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Ridiculously high magnification on the Moon

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#1 magic612

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Posted 27 November 2012 - 11:02 AM

I have had a long focal length 6" mirror for several years. Finally got it nicely figured and coated about a month or so ago. Over the last couple weeks, I have been building a "prototype" tube for it - two concrete pier cardboard tubes, solidly taped together - so I can test the mirror and secondary. Oh, and about the secondary: I built a 3-vane, curved spider for it. At f/10.9, it's a pretty long tube with the additional I left on both ends to reduce extraneous light.

My dad helped me finish up the prototype this Thanksgiving weekend, and despite being realistically too long (though not too heavy) for my SkyView Pro mount, it was the only thing I had available, as I plan on building a split ring mount for it eventually. So I collimated the mirrors, put it on the mount, and aimed it at the Moon, starting with a 25mm eyepiece, yielding 66x.

Nice, SHARP view.

I kept bumping up magnification. First a 15mm EP. Then a 9mm, and a 6mm at 275x.

It was incredible at 275x. Still tack sharp.

Not having a 4mm or 5mm EP, and recognizing that the Moon is bright and might handle it anyway, I put my 3mm EP in there, producing 550x of magnification.

WOW!!!! :bigshock: :jawdrop:

To be honest, I don't even remember what part of the Moon I was looking at - northern area, somewhere near the edge of Mare Serenitatis, I think. It was around First Quarter, and obviously somewhere near the terminator. I was just simply blown away by the view, and my dad's jaw was hanging open like mine was. I don't think I've ever look at the Moon at that high a magnification before. 300x and 350x, yes, for sure. But this was just like a whole other level, and the well-figured mirror no doubt contributed the the amazing view.

What magnification(s) have others pushed their telescopes to when viewing the Moon?

#2 David Knisely

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Posted 27 November 2012 - 11:55 AM

I once did some tests with various magnifications and found that the overall view of the moon seems to "max-out" in terms of sharpness and detail at between 35x per inch of aperture and 40x per inch of aperture. It looks really big and impressive at even higher powers, but things like floaters and the lower light level start to make the view less satisfactory as you go too much beyond the 40x per inch level. Beyond 60x per inch, things start to look downright fuzzy, so I rarely go that high on the moon, although on some other objects like planetary nebulae or double stars, I have used considerably higher magnifications. I have used over 800x when viewing the moon in my 14 inch f/4.6 Newtonian, but quite frankly, I can see about the same level of fine detail at between 500x and 600x (and the view looks a little better to boot). Clear skies to you.

#3 Dave Mitsky

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Posted 27 November 2012 - 01:29 PM

The results weren't all that pretty but I've observed the Moon on a few occasions at over 900x with a 17" f/15 classical Cassegrain. Magnifications in the 600x range worked far better, as David mentioned.

http://www.astrohbg....ory_Tour.htm...

I've seen a number of planetary nebulae at magnifications of around 1200x through large Dobs belonging to fellow CAS members. NGC 2392 (the Eskimo Nebula) really is amazing when viewed at that kind of power.

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#4 Tim2723

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Posted 27 November 2012 - 02:38 PM

Yeah, it's a ridiculous thing to do. There's no sensible reason for it at all. That's what makes it fun though. I've gone well over 100x/inch on good nights.

I'll make my usual disclaimer for newcomers reading along: Don't run out and buy eyepieces to get these crazy high magnifications. This is just a fun game some of us like to play.

#5 magic612

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Posted 27 November 2012 - 02:56 PM

Tim, it definitely was a good, steady night. It had been cloudy earlier in the day, so the pavement wasn't releasing heat, and the atmosphere was steady overhead at night. I could just keep upping the power and it stayed rock steady. It likely helped that the Moon was higher up too, as my neighbor's garage was limiting the magnification I could apply to Jupiter to 184x the same night - as the planet was lower in the sky to the east.

