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Mars magnification

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#26 Chucky

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Posted 31 October 2020 - 07:36 PM

Great stuff Jeff. Enjoyed. Yes I noticed the part "Seeing 10". Jealous of your Florida location and higher chances of such seeing.
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#27 visualastronomer.com

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Posted 08 November 2020 - 06:03 AM

Amazing drawings, Jeff!

 

Here's one of my sketches with larger apertures, made on October 13, with the 20-inch working at 425x. The pale spot at lower left is Olympus Mons.

 

Clear skies,

Ronald



#28 visualastronomer.com

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Posted 08 November 2020 - 06:06 AM

Sorry, wrong link, this is the correct one


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#29 WoodlandsAstronomer

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Posted 08 November 2020 - 06:19 AM

Proof is in the pudding when imaging Mars. Using SCT, 2x Barlow camera, I get a fairly large disk, can make out dark features generally, and can make out an ice cap generally, but nothing is sharp. This season I have shot many minutes of cam footage in the hope that lucky imaging would produce some fleeting moments of good seeing. Nope, 50 to 100k frames shot per session, best 5, 2, and 1 percent still looks bad. So lucky imaging exposes just how bad seeing is when you can’t even get precious few frames.

#30 Jeff B1

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Posted 08 November 2020 - 07:00 AM

Great stuff Jeff. Enjoyed. Yes I noticed the part "Seeing 10". Jealous of your Florida location and higher chances of such seeing.

Yes, seeing here is great a lot of the time.  It must help  he bugs because they observe with us. :) 



#31 Flaming Star

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Posted 08 November 2020 - 07:21 AM

I agree with the magnification, Mars supports well high magnifications.

From Belgium the real problem is the seeing.

 

I am using a Vixen 100mm x 660mm ED refractor and on 22 october 2020 around 19h23TU

I had my best view of Mars at a magnification of 194x wiht a Vixen HR 3,4mm Oc.

But i could also see that without the turbulence my Vixen HR 2,4mm Oc could give a great and usable magnification at 275x

 

My previous good views of Mars:

 

8 July 1984 with Vixen 80mm x 910 mm and Vixen Ortho 6mm magnification 152x

23 september 1988 with Dobson 150mm x 1200mm and Meade serie 4000 6,7mm UWA magnification 179x

16 december 2007 with Dobson 150mm x 1200mm and Meade serie 4000 6,7mm UWA magnification 179x

 

Last nights,  with my 100mm refractor, i was unable  to use more than a magnification of maximum 110x with my nagler zoom 6 - 3mm on 6mm.

 

Conclusion : Turbulence was always my limiting factor.

 

Clear Skies


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#32 davidc135

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Posted 08 November 2020 - 03:11 PM

My usual mag on Mars using an 8'' Meade sct in average seeing is a modest x160. In better conditions this can be increased to x270 whilst still keeping good contrast.  David


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#33 E_Look

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Posted 10 November 2020 - 01:12 AM

I'll second your observations on powers with Mars.  Mine is a Newtonian, but still also 8".

I've found that generally, Mars is still tack sharp at 150x ± 20x, but annoyingly small.

At 250x ± 50x, it's admittedly slightly softer, but the internal features are bigger and so more satisfying, as they are still quite resolved.



#34 Dave Mitsky

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Posted 10 November 2020 - 02:34 PM

The seeing was very good, comparatively speaking, on Saturday and Sunday nights.  I had some excellent views of Mars at 324 and 360x using the Naylor Observatory's 17" f/15 classical Cassegrain.



#35 luxo II

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Posted 10 November 2020 - 05:50 PM

Last night started at 250X in poor seeing, and increased to 350X as it improved somewhat but not great.



#36 JAC51

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Posted 11 November 2020 - 06:07 AM

Mars3rdNov2020Smaller.jpg Mars10thNov2020small.jpg

Interesting - explains my experience that after about 3 weeks of rain, and finally being able to observe Mars for the last 2 nights, I can barely detect any features - perhaps a large dark smudge across most of the planet ringed by a brighter rim?  Using 11 inch SCT with 26, 18 and two inch eyepieces and 9 inch 1.25 inch all with or without 2x Barlow i.e. magnifications ranging from 60x to 285x, in all cases it simply looks like a smaller or larger beautiful ochre-pink soft ball ...  amazingly large of course .. very impressive and all ... to get Mars that large in the eyepiece!  And it is so bright!!  Holding a red filter up to my eye (because red filters only seem to come in 1.25 inch) it perhaps makes the dark central area a tad clearer, although it could be my imagination ... the image is really only clear at the 60x magnification, when a faint darker smudge across the whole of the centre may be discerned/imagined.  

 

A week ago I used my 93mm triplet apochromat refractor at 57x and saw perhaps a faint dark line across one side of the planet, may be.

 

I suppose the seeing is just terrible?  One of those websites says the seeing is 2 at the moment.  It is only 4 or 5 sometimes at dusk or dawn, but

I can't see Mars then, because it is behind the hedge/neighbour's house. 

I have been using high x100's to low x200's on Mars the upper end limited local seeing here in the UK.  

