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Misty Mars, 200mm vs 100mm


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I almost didn't bother observing after seeing dense mist covering the Moon and brilliant Mars looking quite dim. However I though I'd take a quick look through the 200mm Orion Optics F6 Newt', as it was already in the observatory and thermally stable. The view of Mars in the 200mm was quite impressive and the basic forms of Syrtis Major, Hellas being immediately obvious. I decided to make a sketch through the 200mm as sketching always draws my attention to more subtle features not immediately obvious. I used a 5mm Ultrascopic eyepiece which gave X240.

After being impressed with the view in the Newtonian, I though it would be a shame if I didn't make another sketch using my 100mm Tak, so I rushed into the house and brought out the FC100DZ, still warm to the touch.  I set the 100mm up on the GP after removing the Newtonian, aimed at Mars using the same 5mm Ultrascopic eyepiece I'd used on the Newt', and saw, beautifully defined, all the same detail I saw through the 200mm only the magnification was much lower at only X160. The view through the refractor was noticeably sharper than the view in the Newtonian, but it was noticeably dimmer too.  I decided to try and match as closely as possible the magnification in the 100mm as I used on the 200mm, so that meant using my Vixen HR's. I cautiously increased the power to X235 using the 3.4mm HR and the view remained sharp. The darks appeared darker and more sharply edged, while the lighter regions appeared whiter in the 100mm. I made another sketch using the 3.4mm HR, and just to ensure I wasn't missing anything I changed the 3.4mm for a 2.4mm HR giving X333. Still sharp but now considerably larger in the eyepiece,  I confirmed the detail seen at the lower X235.  A truly delightful nights observing that reaffirmed my love for the simplicity and ease of use of the smaller, sharper refractor. The Newtonian was very nice but its the refractor that pleased me more on this occasion.

The sketches below show the view through the brighter but softer 200mm reflector vs the less bright but sharper 100mm Takahashi. The prism view in the refractor shows a mirror image!

IMG_7736.thumb.jpg.23c9aee05203a88ca6a1e76367b52153.jpg

 

 

Edited by mikeDnight
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Nice sketches Mike.

Regarding the comparison, it's no surprise that the image in the Tak was both sharper and dimmer, it would have been more surprising if it hadn't been. Its exactly the same when comparing my SW 120ED and Bresser 203mm f6 Newtonian of course.

In terms of what detail can actually be seen, a more useful comparison would be with the two scopes set up side by side - and in seeing conditions that permit your 200mm to perform to it's full potential.

This is the comparison I'd like to make between my 120ED and 203 mm Newt - though I might not live long enough to do it under the seeing conditions I generally have at home 🙂.

The best view I have ever had of Mars was some years ago when we took a 16 inch SC from The Astronomy Centre to Kelling when the seeing was extremely good. For Saturn, my best view was over 15 year ago with a Fullerscopes 8 1/2 inch f6.3 Newtonian.  It still gives me goose bumps when I think of how stunning that view was.

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Superb sketeches Mike and a very interesting comparison. I have really enjoyed observing sessions where I have had the C8 and the Tal 100RS side by side, it adds an interesting additional perspective to observing. Under good conditions the C8 easily outperformed the Tal (or at least MY Tal!) on Jupiter and the moon (but not on doubles). I now have an ED100 and am really looking forward to doing a side by side with the C8 on Mars.  

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Thanks, a lovely report and engaging illustrations. Particularly since I was using a OOUK 8" F6 1/10PV mirror dob last night. This account is educational for myself, SGL certainly is a feature of the University of Life.

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5 hours ago, paulastro said:

In terms of what detail can actually be seen, a more useful comparison would be with the two scopes set up side by side - and in seeing conditions that permit your 200mm to perform to it's full potential.

This is the comparison I'd like to make between my 120ED and 203 mm Newt - though I might not live long enough to do it under the seeing conditions I generally have at home 🙂

Sadly I couldn't mount both together and had to remove the 8" to mount the 3.9". Of course if I hadn't sold you my DX mount....!  Does you wife know about that?

I think you've touched on the real make or break issue, that of seeing. Although I consider myself very lucky to have a site that's often blessed with reasonably good seeing, it is of course only relative, and my preference for refractors may in part be due to their being less sensitive to my local conditions. As for Jupiter, the best view I've ever had of its incredible complexity was through your Takahashi FC100DL,  while my best ever view of Saturn has to be through a Skywatcher 120ED Pro. I've only once seen a SCT give a good planetary view and that was an old 1980's Orange C8. On all occasions the planet's were high in the sky, unlike at present.

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Interesting comparison between the two scopes.

I truly enjoy my 10" OOUK and use it a lot, but it needs time to cool and of course then comes on song, 
but often the seeing is the issue with the larger aperture.
In steps the ED103 Vixen and a smaller lower magnification view just pops out and sings.
A case of horses for courses and prevailing conditions for sure.

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