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#51 payner

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Posted 01 August 2014 - 03:57 PM

Hi Neil: Thought I'd jump on this train, albeit late. I am a fan of both apochromatic refractors and MCTs (preferring the RuMak design of MCTs). Nevertheless, I've owned the Gregory Mak, too, and found it to be a worthy variant (original) of the Maksutov design. These telescopes are especially great for solar system objects, double stars and DSOs that fit the FoV (few DSOs will not [compared to the number that will]).

Enjoy your newfound Cornelia. She will inspire.

Best,
Randy
 

#52 astroneil

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Posted 01 August 2014 - 05:11 PM

Hi Randy,

Thanks for the thumbs up!

You know, I figured that it might be more instructive and educational if instead of producing a bona-fide review, I would provide a live feed instead, in order that others may learn from my experiences. So, if you'll permit me; here we go!
Feel free to check my local weather: Stirlingshire Scotland.

Clear sky again tonight. Little or no scintillation. I reached for the largest telescope in my possession; Cornelia.

Instrument set out at 21:30h local time
Temperature; 15C, 1004mB, rising. No wind.

22:08h Epsilon Lyrae tracked down in twilight. All four components calm and razor sharp at 113x but much better seen at 226x.

22:27h: Delta Cygni; Incredible! You coud drive a truck through the components at 227x.

22:42h; darker sky allowed me to track down Pi Aquilae( ~1.5"). Easy as pi :lol:
22:49h: Lambda Cygni (0.9"); companion plainly seen at 340x. Very impressed with how bright the images are in comparison to my 5" glass.

I have a makeshift dew shield for Cornelia but no dew heater. I never use them. I worry that it might destabilise the images. There may be nothing in this. What do you think?

Out again to gaither mair wheat.

Mair anon.

Thanks

Neil. ;)
 

#53 astroneil

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Posted 01 August 2014 - 05:25 PM

23;20h
Zeta Herculis well past meridian passage in west south-west.
340x delivered a beautiful image. Primary intensely bright, faint companion associated with a diffraction ring; cannae mind which one (second?) Will do the math later.

S.W Burnham would have been proud of this telescope! Powerhouse!
 

#54 astroneil

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Posted 01 August 2014 - 05:41 PM

23:39h

Iota Cassiopeiae:Showpiece triple. Superb at 340x, calm refractor-like image rendered.

Is this an f/15 'scope then?
 

#55 astroneil

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Posted 01 August 2014 - 06:10 PM

00:03h Gamma Delphini; peach! At 340x the Airy disks are solid, slight shimmering of the Fraunhofer diffraction rings but nae bother; comely as they come! Backed down to 226x. The fainter member is just sightly greener to my eye, the primary radiating the colour of ripened corn.
 

#56 astroneil

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Posted 01 August 2014 - 06:36 PM

00;24h

Mu Cygni: a corker at 226x

Went back to Delphinus and pointed the instrument at a patch of sky just southwest of Epsilon Delphini. My friend, Der Admiral, alerted me to a system known as BU 63. The primary is magnitude +6.2, the secondary +9, separated by a mere 0.9". One hell of a challenge!

Gave it a go but got lost, then the finder dewed up. Sorry John.

There will be other nights though.

Final temperature recorded at 00:46h @ 11C

Time to turn in now.

Thanks,

Neil. ;)
 

#57 Ed Holland

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Posted 01 August 2014 - 07:49 PM

Good luck mate!

Am in Oxford at the mo, with only 10x50 binos and thick clouds. Ironic.... now I have time, no telescope to hand...

Thanks for the reports,

Ed
 

#58 astroneil

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Posted 02 August 2014 - 06:17 AM

Mornen All,

Ed, some time away from a telescope can do you the world of good. Besides, Oxford is an inspiring place to be.

Some comments about last night:

The instrument displays a small but wholly acceptable amount of image shift while focusing. Not an issue for me though.

Maksutovs are rugged telescopes and collimation hasn't flinched since I acquired it.

The locus of the first diffraction ring from the Airy disk is 185/D where D is the aperture in mm. Thus, if I saw the secondary to Zeta Her on the first ring - as I now think - its angular distance from the primary is 1.02". No' bad, ken. But my source says 1.1". Something interesting occurred to me when I set the formula to find D for a 1.1" separation. Thus 185/1.1 yields 168.2mm. Then I remembered a review on a lady's website from the UK where she talked at length about the same (albeit Sky Watcher incarnation) telescope and reckoned the actual true diameter was nearer 170mm than 180mm;

http://www.astro-bab... 180 Review.htm

I wonder whether, in light of my calculation and the lady's findings, there is any truth in this assertion?

All in all, an excellent night of testing and as always a joyous experience.

