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Evaluating a Large Maksutov in the Field

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#176 schang

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Posted 03 November 2014 - 02:15 PM

I am late in reading this thread... though I have opined in the grab-n-go scope in the refractor forum a while ago that my GnG scope is a C90 Mak for quick observation of planets, double stars and terrestrial landscope.  Granted, it is small, not a 7" Mak for light grasp or resolving power, but it has all the attributes describe previously,  without the weight and cool down penalties. And it cost much less.   I do have several binoculars to make up for the wide field viewing, and a 10" dob for light grasp viewing.  The cost and portability considerations were the main reason for me to go for this baby rather than a 80mm APO.  No regrets :cool:  here so far.

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Edited by schang, 03 November 2014 - 02:15 PM.


#177 jrbarnett

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Posted 03 November 2014 - 04:26 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.

You, you, you willful scaremonger, you!

 

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Edited by jrbarnett, 03 November 2014 - 04:38 PM.


#178 astroneil

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Posted 08 November 2014 - 07:16 AM

Date: 08.11.14

Time: 0300-04:00h

Ambient: 8C (unchanged throughout vigil), 989mB, rising. 91% humidity. Wintry periodic showers blown in by westerly winds.

Seeing improved somewhat, as evidenced by the images of double star tests in an acclimated 5" f/12 refractor and a 7 inch f/15 Maksutov Cassegrain.

The latter instrument was taken straight outside from an unheated shed, with no thermal issues.

 

Object: Jupiter.

 

Filter worked commenced. Optimal magnifications established.

 

 

Result: Habemus victrix!

 

Thanks.

 

Neil. ;)



#179 Asbytec

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Posted 08 November 2014 - 08:34 AM

Habemus victrix!

 

 

Cornelia, I presume?



#180 astroneil

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Posted 08 November 2014 - 08:40 AM

I had a good night last night. I set up my two instruments; my 5" f/12 refractor and my 7 inch SkyWatcher Maksutov about 01:30-45h initially ( temperature recorded at 7.5C at this time) just to see what Jupiter looked like. To my delight, I found that the seeing had improved from my previous vigil. Still, Jupiter was quite low at this time, so I packed away the 'scopes and set my alarm clock for 0300h and began more observations of the planet. Vigil ended at 04:00h ( temperature 8C).

 

This time there was a clear winner; the 7-inch Maksutov.

 

The image of Jupiter was magnificent! At 225x (it was too bright at 160x) seemed to be the best under the prevailing conditions (good but not excellent) but it was enough to show the superiority of the larger aperture telescope nonetheless. Both the SEB and NEB were of roughly equal intensity and a wealth of fine structure seen clearly in the Maksutov whereas they were only glimpsed in the 5 inch refractor. The same was true of the polar hoods of the planet. No interesting satellite phenomena recorded at this time however.

The unfltered image in the Maksutov was very bright to my eye, as I have seen before with a few 6 inch apochromats. I started with a variable polarising filter, which cut the glare fae the planet doon somewhat without changing the colour balance of the various atmospheric features (it cuts all visible wavelengths equally). The inclusion of the filter produced beautiful images to my eye.

 

From my notes and memory of testing a variety of apochromats in the past ( a Meade 127mm doublet f/9 ED, an Astrophysics 130mm f/6.3 triplet apochromat, an iStar 152mm f/7.5 fluorite triplet apochromat and an APM 152mm f/8 Super ED doublet ( not the 'econo' model) ) that the views in the Maksutov are strikingly similar in performance to a 6 inch apochromat.

 

This is indeed an impressive result from such a cost effective instrument and based on these tests it is destined to become my preferred planetary 'scope. Only under sub-optimal conditions are the 5" f/12 and 7 inch Mak comparable but it's not really worth mentioning, as no good planetary work can be made under those conditions.

 

Later in the season, I will be acquiring a 203mm f/6 Dobsonian to compare with the above but even if the Dob pulls ahead, the ultra portable Mak will remain in my stable. I am so very glad I acquired it at such a modest (secondhand) cost.

 

Eye,

 

Neil. ;)


Edited by astroneil, 08 November 2014 - 11:33 PM.


#181 astroneil

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Posted 08 November 2014 - 08:42 AM

 

Habemus victrix!

 

 

Cornelia, I presume?

 

Yes; Cornelia Victrix!.

 

Best,

 

Neil. ;)



#182 Asbytec

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Posted 08 November 2014 - 01:57 PM

From my notes and memory of testing a variety of apochromats in the past ( a Meade 127mm doublet f/9 ED, an Astrophysics 130mm f/6.3 triplet apochromat, an iStar 152mm f/7.5 fluorite triplet apochromat and an APM 152mm f/8 Super ED doublet ( not the 'econo' model) ) that the views in the Maksutov are strikingly similar in performance to a 6 inch apochromat.

