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Mars magnification

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#1 visualastronomer.com

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Posted 27 October 2020 - 09:13 AM

Hello,

 

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 Many adhere to outdated rules of maximum magnification with their scopes. Others stick to low or medium powers because they do not like when the planet looks a bit fuzzy. In my eyes, they are missing the best of what Mars has to offer.

 

I have written a blogpost about my experiences and recommendations: http://visualastrono...ars-to-the-max/

 

I would like to encourage other observers to share their thoughts in this forum!

 

Clear skies,

Ronald


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#2 Dave Mitsky

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Posted 27 October 2020 - 01:09 PM

Well, obviously seeing is a major factor.  I have been unable to use more than 324x (19x per inch) on Mars so far this apparition with the Naylor Observatory's 17" f/15 classical Cassegrain.  The 50x per inch rule yielding 750x obviously can't be met, let alone exceeded, unless some miraculously excellent seeing were to take place.

Attached Thumbnails

  • 17-inch Mars 10-24-20 IMG_8718.jpg

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#3 mich_al

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Posted 27 October 2020 - 02:18 PM

I got by far the best look at Mars this season by covering half the aperture of a 250mm reflector.  Seeing was not great and mag was around 200.  The image was many times better than full aperture.


Edited by mich_al, 27 October 2020 - 02:19 PM.

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#4 Unknownastron

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Posted 27 October 2020 - 03:03 PM

Everyone just has to experiment, and seeing conditions can change from minute-to-minute.  I usually make my best estimate of the conditions naked eye and start with a magnification I think will work.  I try up or down to find the best view.  I usually stay with the highest magnification before the image begins to become mushy.  That too is very subjective.

Clear skies and clean glass,

Mike


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#5 kb58

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Posted 27 October 2020 - 03:47 PM

Took the scope out last night in anticipation of doing another Mars session. We have this regional thing called "Santa Anas", warm winds that blow the opposite direction that the usual onshore west-to-east direction. No problem, I thought, shouldn't matter much since it's clear out. Yeah well... looked at Jupiter to start with since it was already up high, and rolled the scope back inside. The best I can describe it is that it was like trying to identify a car a mile away, on a hot day, across a dry lake bed. The heatwaves visible in the eyepiece were just amazing, to the extent that they ruined the views of everything. Live and learn!


Edited by kb58, 27 October 2020 - 09:05 PM.


#6 MellonLake

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Posted 27 October 2020 - 04:00 PM

Being able to use more magnification is really dependent on seeing and seeing is really dependent where you are in the world.  Those living in the tropical zones with no frontal systems and no jet stream are going to get seeing on an average night that those living in the high northern latitudes see only relatively rarely.  I have spent the last 2 months going out every night it is clear to check out Mars.  Only on one night could I push the magnification past 230X in my 254mm diameter  (I live around the great lakes and under the jet stream most of the time).   If I lived in Jakarta or the middle of the Serengeti, I could probably view at 350X regularly. 



#7 Napp

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Posted 27 October 2020 - 04:01 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.


Edited by Napp, 27 October 2020 - 04:04 PM.

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#8 planet earth

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Posted 27 October 2020 - 06:13 PM

So when Mars is fuzzy, raise the magnification.

OK that makes sense, but not in my little world.

I agree to disagree.


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#9 csphere.d

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Posted 27 October 2020 - 06:33 PM

I generally think in terms of an exit pupil between 1 mm and 0.5 mm when viewing the planets.  (Exit Pupil = Eyepiece Focal Length divided by the Telescope Focal Ratio)  That equates to the 25x to 50x per inch of aperture that is recommended by many.  I see this as a guideline, not a rule..  

 

Mars is certainly the exception to this guideline, as it at times almost begs for higher magnification.  The limiting factor, of course, is the seeing.

 

In my 4" f/7 ED refractor, I pretty much always start with 187x on Mars and I quickly go to 204x if the seeing allows.  On nights of really good seeing, I bump it up to 238x and the views generally hold up just fine.  On such nights, the only real limiting factor becomes my floaters, which become bothersome at exit pupils of below 0.5 mm.