Big Mak: I'm luvin it.

Cheerio the noo,

Neil. ;)
 

#59 astroneil

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Posted 04 August 2014 - 10:44 AM

My achromatic culture won many medals o’ achievement, trophies that were lovingly arranged on the mantle piece o’ the astronomical pantheon. But when these telescopes got large, they quickly became too unwieldy. Professionals left them behind but amateurs didnae. Other designers resolved tae make them mair portable by introducing other very expensive gless prescriptions that made them shorter. But at what expense?. These are the apochromats, the poodles o’ the amateur world. But the poodles stole some medals fae the achromatic mantle piece, passing them off as their ain, and I resolved tae hunt them doon and retrieve them, one by one.

 

And that felt guid, ken. ;)

 

Yet, Cornelia, wi' her ingeniously simple design is mair portable than any poodle in the same aperture class. She wins hands doon. I need tae get a containing vessel fur Cornelia, so that I can take her on excursions tae places in Caledonia where I ken fae experience that the seeing is excellent. Does awbody ken a retailer in the UK where I can purchase a hard case that’ll fit her? Then I’ll no’ be clogging up valuable space in me car tae sate me appetite fur refractor aperture.

 

I love my Gregory-Maksutov-Bouwers-Schmidt-Cassegrain-Gregory telescope. :flowerred:

 

 

Eye


Edited by astroneil, 04 August 2014 - 11:44 AM.

 

#60 astroneil

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Posted 04 August 2014 - 12:59 PM

Stay tuned,

 

Taste o' winter the nicht, ken.

 

Temperatures tae fall to 4C in the glen according tae the forecast.

 

Test everything; assume nothing. ;)


 

#61 Ed Holland

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Posted 04 August 2014 - 02:05 PM

For aperture, there are other tests you can make. I have found the "flashlight" test very reliable on my telescopes, and it is easy to perform. I verified it against another method whilst evaluating my Mak, to within about 1/2mm of uncertainty. I'll see if the new search turns anything up, otherwise will post a description of the technique.

 

Cheers,

 

Ed


 

#62 astroneil

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Posted 04 August 2014 - 04:17 PM

I kept my lady oot o’ direct sunlight all day, as her dark surfaces absorb heat and radiate that heat poorly. But she weighs less than 20 pounds all in, so she should always acclimate; the laws of physics assure me of that. Only the seeing limits her capabilities.

 

After a late supper, I strolled doon tae the unheated shed where she’s stored, opened the door and removed the lens cap fae the instrument.

Instrument was set out on her mount at 9.30pm local time, starting temperature 11C.

 

1015mB, rising.

No’ much midgees; getting cauld.

 

Well, lady Cornelia is geein it laldy fae the start.

 

21:52h: Epsilon Lyrae: twilit sky, Temp 10C, nicely resolved and acceptably calm at 340x.

 

22:08h Epsilon Bootis, dusk, 10C, much lower in the west-southwest, companion easily resolved from primary. A tiny bit more shimmery, owing to lower altitude. Bonnie.

Race against time wi’ dew.

 

Mair anon


 

#63 astroneil

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Posted 04 August 2014 - 04:29 PM

22.23h, 10C

Delta Cygni: first good test. Companion seen well at 227x, seeing not as good as the other night, so no inclination to go higher.


 

#64 astroneil

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Posted 04 August 2014 - 04:40 PM

22:35h, 10C

Pi Aquilae (1.5") Not yet culminated yet but the pair were just discerned at 227x. Seeing and lower altitude hampering the view.


 

#65 astroneil

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Posted 04 August 2014 - 04:59 PM

23:50h, 9.5C

Lambda Cygni (0.9") examined at all powers up to 340x. Heewhaw sign o' the companion. Seeing seems to have bottomed out at 1.5-2".

Could always improve later, need to be there though, ken. ;)

 

A weather system moved through the region over the weekend - awbody seen the taps oan at Weegie Games? :lol:  Tail end o' a turbulent air mass.

 

Conditions guid enough for deep sky though. Need tae gi' her an' mysel a break the noo.

 

Will be back amarach.

 

Cheerio the noo.

 

Thanks,

 

Neil. ;)


Edited by astroneil, 04 August 2014 - 06:43 PM.

 

#66 astroneil

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Posted 04 August 2014 - 06:52 PM

Okeydokey: didnae think I'd be reporting back so early in the new day. :)

 

Some cloud moved in by 23:30h and I watched the temperature rise by one degree (10.5C) with no improvement in the seeing. The cloud slowly dispersed over the next half hour during which time I examined some wider pairs and just swept the holes in the sky fur treasure.

