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Askar 200mm F4 Astrophotography Lens / Scope

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34 replies to this topic

#26 Astrojedi

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Posted 08 October 2020 - 10:40 PM

Great. Actually from the photos it does look like that dew shield part is always stationary. Good to have this confirmed. 

 

I will wait for your CR3 drop before I place my order. Thank you again for answering all these questions. 

I am unable to find a good CR3. All the subs from the image above were taken unguided on the Az-GTi and hence have small tracking errors (only visible when you pixel peep) making it hard to evaluate the performance of the lens.

 

Let me take a sub on a better mount with good focus when the clouds clear up which can help you evaluate the lens better. Post #7 above is from a full frame with better tracking.



#27 B 26354

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Posted 08 October 2020 - 11:33 PM

I didn't "presume" anything. I offered a suggestion, prefaced with "Perhaps it would be useful... if you provided...".

 

I'm happy to move on.



#28 w7ay

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Posted 19 October 2020 - 01:58 PM

Umm let me rephrase - does the dew shield moves in the direction of arrows in image below when you use the coarse focus ring? 

I received my Askar 200 a couple of days ago and just opened the box.  

 

In answer to (I think) your question, the distance from the end of the lens hood to the dovetail screws changes when you turn the main focuser ring.

 

With the main focuser ring fixed, and with the lens pointed towards zenith, I do not notice any movement when I press down on the lens hood (no backdrive :-).  So, while the distance does change with focus, I don't think that you need to be concerned about the weight of your flat illumination panel defocusing the lens.

 

The micro-focuser ring does not appear to change the distance from the lens hood to the dovetail screws.

 

Chen


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#29 Astrojedi

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Posted 30 October 2020 - 09:57 PM

Thank you for getting back. This is excellent. Can you also confirm that the dew shield / lens front element does not move linearly when you adjust focus? 

 

Looking forward to see CR3 files. 

Sorry for the delay. Work and clouds got in the way. Here is the CR3 file. It is a full frame 5s exposure centered on Vega. The lens is fully open at F4. This was taken on the RST-135 with the Canon Ra.

 

There may be some uneven illumination and/or reflections due to clouds and a near full Moon. So ignore that and focus on the stars.

 

https://www.amazon.c...7KYLeG62LKMHaYC

 

Here is the PixInsight aberration inspector image. There is the very slightest of tilt in the middle left square of the mosaic below but the image is still many times better than I got with any other lens or small scope. Truly excellent performance.

 

 

Vega_Test_2_LIGHT_5s_3200iso_32c_20201030_19h12m56s794ms_mosaic.jpg


Edited by Astrojedi, 30 October 2020 - 09:58 PM.

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#30 deepanshu29

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Posted 31 October 2020 - 12:31 AM

Thank you for the raw file. This does look very good for such wide lens. 



#31 astroseyer

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Posted 01 November 2020 - 04:10 PM

Askar has some really interesting offerings. Thanks for posting and following up with the test frames. Great stuff.



#32 Mattek

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Posted 18 February 2021 - 05:33 PM

Hi, I just purchased my ACL200 (and shop had to change it because m48 thread was bad and didn't turn on adapter), my concern is the hood: it's labelled like "removable" but I'm not able to unscrew it and this is a problem for the fact that in this way it's impossible to put any 82mm filter on it (that I purchased for it too..) suggest?

#33 TxStars

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Posted 21 February 2021 - 10:27 PM

I don't have one, but from the pictures on the web page the lens shade seems to come off with a 1/2 turn (don't know if it is to the L or R tho)

 

*The online manual says that it screws on.. but not if it is L or R threads...  (Most are R )


Edited by TxStars, 21 February 2021 - 10:32 PM.


#34 Mattek

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Posted 22 February 2021 - 05:05 PM

Thx, also in the paper with the box I found this same info but it didn't unscrew! By now I manage to screw my clear sky with the help of the lens cap.. not the easiest way but work..

#35 tonyt

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Posted Today, 11:22 PM

Hi, I just purchased my ACL200 (and shop had to change it because m48 thread was bad and didn't turn on adapter), my concern is the hood: it's labelled like "removable" but I'm not able to unscrew it and this is a problem for the fact that in this way it's impossible to put any 82mm filter on it (that I purchased for it too..) suggest?

The hood on mine is removable - it has a very fine thread and unscrews several turns. You could try heating the hood with a dew heater on a cold night and then try to unscrew it.




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