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Askar FMA 180, 40mm F4.5

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#1 vilchez

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Posted 22 October 2020 - 02:49 AM

Askar FMA 180, 40/180 f4.5 Magnificent and very small sextuplet refractor:

 

http://www.askarlens...class3/186.html

 

 

 

 

With a takahashi prism it can be used as a 40/180 flat-field refractor(has mounted the reducer-flattener), it focuses perfectly with Delite and TV Ploss eyepieces, unfortunately the baader zoom cannot focus.

 

 

EacQkoo.jpg

 

 

 

 

In this image it can be seen in its visual configuration with the takahashi prism, the dovetail serves to use as a telescope directly on the mount, the "extender" uses an extendable t2 adapter to achieve the correct distance for photography and get a flat&corrected field. To use it for photography, I just have to loosen the clicklock, remove the prism and place the extender.

 

2N56ovu.jpg

 

 

 

It can be used as a finder, or a secondary wide-field telescope.

 

86ZCYq1.jpg

 

 

 

Or as a dedicated telescope.

 

fRr7sxy.jpg

 

 

 

 

 

ASKAR FMA180, zwo294mc(planetary version, not refrigerated) and zwo duo band filter. It's only 30 minutes, 30x1' at 120 gain, and with 5 dark.   

 

 

Lagoon & Trifid Nebula

 

Sharpcap live stacking direct result

tWHl1xL.jpg

 

 

A little processed

 

Sr0ij8J.jpg


Edited by vilchez, 22 October 2020 - 03:04 AM.

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#2 Cziffra

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Posted 22 October 2020 - 11:22 AM

Thanks for posting this. I'm thinking about gettging one for wide field AP. I'll probably take the plunge.



#3 Rodrigo C.

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Posted 24 October 2020 - 11:49 PM

Thanks, I have one of these and I was searching a way to use it visually with the reducer. I now know it is possible.



#4 Astrojensen

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Posted 25 October 2020 - 02:32 AM

Highly interesting. I've been thinking of using this little scope as the ultimate finderscope, as it would have a FAR better corrected field than any of the ubiquitous 30-50mm finderscopes available. At 180mm focal length, with the reducer/flattener in place, you would get 9x, 4.4mm exit pupil and a 7.8° TFOV with a 20mm/70° crosshair eyepiece. With a 26mm/70° eyepiece, you would get 7x, 5.7mm exit pupil and a whopping 10° TFOV. A Baader T2 amici prism would give an erect and correct view, while also have a larger fully illuminated field than a standard 1.25" diagonal. 

 

 

Clear skies!

Thomas, Denmark


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#5 desertlens

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Posted 25 October 2020 - 03:18 AM

I've yet to give this combination a good shakedown but first light was promising. It's nice to know that the reducer can work visually as well with the 40. Wide field entertainment.

 

Ss76As40.jpg


Edited by desertlens, 25 October 2020 - 03:22 AM.

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#6 emilslomi

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Posted 25 October 2020 - 11:42 AM

I was already tempted by the SW50ED, which thankfully (or regrettably) did not have enough back focus. But I'm sold trying this one - also because the 60ED is a little bit bigger than I expected. And with extension tube, flattener and the cute rings, it promises quite some playtime. My piggybank cannot miss more than a handful of coins ... What size airy disk will it have?

 

Emil



#7 Astrojensen

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Posted 25 October 2020 - 02:53 PM

I was already tempted by the SW50ED, which thankfully (or regrettably) did not have enough back focus. But I'm sold trying this one - also because the 60ED is a little bit bigger than I expected. And with extension tube, flattener and the cute rings, it promises quite some playtime. My piggybank cannot miss more than a handful of coins ... What size airy disk will it have?

 

Emil

Per Airy's formula

 

a=2.76/r

 

Where a is the radius of the Airy disk to the first minima and r is the radius of the aperture in inches, then a 40mm will have an Airy disk with a diameter of 7". That's a bit misleading, since the spurious disk of the star will be smaller and in the case of faint stars, very much smaller. The common Dawes limit calculation

 

n=114/d

 

where n is the narrowest double star you can still barely resolve and d is the aperture in millimeters, suggest that you can resolve double stars down to 2.85". This of course assuming that the optics are diffraction limited (which I suspect they are). 

 

 

Clear skies!

Thomas, Denmark


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#8 Gavster

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Posted 18 November 2020 - 03:57 PM

This thread gave me ideas smile.gif

I was trying to find a setup that would work with my nv monocular (which requires a lot of in focus) and I think I’ve found a way to make this askar work. By using a Baader t2 prism and screwing the t2 thread straight into the reducer, it comes to focus with about 5mm to spare and will be pretty close to the ideal 55mm distance from

reducer to focal plane. For other eyepieces I can easily use a t2 extension tube as required.

Its certainly a small thing but will give a nice 6 degree fov with my nv monocular.

 

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#9 Memo Tron

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Posted 23 November 2020 - 12:12 PM

Any experience with it as a guide scope? I´m looking as a guiding one for my small refractor and this would be a great one as it could be use as a separate AP scope.

 

Would it be a good fit to a ZWO ASI 174MM mini?




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