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How should Mars look in my 12 inch Orion Dob

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#1 calibos

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Posted 22 December 2007 - 12:17 PM

I seem to see conflicting information about what Mars should look like in a large apeture scope like my 12inch.

On the one hand I hear that the disc should be anything from orange ,pink, salmon peach with darker areas and the polor cap/hood visible. Maybe even the possibility of some clouds.

Pictures in the sketching forum would seem to bare this out. I am told that these are what I should reference to give me an idea about what I should expect to see rather than stacked photo's. That makes perfect sense.

Then on the other hand you have what I see in the scope which is a white disc with the barest hint of slightly darker areas. No white polor cap visible on a white disc obviously. No colour whatsoever. My brothers see the same thing so its not my vision. Now I did find one thread where the sketcher had done an eyepiece view sketch. ie a sketch with a circular black FOV of an eyepiece with the small planetary disc of mars in the middle. This was a white disc with the slightest hint of yellow and with some very lightly shaded darker areas. Several posters commented on how this was a great sketch as it accurately represented exactly what they see through the eyepiece.

So which is it. Off white disc with the barest hint of darker areas or coloured disc much more contrasted darker areas and polor caps. Or are the coloured sketchers taking liberties with their colour palette and exageratting what they actually see? Most posters in those threads also say how accurate they are?? Accurate, as in everything about the sketch perfectly matches their view right down to contrast levels and colour...or accurate as in.."Yes indeed, you have drawn the darker areas in exactly the same place they were when I looked the same night. Way OTT on the contrast and colour compared to my view though...."

Seeing was great for me the other night. Got to use my 3.5mm 400x on mars and saturn the other night. Steady and sharp 50% of the time. My scope is very well collimated using both a cheshire and barlowed laser collimator(collimated itself) But little or no detail on either planet.

The reason I ask is not so much that I am disappointed at the views. I am still thrilled. Wow, I can just about see see darker surface features on a planet 50 million miles away! Its just that going by some of the sketches it seems I am missing out but going on other sketches it seems I am seeing what others are seeing.

If I should be seeing this detail then I want to tweak my scope further and get the best out of it and get these views. If I shouln't be seeing the detail from these sketches because the sketches are exageratted then I don't want to waste my time and/or risk breaking something tweaking a scope that doesn't need it and is already giving its best.

Sorry for the long winded post but I just need to put my mind at ease whichever way it goes

BTW the scope is an Orion XT12i Intelliscope.I have tried stepping down the apeture to 4inch with an apeture mask. I have tried my orion Moon variable polorizer and even in combination with my Baader moon and skyglow. All dim the planet but it remains a white almost featureless disc albeit dimmer. Coplour filters only seem to add false colour and do not enhance any feature other than the darker areas and even at that not as much as the baader M&S. The enhancing effect of the M&S is minimal as it is.

So.....Something is wrong with my scope ......or.......some people are telling fibs and exageratting what they say they see?? :grin:

#2 walt r

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Posted 22 December 2007 - 01:17 PM

So.....Something is wrong with my scope ......or.......some people are telling fibs and exageratting what they say they see??


Well maybe some of both.
Seeing can be very variable, changing in seconds, minutes and hours. I've had nights when Mars was just a yellow ball, nights when I can see the polar hood and just a hint of dark features then a night when the dark features, polar hood and more were closer to photographic.

Collimation: you seem to have that.

Cooling: has you mirror reached ambient? Do you have a fan?
If so does the fan induce vibration.

Flocking: Any stray light getting into the eyepiece will reduce contrast. Remove the EP and adapter and look into the focuser. Flock any part of the tube you can see. If you can see past the end of the tube then a flocked extension will help. Lastly, look at the reflection in the secondary, flock or darken any part around the primary you can see. Also check the focuser drawtube and the bottom opening of your eyepieces. Darken any reflective surfaces.

Conditions: Seeing? Star test and splitting close doubles is a good indicator. I've read reports from observers in Ireland and Britian about how bad the normal seeing is.

Optics: Orion optics are massed produced but seem to be good from reports I've read. Star test.

Experience: I've been observing for many years and am still learning how to see more. Other say the same thing so observe ofter.

Mars: Is the toughest planet to see well.

