20251224 Testing of 8" SCT with reducer

Merry Christmas.

The forecast was swinging so I was never certain.  I tried to setup as planned.

Cloud rolled in, but I kept on.

I didn't do a rough focus first with distant terrestial target.  That makes the initial focus pretty hard.  I had to pull out my eyepiece to knee on the ground to have rough focus first before letting the EFA took over.  But then the EFA was not functionally well at first, maybe due to suboptimal collimation?

(Later I found that the stars from S30 was sort of bloated at the same night, too.)

Polar alignment was done by the guidescope by swapping the main camera with the guide camera, a method developed on the fly.  Not bad.

And then GOTO is a problem.  Plate solving with a narrower field of view did not perform well, I have to use the guidescope for GOTO autocentre.

(But then the guidescope and the main scope is not perfectly aligned.  Pumping up the exposure time for GOTO auto centre resolved most of the problem.)

Focusing could go very wrong again, I believe it's more like collimation issue?

Dew formed shortly on the large exposed corrector, and I tried to clean them up but it ended up forming a thin layer of ice there.  I have to connect two dew heaters to warp around the front, see if it helps?  

(After more than ten minutes, the thin layer of ice was still there.  Maybe I will need to attach it at the very beginning, or the output power was not enough?)

I have tried 30s exposure, 60s exposure, see how they work out.  Not promising.

Collimation screws were ordered by asking Gemini AI, see if it comes out well.

My LiFePO4 battery failed repeatedly, but after connecting to the charger for more than ten minutes, at least it seems to work now.  

But I'm using a small power station already, let's see.

Going back to the LiFePO4 battery at around 8:00pm, much more stable power source.

In short, Murphy's Law works perfectly tonight.   Everything went wrong.

Not exactly an enjoyable experience, but so much to learn.

Fortunately, the S30 is up and kicking.  Took some C23 Silver SIlver Galaxy, and some more IC 434 mosaic.

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Notes after the observation:

1. I will not use the 8 inch SCT until I spend time on better collimation.

2. Even with the reducer on, the focal length was still a bit too much for me.

3. Aligning the guidescope will be very useful, for guiding it's no need, but for aiming it's very helpful

4. A dew heater is very important for the SCT, since the corrector is very much exposed

5. I have spent some effort to mount the guidescope on the original finder bracket of the 85mm refractor, it should make the setup easier to use

6. I shall use the 300mm f2.8 again until I can sell it eventually, see if I can get something more with it.