First light ASI2600MC

(Click on the image to enlarge)

M51 14x300s SQM20 27MEI2020 ASI2600MC ESPRIT120 F7 Gain0 -10C 100% V2

Really need to learn how to use this camera and process the images, very different again from B/W and DSLR. The gain was set to “0” (“Maximum dynamic range”). Using the 120mm Esprit @ F7 native focal length of 883mm. As a first impression also the camera takes a lot longer to cool down compared to the ASI183MM and the files are pretty large at 50 Mb.

Collimating the C11 & ASI290MM

It’s been a while that the C11 was put to use, today I could clean the corrector, and also I found the very very small engraved numbers close to the edge, that line up with the line (and the same number next written next to it) found on the back of the primary. With the tri-bahtinov I could focus and collimate the optics. See also the links here and here.

make sure the three area’s of the mask line up with the three collimations screws of the secondary. The procedure is to focus like a normal bahtinov (ate least one set of lines), and then to look for the area (one of three) where the central line is not nicely central between the spikes. That becomes easily visible when covering an area: when that dims or obscures that is the guilty area, and the corresponding collimating screw needs to the turned (very very slightly). You see the effect on the central line. When centralized, repeat for the third area when necessary.

This is really easy, choose a star high in the sky. On the accuracy of this method I have little data or calculations unfortunately. What I do see is that (with a star in-focus) a very slight turn on the collimation screw (Bob Knob’s in my case), like 1/8 of a turn, gives an immediate effect on the Bahtinov image. The lines across the three sections will not be symmetric anymore. The area that corresponds to the collimation screw that was changed, will display a Bahtinov cross that is not centralised. From this observation I do believe that this method is accurate enough for collimating a SCT.

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New images with the 76EDPH

A clear evening, just before the Moon appeared, allowed me to take some more images with the new TS76EDPH. What was really evident was how fast this scope is capturing the photons. A single frame on ISO800 with a Nikon D750, 300 seconds exposure, taken at about 50° above the horizon, would have a DSLR histogram peak about halfway.

Orion Widefield, Nikon D750, TS76EDPH, cropped 10% downsized to 66% about an hour of data in 180″ and 30″ frames. SQM 20, Optolong L-Pro filter in T-ring. MGEN tracking Manual Focus. SQM 20

The file above is an original Nikon D750 FF NEF that was converted to JPG by ViewNX, using a ‘good balance’ quality conversion. The “highest quality” file was too large to upload on the website.

It was lightly stretched. The quality of the file allows to check the star shapes. It is no match for the original NEF quality out-of-camera.

This is the “official” provessed version 🙂 like in Astrobin.

Finalized version 20×180″ ISO800 SQM20 Optolong L -Pro Nikon D750 TS76EDPH