#3 mathteacher

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Posted 22 December 2007 - 02:13 PM

I'm new at Mars observation and I just tried my first sketch. In the beginning, you will not see what is in the sketches. It takes a fair amount of time at the eyepiece to see the subtle details shown in the sketches. Also, the sharpest details will only be visible for fractions of a second, when the atmosphere momentarily gives you a clear glimpse at Mars. With my 100mm, I get about 2 or 3 really good looks per session. Theoretically, your 12" will have very good resolution but will be more susceptible to seeking because you're looking through more sky. Mars rewards persistence and patience. Keep looking, you _will_ see more. You may consider using some kind of filter to cut down the brightness and increase contrast. People use moon (ND) filters, colored filters, and even light pollution filters on mars. You may also try making an aperture mask. These topics have all been discussed on this forum. Do a search.

As for the sketches, I don't know if people are taking artistic license, or perhaps more appropriately, "interpolating" what they see to match known images of mars. I can say for certain the sketches are made by very experienced observers. Until we attain the same level of experience, let's give them the benefit of the doubt.

Someone recommended the Calsky website to me. I like it because it gives a simulation of what you can see for a given aperture. www.calsky.com. Click on planets, mars, then look for "apparent view/data". Clear skies.

#4 rusirius6278

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Posted 22 December 2007 - 02:48 PM

both are true.

imho, 1st, trust your eyes over what others see...i`ve been observing planets for nearly 40 yrs...from what i`ve seen, in most cases, the results which observers are reporting/sketching are typical for the apertures that they`re using when filters, etc., aren`t being used...that is, the larger the scope, the more that the glare/brightness of mars is washing out detail...and, at 12" of aperture, i`m certain that the image/detail is pretty washed-out.

some have found the right filter/filters, others have switched to smaller scopes of much higher quality, others have stopped down their large scopes, while a few others have switched to less bright diagonals.

the end result is that, generally, those with the smaller scopes up to about 6" or so are seeing/reporting/sketching more detail than those not using filters, etc., on their larger scopes.

but there`s still a few more things which can and often factor into it...and that appears to include this mars apparition...as well as the Jup apparition this past summer.

more specifically, aperture doesn`t always win necessarily...it may win most of the time...but still not nearly as often as many think...especially on bright planets at and around opp...and sometimes during entire apparitions...we`ve already seen 1 observer switch to a smaller Apo which is providing him with better views of mars than his 8" scope...in large part because of the washing out effect...

each of these web pages provide different reasons why all this is so...especially the last one where contrast is shown to be a huge factor,

http://legault.club.fr/what.html

http://www.telescope...r-medium_errors

http://legault.club....bstruction.html

and from our sponser`s article/Astronomy Mag. on picking a telescope,

http://www.astronomi...fractor?/Page/1

Please note how this article states that the results of a refractor's lower diffraction and higher light transmission when given favorable seeing conditions with a modestly-sized refractor can show you subtle lunar and planetary features with a wider and more easily observed contrast range, and with more sharply etched detail, than is possible with the light-scattering optics of many larger reflectors and catadioptrics. This is especially true on nights of less-than-perfect seeing, when the details visible in a larger scope are often blurred by turbulence in our atmosphere. A smaller refractor looks through less of our unstable atmosphere and its images are consequently less affected by this turbulence.

this is proven with the derived formulas at the 2nd web page linked to above.

and much more importantly in the case of mars here,

Since the Moon and planets are all brightly lit by the Sun, a large light-gathering capacity is not as important as high magnification within the solar system. The relatively small aperture of a refractor is therefore often an advantage for this kind of observing, as is the high magnification capability of its long focal length in achromats and premium optics in Apos, as there is less glare from brightly lit planetary surfaces to wash out faint detail.

now, Please consider carefully all the posts we saw throughout these forums from owners of relatively large scopes who weren`t seeing any detail on Jupiter...or just seeing some very faintly, with a somewhat large, washing out effect...due to glare/brightness...that is, much of it just looked like a huge, boiling but extremely bright featureless to somewhat featureless blob to them...at it`s relatively low pos. in the sky, where the seeing`s bad to average...

now consider many of those who got good views of Jupiter and gave much of the advice to get better views to owners of large scopes who were having trouble...if one checks as i have, they`ll find that many were observing Jupiter at relatively small apertures...for ex., i got nothing but outstanding views with nothing larger than a good 4" Apo and tried to provide all kinds of advice...i sincerely hope it helped.