 

 

Excuse me while I duct tape my jaw shut. It tend to drop to the floor sometimes. This thread should erupt any time now. I have some really nice views of Jove, too, with plenty of bright low contrast detail seen with patients and calm conditions. And the same problem with my jaw.

 

You know, Neil, for the brightness issue, I like a bit more magnification from 30x/in closer to 40x/in rather than a filter. Try it. You lose a little on the perceived contrast of a bright image, but those small low contrast details really come into their own. I suspect is something similar to observing planetary nebula at higher power. They're dimmer, but their contrast features span more of the eye's retina and, I think, they register more easily. I suspect this is at work on the planets, as well, even though we're in mesopic or photopic rather than skoptic vision.



#183 astroneil

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Posted 08 November 2014 - 04:23 PM

Hi Norme,

I would never claim to be a 'die hard' planetary observer. I spend most of my time looking at doubles. But I do love to look at Jupiter though. Who doesn't?

 

My not too infrequent use of achromatic instruments over the last few years has accustomed my eye to dimmer images and in searching the historical literature discovered that - with some interesting exceptions - the mean power many amateurs using achromatic refractors gravitated towards was of the order of 30x/ inch aperture. Above apertures of 8 inches or so, the mean fell back a bit.  And I found this figure worked well with the 5" f/12, where I enjoyed some excellent images employing a power of 154x (also 30x/inch) on that instrument. Above that magnification, the image become a tad too dim, and was exacerbated by using any kind of filter.

That said, there were some interesting exceptions to this trend and many came from the users of the new silver-on-glass reflectors, who indeed employed higher powers per inch.

 

I love to experiment with my visual system and consider filters of various kinds worthy tools to carry with me on that journey of exploration.  I can't wait to thread a light blue 82A filter into the zoom on a night of very good to excellent seeing. I’ve found it’s great for picking out very fine banding at higher and lower latitudes away from the main belts, whilst retaining a high overall light transmission – very important in a five inch aperture.

 

Last night, the seeing was only average, but it was clearly enough to show that the Mak is operating nearer what I'd expect from a 6-inch glass than its 5-inch counterpart under the same conditions. You see, I can draw all the details seen in the 5-inch, but I cannae draw the details served up in the 7 inch.

 

I did indeed crank up the power some more but the conditions wouldn't cooperate. I will try this again on a better night. But I will say this; delicate little bands that look grey in the achromat were revealed to be a very pale shade of brown in the Maksutov. Features that appear almost monochrome in the smaller instrument are shown in the larger to possess fine gradations of colour.

 

Achromatic refractors are good at recording ‘contrasts’ but the perfect achromaticity of speculum reveals ‘authentic’ colours.

 

My experiments will continue.

 

Regards,

 

Neil. ;)


Edited by astroneil, 08 November 2014 - 11:16 PM.


#184 kcb

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Posted 08 November 2014 - 07:55 PM

the views of jupiter last close approach with my apm designed  6 '' f/8 e.d doublet apo ( econo ) refractor were up there with the best views,and with the huge feathertouch focuser you can get as sharp as can be,i could not imagine i would need an orion 7'' maksutuv,too much glass for my liking, the apm designed refractor gives me the wide range of rich field to high power ( and in the same weight category as the orion 7'' maksutuv),in that range it gives you an all purpose scope for that aperture with stable views  , and somebody who wished me good luck on my apm designed 152mm e. d doublet f/8 apo refractor purchase i must say thankyou as the luck was on my side !( a reasonably priced apo refractor that is not just a sight to behold through the eyepiece but a sight to behold to look at ),from the double star cluster with a 2'' 31 nagler to delta cygni with a 2'' 3.7 ethos,it has the whole range in that magical 6'' aperture of no obstruction,happy observer :waytogo:


Edited by kcb, 09 November 2014 - 09:14 AM.


#185 astroneil

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Posted 09 November 2014 - 05:09 PM

Date: 09.11.14
Time: 21:45h
Ambient: 3C, 1002mB, rising, 100% humidity. Intermittent fog.

 

Seeing excellent! Ant I for stars high in the sky, as evidenced by sub-arcsecond splitting of Lambda Cygni in both my 5” f/12 classical refractor and my 180mm Maksutov at 286x and 340x, respectively, from my back garden. The Maksutov was again taken directly outside from a dry, unheated shed and immediately assessed for performance. It achieved these splits right from the get go. I then turned both instruments on an early rising waning gibbous Moon; its low altitude showing a very minor amount of turbulence but details were razor sharp in both instruments at high powers. A magnificent desolation!