 

By 00:10h something dramatic happened, the stars started twinkling less energetically and I again turned the telescope on Delta Cygni. This time it was spectacular; very calm like in Tiberius, my classical refractor, but even more dramatic owing to its superiority in resolution and light gathering power.

 

00:22h: temperature falling away again and now at 9.5C. Lambda Cygni companion seen distinctly at 340x. Fab!

 

Need to rush away again tae see if I can find BU63.

 

See you all later.

 

Thanks,

 

Nelly ;)


Edited by astroneil, 04 August 2014 - 06:56 PM.

 

#67 astroneil

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Posted 05 August 2014 - 07:06 AM

Afternoon all,

Ed: I haven’t followed anything up. I’m not overly fussed about a slight drop in aperture but I suppose the smaller models should be checked for true aperture.

 

 

00: 45h (9C) I was unsuccessful yet again with Bu 63. I am not sure it was even the right star. Will try again.

01;15h (8.5C): My final high resolution test of the evening was 36 Andromedae, by now a good altitude in the east; a pair of 6th magnitude stars separated by 1.06”. The Maksutov showed the deep yellow pair beautifully.

By 01:30h, the temperature had reached 8C and the seeing was beginning to deteriorate again as judged by the degree of scintillation. With the first quarter moon by now long set, the sky looked gloriously dark and the Northern Milky Way through Cygnus was magnificent.

The slow drop in temperature had no effect on the efficacy of the large Maksutov. Only the changing seeing conditions limited its capabilities.

How much of the ‘thermal issues’ associated with these telescopes are attributed to;

1.            Ill-preparedness?

2.            Laziness?

3.            Wilful scare-mongering?

 

Refractors should not hold a monopoly on high resolution double star targets. The Maksutov appears to be a fine instrument for doing such work, as well as an optimised Newtonian. These are conclusions that have been reached by other experienced observers.

It’s not rocket science!

An unsettled spell of weather ahead.

 

Thanks,

 

Neil. ;)


 

#68 payner

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Posted 05 August 2014 - 04:10 PM

Hi Neil: Good report and, like you, having both refractors and MCT the MCTs are great for any solar system and most deep sky objects.  I primarily observe the planets, double stars and PN; the long focal length is a plus.  The use of longer focal length oculars is a tangible 'luxury' in my opinion.

 

I'm enjoying following your experiences with this design.  Clear skies and keep the findings coming.

 

Best,

Randy


 

#69 Asbytec

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Posted 06 August 2014 - 09:17 AM

Sweet scope, Randy. Don't mind me whilst I drool...

 

I actually discovered planets, lunar, and doubles (and old favorites, the planetary nebula) with my smaller MCT, absolutely some of the finest observing I can remember.


Edited by Asbytec, 06 August 2014 - 09:19 AM.

 

#70 astroneil

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Posted 06 August 2014 - 11:00 AM

Hello,

 

I understand the Rumak has an adjustable secondary that introduces another degree of freedom over a Gregory Mak. This results in lower spherical aberration, an even flatter field with better correction of off-axis aberrations and slightly smoother optical surfaces. The English Radio astronomer and amateur observer, Professor Ian Morrison, wrote a review for the magazine I write for, ‘Astronomy Now’, about one such instrument provided by Altair Astro, UK. Sounds as though he very much liked the design and highlighted the relative unwieldiness of both the Mak-Newt and a poodle of this size in comparison to the 6-inch Rumak;

 

http://www.altairast...gazine-2010.pdf

To be honest though, the stellar images delivered by my Gregory Mak seem bonnie enough to my eyes that I don’t know if the extra dosh incurred in acquiring a Rumak would confer any practical advantage over what I already have.

 

You see, my telescopic ancestors, whose skill with the telescope greatly exceeded my own, would have marvelled at this large compound telescope in my possession and its already excellent optical correction.

 

Maybe I’m different to other folk in that I’m happy with ‘good enough.’

Is there anything wrong with that?

 

I came across this bloke’s website where he waxes lyrical about the ingenious design of his 150mm Orion Mak as a giant telephoto lens. He doesn’t seem to be interested in the sky all that much but has taken many fine images of birds.

 

Geein it laldy wi’ a big Mak an’camera:

 

http://www.billmajor...Lens/index.html

 

Thanks,

 

Neil. ;)


 

#71 astroneil

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Posted 06 August 2014 - 11:31 AM

My editor at 'Astronomy Now' has commissioned me to write a full review of my 180mm Maksutov. :flowerred:

 

Braw!

 

Need tae reach the widest possible audience, ken.

 

Thanks,

 

Neil. ;)


 

#72 payner

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Posted 06 August 2014 - 04:34 PM

Hi Norme: Thanks for the compliment on the Santel, I was very fortunate to find this for sale about five years ago.  It makes me a happy observer, as your MCT does for you.

