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Celestrons C8 XLT vs Intes MK-67 vs Takahashi TSA-102 on Jupiter

Posted by Ralph Aguirre   10/03/2011 00:15:AM

Jupiter is well positioned in the evening sky again, and to me, begins the observing season for viewing Jupiter as a back yard astronomer in the evenings. Currently, the planet rises before 9pm, making it an ideal back yard target for astronomers who want to get out for a few hrs and have fun with their gear, observing the our biggest Gas Giant.

Earlier this week, I did a side by side comparison on Jupiter with both my TSA-102 and my Intes MK-67. The seeing conditions were fairly bad, viewing in 9 mph winds with 3/5 seeing conditions. I posted this in the Solar System forum in Astromart which started a fun series of conversations on optics and Maksutovs vs Refractors vs Schmidt Cassegrain at every level. In that comparison, the Mak performed better and gave better views of Jupiter, than my TSA. Both scopes were performing at a very low level due to the seeing conditions, with neither scope able to perform much above 120x.

Tonight (Saturday night) I had a chance to again compare 3 of my favorite scopes on Jupiter. The difference between tonight and my previous report on my MK-67 vs my TSA, is that the conditions were much more favorable, with the Clear Sky Clock for my area reporting varying conditions from 3/5 to 4/5 conditions for both seeing and transparency. I also checked the Jet stream over Calif and non were to be present tonight. The temperature was reported at 58 deg F and clear, with 1mph wind from the WSW, so fairly ideal conditions for back yard astronomy considering the season. The huge advantage in tonights observing, was that there was no wind, and the seeing and transparency appeared to be much better.

Since it's the weekend and there is no need for me to get up early for work, I took out my 3 smaller but all potent scopes. My Intes MK-67, (standard model), My Takahashi TSA-102, and my Carbon Fiber C8 XLT. All three scopes are perfect examples of each type of scope, all 3 scopes are in 100% new condition and all 3 appear to have perfect collimation during my observing session. Tonight, I used my G11 for all 3 scopes, and the diagonal was an AP 2" Maxibrite.

I placed all 3 scopes outside at 8pm, so they had plenty of time to acclimate to the night conditions, by the start of my observing at 11pm. Jupiter was my only target.

The attached drawing on Jupiter's Clouds and Bands, can be used to understand the surface details I describe in this article.

First on the mount was my MK-67. Since it won out over my TSA last time in windy mediocre conditions, I wanted to use it as my starting scope. Jupiter was 2 hrs from its transit position, and was roughly 65 degrees up in the sky, fairly high and perfectly placed for this comparison.
The rock solid G11 for all three lightweight scopes made any high power viewing effortless.

Using my 31 Nagler to center Jupiter in the eyepiece, tiny Jupiter and 5 of its moons were clearly in view. I immediately put in my 14 meade UWA, and was presented with a sharp view of Jupiter. The GRS was just rolling into view, and was easy to see protruding from the Southern Equatorial Belt.

Clearly tonight, the conditions were more favorable, and the little MK-67 was begging for more power. Last time, the 14 Meade UWA hit the ceiling of magnification as what I was able to get out of this scope, due to the windy conditions. I inserted my 12Nagler and Jupiter was larger with no loss in resolution or contras. The North and South Polar Hoods and NEB and SEB were easy to see also. At 150x, I thought the view was perfect. The GRS looked like a big eye on the SEB. Still looking for the ceiling, in inserted my 9 Nagler. at 200x, the view softened up just slightly in that the crisp lines from the bands were softer, though the permieter of the planet remained very sharp and the 5 moons were perfect points of light, with two of the moons taking on more size than points of light. The Planet was larger and the details were easier to see, however I could not make out any festoons, and the North North and South South Temperate belts were just coming in and out of view. Also, the lighter Zones on the planets surface were no longer white, and seemed slightly washed out or gray in color, maybe due to over doing the magnification slightly for the seeing conditions tonight. The best magnification for tonight I think was between 150x and 200x. When using the 12 Nag, the scope seemed to want more magnification, but the 9 Nag seemed to be slightly too much Magnification. My daughter and her friend both thought the 9mm gave an excellent view of the planet and said it looked like a photograph from their science classes. Since I was being as critical as possible, I thought maybe a 10mm eyepiece would have probably been ideal, giving me maximum size while maintaining its sharpness. Maybe even the North North and South South Temperate belts would have been more steady and solid in the eyepiece. Nevertheless, Jupiter was stunning at 150x and if this was the only scope I ever owned and if I could see Jupiter this way all the time, Id be a pretty happy camper!

For now, I removed the MK-67 from the mount and put up my C8. As before, the 31 Nagler was the first in the scope to center the planet in the eyepiece.

Jupiter was very bright and full of details, even at low power. Right away I inserted my 22 Nagler. The planet was large and bright, but surface details were soft. The Moons had slight flairs to one side, so I pointed the scope at the brightest star I could find and noticed the out of focus donut was slightly out of round. In went a high power eyepiece, and a slight adjustment to one of the colimination screws on the secondary made everything perfect. In and out of focus was perfectly concentric, and the stars in the field of view became perfect tiny O-rings on both sides of focus.