 

When I set up my 10" Dob, I am routinely at 240x to 300x on Mars, depending on the seeing.  On rare occasion, I bump it to 343x in the 10" Dob.  I have yet to have had the seeing that would support anything higher.

 

Scott



#10 ron scarboro

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Posted 27 October 2020 - 10:07 PM

With my AP130GT 300X was a beautiful sight tonight.  I use a binoviewer for planetary viewing which (for me) really helps resolve the details of the planet.  Additionally, a Baader contrast booster filter also helps my setup on Mars.

19378AF9-2881-4BEA-8A1A-9B01A403D4A1.jpeg


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#11 mintaka77

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Posted 28 October 2020 - 04:33 AM

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.  NB I have defocused to check collimation of the SCT and it is absolutely fine.  There is a kind of mottling all across the objective due to dried remnants of innumerable dew drops over time, despite use of dew guard - I suppose everyone gets that. 

 

Before going out I have to choose between the 11 inch SCT and the 93mm refractor.  The 11 inch SCT gives me 3x the magnification (being around 1500mm as opposed to 500mm) of the refractor for the same eyepieces.  However, the refractor is sharper.  So - which should I take out next time it's clear? This question is not about reflector vs refactor but about large SCT vs small refractor ....???

 

The article about observing Mars (note, not photographing Mars) in sky and telescope implies that one should be able to see all sorts of features this opposition.  Is it a myth? Or, possibly no, provided you to go Mauna Kea ??

 

[So may be I should stick the camera on to the refractor but then I won't have the eyepiece and magnification will be just that of a 500 mm lens - not really a lot of use for Mars. 

 

I can't stick the camera on to the SCT eyepiece because it makes it too heavy at the eyepiece end and then I have to add a weight near where the objective is and the whole thing becomes too heavy for my mount ...]



#12 mintaka77

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Posted 28 October 2020 - 04:53 AM

... looked further at website in first post in this series where it reads '… with 100-120mm high quality apo a power of 3x aperture in cm is possible on 50% of nights'

OK so this for me then is roughly speaking my 93mm triplet APO ... 3 x aperture in cm is 28x.  

Since it is f5.5 I have 93x5.5= about 500 and so my lowest power eyepiece which is 26 mm gives a magnification of about 50x.

Which suggests that I should be using even LOWER magnification??!!  (despite the whole article being about higher magnification).



#13 phillip

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Posted 28 October 2020 - 06:39 AM

Was another post that 30x per Inch in reflectors, and 50x per inch in refractors. 

 

Tho I go for what I'm seeing per given night, above numbers seem about correct. My 65mm Swift achro refractor over f/10 certainly the above released refractor 50x per inch and then some at over 135x easily. My current XT10 using on Mars seems to match the 30x per Inch tho on excellent sky. 

 

There is another factor not mentioned is an extremely rare Steady Sky, only witnessed this marvelous condition 3 times in my 6 decades of Viewing! Like focusing clearly on a fence post, unbelieveable! My Xt8 then used happened at work in parking lot able to share the View! So many markings on Mars difficult to label the features, Awesome! Power here barlowed 4.8 Televue well over 400x and image Held! 

 

Your scopes must be aligned or you'll miss these amazing Mars features, and it rises so high fantastic possibilities. 

 

Just Now My first view in way to many cloudy days just after midnite was a clearly lined SPC Polar Cap tho tiny now, and Mare Sirenum was well shaped, great at modest over 170x 7mm Pentax, but even better at 200x takahashi ortho 6mm. Rarely hit 300x as needs best sky, but enjoyed several. 

 

If you enjoy just low power views your limiting catching the finer features, but that' just my 6 decades experience. 

 

Hope everyone eventually is treated to the rarest steady sky, Unforgettable! 

 

Clear Sky

 

Note on even average sky be patient at the eyepiece, venture then are flashes of clarity but must be at the eyepiece to catch. Are serious observors out here as caught posts those looking consistently over 1 1/2 hours, persistence required and pays off, I bow to these observors, well Done! 