I'm sure I won't be able to replicate it again any time soon, and no, I don't expect to be able to push it past 50x or 60x on most nights. But it was fun to do. And I don't recommend it for typical viewing either. ;)

#6 azure1961p

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Posted 27 November 2012 - 09:59 PM

Highest I went initially was 600x and change and it was wild to see Clavius a wide field spanning feature. Then about a year ago I put in a 4mm ortho and stacked my two Barlow's and had a whopping huge view of the Mare Crisium at 2042x. Naturally this was only seeing a part of this Maria. But the scale was nuts - the highland cliffs boardering this Maria were up close and personal. It was also a study in atmospheric refraction on a night of 3/10 seeing. Yes this was excess unchecked. For fun it was all that and thru an 8" mirror not as dim as you'd think. No practical application anywhere but a humorous exercise.


The moon through the 8" on the best nights seems to top out around 364x on the smallest craterlets tho floaters aside, 400x was nice too but again on the smallest details only where even at that mag they were still small. In practice I've never seen over 500x yielding an improvement and much beyond 400x was iffy. Typical seeing in CT makes 173x to 240x seeing the most use.

You sound like you have an impressive long tube newt but don't do what I did and wait years and years to install a full-time running fan. You truly need this and you'll see less flaring and fuzzings with it. And its so darn cheap. Paramount tip: seal the rear of the tube so the fan intake is forced to send it straight up the tube or you lose too much air movement up the tube tho in fairness even an open backed tube with a full-time fan is a big improvement. suspend the the DC computer fan (get a 4" not 3") with rubberbands and for starters get a nice blocky 6v DC flashlight battery. It'll last a decent while.

Nice to hear your efforts payed off. :bow: :)

Pete

#7 Moey

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Posted 28 November 2012 - 12:31 AM

I was up at 600X not long ago in my 14.5" dob. The views along the terminator were absolutely gobsmacking :D Unfortunately at the time that was the highest magnification I could go with my eyepiece line up. I purchase a 3x barlow the day after in hope that I would get another night like that and have had nothing but clouds since :(

#8 Tom and Beth

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Posted 28 November 2012 - 01:17 AM

One of my scopes is a 7" F10, home polished and breathed on to get a Parabola. And it's been north of the 75X/inch a few times ;) Sounds like you have a killer of a scope for Planets and Double Stars. Add in that the mirror will track temps nicely due to it's low mass.

Congratulations on such a fine instrument.

#9 Tim2723

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Posted 28 November 2012 - 08:00 AM

I purchase a 3x barlow the day after in hope that I would get another night like that and have had nothing but clouds since :(


That's one good reason you don't run out and buy gear to try to do this! :grin:

#10 Ed D

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Posted 28 November 2012 - 09:11 AM

6" f/10.9 - I'm green with envy! Anyway, I have exceeded 500x in my 6" f/8 but the heat waves were too much and the image seemed to fly through the field of view like a bat out of hell. I usually use around 160x to 200x, 300x tops and only for a short view of a specific feature. I second what Pete said about the fan. I installed a 12VDC 80mm fan on my Dob and use a 6V lantern battery to run it at mild speed. For observing fine planetary and lunar features it makes a world of difference.

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#11 Tim2723

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Posted 28 November 2012 - 10:25 AM

A fan is a good idea as is a driven EQ mount. Once you're over about 300 the Moon flies by too quickly and even the tiniest vibration from hand guiding makes life very hard.

#12 magic612

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Posted 28 November 2012 - 11:13 AM

Typical seeing in CT makes 173x to 240x seeing the most use.


Typical seeing in Illinois is much the same. I had a good night happen at the right time. :grin:

You sound like you have an impressive long tube newt but don't do what I did and wait years and years to install a full-time running fan.


Pete (and others who have mentioned the fan, along with an eq mount) this is just the first step. I should point out that I am surprised I saw what I did as clearly as I did, given that the concrete pier tubes I used are uncovered - meaning the waxed interior had every opportunity to bounce reflections all over the place. I have purchased some black posterboard to tape in place on top of the waxy ID - all temporary measures for now.