I moved the C8 back to Jupiter and inserted the 14 Meade UWA, and the planet just snapped in focus. The contras was excellent. The planets Temperate and tropical Zones were very bright and white, showing much more contras than the MK-67. The Great Red Spot was darker and the NEB and SEB was darker than what was showing from the MK-67. This was at 142x. Both the North and South Temperate belts were more visible and unlike the MK-67, stayed in view, instead of coming in and out of view.
In went the 12mm Nagler at 166x. Everything was larger and just as vivid. Focus became tougher to find but when it came in, it showed the C8 was out performing the MK-67 on both surface details and especially contras. The larger aperture of the C8 was bringing in the North North and South South Temperate belts easier than the MK-67. Just a slight amount of focus image shift was starting to be noticeable on the C8, compared to the focuser on the MK-67 which had a crisper and more stable view during focusing. With the C8, the contras between the lighter Temperate zones and the darker Temperate belts were more obvious. Where the MK-67 was starting to show slightly washed out Whites" from the Temperate zones, the C8 was showing "brighter whites, and darker darks" just like the detergent commercials use to advertise. The GRS was more obvious and darker also.
Increasing the Magnification another notch using my 9 Nagler (222x)showed an even large Jupiter, but with slightly softer resolution. Even at this magnification, the view was very good, but the south south and north north temperate belts began to disappear and reappear, probably from the unsteady seeing conditions. For tonight, the C8's maximum magnification on Jupiter was probably around 200x. At this magnification and above, an external crayford type refractor focuser would help keep the scopes focus more precise. Again I asked my Daughter and her friend to look at Jupiter and they liked this view better, because they said the planet was brighter and larger, but the focusing wasn't as good, making the sweet spot in focusing harder to find.

Out came the C8 and in went the TSA. On the larger G11, the TSA looks very showy and potent. The larger mount vs my Vixen GP-DX from the other night, showed off the beauty of the classic refractor look of the TSA 102 on an over sized German Equatorial mount.

With the shorter focal length of the TSA vs both cassagrains, I started with the 14 Meade UWA. Immediately the jet black skies produced by the TSA became obvious. At 60x, Jupiter was showing off the sharpest views of the night so far in the TSA. The moons were perfect points of light and even at 60x, the tiny GRS was easy to see on the Southern Equatorial Belt. I went straight for the 5mm Nagler this time. Unlike last time, were the windy weather conditions would not allow the scope to be usable at this magnification, Jupiter was showing the best view of the night so far in the TSA with the 5mm Nag at 164x.

Similar to the C8, the lighter temperate zones on the surface were very vivid and white, although the darker belts of Jupiter were not as dark, they stood out more in the TSA. The North North and South South temperate bands were well defined as visible bands on the surface.

Upping the Magnification one more time, I inserted my 3.5mm Nagler. At 234x. this was the view that stole the night. Jupiter was almost directly overhead, so it seems to be at a slight advantage in the TSA. The focus was positive and three of the larger moons took on the shape of perfect round balls of light instead of just tiny dots of light. With the larger moons, out of focus showed several diffraction rings.

Back to the surface details, I noticed the light gap around the GRS was visible, separating the GRS from the Southern Equatorial Band. Slight traces of festoons were showing up now, where they weren't visible with either of the two Cassegrains. Although both Polar hoods and all the visible bands were not as vivid and dark as with the other two scopes, the very thin temperate belts were sharper even including the equatorial area of planet. The crisp focus and razor sharp optics made the separation of Jupiter's band more obvious, and gave the appearance of the overall surface details to be very sharp and always in focus. This resolution was most obvious by seeing small details inside the bands, including some of the festoons despite the bands being lighter in color than on the other two scopes.

To be fair, I put both scopes back on the mount, to see if the position of Jupiter in the sky had given the TSA a slight edge. On both Cassagrains, I didn't notice any noticeable difference as the planet moved higher in the sky.

So tonight, unlike last time, the TSA was shown to have the superior resolution for pulling out surface details that the other two scopes couldn't even see. The C8 XLT was also a formidal opponent. The larger aperture was apparent, in that it was pulling in more light, making the contras from dark surface details to lighter surface details more obvious. Only the SCT focuser put the C8 at a disadvantage. The MK-67 was the most consistent of the group from last time to tonight. Normally I give that edge to the TSA, where outside conditions don't seem to effect its optical performance much.

For tonight, with steadier seeing conditions, the smaller, but very potent Takahashi TSA-102, was clearly showing more resolution by pulling out surface details, that larger mirrors couldn't even see.
The next time I try this comparison, will be when the seeing conditions are forecasted to be 5/5. The results then could be completely different then they were tonight.
Either way, it was a very fun way to spend the evening, at the beginning of Jupiter's viewing season on my back yard patio.

Hopefully, more get out to view Jupiter, with any scope you have. Even under full moon conditions, Jupiter is an excellent target, and a nice show piece to show your friends and family for an evening of fun. Its all fun and very relaxing and very enjoyable.

clear skies always,

Ralph Aguirre
Sacramento Valley Active Astronomer