all this fits our experiences in this area perfectly...i understand that YMMV depending on several different factors...Sol, Carlos, and Michael are proof of that.

i think, at the very least, the info at the links above combine to answer this question to a large extent...i`ve also noticed that it appears to be dependent on location somewhat too...realizing it may just be a coincidence, tho...

but you stated that you tried stopping the scope down and filters...and, yet, still saw mostly no details...this is most likely due to either the wrong filter/filter combinations, bad seeing...or you just need to look at the image longer, when observing it higher in the sky in good seeing...and with the scope stopped down or while using the right filter/combination of filters.

i find that the longer i look at the image, the more my eyes adjust and the more detail i see...i also see more, with the detail much easier to see, the higher mars gets in the sky...and, lastly, i find that the more nights observers look at it, the more thay see...especially newbies just, 'learning to see', detail thru an astronomical telescope on worlds millions of miles away... :cool:

click here for much more good info,

why is mars so hard

hope this helps, :) :cool:

Jim

#5 ngc2289

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Posted 22 December 2007 - 05:50 PM

You have to take into account that what you see will be affected by how experienced you are!!!!!! Generally new observers see less then experienced observers!! What I saw in a scope 30 years ago is different from what I can see now! This may be part of your problem and as your eye gets trained you will see more in the eyepiece!! My two cents and worth every penny! :)

#6 calibos

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Posted 22 December 2007 - 06:53 PM

Thanks everyone for the fabulous replies!! Very very informative.

Can anyone comment on the calsky 'apparent view' of mars in a 12inch? To me that looks better then all the mars photos I have ever seen never mind eyepiece view.

Like I said, I am pretty sure my collimation is good. I have tried a load of filter combinations. Full/half of the variable Moon Polorizer, Baader M&S, Coloured planetary filters .(Set of six Baaders) Offset 4 inch Apeture mask 4. Is this not the equivelent of a 4inch Apo, ie 12in Reflector stepped down to 4in unobstructed??? All combinations of above.

As for seeing. I had been told by a veteran on an Irish forum that I would be lucky to get to use my 3.5mm Hyperion once or twice a year given our average seeing conditions. This proved true for the first few observing sessions with my new scope. Then bingo! The night in question I was able to use it. Sharp views for like 4-5 consecutive seconds every 10 seconds or so.

Sure enough, I caught glimpses of the cassini division at the tips of the rings and I think I started to see a cloud band above the rings(South). Going back to Mars with the same Ep I was getting rock steady views and the darker patches were a little more distinct.

While I do know what you guys are talking about with regard to spending time at the Ep, as I did feel I was beginning to see a bit more by session-end I do get the feeling that I should be taking the sketches with a grain of salt too. I can't imagine that learning to see will ever get me to the stage of seeing the 4in calsky representations of Mars never mind the 12 inch.

What has happened I think is that I lowered my expectations of eyepiece views after learning not to trust scope box images etc ie Long exposure ground based or hubble stuff. The problem was that in some peoples enthusiasm to encourage newbies they are inadvertently hyping the newbies back up a little too far. Semantics might come into play. "You should/Might see Cloud Band/s on Saturn" Both sound similar but might interpreted quite different by a beginner when setting the bar of their expectations.

However! Like I said in my last post. I am only disappointed in so far as...."For a second I thought I would see this. No?? Ah Ok :D "For a second I thought I was getting a half day at work. No?? Ah OK :D Wasn't expecting it to begin with. thought I would get it for a little while but back to reality and am happy to finish the full day in work. Do you get my analogy? :D

Thrilled to see the shadow of the rings, thrilled to barely see the cassini division and one cloud band on saturn. Thrilled to see the tiniest surface detail on Mars 50 million miles away. Not thrilled that I let my expectations rise back up a little too high for a while.

#7 Jeremy Perez

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Posted 22 December 2007 - 07:05 PM

Hi Calibos,

You raise a good point about whether planetary sketches necessarily represent the moment-by-moment view through the eyepiece. For many planetary sketchers, the sketching process is a very useful means of eking out every last bit of detail they can discern. These details rarely present themselves for more than a moment through small windows of good seeing. And these details very rarely coalesce across the entire disc of the planet all at once. So it would be a very rare occasion that an observer would be able to take in a view of all albedo features sharply defined at once. The sketch is really going to represent a composite of a half hour or more of briefly glimpsed details combined into a single whole. Sometimes an observer will compliment their detail sketch with more of an at-a-glance impression of what the features looked like with all the glare and blurred seeing incorporated. Usually though, the goal is to present all the details their extended observation was able to grasp.