Edited by phillip, 28 October 2020 - 06:53 AM.

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#14 ron scarboro

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Posted 28 October 2020 - 08:20 AM

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.

Have you tried binoviewing on your scope for planetary?  For me, a binoviewer allows me to resolve details I can't discern monoviewing.  Contrast is better and there are more details in the image.  It feels like my eyes combine the best of what each sees.

 

Last night, the lower pole was clearly visible and well defined, the center had a well defined dark structures that actually had subtle graduation, and the top of the planet had the greenish hue on the edge.  I stared at it for a couple of hours before the dew forced me inside.  298X in an AP130GT with a Mark V binoviewer (1.7X CPC, 7mm naglers and 1.5X Magic Daikin Barlows on each eyepiece).  I also use a Baader Contrast Booster.

 

Transformative for me, but my eyes are 54 so YMMV.

 

Clear skies,

 

Ron 


Edited by ron scarboro, 28 October 2020 - 08:25 AM.


#15 kb58

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Posted 28 October 2020 - 11:23 AM

... The article about observing Mars (note, not photographing Mars) in sky and telescope implies that one should be able to see all sorts of features this opposition.  Is it a myth? Or, possibly no, provided you to go Mauna Kea ?...

This might be a bit of a rant...

Visual astronomy is (to me) a bit like panning for gold. That is, someone (real or imagined) finds an enormous nugget and becomes rich beyond belief, and human nature is to apply that rare exception to the rule as the ultimate goal. Like a parent telling their kid, "sure you can grow up to be a professional basketball player", never mind that the number of pros compared to the number of people playing the sport is probably 0.00001%.

 

We can't help but always compare what we see through the eyepiece to the rare report from others as being awesome, amazing, and terrific. As a result, we're often disappointed when what we see doesn't measure up to this imagined picture of perfection. So we often then spend more money on "stuff" to improve our setup, only to have the same thing happen.

 

The telescope industry has seized on this and the imagined lack of capability, always showing accessories or parts with a Hubble telescope picture behind it, implying that one has something to do with the other. Just remember who it was that actually made money during the gold rush, the stores selling the picks and shovels! They're selling the dream, and whether customers actually find it isn't their problem. My point is that what you see is far more common as a reality than the subjective (and sometimes imagined) perfect viewing reports. Don't be sad, just be happy that you're out there seeing things for real, don't worry about what others claim.


Edited by kb58, 28 October 2020 - 03:05 PM.

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#16 Rick Runcie

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Posted 28 October 2020 - 11:54 AM

As stated earlier, magnification is seeing dependent. I go up and down in magnification all night or morning long dependent on the seeing conditions. I've used over400x on my 6" refractors and about the same on my 10" reflector for the planets. For planetary nebulas I've used close to 700x on the 10", but these are rare nights/ mornings. Usually I max out at 200x-250x on planets on both scopes on an average night with binoviewers. If the seeing is steadier I go higher if it's not I go lower. Depending on the planet observed and the features to be observed, the range of magnification can be different. For instance if you go too high on Saturn you lose the finer bands though that same magnification may be fine for Mars and maybe even higher will be useful. Each planet has a different useful magnification for the features that are trying to be observed and all of this is dependent on the seeing.

#17 Rick Runcie

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Posted 28 October 2020 - 12:05 PM

The aforementioned information is though dependent and assumed, you have decent optics, eyepieces included, your scope is collimated, is close to ambient temperature and your not observing on or over heat absorbing materials, asphalt, concrete, roof tiles or shingles etc. You have to optimize your observing conditions to optimize the seeing conditions

Edited by Rick Runcie, 28 October 2020 - 01:22 PM.