The fan is another addition to add, a long-planned one at that. I have a number of DC motors and fan units to try, from computer fans to radio-controlled airplane propellers and ducted fan units. This tube will serve as the "test prototype" for all of that. The mirror will eventually wind up in a Hastings aluminum tube, with Protostar flocking, and a fan unit that suspends its vibrations from the tube using several methods (to be determined, based on best results from my tests). And indeed, the battery in it will help counterbalance a number of things.

Cool to hear everyone else pushing the crazy magnifications too. I realize it doesn't improve resolution, but when the image size is that large, it sure is fun when the atmosphere cooperates. :jump:

#13 Asbytec

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Posted 28 November 2012 - 12:26 PM

What magnification(s) have others pushed their telescopes to when viewing the Moon?


My best view of the Cat's Paw was at 50x/inch. I didn't feel it lost any luster. Also, at that same magnification, tracing the limb was stunning. In good seeing, foothills descending on front of one another. Also, Plato crater-let challenge was done at 50x/in.

I have gone higher, trying to see the Alpine rille. Failed to see it, but power held up pretty well to mid to high 300x, about 60x per inch. I have gone even higher, to "stupid power" about 80x/inch or more. But, the view was getting quite dim, a little soft, and not worth it. Nothing new to see up that high.

#14 simpleisbetter

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Posted 28 November 2012 - 12:41 PM

If seeing allows I'm usually at least 200x on the Moon. And if seeing is really good, I'll push my C6R max of 375x (which would be just cruising along in my old 12" dob).

#15 mwt

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Posted 30 November 2012 - 05:09 AM

I'm limited to 300x due to my small assortment of eyepieces.

#16 killdabuddha

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Posted 30 November 2012 - 12:20 PM


Same as the others--600x @ 50x/inch with a Barlowed 4.7mm, but 400x (un-Barlowed and filtered) is almost always better.

#17 Sarkikos

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Posted 02 December 2012 - 01:21 AM

magic612,

Personally, I don't like "ridiculously" high power for lunar observation. It makes my eye floaters irritatingly obvious. I like to keep the exit pupil at about 0.8mm or wider (usually much wider). That's about 200x or less in my 10" f/4.8 Dob. The Moon is bright enough that - as long as the scope is well collimated and the seeing allows - you should be able to see fine detail at moderate magnification.

On the other hand, I have pushed the same scope up to 600x when viewing Mars at about 6 arcsec apparent diameter.

Mike

#18 RobDob

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Posted 02 December 2012 - 02:33 AM

Such is the beauty of the moon! Ridiculous high power and ridiculous low power, and everywhere in between, it always looks good!

Rob

#19 azure1961p

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Posted 02 December 2012 - 09:11 AM

It'd be great if Jrbarnett would chime in here. With well over 100 eyepieces he's gotta have some stacked Barlow experiences just for the fun of it - which is the threads jist anyway.


Pete

#20 simpleisbetter

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Posted 02 December 2012 - 09:38 AM

In Jim's case, his barlow stacking result might be him viewing the Earth from the Moon's surface.

#21 Astrojensen

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Posted 02 December 2012 - 01:33 PM

In Jim's case, his barlow stacking result might be him viewing the Earth from the Moon's surface.


Yeah, from the far side. :grin:


Clear skies!
Thomas, Denmark

#22 Sarkikos

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Posted 02 December 2012 - 07:07 PM

Such is the beauty of the moon! Ridiculous high power and ridiculous low power, and everywhere in between, it always looks good!

Rob


Yep. For lunar observation, there is a level of image scale to suit everyone!

Mike

#23 azure1961p

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Posted 02 December 2012 - 07:52 PM

LOL, I dont know if it looks GOOD but its a fun exercise.

Pete

#24 Brian Albin

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Posted 05 December 2012 - 03:49 AM

My calculator says 550/6 = 92 diameters per inch of aperture. That is excellent performance. I should like to have a scope like that myself. I imagine the slow focal ratio is responsible, as Newtons get a lot of coma at the faster ratios.

#25 Sarkikos

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Posted 05 December 2012 - 07:09 AM

You can always bump up the power. But will you see any more detail than at a more moderate magnification?

Mike






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