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January 2019 Lunar Eclipse


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#1 SBacon

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Posted 21 January 2019 - 09:28 AM

Finally got some clear skies over North Alabama just in time for the eclipse.  While it was 27F outside, I was really enjoying the warm room in the observatory! 

 

Steve

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  • Lunar Eclipse 1-20-19.jpg


#2 MistrBadgr

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Posted 21 January 2019 - 04:47 PM

Hi Steve!

 

Nice!....both the images and the warm room! :)

 

I was out doing some testing on the Polaris 127 I have been modifying.  Mostly, I enjoyed the darkness during the eclipse itself.

 

Bill


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Bill Steen, Sky Hunters' Haven Observatory, Broken Arrow, Oklahoma

#3 SBacon

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Posted 22 January 2019 - 06:19 AM

Thanks Bill.  How is the Polaris project going?

 

Steve



#4 MistrBadgr

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Posted 22 January 2019 - 01:08 PM

Hi Steve,

 

Interesting project.

 

I am going to post about it soon.....f/3.5 spherical primary mirror....2.2x booster lens with lots of spherical correction in it, but not enough.  Large amount of field curvature.  I have lined the whole thing with flocking, plus I built a light shield out of a one gallon paint can and flocked that.  With all the flocking, all the coma went below detection for my eyesight as long as there is reasonable transparency (back yard Bortle 6.0)  With transparency of 2, coma starts showing up again.  Apparently almost all of the coma is coming from reflections off of things you don't want and from light pollution outside the actual light cone.

 

Finally got a good enough collimation....I mean really dead on....using a Howie Glatter laser collimator, a Cheshire eyepiece, a black dot in the middle of the primary, and a cardboard circle with a hole in the middle (use in place of the primary and look through the hole to see if the secondary is aimed well enough to start collimating.

 

With a good collimation and using Epsilon 2 Lyra, I found the space between the two disks to be at least 1.5 times the disk widths.  Doing the arithmetic, if that value is 1.4, with the double star's seperation at 2.4 arc sec, the two disks would be kissing with a separation of 1.0.  With the space  between the disks being 1.5 diameters, the kissing separation would be 0.96.  If the space is 1.6 times the disk width, the kissing separation is 0.92.  So I think this thing will operate very near the Dawes limit for its diameter.

 

With the field curvature, the outer half of the field is not very useful with stars....pretty ugly with bloated stars.  With Saturn and Jupiter, had pretty good detail and really good contrast.  Contrast is great on the Moon, but no depth of field....keep fighting with the focuser knob all the time.

 

With the f/3.5 of the light cone, a change in focuser position (booster lens also) the width of the image entering the booster lens changes significantly.  A change of 3.5mm on the focuser changes the width of the image 1mm.  The best I can tell, the image entering the booster lens should be 14.2 mm.  I am seeing enough change in focuser position to vary the image size by over 1mm, which explains why one eyepiece will be fuzzy and bland, while another with more back focuser beats the closer focused eyepiece that is supposed to be better.

 

I will be talking to the Meade folks about this scope design.

 

Bill


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Bill Steen, Sky Hunters' Haven Observatory, Broken Arrow, Oklahoma

#5 RickScofield

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Posted 23 January 2019 - 07:34 PM

Steve,
We had very poor weather and was not able to see anything of the eclipse. That’s been the story here all winter so far. Hopefully will get a break.

Bill,
Sounds like Meade should put you on their payroll for all your work. I hope all is well with you.

Take care,
RickScofield
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