#18 Ihtegla Sar

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Posted 28 October 2020 - 02:58 PM

In response to the OP, I have a Tak FC100DL and I typically observe Mars at magnifications between about 125x and 225x, which translates into 1.25x to 2.25x per mm, so at the upper limit of the 50x per inch rule of thumb but not much over it.  I have tried higher magnifications on Mars but I am somewhat seeing limited at my location and the image becomes dimmer making it harder to see the subtle  contrast differences between the bright and dark albedo features.  However, when seeing allows I routinely use higher magnifications (as high as 375x, or 3.75x per mm) on the Moon, sometimes on double stars and sometimes on other planets, particularly Saturn which takes on a more three dimensional appearance for me at higher magnifications.  The images at 375x in the Tak remain sharp when the seeing allows and the image scale makes it easier to see some things.

 

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.  NB I have defocused to check collimation of the SCT and it is absolutely fine.  There is a kind of mottling all across the objective due to dried remnants of innumerable dew drops over time, despite use of dew guard - I suppose everyone gets that. 

 

Before going out I have to choose between the 11 inch SCT and the 93mm refractor.  The 11 inch SCT gives me 3x the magnification (being around 1500mm as opposed to 500mm) of the refractor for the same eyepieces.  However, the refractor is sharper.  So - which should I take out next time it's clear? This question is not about reflector vs refactor but about large SCT vs small refractor ....???

 

The article about observing Mars (note, not photographing Mars) in sky and telescope implies that one should be able to see all sorts of features this opposition.  Is it a myth? Or, possibly no, provided you to go Mauna Kea ??

 

[So may be I should stick the camera on to the refractor but then I won't have the eyepiece and magnification will be just that of a 500 mm lens - not really a lot of use for Mars. 

 

I can't stick the camera on to the SCT eyepiece because it makes it too heavy at the eyepiece end and then I have to add a weight near where the objective is and the whole thing becomes too heavy for my mount ...]

How high is Mars in the Sky?  Are your scopes fully cooled?  You need a cooled scope and Mars should be at least 30 degrees above the horizon as a bare minimum for a decent view but over 45 degrees is much better.  The higher the better to get out of the atmospheric soup.  I have problems viewing Mars with my 8" SCT due to cooling and seeing issues, but my 100mm doublet (FC100DL) provides stunning views that look very much like photographs of mars taken with amateur equipment, even on nights of poor seeing.  But on such nights I need to spend a lot of time watching and waiting for moments of clarity, so it takes patience.  

 

I live in an area under the jet stream with highly variable weather and pretty crappy seeing most of the time but even in crappy seeing I can easily spot the south polar cap and the major albedo features like Syrtis Major, Sinus Sabaeus, the Margaritifer, Mare Cimmerion, etc.  Last night seeing was a little better than usual here, but by no means great and I could see the South Polar Cap, Mare Sirenium, Mare Cimmerion and Mare Sirenium, as well as the North Polar Hood and Solis Lacus in my 100mm doublet. 

 

Your 93mm triplet is almost the same aperture as my 100mm doublet and should be giving you better performance than what you are describing on Mars.  Have you tried magnifications in the 150x to 200x range with it?

 

I typically observe Mars at magnifications between about 125x and 225x, which translates into 1.25x to 2.25x per mm.  I have tried higher magnifications but the image becomes dimmer making it harder to see the contrast differences between the bright and dark albedo features.  I routinely use higher magnifications on the Moon though and have sometimes used higher magnifications on Mars.

 

... looked further at website in first post in this series where it reads '… with 100-120mm high quality apo a power of 3x aperture in cm is possible on 50% of nights'

OK so this for me then is roughly speaking my 93mm triplet APO ... 3 x aperture in cm is 28x.  

Since it is f5.5 I have 93x5.5= about 500 and so my lowest power eyepiece which is 26 mm gives a magnification of about 50x.

Which suggests that I should be using even LOWER magnification??!!  (despite the whole article being about higher magnification).

That "3x per cm" was a typo.  It's supposed to be 3x per mm (higher than the oft quoted rule of thumb cited earlier in the article of 50x per inch or 2x per mm), or 279x in your 93mm triplet.



