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Collimation humour...
Hi all,
I finally got around to collimate my Meade 8 inch SCT and thought would share my experience, a few questions and tips on what to avoid!
1. I have owned the scope for close to ~18 months and knew that the collimation was slightly off all along. I was nervous about touching the allen screws in the dark, so ordered Bobs Knobs. Installed them over the weekend, and it was relatively straightforward for a newbie.
2. I left the scope out for a couple of hours for it to cool down last night.
3. When I was ready, I strapped on the dew heater (I had a lot of trouble with dew last month watching the "super moon"). In hindsight, I don't think this is such a good idea. I think the dew heater creates internal thermal currents - so my out of focus star images were very wavy. Is my understanding correct? Should I skip the dew heater for collimation, esp. if humidity levels are low, as it is this week?
4. I figured tracking will help me center the star so I have more time to collimate the scope. So I went through the calibration procedure on AVX mount. I am not sure whether this is necessary. If I don't need GoTo functionality, can I just turn on the AVX and slew to a star manually? Will it then track from there? Or do I have to go through the 2-star alignment + calibration stars procedure to enable tracking?
5. After completing 2 star alignment (+ 2 calibration stars), I pointed to a bright star close to the zenith and started collimating. I really struggled to get the in-focus and out-of-focus star images in concentric circles. It was always a bit funny shaped. After close to an hour of frustration in the cold, I realised I had pointed to Regis Kantarous - a bloody double star! Talk about poor selection! I had a wry laugh, located Antares and went through the collimation process. This seemed to yield better results.
I think I have achieved coarse collimation. I could easily split Regis Kantarous by the end of the night. But I feel I can improve it further. Would appreciate any tips/advice!
Btw, what is the best EP focal length to do for collimation to get good results? I used 15mm, 10 mm and 6.7 mm EPs last night. I could get decent results with 15 and 10 mm, but 6.7 mm was just too wavy (may be because of the dew heater).
In summary, happy with progress so far. Bobs Knobs do make things easier. Dew heaters are a bit of a question mark. But most importantly, if you are new to this, avoid bloody double stars to do collimation!
Clear skies!
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