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First High Res images with the 400 mm F/12.8 'Cassegrain'

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#1 rik ter horst

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Posted 24 February 2018 - 03:47 PM

After two years of construction, I have (well, almost) finished my 400 mm F/12.8 Modified Dall Kirkham Cassegrain with integrated ADC. Tonight I had a good chance to test the optics as the seeing was quite good at times.

This image Clavius was made at the 5100mm Focus of the telescope and I've used a red filter to reduce the turbulence a bit. This is just a small crop of the Original larger image that shows Tycho as well.

 

For full resolution, please have a look here: https://www.flickr.c...tetaken-public/

 

Below the crop of the original image:

 

Tycho and Clavius detail.jpg


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#2 c p ron

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Posted 24 February 2018 - 04:02 PM

Well done the full Res photo is like standing on the Moon.

 

Thanks for sharing.



#3 jerobe

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Posted 24 February 2018 - 04:38 PM

Rik, this is absolutely spectacular, amazing detail.  I'm looking forward to more of your lunar images with this gear.


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#4 Jon Isaacs

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Posted 24 February 2018 - 05:43 PM

Unbelievable.  I am glad you didn't have to sketch all that.  :)

 

Jon



#5 John Boudreau

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Posted 24 February 2018 - 06:05 PM

Rik, this is and outstanding result!  waytogo.gif

 

Looking forward to seeing photos and a description of your new scope when it's completely finished! laugh.gif



#6 ToxMan

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Posted 24 February 2018 - 06:05 PM

Nice work, Rik. Would you have time to share a picture of your Cassegrain?



#7 starcanoe

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Posted 24 February 2018 - 06:35 PM

Wow.

 

At first glance things look kinda blurry....but looking more closely you realize that those are areas of the moon's surface that would always kinda look blurry...like sand dunes (yes....I know thats whats not in the pic....)



#8 Kokatha man

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Posted 24 February 2018 - 06:36 PM

waytogo.gif waytogo.gif waytogo.gif



#9 rik ter horst

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Posted 25 February 2018 - 06:55 AM

Thank you all for your kind words!

 

Below an image of the instrument, which is a Modified Dall Kirkham with a three-lens field corrector. The third lens can move laterally in order to correct for Atmospheric Dispersion, so there are no extra prisms required. Guiding is done on an Equatorial Platform and this whole set-up is quite stable despite the strong wind of yesterdays night.

 

20170614_205117 klein.jpg

 

 


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#10 rik ter horst

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Posted 25 February 2018 - 07:01 AM

This is a crop of a larger image, showing Stadius, again at prime focus of the 40 cm telescope.

 

STADIUS_193112_g3_ap1617_Drizzle15_conv.jpg

 

 

Full image in full resolution: https://www.flickr.c...tetaken-public/


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#11 rik ter horst

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Posted 25 February 2018 - 07:07 AM

And the last one, the northern polar region.

 

Moon_193621_g3_ap476_Drizzle15_conv small.jpg

 

 

Full resolution: https://www.flickr.c...tetaken-public/


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#12 Erik Bakker

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Posted 25 February 2018 - 12:20 PM

Beautiful work Rik, a fitting reward for finishing your superb new instrument waytogo.gif


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#13 dr.who

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Posted 25 February 2018 - 12:25 PM

Beautiful work Rik! That is really stunning!

#14 flt158

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Posted 25 February 2018 - 01:19 PM

This is a crop of a larger image, showing Stadius, again at prime focus of the 40 cm telescope.

 

attachicon.gif STADIUS_193112_g3_ap1617_Drizzle15_conv.jpg

 

 

Full image in full resolution: https://www.flickr.c...tetaken-public/

That image of Stadius is precisely the area I was observing on Saturday evening 24th February 2018. 

I am curious to know as to what is the curious jagged feature at 11 o'clock in Rik's image. 

Does it have a name? Is it a Catena of craters?

I have never observed it before. 

I saw it in my William Optics 158 mm F/7 apochromatic refractor at 112X. 

I cannot discover its title anywhere. 

Perhaps some Lunar expert can help those who might be interested. 

The Stadius crater was hauntingly beautiful on Saturday night after dark very near the spectacular crater Eratosthenes!

It had been many years since I had observed it. 

 

A big thank you to Rik for publishing these stunning images -especially the Stadius image. 

 

Aubrey. 