I live about 50 miles south of your location in the UK and the sketches attached give some idea of what I have been able to observe on Mars with a 130mm Apo. Please forgive the roughness of the drawings they are literally early days for me.

 

Can ask what website are you using to estimate seeing in the UK?

 

Thanks John


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#37 Stefano Delmonte

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Posted 11 November 2020 - 05:15 PM

Hi, interesting post!

 

I live in front of Mediterranean Sea and like everywhere seeing rules, when a high pressure zone keep the atmosphere quiet I can push mag, with the C8 310x and an orange 21A or light red filter 23A .

 

But observing with a friend's C11 and my filters we pushed to 400x , really enjoyed the view of Valles Marineris and Olympus Mons between other features, here a edited photo in order to show the aspect of Mars at the C11.

 

IMG-20201018-WA0026.jpg

 

Now I bought the C11 to my friendlol.gif

 

Ste


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#38 BillP

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Posted 11 November 2020 - 11:00 PM

while observing with fellow amateurs using various telescopes, it appeared to me that most observers seem to use too low powers to really take advantage of the current large martian disk. Many adhere to outdated rules of maximum magnification with their scopes.

Magnification relative to aperture, or exit pupil, is very much a personal thing.  The rules that are out there, namely the 50x/inch or 0.5mm exit pupil, are there for a reason, mainly that for many people beyond this limit on a planet and one starts to lose the low contrast definition.  I routinely go above this limit for image scale convenience, but I also see the loss of detail when doing it.

 

For normal acuity eyes, direct vision has about 1 arcmin of resolution.  Some folks of course will have somewhat better, others somewhat worse.  In your case, with a 120mm optic which has a resolution of 0.96 arcsec in green light, to get that 0.96 arcsec resolution of the main objective seeable by the human eye you need to magnify that resolution number until it reaches 60 arcsec (i.e., 1 arcmin) which is what the human eye can just resolve.  So in your case that would be 60 arcsec / 0.96 arcsec = 62.5x (13x/inch aperture).  Magnifications beyond that point are essentially empty, however that is not a bad thing as it is just at the edge of the typical eye's resolution so more is needed to make it easier to see.  So to account for how people's eyes vary in resolution it is safe to double that and use as a rule of thumb say 25x/inch aperture.  So at 118x everything is easily there to be seen in your 120mm that can be resolved by your main optic.  But the story does not end there as sometimes, depending on the object, if it is very bight then the brightness can easily mask other features.  Increasing magnification more will dim the view allowing those features masked by the brightness show through.  From experience I have found on planetary viewing that going much smaller than 50x/inch will cause subtle contrast features to fade away due to the dimness.  But sometimes that may not matter depending on what features one is focusing on on the planet as they may want more image scale for those.  Planets like Jupiter, that have many subtle low contrast features, can't take as small/dim of an exit pupil as Mars and Saturn can.  So on Mars and especially on Saturn, using more magnification than 50x/in does not show loss of features (generally) as their features are very stark.  More so true for Saturn than Mars as with Mars I note the loss of subtle edge details on the Maria when the exit pupil gets much smaller than 50x/in.  Then of course if the seeing is good, but the humidity/water vapor or particulates in the atmosphere is high, then contrast is lowered due to that and even 50x/in can lose details.  So in the end it is all really an interplay of many variables relative to one's eye, the atmosphere, the components in the optical chain, and personal preferences that will determine maximum useful magnification on any given evening. 

 

So the rules are not laws, but just guidelines.  There are rational and and experiential reasons that those rules of thumb came to being from the collective experience of amateur astronomers over the decades.  But they are not hard and fast.  Bottom line is always to go as high as you can as long as the view is being productive for you.  IMO also good to know what the general limits are and why those limits are there so you can move forward beyond them with knowledge and insight instead of haphazardness so the observer becomes more adept at knowing where and when and why pushing the limits might be done without detriment.  Knowledge is power after all.  So IME the max magnification an observer can use for their scope is a moving target.  It will vary depending on many factors, some being outside their control like the atmosphere.  And all the various rules are not "rules", even though some call them that.  Instead they are general guidelines.  Observers IMO should know them, understand them, use them, exceed them when circumstances permit, stay below them when circumstances warrant.  FWIW, with my 4" Apo, on Mars, I use between 150x - 350x, just depends on many factors where the magnification ceiling happens to be on a particular evening.

 

Btw, on the Barlow issue (from your blog), I would say opposite and nothing wrong with using a Barlow to get to higher magnifications.  Any modern quality Barlow or Telecentric (i.e., Powermate, etc.) will not degrade the views.  And as we all know many modern eyepieces actually have Barlows already built into them, so the concept of using a Barlow element is not detrimental.  If one sticks with the name brands then the Barlow is likely well executed.  They are handy things to have in the eyepiece arsenal.  I have three in my case and use them all - 1.3x modified Meade 140 Barlow, 2x TV Barlow, 2.5x TV Powermate.


Edited by BillP, 11 November 2020 - 11:02 PM.

