Astrophotography 2021

For 2021 I tried to use -10C cooling for my QHY294C for all subjects. Only one hot summer evening where the air temp was 24C forced me to go back to 0C. I log both the total current used by my system and also the PWM output for the cooler as it is a parameter available via the QHYCCD.dll The temperature actually rose a little bit during that hot evening and I could see that the PWM output was quickly climbing. QHYCCD claims that the cooler is capable of -35C below ambient. My experience is that it may be capable of -35C but it would require high currents that might wear out the cooler. Keeping to -32c below ambient is a better recommendation. I log all of this data so I should put together an article detailing my experiences with controlling this cooler.

I also used the light table I bought on Amazon for all of my FLAT frames. I think it works very well. It is very light weight and has continuously variable light output. It’s output is pure white light. I always tried for roughly 1 second FLAT frames. Light Pollution Filters required low light output. The LeNhance Narrowband filter required full light output and it required 2 second FLATs. I don’t believe I saw any issues with my FLAT frames so I am very please with this item. My approach for taking FLAT frames is also unusual. I will put out an article detailing my experiences with this light table.

As I was preparing the photos for 2021 it really struck me how the forest fire smoke that blanketed Ontario during June and July really trashed my astrophotos. There were some nights where I new it was hopeless. Many of the nights that I did try resulted in very dim noisy images that were unusable. Climate change really sucks.

I also tried using a GAIN of 2500 for a few DSOs. Overall I was not happy with the results. 200 or 300 second exposures all seemed noisy even though the read noise of the QHY294C is lower at GAIN=2500 compared to GAIN=1600. My gut feeling is that GAIN=1600 is the “sweet-spot” for this camera. I have to admit that the forest fire smoke may be the main culprit here. Maybe next year will prove me wrong.

Control software changes that I performed were a new user interface for the Differential Flexure Comp camera angle determination. I also incorporate the PHD2 Server to move the mount for this interface. I like this approach because it takes into consideration any calibration errors that PHD2 may have experienced with the guide camera. I think the Differential Flexure Comp logic is more stable as a result.

My telescope control software, that I wrote, incorporates an image preview feature where a quick image stretch is performed so that a pleasing color image is displayed. As you move the cursor over the image the XY position and the RGB pixel values are shown in the title bar of this window. This year I incorporated plate solving into this preview. A click of a button causes the newly acquired image to be plate solved. Once the plate solver successfully completes the cursor position is converted into RA and DEC values. The values shown in the titlebar are now the Right Accession and Declination at the cursor.

I went one step further and modified my plate solving control so that I can reposition the mount using this image preview. If I move the cursor to a location on the image preview and double-click a little red cross appears on the image and the RA DEC information is used to preset the plate solving control. I just click a button on the plate solving control window and the mount is re-positioned so that where I double-clicked on the image preview has been moved to the center of the image.

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