Taken on the morning of December 29, 2018 using a Astro-Tech AT72ED (72mm aperture, f/6), a Tele Vue 2X Powermate, a ZWO ASI183MM Pro camera, and a stacked set of Baader Semi-APO and 610nm Long Pass filters (to limit the bandwidth to between 610nm and 675nm). Best 20% of 1000 frames using Autostakkert!, sharpened with Registax, and finished with Photoshop CC2017.
With the Powermate the AT72ED was working at about f/12 and an effective focal length of 860mm. The original image scale was thus near to 0.6 arc seconds per pixel (critical sampling for the camera/scope combination).
This was a test to see how much detail I could obtain by matching the moon's full disk to the frame bounds of the ASI183 camera. To do so you need to use a focal length of about 820mm, so at 860mm I was a little over the maximum. At full scale the moon was 3370 pixels high which is still a little under the height of the ASI183 sensor (3672 pixels). However, on occasion the moon will be larger than on last night, so that's why my target focal length is closer to 820mm.
I'd rate the seeing conditions when this image was taken as poor as we are currently having a weak Santa Ana condition (and the image on the liveview during capture looked very turbulent).
In addition to the image of the moon, I've included a picture of the AT72ED with the extensions used to mount the Powermate and the ASI183MM camera. The actual "stack" when imaging was a little longer than shown here, since in this picture the dew shield was retracted and the focus was fully inward (when imaging the focuser drawtube was extended by 17mm, so I probably need to add another half inch to the extension tubes).
You can see an image of the gibbous moon that I took a few days ago using a smaller Stellarvue SV50ED at a similar image scale using the ASI183MM:
I had better seeing when using the SV50ED so both scopes seemed to have produced about the same limiting resolution. Actually, at higher reproduction scales the image from the session with the SV50ED looks better than what I got last night with the AT72ED, but I think almost all of that was from the differences in the seeing conditions. Also, the images taken with the AT72ED were done well after the start of dawn, in fact the sky was already blue although the sun hadn't yet risen (sunrise was at 6:53AM, this image was taken just after 6:30AM).
Edited by james7ca, 29 December 2018 - 09:21 PM.