#19 Jeff B1

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Posted 28 October 2020 - 05:46 PM

Using my 16" f/6.9 Newtonian for the last time in May 2012 I was using fairly low magnifications for me.  Often I would push the scope above 1,000x, but usually observed around 500x  depending on seeing and my eyesight. Here are only two of my last drawing of Mars.  They are not as detailed as I usually drew, but my age caught up and my skills dwindled. These just show a typical mag Mars obs.

 

MyLastMars.jpg


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#20 Jeff B1

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Posted 28 October 2020 - 06:01 PM

Three drawings from 2001 and 2003 shows my eyes were a but younger nd I was paying attention at magnifications of 810x, 590x, 670x and 1175x:

 

M2001-11-07-JDB.jpg   

 

JBs04Aug03.jpg   JBs27Aug03.jpg

 

I should have h=used a finer pencil  cool.gif


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#21 chuckles

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Posted 28 October 2020 - 10:46 PM

Nice sketches! I’ve not seen that level of detail, but seeing the polar cap, hood, and major albedo features have been pretty easy this apparition. In mono mode Ive been using between 120 on the low end up to around 300 on the high end in scopes from 80 to 160mms. The bino helps a lot, and Ive seen much more with that at 200-250 than mono at higher power. I’ve noticed that if I look at the planet for several days in a row I begin to notice the features more easily. Its been a lot of fun!
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#22 hypergolic

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Posted 28 October 2020 - 11:15 PM

I didn't realize how many floaters where in my eyes till I popped in the barlow + 17mm eyepiece. 

Fleep



#23 Jeff B1

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Posted 29 October 2020 - 10:40 AM

I didn't realize how many floaters where in my eyes till I popped in the barlow + 17mm eyepiece. 

Fleep

I wish the surgeon had removed some of my floaters during cataract surgery, but both he and my eye doctor advised against it.  My cataracts were so bad I could not drive at night due to the star burst images from headlights.  Afterwards I could see great and with no night vision problems.  Still yet, floaters at high powers can be irritating for sure.  



#24 mintaka77

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Posted 29 October 2020 - 04:33 PM

Wow- amazing sketches.  Very interesting replies to my questions ... well I went out 24 hours later, and the seeing was much better.  So, I think reason it was sooooo bad, was, simply turbulence.  Last night I could see very clearly the dark central variegated shaped area - no doubt - and sometimes I could see a dark outdentation, and sometimes an isolated 'island' of darkness.  Also, one side was brighter so - a sign of the polar cap. 

 

I also found, that I could see more clearly without my glasses on and re focusing.  I have  a few floaters, yes annoying aren't they.   Bino viewer sounds like a really great idea.  May be I don't have very good vision. It is possible,  I have very strong glasses for short sight and astigmatism.  

 

My scopes are cooled, but I think there may be condensation inside my SCT ?  Some of the 'dew' that penetrated the dew shield seems to be on the inside??!

Next time I will try the refractor again.

 

Question:  I have a Baader scientific 26 mm two inch eyepiece, 18 mm two inch eyepiece and 2x barlow, and a 9 mm Plossl 1.25 inch eyepiece.

 

It is worth also buying a 5 mm two inch eyepiece to improve the view through my refractor? Or would it be better to up the 9mm from Plossl 1.25 inch to Baaser 2 inch?

 

Now 'my scopes must be aligned'.... do you mean aligned sufficiently so that I can stare at Mars for minutes on end (which they are?.. but mars does move, slowly)

 

Or do you mean, aligned so that I could do astrophotography well (which they are not)?

 

Mars is getting higher every night ...I am at 52N.  


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#25 MellonLake

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Posted 29 October 2020 - 04:48 PM

 

Question:  I have a Baader scientific 26 mm two inch eyepiece, 18 mm two inch eyepiece and 2x barlow, and a 9 mm Plossl 1.25 inch eyepiece.

 

 

There is optically no reason to use 2" eyepieces below about ~15mm as the field stop will be smaller than the internal diameter of the 1.25" barrel.  The only reason to have a 2" barrel below 15mm is so you don't need to use an adapter (which is an advantage), but there no optical advantage.   




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