Re: AP130GTX Imaging First Light

Jeff B

Impressive Wade!  I find an appealing, almost ghostly quality to it.

Well done.


On Tue, Apr 6, 2021 at 5:07 PM W Hilmo <y.groups@...> wrote:
I was planning to use my new AP130GTX just for visual observing through the springtime, so that I could capture galaxies with my SCT, but it didn't work out that way.

Part of it is impatience on my part to get imaging with the scope, and part of it is weather.  In terms of imaging, I suspect that my site is not going to be great for very high resolution imaging.  Since we're on the leeward side of the Cascade mountains, the seeing is quite a bit softer than what I was used to on the west side of the mountains.  Because of that, imaging at 0.3 arc seconds per pixel doesn't give awesome results.  My QSI camera on the AP130GTX is just about 0.8 arc seconds per pixel, which works out better.  The second weather impact is that visual observing at this time of year is less than pleasant.  We're in the mid to low 30s at night, which isn't bad in itself, but combine that with 30mph winds, and it gets really cold, really fast.  So with all of that, I moved the camera gear from the SCT to the new scope.

I'm posting here, instead of AP-UG, since the thing that I am blown away by is the performance of my AP1600 with absolute encoders.  I've known all along that I've been fighting with mirror shift and flex with my SCT, but I had no idea how much - until now.

The weather conditions last night were pretty poor.  The sky was cloudless, but that was the only good thing.  The transparency was marginal, the seeing was poor, and it was windy.  The winds were about 25mph to 30mph for most of the night.  There were gusts that rattled the windows (unfortunately, this is not uncommon here).  When I was exercising each part of the system, I ran for a while with my OAG and PHD2.  The best I could get was about 1.2 arc seconds RMS, with the scatter plot pretty much random within about a 3 arc second circle.  I went ahead and built an APCC Pro pointing model with about 180 points and then did some more testing.

The pointing accuracy was striking, as compared to what I am used to with the SCT.  It was pretty much putting any target I selected right at the center of the field, no matter where in the sky.  But what really impressed me was the unguided performance.  After creating the pointing and tracking models, I ran a sequence in NINA of 10 minute exposures for the rest of the night, unguided.  Even with the gusty wind, the subs looked great (even if soft from the seeing).  When I processed the image, there were no subs that needed to be tossed, so I kept them all.

To say that I am happy would be a huge understatement.  Even though I've been using Astro-Physics mounts for almost 10 years, I am simply amazed at what they can do when you put a top shelf scope on them.  Wow.  The biggest downside is that the data is so good, that my processing skills are well short of taking advantage.

Speaking of processing, the processing of this data was minimal.  After calibration/integration, I spent between 25 and 30 minutes processing the combined channels.  I did not do any noise reduction (except for MureDenoise) and sharpening, since I wanted to show the quality of the data from the system.

The full resolution image and capture details are available at:


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