 

Plato re-examined for craterlets. A, B and C detected in a neat little triangle in the 5 –inch but seen more distinctly in the Maksutov at 340x.
D ( ~2 kilometres) remained more elusive in the 5 inch but clearly seen in the larger Maksutov. Exciting stuff!

 

A good night ahead if the fog – the finest filter of all - continues to play its magic; more to come.

 

Thanks,

 

Neil. ;)



#186 kcb

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Posted 09 November 2014 - 05:19 PM

interesting stuff, sounds like the maksutuv is almost on par with my 152mm f/8 e.d apo refractor but like i said ( almost ) ! out observing last night as well, no technical vocabulary needed just textbook views :grin:


Edited by kcb, 09 November 2014 - 05:37 PM.


#187 astroneil

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Posted 09 November 2014 - 06:18 PM

 out observing last night as well

Good for you Kev. :waytogo:

 

That's what it's all about, right?

 

Best,

 

Neil. ;)



#188 Procyon

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Posted 09 November 2014 - 06:22 PM

Hi astroneil, what type or focal length eyepieces do you use every session, would be fun to know! Good stuff, thanks.



#189 astroneil

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Posted 09 November 2014 - 06:47 PM

Hi NorthWolf,

 

I use just two with the Maksutov; a 32mm Skywatcher Plossl for the 'plenty tae see in half a degree' feeling and my ergonomic Mark III 24-8mm Baader Hyperion zoom with its short and neat little screw-in  2.25x Barlow for more power as and when required.

 

Thick fog the noo; cannae see heehaw.

 

Best,

 

Neil. ;)



#190 astroneil

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Posted 10 November 2014 - 08:33 AM

Alas, the excellent conditions yesterday evening were not maintained, the sky remaining misted out for the remainder of the night, but yet again, I  was provided with good observational evidence that the larger aperture Maksutov is superior to the 5" f/12 under good to excellent conditions.

 

I have little or no appetite to continue this particular thread and wish to end it here.

 

I believe I have provided sufficient evidence of the telescope's character (exposing  its supposed 'thermal issues' as mostly hype) under a wide range of observing conditions to enable people to make a more informed decision about its capabilities.

 

I wanted to include some observations of targets in Orion but this is not the place to discuss them. My apologies for this.

 

But that is not the end of the matter.

 

I wish to cultivate a richer portfolio for this telescope and, in this capacity, I will retire to the sketcher's forum (to be initiated soon) where I will report my continued experiences with the instrument under the night sky.

 

 

 

Thanks and farewell,

 

Neil. ;)


Edited by astroneil, 10 November 2014 - 08:44 AM.


#191 kcb

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Posted 10 November 2014 - 07:31 PM

thats great,the only thing sometimes with sketching is that people tend to over exaggerate, i will follow and evaluate in comparison to my 152mm e.d f/8 apo



#192 astroneil

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Posted 24 March 2015 - 07:26 AM

Sha la la la la la DDay :lol:



#193 Eric63

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Posted 24 March 2015 - 10:27 PM

Hey Neil

I had my 127mak out tonight. I had not used it since last fall (I usually put it away when the deep freeze arrives). The view was simply stunning. I did not realize how much I missed that scope :) I also discovered the joy of double star observing tonight. That scope is the little engine that could.

Eric

#194 ChristianG

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Posted 24 March 2015 - 11:12 PM

Hi all.

 

Since we're talking about the 180 Mak, here's a little comparison. Tonight, temperature was about -5 C and my 180 Mak f/15 had been outside for 3 days under a tarp on my balcony. Still, as I found out this winter, it may not be in equilibrium, the whole thing being under the Sun all day. So I removed the tarp, pointed the corrector down, removed the dust cap (well, it fell...) and let it air out with the diagonal attached. About 20 minutes later I started to observe. Very steady. I checked on a star, and out of focus there was no trace of tube/mirror currents--just atmospheric turbulence.

 

Jupiter was on the menu. So at prime focus with a Neximage 5, 1000 best frames  processed with Registax 6, see image below. I had my little Lunt 70ED f/6 out, and imaged Jupiter as well with a 2X Explore Scientific focal extender (not a barlow!), same camera and processing, second image (this was intended for a fellow asking about what can be seen in a 70 mm telescope). Notice that the GRS had rotated out of view between the two images! A 10 hr day is short...

 

One thing I am happy to have bought (used) is a Sky-Watcher HEQ-5. It is the minimum capacity mount that can hold the 180 Mak steady enough for imaging, and that's for planets where you collect videos. I have not tried it on deep sky objects yet, this will have to wait for snow to melt in the parking lot near Meech Lake... Cheers!

 

--Christian

 

video0002.jpg

 

video0018.jpg


Edited by ChristianG, 24 March 2015 - 11:15 PM.


