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Mars - 5" v 8"

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#1 dweller25


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Posted 08 March 2010 - 02:44 PM

Evening of 7th March 2010, around 21:00UT

I was really enthusing about how good the seeing was so Mrs Dweller25 decided to come out to have a look.

Now this is a rare event as Mrs D and the cold night air don't mix, so to spice things up a little I suggested a shootout between the 5" Takahashi FS128 and the Skywatcher 8" F/6 Newtonian. Each of us would take a turn observing and drawing Mars in each scope so we could compare and contrast.

Seeing was very good - AII, temp was -4'C.

We concluded :-

1. Mrs D25 has better eyesight than me :bawling:

2. On nights of good seeing the humble Skywatcher outperforms the Tak :shocked:

Aperture really is king.

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#2 mathteacher



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Posted 08 March 2010 - 06:19 PM

That's really neat. So cool that Mrs. Dweller got in on the comparison. Thanks for sharing that.

#3 S1mas


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Posted 08 March 2010 - 07:17 PM

Hmm, quite different results... Very interesting, thanks.

#4 Tommy5



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Posted 08 March 2010 - 07:45 PM

Cool comparison sketches, great idea, just don't post this on the refractor forum :bawling:

#5 CarlosEH


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Posted 08 March 2010 - 09:47 PM


Excellent observations of Mars by you and your wife. You have both recorded a good amount of detail. Thank you for sharing them with us all.


#6 frank5817



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Posted 09 March 2010 - 12:26 AM


Great sketches by the both of you. :bow: :bow: It is always fun to compare scopes in this way.

Frank :)

#7 dweller25


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Posted 09 March 2010 - 05:34 AM

Thanks for the comments.

Just one point I should mention.....

The seeing was unusually good for the UK which allowed the larger aperture to work to it's capability. On most UK nights the 5" will match or outperform the 8".

#8 Michael & Louise

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Posted 09 March 2010 - 04:08 PM

Neat to see the comparison. Thanks for sharing!

#9 ladip63


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Posted 09 March 2010 - 06:09 PM

Nice job:D A lot of detail :waytogo:

#10 Uwe Pilz

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Posted 10 March 2010 - 02:40 AM

On really good nights you may have an advantage form a large Newton. The main problem I see(sic!) is the field curvature. If you are using a Dobson, the image degrades substantially if the planet is not in the middle of the FOV. Sharpness is onethe main point, but may be fixed be refocusing. But I can see at F/5 or so instrumetzs false color at the edges of the planet, if it not in the middel of the FOV. This could be mixed with oographic clouds. A mount could help here, but you have to ensure, that the planet is in the very middle of the FOV.

I do not know the Apo fraction of telescopes well enough. But my Maksutov telescope gives more comfortabel views. In the middle half of the FOV ther is no hint of false color. It is near the edges, but that may be an eyepiece effect. The planet is sharp all over the field, you do not need any sharpness correction (which causes vibration). If the seeing is in the near of 1", the smaller instrument may give the better or at least mor comfortable view. To bring house the capability of short Newton you have to observe very carefully.
I saw it yesterday at my Mars session.

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