Edited by astroneil, 03 November 2014 - 10:26 AM.


#175 Starman1

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Posted 03 November 2014 - 12:49 PM

Therein lies the reason why thermal comparisons are sometimes difficult to make.

At the site where I observe, the temperature may go from 20C at 4pm to -10C at 11pm this time of year.

Under those conditions, most, if not all, scopes require some form of active cooling to even keep the optics

in the same ballpark as ambient temperature.  Even 5" refractors take a while to cool down.

For the observers who have a 5 degree C temperature change over the course of a night, thermal issues

are minor, and temporary.

It is the wide variety of observing conditions that makes it hard to generalize.




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