So, for observers who go really 'deep' with their planetary, or deep sky sketches, the sketch itself is often not so much a picture of what you 'will' see at a glance, but a composite of what you 'can' see with the good conditions and a lot of patience.

Thanks for raising a really good point, and I hope your Mars observing goes well.

#8 mathteacher

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Posted 22 December 2007 - 07:34 PM

For what it's worth, the 4" simulated view at calsky is close to what I saw through my 100ED during moments of good seeing. I was using 180x.

#9 Bill Weir

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Posted 23 December 2007 - 03:41 AM

If your scope is collimated well and cooled properly you should be able to see Mars well. My best views ever of Mars were with my 12.5" dob. Like Jeremy mention though, you do need to practice patience to gather glimpses of detail when the seeing allows.

Seeing colour can be an issue with many and I have found that the colours seem more vibrant when I'm observing Mars with my 6" dob. The physics of aperture and resolution allow me to resolve more detail with my 12.5". Sometimes I will do planetary observing with the two setup side by side. The big one for detail, and the other for colour data collection.

Something I've found that helps more in dealing with the glare is an apodizing screen. It functions much better than an aperture stop.

I have found that there is more scatter/glare with the mass produced mirrors. I chalk this up to the "dog-bisquits" created by the machine polishing. An apodizing screen definately helps with this on bright objects.
http://www.kitgear.com/apodiz/
Use black metal screen not the nylon stuff. It produces better results.

Mostly on planets, practice, practice, practice.

Bill

#10 rusirius6278

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Posted 23 December 2007 - 04:38 AM

i find the cal sky simulations pessimistic for 4" scopes...i see much sharper/clearer images of mars with lots more detail than they`re showing...especially at 227x -267x thru a Vixen ED103SWT...

back to the OP...many good points have been made...however, there is 1 other possibility...that is, you actually are seeing the same detail others are...they`re sketching...but just leaving out the glare/blur effects...or, that is, minimizing it...in order to provide a better idea of the detail which they saw...even if just barely seeing some of it...at the same time, there`s also a few sketching the ep view to give an idea of the glare/blur effects...

to find out for sure, you could provide a sketch of what you`re seeing in the Syrtis Major region...just leave out/minimize the glare/blur effects...your sketch may then turn out looking like many others here.

Jim

#11 Rick Woods

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Posted 23 December 2007 - 02:11 PM

I didn't think much of the calsky simulation. I've seen Mars far, far better in an 8" f/6 reflector than the 16" simulation would suggest.

Try the dark red filter, and be ready to spend a couple of hours looking at nothing but Mars. Cover your other eye and keep it open to reduce strain. Remember to breathe.

The sketches we all make represent the sum of everything we were able to glimpse during the observing session. Walt was dead-on: Mars is TOUGH! And, to boot, this has not been it's best apparition, detail-wise. I'm no newbie to Mars observing, and I've had a devil of a time seeing the details this time around. You can find me whining about it in several threads in this forum.

Keep looking for contrasts. Interrogate every part of the disk minutely - is there any difference in shading? Are the poles just a little brighter?
Wait for those split seconds of sharp seeing. It's just something you have to learn and get used to. Mars definitely does NOT give up its secrets easily.

#12 calibos

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Posted 23 December 2007 - 07:50 PM

Sketch thread similar to my view

This is almost like what I see. The EP FOV part of the sketch. Now add glare, take away any hint of colour and make the shaded area's even lighter to the borders of perception (ie am I imagining that, is that an eye floater? etc). Then you will know what I am seeing.


There was another thread with a sketch which was exactly what i see but I have spent the last hour searching the forums and can't find it.

Forgot to mention that the scope is stored in a shed outside so cooldown should not be an issue.

#13 Houdini

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Posted 23 December 2007 - 08:06 PM

What you see on sketches made by seasoned observers requires not only a good performing telescope but also a lot of training. It is quite possible that your telescope is not particularly good, but you can probably start from the assumption that you are the weakest link in the chain.
Your saying that "my brother sees the same thing so it's not my vision" is the clearest sign that your eyes have had little planetary observing training. Any experienced observer will see a lot more than untrained people. This is true for planets and for deep-sky.

