I was reminded last month when answering an equipment database question for Mr. Iovene that I restarted this hobby doing wide field imaging. I had a T5i which I modified myself, and bought used lenses off of eBay of various focal lengths. It was a lot of fun to capture huge areas of the sky all at once, and at the time I thought these were pretty good pictures. I moved away from this equipment because of the lack of cooling and poor star shapes from the cheap glass I was using.

I still enjoy looking at quality wide field astrophotography. If you follow @Łukasz Żak you can see from his wonderful images that there are many DSOs that are simply too big to image with a normal telescope.

I wondered if there was a good short focal length scope out there that could produce quality images using my ASI1600. This 4/3 camera takes up a very small amount of back focus so it can be used with a wide variety of optics. I wanted an even wider field of view than the RedCat.

Enter the FMA135 from Askar. I had heard of the brand from a Cuiv The Lazy Geek video and took a look on their web site. The FMA135 is advertised as an f4.5 astrograph, consisting of 2 parts - the objective and a flattener. It is a strange looking thing when assembled, and has a helical focuser about mid way along its length. The lens cap has a smaller section which can be removed in favour of a 1.25 inch filter.

Askar indicates that the FMA135 is good up to an APS sensor size and has a 55mm backfocus. I connected it to the standard spacer plus another spacer I had lying around, an 8 x 1.25 inch filter wheel and the ASI1600. I also committed to a new set of 3nm Antlia narrowband filters. I bought 1.25 inch versions even though they should be slightly bigger for the 4/3 sensor. I repurposed my Baader RGB filter set from my planetary rig that has not been used for a while.

I assembled it all within some SmallRig knock-off parts from Amazon, shown in Version D. This framework allowed me to make use of a surplus focuser that I made a while back using a gear head stepper motor and an Arduino microcontroller. It is loaded up with Robert Brown's My Focuser Pro2 and works like any other focuser. I could have just used an EAF if I had an extra one. The astrograph is supported by the red vixen based tube ring provided with the scope, to ensure there is no physical distortion introduced by the focuser belt tension.

So, how did it all work out? After some basic testing on the patio beside my home to get the focuser working and ensure everything was ready, I moved it into position near the centre of my yard to start the project and shot for several nights.

A lightly processed version of the Ha image is shown in revision E, and an aberration inspector of a single Ha sub in revision F. I may have been off by 1 to 1.5mm with the backspacing, but the aberration near the corners was clearly visible. Overall, it is MUCH better than a camera lens, and probably right where Askar wanted to be at this price point. However, I did not want that level of coma in the final result and wanted to keep the wide field of view without cropping. I chose not to do a single star image, and did a 2x2 mosaic for just the stars to keep them as round as possible in the final version. Given the pixel scale, I dithered all the channels.

I'm quite happy with the final result of the image, and I will continue to use this setup on the CEM25P for a while. With this $300 USD scope it appears you can get some good images of larger objects in the sky, and you do not have to worry so much about guiding!