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#39 luxo II

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Posted 12 November 2020 - 02:15 AM

Magnification relative to aperture, or exit pupil, is very much a personal thing.  The rules that are out there, namely the 50x/inch or 0.5mm exit pupil, are there for a reason, mainly that for many people beyond this limit on a planet and one starts to lose the low contrast definition. 

This is highly dependent on the scope. APO's and high-end maks yes, but for SCT's and doublet achro's 50X per inch is definitely pointless.


Edited by luxo II, 12 November 2020 - 02:17 AM.


#40 BillP

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Posted 12 November 2020 - 08:23 AM

I would not call it useless, but definitely harder to reach.  As aperture increases getting to 50x/inch becomes less and less likely simply due to seeing.  If I had an 11" SCT then getting to 550x would be a super rarity as 1) local seeing would only allow that a few times a year, and 2) getting the SCT thermally stable enough to do that was a rarity as well.  With an anchromat however, your point is quite true for lunar/planetary due to CA, but it is perfectly possible for other targets.  I had a 6" f/6.5 achromat and I would often be able to go to 300x and more with it very productively.  Not on planets though, but on dense open clusters, globulars, and double stars all the time.

 

But for sure the 50x/inch rule is more for smaller aperture instruments that will not hit seeing limits as often at that magnification.  Larger than 6-8" and most likely the only rule or guideline that stands is whatever the local seeing permits.  Thanks for pointing that out. waytogo.gif


Edited by BillP, 12 November 2020 - 08:25 AM.

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#41 JAC51

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Posted 12 November 2020 - 03:51 PM

I can add that I am using Barlows all the time as well to push up the magnification, and eye relief from the Brandons I have. Currently my main planetary eyepieces are a 12mm and  8mm Brandon coupled with a x1.25 and x1.5 Magic Darkins giving me in effect a 12mm 9.6mm 8mm (twice)(x150) , 6.4mm(x187.5) and 5.3mm (x226)(exit pupil 0.57mm).

 

With my local UK seeing conditions I often find I alternate between  6.4mm and 5.3mm with a 130mm refractor or 37x to 44x per inch. The highest magnification I have used I ever have used has been about x300 on double stars, moon and Venus at the start of the year. Personnel circumstance and preference I suppose like so much.

 

Does using a binoviewer change what people would consider the maximum magnification they would use on Mars?



#42 E_Look

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Posted 12 November 2020 - 09:32 PM

I don't follow any rules when selecting an eyepiece.  I experiment to select what I feel offers the best view.  I have pushed it a bit and I have backed off depending on what my eye was experiencing.  Most of my planetary observing is done at home where I have to set up on driveway in a neighborhood with too close houses.  So the eyepiece chosen has to meet conditions.

Your observational situation is just about exactly like mine, except maybe you got some better weather.  Fortunately, Mars is high enough up in the sky this season we don't have to worry too much about those housetops, unlike the other night, I moved about 50' from my usual spot so I can catch Jupiter and Saturn away from some houses.  Unfortunately, even though I got a gap for the planets to move through, by then they were so low in the sky all sorts of thermal agitation was painfully seen.


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#43 barbie

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Posted 15 November 2020 - 07:12 PM

The last time I observed Mars back on November 3rd, it looked its best at 127X in my 3" apo with my Takahashi TOE 3.3mm eyepiece. Earlier that same evening, I used an orange filter in my Takahashi TOE 3.3mm eyepiece which worked out excellently. This magnification seems to be the best for my skies when viewing Mars.



#44 mikemarotta

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Posted 17 November 2020 - 11:01 AM

Thanks. You take good notes.

 

I always have a notebook for every project, work and hobbies alike. 

Yours is very nice.

 

attachicon.gifMars3rdNov2020Smaller.jpgattachicon.gifMars10thNov2020small.jpg

I have been using high x100's to low x200's on Mars the upper end limited local seeing here in the UK.  

I live about 50 miles south of your location in the UK and the sketches attached give some idea of what I have been able to observe on Mars with a 130mm Apo. Please forgive the roughness of the drawings they are literally early days for me.

 

Can ask what website are you using to estimate seeing in the UK?

 

Thanks John



#45 JAC51

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Posted 18 November 2020 - 01:50 PM

I always have a notebook for every project, work and hobbies alike. 

Yours is very nice.

I have just started keeping notes this year and even more recently begun to draw my observations, mainly Mars so far .

 

I think that trying to sketch what I'm seeing has improved my observational skills without a doubt. Some of the  improvement  has simply come from concentrating for longer and so also being more patient in waiting for that split second of improved seeing.

 

John


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#46 E_Look

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Posted 18 November 2020 - 06:08 PM

... Mars ... being more patient in waiting for that split second of improved seeing.

 

John

Yeah!

That's all I've been getting with Mars lately.  Someone agreed with me that Mars is high up in the sky this season, but still, after 7 PM here, the seeing degrades.  But even in that 5-7 PM little window, there is only that split second of real clarity when you can see truly sharper image.  But you need several to many of those moments to really assemble a mental impression of what Mars was "really" like that night.  Sounds like astrophotography except it happens in our heads...




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