[ap-ug] Last image from Hawaii

Pete Lardizabal

Wonderful collection Roland! Proof of concept and execution!

Amazing demonstrations of dynamic range capabilities achievable and available to Astro-imagers these days. 



On Mar 30, 2023, at 3:12 AM, Roland Christen via groups.io <chris1011@...> wrote:

The clouds moved in so my imaging session here is pretty much over, The last session I imaged the Seagull Nebula thru holes in the clouds. Seeing was very good, but because of clouds I was able to get only 8 usable 5 minute subs over a 3 hour period. 


I want to comment on the 110 as a visual telescope and astrograph with wide field capability. 

As is the case of this object, it spans 4 degrees of sky, so it needs a short focal length instrument. There are a few refractors that can cover this field while at the same time provide resolution on par with much larger apertures. In the case of this image, the sky was very steady with resolution of 1.3 pixels (1.8 arc sec), which is pretty much the limit for this short focal length and pixel size. At the F5 focal ratio, the scope puts 100% of the light over the entire format, which is something almost no reflective system does. Therefore the deep illumination and high resolution extends to the edge of the circle overage of 44mm. In my case the filters cut off light in the corners, not something I'm that concerned about. For a lot of the images posted below, I was able to get lots of very deep sky detail using very few subs, thanks to the fast F5 optics and the 100% illumination.

As a visual instrument it is limited by the aperture, both for resolution and for showing faint deep sky objects. It is 110mm, and was designed to fit the most aperture into a carry-on case. It will not show detail on the planets like a scope of twice or 3 times this aperture. It has a very hefty focuser and tube mechanics, so it isn't a light-weight shorty grab&go. It was made for astro-photography but at the same time meets a high level of correction visually. 

Anyone who has unrealistic expectations for visual performance is encouraged to read more about the capability of optics with respect to aperture size and focal length. The 110GTX will do visually what a 110 aperture is capable of - nothing less and nothing more.

Imaging-wise it will produce nice high resolution images over a very wide field, which was the goal. It will require a very collimated chip with less than 5 microns of tilt corner to corner. Here is a list of objects that I was able to image at home and in Hawaii over the last few weeks. My skies here have been clear and good about 20% of the time, so I was forced to limit the number of subs for each object:

https://www.astrobin.com/bfyydi/, https://www.astrobin.com/2dm87i/

Roland Christen
Astro-Physics Inc.