Hello. First of all, I have not a clue what I am doing. I feel like a dust mote floating in a sea of overwhelming information!
I recently upgraded my imaging system to include an Astro-Physics AP1100GTO with absolute encoders. I replaced the entire focuser on my Takahashi FSQ-106EDXIII with a Moonlight WR-35. It is very robust. At the same time I added a Takahashi QE .73x focal reducer. I verified the math on the backspacing of the latter, and had several other imagers confirm I had the correct back focus distance. However, it turns out one piece of my imaging train between the QE and the CCD chip (an adapter ring) is 0.65mm too long. I do not know if this is critical enough to be an issue. But I digress.
When I first installed the new equipment, I had a lot of very odd shaped stars, primarily on one corner of the field of view (the lower left). I subsequently installed a camera plane adjuster between the WR-35 focuser and the QE focal reducer in an attempt to make sure the chip was perfectly parallel to the scope. There is no detectable flexure in my imaging chain.
Attached is a test image I shot recently. It is five 600s guided images combined in PixInsight, with just histogram transformation. When I performed BLINK I was amazed that there did not appear to be any field drift. All five images were perfectly aligned. I did perform a StarAlignment. However, I am not impressed with the roundness of the stars themselves. There still seems to be corner issues. Only one focus routine was made prior to the five images being taken. I am not so much concerned about the star bloat as I am the out-of-roundness. And please do not consider the lack of data or the prettiness of this series. It was just to check for optical errors. I'd be very interested in ways to statistically check the roundness of stars using either Maxim or PixInsight!
M31 Test
I do not know if I am looking at guiding errors (the guiding seemed OK as far as the MaximDL graph showed; 5s, aggressiveness 6) or something more sinister like an out-of-collimation issue regarding the chip. Or an optical issue with the reducer. I'm in a dome so no wind. Great balance. Looking back at my first attempts at imaging earlier in the year without the reducer showed similar issues with stars being larger in one corner. So I wonder if perhaps there has been an issue all along and I just didn't see it or notice. Perhaps it isn't the reducer but that the chip is tilted relative to the plane of focus? I am still messing with the camera plane adapter, but unsure how to proceed. However, things seemed to get better upon adding it (perhaps quite by chance). Maybe it's poor polar alignment or a tracking issue I am seeing?
Maybe I'm being too critical in what the system can do? I welcome all honest critiques of either my methods or machinery! I did upload the raw .FIT file but am not clear on how to share this.
Kind regards, Chris
I recently upgraded my imaging system to include an Astro-Physics AP1100GTO with absolute encoders. I replaced the entire focuser on my Takahashi FSQ-106EDXIII with a Moonlight WR-35. It is very robust. At the same time I added a Takahashi QE .73x focal reducer. I verified the math on the backspacing of the latter, and had several other imagers confirm I had the correct back focus distance. However, it turns out one piece of my imaging train between the QE and the CCD chip (an adapter ring) is 0.65mm too long. I do not know if this is critical enough to be an issue. But I digress.
When I first installed the new equipment, I had a lot of very odd shaped stars, primarily on one corner of the field of view (the lower left). I subsequently installed a camera plane adjuster between the WR-35 focuser and the QE focal reducer in an attempt to make sure the chip was perfectly parallel to the scope. There is no detectable flexure in my imaging chain.
Attached is a test image I shot recently. It is five 600s guided images combined in PixInsight, with just histogram transformation. When I performed BLINK I was amazed that there did not appear to be any field drift. All five images were perfectly aligned. I did perform a StarAlignment. However, I am not impressed with the roundness of the stars themselves. There still seems to be corner issues. Only one focus routine was made prior to the five images being taken. I am not so much concerned about the star bloat as I am the out-of-roundness. And please do not consider the lack of data or the prettiness of this series. It was just to check for optical errors. I'd be very interested in ways to statistically check the roundness of stars using either Maxim or PixInsight!
M31 TestI do not know if I am looking at guiding errors (the guiding seemed OK as far as the MaximDL graph showed; 5s, aggressiveness 6) or something more sinister like an out-of-collimation issue regarding the chip. Or an optical issue with the reducer. I'm in a dome so no wind. Great balance. Looking back at my first attempts at imaging earlier in the year without the reducer showed similar issues with stars being larger in one corner. So I wonder if perhaps there has been an issue all along and I just didn't see it or notice. Perhaps it isn't the reducer but that the chip is tilted relative to the plane of focus? I am still messing with the camera plane adapter, but unsure how to proceed. However, things seemed to get better upon adding it (perhaps quite by chance). Maybe it's poor polar alignment or a tracking issue I am seeing?
Maybe I'm being too critical in what the system can do? I welcome all honest critiques of either my methods or machinery! I did upload the raw .FIT file but am not clear on how to share this.
Kind regards, Chris
