My Epsilon is mounted non-tracking alt-az which will probably degrade the NiteCap stacking.
The good news is a Losmandy G11 is in the works (primarily for another scope, but you know how that goes). Just waiting on the next production run. Joe at Parallax is already making the required rotating ring set. So, that will eliminate the trailing and field rotation issues.
Jeff, if you can select targets closer to Polaris, you should be able to stack for about 2.5-3.5 seconds at your native Epsilon FR. Keeping the ISO as low as possible will help. When you are using Night Cap, watch the screen as you make adjustments to the ISO & exposure... remember that if you have exposure set to 1/2 sec., the delay for adjustments in either ISO or Exp will take 1/2 sec to show up on screen. I'm looking forward to seeing your results. I'm still traveling at new moon, but I'll be watching for your post in this thread.
There is so much to process in this thread.
Yes there can be a varying amount of FC and/or astigmatism, and I have always seen barrel distortion in all pictures/videos through NV units. But as Eddgie said in a previous post:
Starman, that is for certain! We all have different tolerance levels to distortions and there is a significant difference between using NV for photographic and visual use. But either way, NV opens so many windows of opportunity. This testing has shown me where my tolerance level resides, so in that respect it has been quite helpful. I am, however, anxious to see results from the fast Newt astrograph, because it should show exactly what Eddgie has been proclaiming for a long time... full field illumination. The brighter image will probably be mitigated by a slower ISO in imaging, but the field illumination is what I am really interest in seeing.
Field curvature is the predominant distortion I've seen in my own photos, but I have found that a slower FR scope helps that issue. When I get home in a couple of weeks, I'll try to take an afocal image with the 55P through my TEC 140 which is f:7. I think it will show less curvature than the f:5 ST 120. Here is a prime NV image through the f:7 scope that I took in May of M3, ISO 200, 1/6s, 15s stack:
Field curvature isn't a problem for me in this photo... there aren't many stars at the edge of field! Even in the next photo of Omega Centauri, using the ST 120 at f:5, I can live with what curvature shows up, ISO 1250, 1/2s, 4s stack
What I find objectionable is curvature that shows in the outer field as prominently as is shown by the 40 and 55 Plossls in my afocal images, especially with an added reducer. If I had a PVS 7 instead of the Mod 3C, I'd be forced to live with that curvature. Thankfully, the Mod 3C gives enough flexibility to go the prime focus route, which pretty much eliminates the problem... but at different scale than the afocal images. The 55P is working at the same level as a .5x reducer in prime, which in my scopes vignettes AND shows field curvature. So, reaching appropriate scale for me means that I will be changing scopes. I'm OK with that compromise.
Edited by GeezerGazer, 26 June 2018 - 01:00 AM.