Robert

#14 bpasternak

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Posted 26 December 2007 - 10:52 AM

Hello calibos. Interesting thread as it describes my viewing of Mars last week through my XT8 dob. The sketch image thread you've posted also best describes my viewing of Mars. Very little surface detail in my viewing but I was able to pull out some detail after careful observations, including slight polar caps.

At this point I'm still observing with the stock Sirius Plossl eyepieces, 25mm (48x) and 10mm (120x). I've ordered upgraded eyepieces which should be here this Friday. Now, all I need is a couple of clear nights!

I do agree with everything previous said. Be sure that your scope is cooled down and collimated (as you've stated). Also, experience is a factor.

Best,
Brian

#15 walt r

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Posted 26 December 2007 - 02:26 PM

I've been thinking about Calibos' questions in the original post. It seems that collimation and cooling is good and that the seeing is not to bad but he still has low contrast. I tend to only find low contrast in my 18" when the seeing is poor, the atmosphere is bluring the image. Calibos asked if something is wrong with his scope, it could very well be that the primary mirror is at fault. I only gave minimal information on optics as a cause in my reply post. Here is a more detailed account of possible problems:

1- TDE (turned down edge) is common but easily corrected by masking off the outer edge of the mirror. But since Calibos tried an aperture mask it isn't likely that this is his problem.

2- Over/under corrected (the mirrors figure is not a paraboliod). This can cause a decrease of contrast in the image due to an unsharp focus. Foucault and Ronchi tests will reveal over/under correction but these tests can be hard to setup and read. A star test is very sensitive and may be the best to determine if the mirror is over/under corrected.
This has a fair chance of being the problem.

3- Rough surface. This also tends to be fairly common. A rough mirror surface will scatter light in all directions and greatly lower contrast. A Foucault test should easily show a rough surface.

A few things that lead me to think of this and Calibos' problem.
One is a CN poster with an XTi10 that had the mirror refigure and installed a Protostar secondary. He claims that the images are greatly improved and that the scope can now take higher power. The cost of upgrading was the same as the original cost of the scope but he is happy with the scope's performance now.
Another is my experience with my Obsession. Even without great seeing the images of Mars and other planets are quite good. At a star party this past October I was viewing Mars at 728X and full aperture. Others came by and took a look. They had been observing Mars with a varity of scopes from APO refractors to SCT's. Everyone was impressed at what they could see on Mars through the Obsession.
Lastly, there must be a reason my mirror cost $3200 and the maker guarantees that I'll by happy with it. Mainly its the three items I discussed above. Good figure, no TDE and a smooth surface. Without which images will not be contrasty and the image gets soft or mushy at higher power.

Ok, here are some links to more information:
OMI article, "A Comparison of a Good Mirror to a Mirror with Figure Problems"
RF Royce, "COMPARATIVE IMAGES OF JUPITER"
Stellafane, "Build a Mirror Tester"
And of course look in the ATM forum here on CN for discussions of mirror making, figuring and testing.

I am not intending to degrade anyone's scope but to give a realistic evaluation of the optics and possible problems.

#16 longfocus

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Posted 26 December 2007 - 02:44 PM

I seem to see conflicting information about what Mars should look like in a large apeture scope like my 12inch.

On the one hand I hear that the disc should be anything from orange ,pink, salmon peach with darker areas and the polor cap/hood visible. Maybe even the possibility of some clouds.

Pictures in the sketching forum would seem to bare this out. I am told that these are what I should reference to give me an idea about what I should expect to see rather than stacked photo's. That makes perfect sense.

Then on the other hand you have what I see in the scope which is a white disc with the barest hint of slightly darker areas. No white polor cap visible on a white disc obviously. No colour whatsoever. My brothers see the same thing so its not my vision. Now I did find one thread where the sketcher had done an eyepiece view sketch. ie a sketch with a circular black FOV of an eyepiece with the small planetary disc of mars in the middle. This was a white disc with the slightest hint of yellow and with some very lightly shaded darker areas. Several posters commented on how this was a great sketch as it accurately represented exactly what they see through the eyepiece.

So which is it. Off white disc with the barest hint of darker areas or coloured disc much more contrasted darker areas and polor caps. Or are the coloured sketchers taking liberties with their colour palette and exageratting what they actually see? Most posters in those threads also say how accurate they are?? Accurate, as in everything about the sketch perfectly matches their view right down to contrast levels and colour...or accurate as in.."Yes indeed, you have drawn the darker areas in exactly the same place they were when I looked the same night. Way OTT on the contrast and colour compared to my view though...."

