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World's first 200mm F/4 APO Flat-Field Astro Camera Lens will be released in this month

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#26 sharpstar

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Posted 30 July 2020 - 03:35 AM

Please check our facebook link to see the astro photos that taken by ZWO 094 and 6200 full frame cameras with this lens:

 

 

https://www.facebook...03346594423278/


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#27 nicknacknock

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Posted 30 July 2020 - 03:39 AM

Well, I was convinced already! Waiting for Teleskop Service to bring it to stock. 

 

Question 1: Is the mounting foot Arca Swiss or Vixen?

 

Question 2: What is the thread for the hood to fit the lens?

 

Question 3: What is the hood outside diameter?



#28 Michael Covington

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Posted 30 July 2020 - 08:51 AM

1: Vixen, and also has 1/4-inch and 3/8-inch tripod sockets in it

2: It screws on externally.  The filter thread is 82 mm but the hood does not go into that (the lens cap does).  There is an outside thread for the hood.

3. About 98.5 mm 

 

The usual way to add a filter is to put a 48-mm filter inside the lens.  The hindmost part of the lens, which attaches to the 48-mm T-ring, is removable and has a space in it for a 48-mm filter.  (Not attached to the T-ring despite having the same thread.)

 

I have one here that I'm going to test when weather permits.


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#29 nicknacknock

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Posted 31 July 2020 - 12:13 AM

Thanks Michael!



#30 Sandy Swede

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Posted 31 July 2020 - 07:49 AM

Please go to below link to see the spot diagram and other info of ACL200, it's 6 elements design and 2 ED lenses for a Astrograph design.

 

http://www.askarlens...class1/179.html

 

Also we add the F4-F22 aperture that let customers using it like a normal lens.

 

We just hope customers can use Astrograph very easily and make it as portable as we can.

That will be a big deal for those astro photographers who also love daylight (normal?) photography.  That is one of the reasons I bought the Rokinon 135mm f/2.  Of course, I then had to buy the Canon 200mm f/2.8.  And the RedCat.  Someone stop me!

 

Michael C. makes a good point about some inherent cost savings in the Askar 200 ("The ability to take 48mm filters (is it 48mm?) and the presence of a tripod foot with a  Vixen dovetail.").  Also, we shouldn't overlook the fine focus feature.  Yes, Michael, the Askar will compete against the RedCat to some extent, but I think most folks regard the RedCat and its variants to be petzval design telescopes with all that this brings to the table.  Should WO be more worried about the Askar FRA 72mm aperture, 400mm FL f/5.6 with .7x reducer to f/3.9?  However, this scope is at a much higher price point: $1,100 + $269 for reducer.

 

 



#31 Michael Covington

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Posted 31 July 2020 - 09:01 AM

Askar also has a product with about a 400-mm focal length, as I recall.



#32 Sandy Swede

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Posted 31 July 2020 - 10:12 AM

Askar also has a product with about a 400-mm focal length, as I recall.

Yes, it does.  See my post above.


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#33 Astrojedi

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Posted 05 August 2020 - 02:29 PM

Please check our facebook link to see the astro photos that taken by ZWO 094 and 6200 full frame cameras with this lens:

 

 

https://www.facebook...03346594423278/

Thanks. Those images look promising although they are very noisy and compressed. Do you have any full resolution images available?

 

Also a question: Does the lens come with a petal shaped hood or a round dew shield?  Your website shows a round dew shield but the Agena Astro website shows a petal shaped hood.


Edited by Astrojedi, 05 August 2020 - 02:32 PM.

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#34 sharpstar

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Posted 05 August 2020 - 10:07 PM

Thanks. Those images look promising although they are very noisy and compressed. Do you have any full resolution images available?

 

Also a question: Does the lens come with a petal shaped hood or a round dew shield?  Your website shows a round dew shield but the Agena Astro website shows a petal shaped hood.

Yes, please give us your email and we send to you full resolution image.

 

It's round metal thread hood, please see our website: 

 

http://www.askarlens...class1/179.html


Edited by sharpstar, 05 August 2020 - 10:08 PM.


#35 photobookie

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Posted 08 August 2020 - 01:21 PM

How do you prevent aperture spikes from appearing on bright stars from this lens’s aperture blades?

 

Also hope you will consider designing a 100mm f2.8 next! There’s a real market for wide-field flat field astronomical lenses!

 

Thanks, Rick



#36 Michael Covington

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Posted 08 August 2020 - 03:35 PM

I'm testing the Sharpstar 200/4 right now.  There are no aperture blade spikes at f/4 because the aperture is a circle.  Spikes appear as you stop it down.



