Askar 103 APO 0.6x Reducer

The test I have seen indicated an excess of violet color in blue stars.

I figure you would have to have two different lenses of either fluorite or extra low dispersion glass in order to get really low focal length ratio refractor and either a triplet or petzval design to not use other things to have acceptable levels of low chromatic aberration in the photos. I seen the askar 103 could be reduced down to f 4 and wondered how it would be with chromatic aberration using only one element of ed glass.

Perhaps slightly increasing the back focus would improve the elongation of the corner stars. I would probably try adding a millimeter to see what happens.

Have the same scope with the reducers and have no problems at all, with camera 533 MM

The sensor is smaller in this case, and it's square shape allows a "better use" of the field. Perhaps the best way to use the x0,6 reducer.

I purchased the same items. Last week I installed the 0.6x reducer to test.

I was very disappointed with the stars, even halfway to the center of the field. I quickly removed it and reinstalled the 0.8x reducer to resume my nights shooting.  I am afraid the 0.6x will be in its original box, sitting on the shelf.

I will say that I am very happy with the 0.8x reducer. It does a great job.

Don

I am unable to edit the previous post. 

Update:

I added the Askar back focus adjuster which gives 2mm of adjustment. After some tweaking, I am getting much better results with the 0.6x reducer and can now recommend it using the ASI 2600MC Pro.

Don

Very interesting.
Could you provide an image ?

I purchased the same items. Last week I installed the 0.6x reducer to test.

I was very disappointed with the stars, even halfway to the center of the field. I quickly removed it and reinstalled the 0.8x reducer to resume my nights shooting.  I am afraid the 0.6x will be in its original box, sitting on the shelf.

I will say that I am very happy with the 0.8x reducer. It does a great job.

Don

I am unable to edit the previous post. 

Update:

I added the Askar back focus adjuster which gives 2mm of adjustment. After some tweaking, I am getting much better results with the 0.6x reducer and can now recommend it using the ASI 2600MC Pro.

Don

**I can now say that I have gotten better results with the 0.6x reducer when using some spacer rings. I added into two 1mm spacer rings to my imaging train to increase by backfocus to 57 mm instead of the standard 55 mm. With any of my 2 mm filters it becomes more like 57.67 mm. Thank you to @Jon Bryan for suggesting that idea. 

The star shapes are still not perfect but certainly a lot better than when my imaging train was the standard 55 mm.  That askar back focus adjuster you got would probably make it easier to dial in the backfocus perfectly.

If anyone is interested in selling theirs I am interested.

I found exactly the same issue with the 0.6 reducer. Using an Astronomik UV/IR filter although star shapes were great across the full field, blue stars across the field suffered from horrendous chromatic aberration. I didn't see the issue when using an L-Enhance filter
 
I've since bought the Askar Backfocus Adjuster and managed to dial in the correct back-focus, but not had chance to test again using the UV/IR filter.

Based upon your results, I'm looking forward to testing and hopefully achieving better results using the 0.6 reducer.