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mikeDnight

Mars this summer

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With Mars being at its largest as viewed from Earth since 2003, it might be nice to have an idea of what will be on view. Despite its low angle from a UK observers view point, there will still be plenty to see, if you're patient enough to battle against the potential turbulence. Larger apertures may benefit from being stopped down to 4 or 5 inches, and Wrattan 21 orange and 80A blue may help to enhance the albedo features, or steady the view.

Attached is a cylindrical grid map from observations made during the 2003 apparition, using a 5" refractor. The same should be observable this year for those who keep looking! :happy11:

5a720e5ece76e_2018-01-3113_13_26.thumb.jpg.589e6e28017f159d245522fb239bf221.jpg

5a720e8d221c0_2018-01-3113_15_40.thumb.jpg.06d3d8674e4bb41fb5ff22e3017289e9.jpgNorth Top (diagonal view)

 

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A friend has a Vixen 130SS apo, it will be the ideal time and intrument. I still see the picture of Mars in my mind, two years after watching it through that high-class lens. Contrast was so strong the continents seemed to be painted on a marble, a marble with hard, sharp edges that barely gave way to turbulent breakdown. That was the benefit of a supersmooth wavefront, and a prism diagonal that provided the last bit of sharpening a planetary image needs in order to impress.

Placing a 150mm stop on top of the club's huge 400mm newtonian is another ploy for high-res views, as you recommend. It is a simple off-axis aperture in the cap, but next time we'll experiment with different masks of 130mm, 135mm, 140mm and 145mm sizes, to optimize the diameter relative to turbulence. We cleaned the mirror last week for a serious occultation timing and photometry job, that will be one more bonus for planetary contrast!

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1 hour ago, Ben the Ignorant said:

A friend has a Vixen 130SS apo, it will be the ideal time and intrument. I still see the picture of Mars in my mind, two years after watching it through that high-class lens. Contrast was so strong the continents seemed to be painted on a marble, a marble with hard, sharp edges that barely gave way to turbulent breakdown. That was the benefit of a supersmooth wavefront, and a prism diagonal that provided the last bit of sharpening a planetary image needs in order to impress.

Placing a 150mm stop on top of the club's huge 400mm newtonian is another ploy for high-res views, as you recommend. It is a simple off-axis aperture in the cap, but next time we'll experiment with different masks of 130mm, 135mm, 140mm and 145mm sizes, to optimize the diameter relative to turbulence. We cleaned the mirror last week for a serious occultation timing and photometry job, that will be one more bonus for planetary contrast!

That's a great scope, and some wonderful memories of the views emblazoned on your mind Ben. It's great to hear of the experiences that others had during the 2016 apparition. The planet wasn't well placed but the views at times were stunning. I observed the 2016 apparition using a 4" with prism diagonal and had some amazing results. Infact I felt the results were even more pleasing than back in 2003, but may be that's because of gaining greater experience over the years.

5a7228fa275ec_2017-09-0509_09_51.thumb.png.397e9c411fd3ea529da9572eb555561f.png

5a72292ddcc73_2017-09-0509_09_00.png.0d5a383692d220ba3a79b1a6881e6234.png

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43 minutes ago, 25585 said:

Any recommendation for Mars filters?

Have a look at this article by Paul Abel on the BAA website.

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6 hours ago, 25585 said:

Any recommendation for Mars filters?

Personally I've found that W21 orange, W80 or 80A are sufficient for observing Mars. However, I rarely use them! Filters can help draw your attention to a certain feature that at first may not have been so obvious, but on removing the filter, the feature is still easily seen. Filters are perhaps of more benefit in larger aperture scopes, as they reduce the brilliance of a planet. From my own experience with coloured filters, I've found they always and without exception, degrade the image somewhat. My observations of the 2003 and the 2016 martian apparitions were almost entirely observed without the use of any filters.

One strange thing I have noticed with regard to the W80 blue filters in my binoviewer, is that when observing Venus, it seems to reduce the effects of atmospheric turbulence, and bright areas can be enhanced.

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Looking forward to seeing Mars increase in size over the coming months. That is a fabulous record of the 2003 event. 