 

Hi Neil: I was not implying you have an 'inferior' MCT to another variant of the design.  I detest that type of stance, I know I'd be quite happy with your MCT if I needed one.  I had a Meade LX200 GPS MCT (7") and loved the views I got through it.  I sold it, reluctantly, but after I acquired the 9" MCT I could not justify keeping both.

 

I look forward to your coming review.  I enjoy reading "Astronomy Now" when I can find a copy; they are always a month behind in distribution in the US when they can be located.

 

Best,
Randy


Edited by payner, 06 August 2014 - 04:35 PM.

 

#73 dweller25

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Posted 06 August 2014 - 05:15 PM

Hello Neil, so you had a minor deviation in telescope direction  - I say minor as I regard Maks as folded refractors :)

 

My preferred weapon of choice is a 5" refractor and I would love a 6" refractor but they are heavy and expensive so I have been looking for something that would give me a little more planetary performance than the 5" without breaking the bank or my back.......

 

Bought a 7" Mak, with a fan in the back, I could sit behind it like a refractor and it was comfy. The views are very good BUT it did not outperform my 5" refractor. It's a keeper though as it only weighs 7kgs.

 

Still chasing the perfect scope dream I bought an 8" mak with two fans in the back right at the limit of my weight threshold and it is giving very nice views - have not fully tested it against the 5" refractor but this winter it will be pointing at Jupiter a lot.......

 

Like you I also find the first diffraction ring much stronger than in the refractor and I never use dew heaters - too unsettling - I use a long homemade dew shield made from a camping mat.

 

I think you will find that you will have to put some effort into thermal management in the winter months - worth the effort though......


 

#74 astroneil

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Posted 07 August 2014 - 05:49 AM

Good morning,

 

Randy; I also detest the mindset: "my telescope is better than yours." I was merely pointing out that I would be quite content with a Gregory Mak irrespective of whether the Rumak might provide slightly better images.

 

We're always looking around, seeing if the grass is greener somewhere else. We lust after better designs and the more we do, the more it corrodes our basic and good intentioned objective- to go out and observe.

 

Dave: Thank you for your comments. Much as I would like to think of Cornelia as a refractor, I think it would be more productive for me going forward not to do so. Cornelia is a catadioptric, a compound telescope, combining the best properties of reflectors and refractors. I also have a very fine 5-inch refractor of classical pedigree and not a Tak like yours.

 

Yet, much as I love my refractor, my observations on double stars and a few of the brighter deep sky objects show that the 180mm compound has outperformed it. I have already provided test systems for others to evaluate. This also agrees with the basic laws of optics; aperture wins when conditions are good and the optics are working at or near optimally.

 

Regards,

 

Neil. ;)


 

#75 astroneil

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Posted 07 August 2014 - 06:47 AM

I have not looked at the Moon or planets through Cornelia as yet, though I am very much looking forward to doing so.

 

I spent some time perusing a number of books written by highly experienced observers on the subject of lunar and planetary 'scopes. The results were interesting in that, while there is some consensus of opinion between them, there are also some divergences.

 

In his book, "Observing the Moon," (2014) Gerald North discusses the various designs of telescopes best suited to 'serious' lunar observing.

 

North's first choice is a Newtonian of 10" aperture and a relative aperture of f/6. His second choice is a 5" classical refractor with a relative aperture of no less than 12 or an apochromatic refractor of f/8. "Not far behind these," according to North, he would recommend a Maksutov no smaller than 6 inches and no larger than 8 inches. The author feels that thermal issues would impede using a larger one. Last, North states that he "would not be happy" with a SCT of less than 8 inches of aperture.

 

Fred Price in his book, " The Planet's Observer's Handbook" extols the virtues of Newtonians in the 6-10 inch aperture range for planetary study, especially since they are relatively inexpensive. He states that are 'tried and trusted.....and deservedly popular." Furthermore, he advises folks to "stay away from catadioptric telescopes." I do note however that his book, in its second edition, was published in 2001, so he may not have experienced the full panoply of mass produced catadioptrics available to amateurs today.

 

Perter Grego, in his book, 'The Moon and How to Observe it' (2005) is also very enthusiastic about the Newtonian with decent f ratios, although ultimately, he avoids giving his own preferences. He recognizes, as I do, that refractors require the least maintenance but are aperture limited. However, he states that while MCTs and SCTs are superficially similar, " MCTs tend to be far better performers for the Moon and planets." Grego attributes the advantage to MCTs as being due to their longer focal length, higher contrast and better correction of spherical aberration.

 

What can be said of these opinions?

 

Thanks,

 

Neil. ;)


 






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