#15 star drop

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Posted 25 February 2018 - 03:18 PM

Impressive images indeed!



#16 cbwerner

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Posted 25 February 2018 - 10:12 PM

Holy cow?!?!? How is that image even possible from Earth?!?!?

 

You're pulling our leg. You're in orbit around the Moon, aren't you . . .

 

applause.gif


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#17 troyt

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Posted 26 February 2018 - 01:19 AM

Good images.

I was expecting the eyepiece to be out the back, but the mounting system explains why it's on top. So the third lens is on a 45 degrees and is this the one that rotates? 

Always enjoy seeing your creations waytogo.gif  


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#18 rik ter horst

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Posted 26 February 2018 - 04:09 AM

Thanks Troyt! ;-)

 

Maybe this explains it a bit better:

 

layout klein.jpg

 

So there is a flat folding mirror under 45 degrees that reflects the light into the direction of the three-lens corrector. This corrector is designed such, that without affecting image quality, the top-lens can be shifted sideways (up to 6 mm) to create dispersion opposite to the Atmospheric Dispersion (without rotation or so). It works very well without adding extra optical components.

 

 

 

 


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#19 Bart Declercq

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Posted 26 February 2018 - 06:42 AM

Thanks Troyt! ;-)

 

Maybe this explains it a bit better:

 

attachicon.gif layout klein.jpg

 

So there is a flat folding mirror under 45 degrees that reflects the light into the direction of the three-lens corrector. This corrector is designed such, that without affecting image quality, the top-lens can be shifted sideways (up to 6 mm) to create dispersion opposite to the Atmospheric Dispersion (without rotation or so). It works very well without adding extra optical components.

If I understand the design right, the ADC would only work on an Alt-Az mounted telescope, right? As soon as you mount equatorially, you need to be able to rotate the ADC.

 

Still, awesome design and great results!



#20 dothead

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Posted 26 February 2018 - 10:09 AM

Nasmyth focus



#21 Jon Isaacs

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Posted 26 February 2018 - 10:51 AM

If I understand the design right, the ADC would only work on an Alt-Az mounted telescope, right? As soon as you mount equatorially, you need to be able to rotate the ADC.

 

 

As I understand it,  it's mounted on an Equatorial Platform.  That would keep the orientation of the focuser axis within about 5° of vertical..  With a GEM , one could rotate the tube .

 

A question for Rik:  Do you have an idea of the smallest resolved detail?  

 

Jon


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#22 rik ter horst

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Posted 26 February 2018 - 02:17 PM

Jon, I found craterlets of 1 km diameter, half white, half black so it must be around 500 meters I suppose...
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#23 Mark Harry

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Posted 10 March 2018 - 11:43 AM

Speechless. Beautiful lunar shots.



#24 james7ca

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Posted 12 March 2018 - 06:40 AM

That image of Stadius is precisely the area I was observing on Saturday evening 24th February 2018. 

I am curious to know as to what is the curious jagged feature at 11 o'clock in Rik's image. 

Does it have a name? Is it a Catena of craters?

...

Aubrey. 

I'm not sure to what you are referring, but if you mean that long string of craterlets that extends from just outside of Stadius to the edge of the frame (and beyond), then I think those are secondary impact craters from Copernicus. With proper lighting those can be seen in fairly small scopes, I'd guess even in an 80mm refractor. I've photographed them using both an 80mm APO and my Celestron C90 Mak and I know that I've gotten a fairly good full-disk image of the moon when those features become detectable (easy with higher magnifications and slightly larger scopes, but challenging when producing an image of the entire disk of the moon -- you need good seeing and a camera with a lot of small pixels, like Sony's IMX178/IMX183 or if you have a small format camera you need to produce a very large matrix to cover the full moon at adequate detail).

 

The following link to a moon map on the USGS website identifies many of those craterlets, but they are named after Stadius: Stadius P, Stadius R, Stadius E, Stadius S, etc.

 

  https://planetarynam.../lac_58_wac.pdf


Edited by james7ca, 12 March 2018 - 06:41 AM.


#25 Mel M

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Posted 24 March 2018 - 04:25 PM

And the last one, the northern polar region.

 

attachicon.gif Moon_193621_g3_ap476_Drizzle15_conv small.jpg

 

 

Full resolution: https://www.flickr.c...tetaken-public/

A refractor like view!smirk.gif




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