Seeing was great for me the other night. Got to use my 3.5mm 400x on mars and saturn the other night. Steady and sharp 50% of the time. My scope is very well collimated using both a cheshire and barlowed laser collimator(collimated itself) But little or no detail on either planet.

The reason I ask is not so much that I am disappointed at the views. I am still thrilled. Wow, I can just about see see darker surface features on a planet 50 million miles away! Its just that going by some of the sketches it seems I am missing out but going on other sketches it seems I am seeing what others are seeing.

If I should be seeing this detail then I want to tweak my scope further and get the best out of it and get these views. If I shouln't be seeing the detail from these sketches because the sketches are exageratted then I don't want to waste my time and/or risk breaking something tweaking a scope that doesn't need it and is already giving its best.

Sorry for the long winded post but I just need to put my mind at ease whichever way it goes

BTW the scope is an Orion XT12i Intelliscope.I have tried stepping down the apeture to 4inch with an apeture mask. I have tried my orion Moon variable polorizer and even in combination with my Baader moon and skyglow. All dim the planet but it remains a white almost featureless disc albeit dimmer. Coplour filters only seem to add false colour and do not enhance any feature other than the darker areas and even at that not as much as the baader M&S. The enhancing effect of the M&S is minimal as it is.

So.....Something is wrong with my scope ......or.......some people are telling fibs and exageratting what they say they see?? :grin:


Just my personal opinion.. Mars looks WAY better in my 4" APO than in my 12" Newtonian dob mounted. There is a lot to say about optical quality above and beyond sheer diffraction aperture for the planets. It is amazing the steady amount of low contrast planetary stuff to be seen in the smaller unobstructed scope.

#17 Mauro Da Lio

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Posted 26 December 2007 - 03:53 PM

I have a few suggestions to try "debugging" this case.

First, You should see details and colours. Here is an example of Mars at 300-400x in a good quality, fine cooled, everything-cared, 10" (it was a XT10i). It is a picture that I resized, reduced cromaticity and saturation to match what I saw that night (it was october 2005, the planet was nearer than during this opposition and seeing was good). The details and colors are more or less what was visible, including the polar caps and the clouds (I then had better views in a 16" dobson). However, the picture shows the details simultaneously, but in the reality they were seen a few per moment (so you have to build the complete picture in your mind by noting one feature every time). Imagine the same picture with continuous defocusing (like at the bottom of a pool) of the different parts (I think you know what I mean).


Now my suggestions are: make a careful star test. I had two SC scopes: one was showing less colors than the other and it was affected by more Spherical Aberration. Poor optics, or poor seeing, or poor thermal conditions mix the colors and they fades. Surface roughness (including micro scale roughness at the coatings may also be the responsible of light scattering). To see colors you need to "split" them into large enough areas of uniform hue. Also look at the suggestions given in S&T articles on how to deal with seeing http://www.skyandtel...iy/3304176.html .
Use sufficient magnification. If the planet is too bright you mighty loose your ability to discriminate colors. 1 mm exit pupil or less should work.

Posted Image

PS last week I had two fair nights at 720x in my 16". The scope was fan-cooled for 6 hours, seeing was good (no jet stream, check it). The details visible were similar. Do not expect to see all the details at the same time. You glimpse one then another than the first again, then a third etc. If you know there is something in a place keep looking there until the seeing lets you glimpse the detail (I found the brighter area of the Olympus Mons in that way). Often switch to 3-5 magnidutes stars and look if you see the airy disk and how the rings appears ( http://uk.geocities....8/pickering.htm http://www.visi.com/...ke6/spike6.html ) The second link shows the airy disc and a cloud of fragmented rings. Note how much light is going in the clouds and how large it is: the size of the cloud depends on the size of the convective/seeing cells, the amount of light depends on the amount of scattered light. See also http://www.astrosurf...qualitoptic.htm for the effects of roughness.

