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The Askar FRA 400 Quintuplet Astrograph

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156 replies to this topic

#151 Poochpa

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Posted 01 April 2021 - 10:24 AM

Stephen,

Here's the link to the almost full-res image. Just a 2% crop to eliminate stacking artifacts.

Mike

https://drive.google...iew?usp=sharing


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#152 StephenW

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Posted 02 April 2021 - 10:41 AM

Here's a boring test image of Regulas from last night.   ASI 6200, no reducer, 500s exposure in Ha, no flats, darks or any processing other than STF

 

Light_ASIImg_500sec_small.jpg

 

Link to full rez fit:

https://www.dropbox....me0002.fit?dl=0

 

There is some tilt and some distortion approaching the corners, but overall I'm happy - it's significantly better than the star shapes I was getting with my Canon 100-400mm zoom.  Also pleasantly surprised at the lack of vignetting on the 6200!

 

 


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#153 Poochpa

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Posted 03 April 2021 - 03:25 PM

I did a second light test with the Askar 400 last night at it's native f/5.6, but this time using a Canon 6D MkII full-frame dslr.  I was disappointed to see what appears to be the mirror box shadow. I have not had the same degree of problem with my WO GT71. Flats helped and I was able to fix it in processing with PI's Canon Banding Script. Would going to a non-tapered M68 to M48 extension tube help? I assume it will only get worse if I get the dedicated reducer and use the scope at f/3.9 with the 6D?

Mike

Unprocessed single sub:

M35-Askar400_CanonMk2_1200.jpg


Edited by Poochpa, 03 April 2021 - 08:24 PM.


#154 trycatchfinally

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Posted 07 April 2021 - 06:47 PM

Got my FRA 400 yesterday!!

Put it on my MyT although I can also use it on my Skyguider Pro.

I added a dovetail plate to go from vixen style to attach to the MyT. This gives the focuser adequate clearance

I added an Optec SVX30 focuser which can communicate with SkyX Pro for doing autofocus

I added the Pegasus Astro Pocket Powerbox Advance for cable management with a custom adapter for attachment to a vixen bar on top

With this rig I am using my QHy268C because the image scale is 1.78 arcsec/px and it should be good for Andromeda. I really like that the FRA 400 came with a M54 adapter

When I put the FRA400 on my Skyguider Pro I will use a QHY247C because of the weight saving although resolution will be about 2 arcsec/px.

I am hoping to take it out to Death Valley next weekend (bortle 1 sky quality smile.gif  )

 

Hi Gene3,

 

I was wondering if you can share about your experience with this telescope using the SkyGuider Pro?  And do you have a photo of the setup (FRA400 + SGP) that you can share?  I have a Skyguider Pro (not looking to upgrade the mount til the end of the year) and I'm interested with the FRA 400.

 

Thank you!



#155 kvastronomer

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Posted 08 April 2021 - 04:56 PM

Please help to understand:

For my regular APO triplet refractor I don't care about "backfocus" if I can focus the image on camera sensor.

If I add a reducer or flattener I have to match exactly the backfocus distance recommended by FF/FR manufacturer.

 

FRA 400 is quintuplet petzval astrograph and it mentions 140mm backfocus in the manual. Does that mean I have to match required backfocus distance even if I don't use optional 0.7 reducer (which by itself requires 55mm backfocus)?



#156 ZL4PLM

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Posted 09 April 2021 - 12:56 AM

Please help to understand:

For my regular APO triplet refractor I don't care about "backfocus" if I can focus the image on camera sensor.

If I add a reducer or flattener I have to match exactly the backfocus distance recommended by FF/FR manufacturer.

 

FRA 400 is quintuplet petzval astrograph and it mentions 140mm backfocus in the manual. Does that mean I have to match required backfocus distance even if I don't use optional 0.7 reducer (which by itself requires 55mm backfocus)?

it is no different than your triplet :)

 

focus using the camera and don't worry about extensions etc as long as you focus

 

if using the reducer - its 55mm behind the threads 



#157 Poochpa

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Posted 09 April 2021 - 08:29 AM

Here's the processed image from my first use of the Askar FRA400 with a full-frame camera, a Canon 6DMkII. Subs were 40x90s at ISO 1600.

Mike

https://www.cloudyni...658_2384473.jpg

 


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