With the "stopping down" reference do you think my Helios 120mm F8.3 refractor will out perform my C9.25?

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Thanks Pete!

That's a difficult question to answer, as the Helios refractors varied so much in the quality of their figure; and the 9.25" is a very good scope! A lot might depend on how thermally stable your SCT is at the time, as the design is very heat sensitive. If its a good lens in the 120 you should get some pleasing results, though there will be some CA to contend with, but the 9.25 would be a hard act to follow if its cool as its aperture isn't excessive!

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On 1/31/2018 at 14:26, Ben the Ignorant said:

 That was the benefit of a supersmooth wavefront, and a prism diagonal that provided the last bit of sharpening a planetary image needs in order to impress.

 

 

Ugh. Stopping down bigger apertures for atmospheric turbulence? Well, I'm gonna have a deeper look...again...never mind that Gary Seronik and Vladimir Sacek say otherwise

http://www.telescope-optics.net/seeing_and_aperture.htm#MTF

But my question is about the prism diagonal. We're getting our first frac and will have to look into this. Thanks

 

Edited by laowhoo
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1 hour ago, laowhoo said:

Ugh. Stopping down bigger apertures for atmospheric turbulence? Well, I'm gonna have a deeper look...again...never mind that Gary Seronik and Vladimir Sacek say otherwise

What people say and compute has no effect on what we see. Stopped-down large telescopes produce calmer images.

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1 hour ago, laowhoo said:

But my question is about the prism diagonal. We're getting our first frac and will have to look into this. Thanks

Ask the scope maker; some refractors work better with a prism, some require a mirror.

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37 minutes ago, Ben the Ignorant said:

What people say and compute has no effect on what we see. Stopped-down large telescopes produce calmer images.

What people say is predicated upon both computational optics (Sacek) and experience (Seronik), hence my inclusion of both. But I'm perfectly willing to run the experiment myself, and even to self-delude (I do it all the time), regardless of neither knowing how nor why my experience may or may not comport with what's been established otherwise, or when it's doing or not doing such. But thanks? And guess I'll just fire off an email about the prism/frac, so thanks again? Any reason why one frac or another will or will not benefit thereby? Or maybe when? Is it a doublet vs. triplet thing? Most helpful (see your avatar).

Edited by laowhoo

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10 minutes ago, laowhoo said:

Any reason why one frac or another will or will not benefit thereby? Or maybe when? Is it a doublet vs. triplet thing? Most helpful (see your avatar).

Oh, several reasons! Many types of lens glass, different grades of cost, age of the design because modern computers optimize the objective's design better, and more recently formulated glasses reduce aberrations. The size of the prism matters, too, because the optical path in a 2" prism is longer.

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4 hours ago, laowhoo said:

 

Ugh. Stopping down bigger apertures for atmospheric turbulence? Well, I'm gonna have a deeper look...again...never mind that Gary Seronik and Vladimir Sacek say otherwise

http://www.telescope-optics.net/seeing_and_aperture.htm#MTF

But my question is about the prism diagonal. We're getting our first frac and will have to look into this. Thanks

 

Well if Gary Seronik says it it must be right! Wasn't he the clot head who reviewed TMB Super Monocentrics using a home grown 6" short focus reflector? I think he was! What a maroon!! And the only Vlad I know of, liked coming out at night, but I'm not sure he knew anything about telescopes, let alone observing through them! :happy11:

As regards prisms on refractors, I think if your scope is a good one and F6 or longer, and providing you use a quality prism, you'll get great results. I use the Takahashi prism in my 100mm F7.4 fluorite frac and the images are simply exquisite, with no trace of CA. Baader prisms and Circle T prisms are top class too! Avoid Celestron prisms! I've had to destroy several of them over the years as they were so poor, and couldn't bring myself to pass them on to anybody else, let alone sell them.

 

Edited by mikeDnight
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Ive NEVER had much luck when observing Mars. Ive seen polar caps and a dark surface feature (shaped a bit like India). Ive not given up on it.

Edited by LukeSkywatcher
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