Decommissioning Celestron 9.25″ SCT

Up until August 2015, all the images that SkySlab produced were using a Celestron 9.25″ Schmidt-Cassegrain optical tube (with one or two exceptions using a William Optics GT-81).  This optical tube assembly was chosen because of it’s ease of use and as a good introduction into astrophotography.  There are a plethora of accessories available for them, they are common, well manufactured (and regarded) and require little maintenance or set-up prior to taking good quality photos.  An ideal first imaging system for SkySlab.

I won’t go into a review of the C9.25 here, Damian Peach does an excellent job of this on his blog as does John Earl on IceInSpace.

As at August 2015, the C9.25 had been taken on long on long journeys (astronomically speaking) and it was time to move on to something with a larger aperture that will gather more light and resolve higher detail, and challenge the Paramount MX.  To these ends, a GSO RC12-A f/8 Astrograph made its way to SkySlab. 

Meanwhile, here’s the process used to decommission the C9.25 – it’s not intended to be an education tool, this is more for interest than education because decommissioning a scope is not that difficult.

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1. Take a few photos of the current set up – for prosperity.

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2. Lock the mount into ‘lock’ position – the pointy bit of the mount lock needs to face the lock.  In these picture the pointy bit faces the star, which is the right position for tracking but the wrong position for commissioning and decommissioning equipment. Do this because removing equipment will unbalance the mount, which risks straining the drives and you don’t want drives, belts, gears etc slipping or grinding while you are doing this work.  Ignore the dust here, that will all be cleaned up soon.

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3. Remove the imaging train, cables, accessories and place them gently in a secure area.  Here’s what SkySlab’s looked like – messy.

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4. Loosen the locking clamp at the end of the counterweight shaft of the mount, remove it and loosen one counterweight and remove it.  Leave one on there for now.

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5. Loosen the bolts holding the scope cradle in place on the Paramount MX, don’t undo them entirely or the scope will fall off.  They need to be loose enough so that you can support the scope with one hand and undo them to the point where you can feel the scope slide a little.  Stop there.

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6. Use both arms (your human ones that is) to remove the scope by sliding it forward gently.  Try to avoid it ‘bumping’ along as it slides off.  A little dry silicone spray helps here (hence the ‘white blobs’ you might see in some of the photos).

7. Place the scope down gently and remove the other counterweight from the counterweight shaft.  Then put the locking clamp back on to the end of the counterweight shaft so you don’t lose it!  After you have done this, you can change the drive lock positions to ‘balance’ (the middle graphic on the drive locking nuts) and move your mount freely until it’s in an aesthetically pleasing angle and take a shot of the end result.

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Here is the scope sitting peacefully, which will eventually find a new home.

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(Edit 26 April 2015)

It was a great scope and has found a new home with Tim Anderson – who took this shot earlier tonight of the Celestron’s new home.

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