PPS Ireland is likely to be often affected by the Jet Stream http://squall.sfsu.e.../jetstream.html

PPPS 6% and 1% of males are respectively deuteranomaly and protanomaly: they have unbalance of M and L cones: the former are "green weak" the latter "red week". Most of them are competely unaware of this difference of perception with respect to the 94% of people. Here is a couple of links http://tjshome.com/selftest.php http://www.city.ac.u...colourtest.html

#18 coopman

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Posted 26 December 2007 - 05:14 PM

Mars is a tough target to eek out much detail on. The planet is small & very far away. Plus, the veteran observer will see more than the novice. Our atmosphere only allows us to see fleeting moments of good detail. Patience is the key to seeing these details.

#19 Brian Albin

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Posted 27 December 2007 - 01:44 AM

Are there any more answers to calibos' question of color saturation? Do you other Mars observers see off-white as he is seeing or do you see red?

2) He acheived 400x with a 3.5mm EP. Could he get better views using one of the 4x compound Barlows (Televue Powermate, Siebert Telecentric) and a 14mm EP? My thought is that the light cone would come to the eyepiece with less severe convergence. Would this help?

3) Would changing to a narrow view EP such as the 30 Degree Monocentric improve contrast? I am not sure why it would, but it somehow seems so. Perhaps I got that wrong.

#20 calibos

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Posted 27 December 2007 - 11:36 AM

Mauro

I got 6/6 in the first test and in the second test I could see the moving coloured square the whole time. I guess my colour vision is normal.

I can't see your photo btw. the link is broken.

Brian. I am seeing off white no trace of red.

As for detail. Look at this photo

http://www.cloudynig...5/o/all/fpart/1

[Edit] That pic might actually be with a coloured filter?? To clarify, I know I will see colour with a coloured filter or combinations thereof but am I right in thinking I should be seeing some colour in a non filtered Eyepiece view?

What I usually see is this without the colour. Ie I can barely make out the detail. Now in the interim I have checked experienced Irish observers reports for the same night and while I disregarded the bad seeing reports for that night from the lads on the other side of the country, two of the lads who live about 20 miles west and about 15 miles north respectively reported bad seeing. I thought the disc being resonable sharp edged and not bubbling with a 3.5mm in my 1500mm scope meant the seeing was good. Maybe not. For instance on Christmas eve I felt the seeing wasn't as good because the planet edges were not as sharp and yet I felt that the L shape of the southern (top in my scope view) darker area and Syrtis Major was a little more distinct than I had previously seen it. I also started to see the darker ring around the Northern Pole (Bottom of planet in my scope view.) So that would seem to indicate bettter seeing on Christmas eve than on the night I originally posted about. I still couldn't see Icecaps though even though I knew the cap should be surrounded by that northern(bottom) darker ring/band. Same white as the rest of the planet. Another thing about seeing is that I now realise that seeing has never been good enough for me yet to do a star test. On the night I thought had good seeing and even on the night of Christmas eve when it seems the seeing was better(because of the greater detail I saw on Mars and Saturn), I was for the first time able to make out diffraction rings. No where near clearly enough to do a star test but I could for the first time at least start to see them. All the little tiny concentric cirles were very fuzzy and spikey.

I have also discovered that even though the scope is stored outside in a shed and should be very close to ambient that tube currents can still be an issue?? Is this correct.? I thought I didn't need a fan because the scope was stored outside. Maybe I do?

I know all the issues raised could be the reason I see so little detail but can they also account for the near total lack of colour. The image from the thread I posted in this post was apparently taken on a 17in scope masked down to 10in. So glare can't be whats washing out my colour. Like I said I still see no colour just a dimmer image when I mask down to 4-5inches!

On other thing. I see colour fringing on Mars. IIRC correctly in my eyepiece view I see blue fringing to the bottom right of the planet and IIRC red fringing to the top left.

Any of this help to diagnose my problem further??


Thanks once again for everyones wonderful contributions to this thread.

Keith

#21 walt r

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Posted 27 December 2007 - 12:47 PM

Hi Keith,
I keep my scope in an un-heated garage and it does need additional cooling when I roll it out. I start with a house window fan behind the mirror until I'm ready to collimate and observe. After that the built in fan is run continously. I borrowed an IR temperature meter from work to monitor the mirror temperature and found the the mirror does start warmer than the outside air and requires a fan for the mirror temperature to follow the dropping air temperature.
Its not so much tube currents but the 'boundry layer' that causes soft images.
So, adding a fan should help.