#195 Eric63

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Posted 25 March 2015 - 06:42 AM

Very nice images Christian

 

It was a nice evening for viewing out in the Orleans area yesterday. The temperature was just around freezing so it was quite bearable (especially after the long winter deep freeze we had) and the sky was surprisingly calm (not great, but good). The GRS was clearly visible in the early evening, in fact the view visually in my 127Mak was very similar to your second picture.  I kept the Magnification at 150X most of the evening but was able to get the odd good glimpse at 170X and even 190X.  

 

Lets hope that we continue to get nice weather from here on.

Eric

 

Meech Lake area eh? Is it nice and dark there?  I ususally go to an old quarry near Navan where I can get Mag 5 skies.  I also will go up to the Mont Ste Marie area once in a while and get mag 6 to 6.5 skies.


Edited by Eric63, 25 March 2015 - 06:47 AM.


#196 astroneil

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Posted 25 March 2015 - 08:13 AM

Hello Eric,

 

I'm so very glad you're enjoying the 127 Mak. I have never used one personally but the overwhelming majority of folk that have used one speak very highly of it. I hope it continues to give you many years of observing pleasure.

 

 

Hello Christian,

 

Thank you for your posts and for those images. Looks like you've been able to manage the telescope's acclimation very well in temperatures significantly colder than where I live.

 

I just wanted to provide some feedback on my progress over the last several months with the Orion 180mm Mak. I have spent many hours this past winter observing in sub zero temperatures (down to about -7 or -8C) and the instrument has performed admirably. I have seen no need to actively cool the 'scope.

 

Sometimes I have to teach late into the evening (until 9pm) and so my office has to be heated throughout this time. But on such evenings I just set the instrument outside on the pavement in my back garden with the caps on and let it cool for about an hour. This strategy has worked really well for me. Indeed, just last night, I was observing mighty Jupiter with my Mak. I made a quick sketch of what I observed (see attached).

 

Time: 23:05-15 UT

Seeing: I-II

Temperature: -2C

Jupiter: CM II 200 degrees

 

The air was nice and tranquil and though the planet had lost some altitude as it had passed culmination in the south, the image was clean, stable and bright at 190x, tack sharp and full to the brim with low contrast details. The background sky is pleasingly dark.  It is a first rate planetary telescope and optically leaves little to de desired. It is also incredibly robust; never once have I needed to recollimate the instrument.

 

I found an old review of an Intes 7" f/15 Mak that dates from 2005: the reviewer compared his Maksutov to a 5" f/15 refractor on Jove and the Moon and concluded that the former was the easy winner in good conditions.

 

http://www.cloudynig...15-deluxe-r1009

 

 

I have concluded the same thing in my own tests with a 5" f/12 refractor.

 

Finally, I am also aware of two optical  tests which were carried out on the Synta 180 Mak;

 

http://forum.astrono...180/2700mm_MAK_

 

http://airylab.com/c... 2012-40001.pdf

 

 

 

Wishing you clear skies!

 

 

 

Neil. ;)

Attached Thumbnails

  • Jove 24.03.15.jpg

Edited by astroneil, 25 March 2015 - 04:16 PM.


#197 ChristianG

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Posted 27 March 2015 - 09:27 PM


Meech Lake area eh? Is it nice and dark there?  I ususally go to an old quarry near Navan where I can get Mag 5 skies.  I also will go up to the Mont Ste Marie area once in a while and get mag 6 to 6.5 skies.

 

Hi Eric.

 

I sometimes go to an empty parking lot in the Gatineau park because I don't want to drive too far. But sky isn't very dark... Near Mt Ste-Marie is an interesting idea! They have new mountain bike trails too. Quarry in Navan... Interesting too!

 

--Christian



#198 ChristianG

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Posted 27 March 2015 - 09:28 PM

Nice sketch, Neil! I wish I could draw. I make great stick people though!

 

--Christian



#199 astroneil

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Posted 28 March 2015 - 12:55 PM

Nice sketch, Neil! I wish I could draw. I make great stick people though!

 

--Christian

Thanks Christian; neither can I!

 

Regards,

 

Neil. ;)



#200 Ed Holland

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Posted 03 April 2015 - 03:40 PM

Hi Neil,

 

Nice to see that you are still getting good results with Cornelia. Have you been able to observe any Jovian shadow transits yet? I was fortunate enough last week to have very steady skies. It also happened that the 127 (118)mm Mak was selected for viewing. In a couple of years of ownership, I don't think I've ever been so fortunate with the seeing with this instrument, let alone coincide with a transit. The detail was excellent, excepting the occasional atmospheric stir-up. Despite having been unused for quite a while, the Mak took up where it left off, and was perfectly collimated.

 

If I didn't have a good C8, a 7" Mak would be an enormous temptation.

 

Cheers,

Ed




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