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AUS-2 and SPA-1 Takahashi FSQ-106 Telecopes


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The AUS-2 and SPA-1 Takahashi FSQ-106 telescopes both produce images with distortion on the left and right sides of the image. Do both of these telescopes have field flatteners? 

The screen shots below are for the AUS-2 IC4812 mosaic panel 1 and generated using the PixInsight AbberationInspector script for a single 300 s light, and the master light, both with the luminancefilter. 

The before and after images show that BlurXTerminator partially corrects for the distortion, but that especially for the master, the stars have halos that impact image quality.

Is this an intrinsic limitation of the Takahashi FSQ-106 combined with the larger image sensor of the QHY600M, or is their performance sub optimal?

master_before.png

master_after.png

300s_before.png

300s_after.png

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Hi Mark, 

What you see is an expected aberration, which was less visible with the CCD because the resolution of the images was about 3 times lower that the resolution we have now with CMOS.

These aberrations are seen only in the corners as we push beyond the optical performance of the Takahashi, which has an image circle of less than 40mm (smaller than the sensor diagonal).. There is also some residual tilt due to variable flexures of the optical train that causes variable distortions. The operators in Australia & Spain did everything possible to minimize it. These distortions have always there but were not visible earlier due to the larger pixel size of the CCDs. They are also only limited to the corners or sides.

We could crop the image, but we think leaving this decision to the user is better.

Clear Skies,
Ernesto

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Hi Marco,

I just checked my plate solving results for recent TL data sets I've processed for SPA1 and AUS2 and found the following: SPA1 plate solve focal length 385 mm; AUS2 plate solve focal length 531 mm. So it seems that only SPA1 has a reducer and AUS2 has the native focal length. The example pictures I posted at the start of this topic were from the recent AUS-2 IC4812 mosaic panel 1 generated using the PixInsight AbberationInspector script. I do understand that its not possible to easily access the equipment in a remote observatory, but currently I'm wondering if the AUS2 Tak, which does not have a focal reducer, is not performing to spec? 

Mark

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  • 3 weeks later...

Mark, are you finding it difficult to merge these mosaics due to the star abberitions in the corners and frame edges?  I was thinking of trying some mosaics, but this could prove extremely difficult if the stars don't align in the merge regions.

 

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On 11/17/2023 at 11:23 AM, Craig Schultz said:

Mark, are you finding it difficult to merge these mosaics due to the star abberitions in the corners and frame edges?  I was thinking of trying some mosaics, but this could prove extremely difficult if the stars don't align in the merge regions.

 

Merging the panels is not a problem, so do not be put off, but the distortions do propagate to the overlap regions, instead of being limited to the corner, as occurs in a single panel. Unless you look at high magnification, the images will look fine. The reason I've asked about this, and have yet to get an unambiguous answer from TL, is the simple question of whether the two TAKs performing as expected, or is their something wrong in alignment of the imaging train. The TAKs are $7k Petzval refractors which should have a flat field, but they are very sensitive to decentering/miscollimation of the four lenses.

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