Here is a good sketch of what I see most of the time (scrool down to Kris Semt's colour sketch) as for colour. During moments of better seeing the edges of features are sharper. I wouldn't call Mars red, Its more of a butterscotch yellow to me.

Thanks for the additional reports. I'll have to think about them before I post anything further.

#22 rusirius6278

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Posted 27 December 2007 - 12:49 PM

well...i`ll just add that if you look at the most recent sketches, including mine, in this forum, you`ll see the surface sketched and colored in as a bright off-white color...in my case, i find this to be true in all my 4"-5" scopes...that is, the image is bright enough that it`s even turning the surface color an off-white in my 4"-5" scopes.

you`ll also note that in my latest observation/sketch, i too could not see any hints of the NPH, etc., because of all the bright white limb haze/clouds.

also note that the NPH is getting smaller now as the Martian Spring is upon us...so, that may have been the smaller NPH you saw at the bottom instead of false color.

also note that your seeing more may be due to your eyes becoming adjusted to the view more...or, that is, you`re seeing more as, 'you`re learning to see', fine detail on a planet millions of miles away thru an astronomical telescope...then again, it may have been the seeing...or maybe both...just keep looking every chance you get...and you`ll see more and more...one way or the other...especially as mars lessens in brightness and it`s natural colors start to return...with a lessening washing-out effect...

also note that in my last sketch, it took all 3 hrs. waiting for moments of good seeing to see/sketch all that detail...mars takes great patience...especially in mediocre seeing conditions...one literally sketches the detail seen after a few moments of good seeing...then waits until the next few moments of good seeing before continuing to sketch more from what they`re seeing during such moments...this process continues until no more fine detail can be seen during these moments.

here`s the finished product from a few mornings ago,

Last Mars Sketch

main areas could be seen both blurred and during moments of good seeing...all that fine detail could only be seen during moments of good seeing.

also note that in good to excellent seeing conditions, this sketch - indeed, any sketch - could be done in 10 mins. instead of 3 hrs...following the same process described above...that is, seeing conditions are a key/main factor here...regardless of everything else...

hope this helps, :) :cool:

Jim

#23 Mauro Da Lio

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Posted 27 December 2007 - 03:39 PM

Mauro

I got 6/6 in the first test and in the second test I could see the moving coloured square the whole time. I guess my colour vision is normal.
I can't see your photo btw. the link is broken.


So, welcome in the 94% ;-). It was only a thing to check. My photo is in this blog article: http://visualreports...0-320-400x.html

#24 calibos

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Posted 27 December 2007 - 06:24 PM

So assuming the fringing is nothing to worry about then it sounds like it really is a combination of Atmospheric Seeing, Boundary layer seeing and lack of Experience at the eyepiece. I can't imagine seeing or glare washing out so much colour from a deep orange red back to off white but going on Kris Semts sketch that Walt referanced and Mauro's photo which are remarkably similar. With the much lighter shades of those I can imagine that level of colour being washed out to off white for the varying reasons quoted.

It seems I have wasted your time trying to diagnose a problem which turns out were basic newbie misunderstandings about what to expect. Hopefully this thread will help quickly put others minds at ease in the future and thats its probably not something wrong with their scope. Ie that Mars isn't the deep orange beginners expect. That active cooling even for a scope stored outside in a shed is important. That it really does take that great night of seeing and patience at the eyepiece before you are rewarded with a truely stunning view. Like I said. I made the classic beginner mistakes of expecting too much too soon.

I think its important to say again how this is not a disappointment to me. I know I could get even better views than some of the pics posted with a scope with better optics and or of a different type. Maybe someday I will get a 4-6" Apo to complement my 12in Dob. I am just happy to know that there probably isn't anything wrong with my current scope. If I can't get the absolute best views of planets in this scope then that is the price to be paid for a DSO focussed large apeture mass produced Dob. you get what you paid for. As long as I am getting the best out of this scope then I am happy. I will be thrilled to see the extra detail on offer in Kris Semts sketch and Mauro's pic which it seems my scope should be capable of when conditions are right, but even if what I have seen to date Was it then I would still be happy. Surface detail on a planet 50 million Miles away!!

#25 rusirius6278

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Posted 27 December 2007 - 07:23 PM

just in case any newbies do read this thread, let me add that mars does indeed appear more of an orange color than bright off-white...greater than 1-2 months either side of opposition...depending on the aperture of the scope one uses, etc...

Jim






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