#37 photobookie

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Posted 08 August 2020 - 03:41 PM

Thanks Michael, Some camera lenses when wide open do still show an edge of aperture blade which does create diffraction spikes. So this is great news. Can't wait to hear what you think. Love that this has a micro focusing collar along with more coarse focusing.   


Edited by photobookie, 08 August 2020 - 08:29 PM.

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#38 calypsob

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Posted 08 August 2020 - 08:51 PM

Id like to see some raw data from this askar. 



#39 mxcoppell

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Posted 30 August 2020 - 12:54 PM

Any consideration of adding AF to this the ACL200 from SharpStar?



#40 Michael Covington

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Posted 30 August 2020 - 03:07 PM

Any consideration of adding AF to this the ACL200 from SharpStar?

I assume you mean autofocus on DSLRs, because with an astrocamera, you could presumably put an electronic focuser into the imaging train with the lens as it is.  (I'm not sure how much space such things take up.  This lens has 55 mm of back focus.)

If DSLR autofocus were added, then it would cost more, and would be more like competing lenses, and it wouldn't be able to use a T-mount -- there would have to be a different model for each brand of camera.

I don't autofocus my astrophotos.  Does anyone?  



#41 mxcoppell

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Posted 31 August 2020 - 12:29 AM

Thanks for the response.

 

No. What I means is some step motor driven belt system configuration.



#42 anat

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Posted 31 August 2020 - 03:29 AM

How good is the color correction of this lens? I am interesred in both ACL200 and FMA180. Thanks.

Edited by anat, 31 August 2020 - 03:29 AM.


#43 Michael Covington

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Posted 31 August 2020 - 09:21 AM

How good is the color correction of this lens? I am interesred in both ACL200 and FMA180. Thanks.

With the 200/4, I am impressed.  Focusing in Live View with an H-alpha-modified camera, most telephoto lenses show considerable color fringing when slightly out of focus, and then when the star image comes into focus, it is white.  (Red-fringed on one side of focus and green-fringed on the other side.)  With this lens, the star images are pure white whether in focus or out.   Focusing consists of making a white disk as small as possible.  There are no color fringes.



#44 mxcoppell

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Posted 31 August 2020 - 09:49 AM

Michael, could you share if this lens holds up the focus with ambient temperature changes? Thanks!



#45 Michael Covington

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Posted 31 August 2020 - 04:45 PM

Michael, could you share if this lens holds up the focus with ambient temperature changes? Thanks!

I don't know yet.  It's probably not a lot different from a lot of other lenses in that regard.



#46 anat

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Posted 31 August 2020 - 06:01 PM

Michael, do you also have a chance to test FMA180? If yes, how does it perfom comparing to ACL200?

Sent from my SM-N960F using Tapatalk

#47 Michael Covington

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Posted 31 August 2020 - 08:53 PM

No, I've only tested the 200/4 lens.  I would expect it to be more highly corrected than the others because it has a more elaborate design (6 elements if I remember right).  But SharpStar is introducing a lot of interesting products!



#48 Helvetios

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Posted 02 September 2020 - 08:07 AM

Will be available in 2 weeks and you can purchase from Agena Astro or Camera Concepts.

Agena Astro just got them in.

 

By the way, the dew shield is metal too, which means one should be able to wrap a dew heater around it and it will conduct enough heat to the lens while keeping clear of the fine focus ring that is close to the front where it could interfere.  Nice that you can lock the focus rings too.



#49 photobookie

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Posted 02 September 2020 - 09:43 AM

I don't autofocus my astrophotos.  Does anyone?  

I would love an autofocus system even with shorter focal length scopes. With my Space Cat, I've experienced focus shift due to temperature dropping over the night rendering my images useless. 



#50 Michael Covington

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Posted 02 September 2020 - 10:14 AM

I would love an autofocus system even with shorter focal length scopes. With my Space Cat, I've experienced focus shift due to temperature dropping over the night rendering my images useless. 

There is electronic focusing for telescopes with astrocameras and computers.  (Amy Astro has videos about it.)  You could do that with this lens if its 55 mm of back focus is sufficient.  (I don't know how much room the apparatus takes up.)  Some observers do re-do the focus periodically during a session as the temperature changes.

I suppose you could make a case for building such a thing into this lens -- not autofocus per se, but computer-controlled electronic focus, so that appropriate software, analyzing your image, could refocus the lens.
 

I thought what was being talked about was making it like an autofocus DSLR lens.  Not much help for astronomy because the autofocus sensors in DSLRs usually can't see stars well enough to focus on them.




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