First Light for Explorer 150PDS and First Newtonian!

[PeterC65]

Last night’s session was first light for the new Sky-Watcher Explorer 150PDS and also my first session with a Newtonian! There was almost a full Moon so this was the main target as it was much too bright to observe anything else.

I checked the collimation with the laser collimator at the start of the session after the scope had been mounted, and adjusted the primary mirror slightly. I’d adjusted both the secondary and primary mirrors a few days ago in subdued daylight.

I aligned the mount with Arcturus and Regulus. With the longer scope, and the straight finderscope mounted at the top end of the scope, it was easy to align the scope with the chosen star by standing back from the scope and sighting along it. I could then align more accurately in the finderscope without stretching my neck since it was positioned relatively high compared with the finders on the Mak and Apo which are much closer to the ground. This scope doesn’t need an RACI finderscope.

I’d been concerned that I wouldn’t get on with the eyepiece position on a Newtonian scope as I’m used to canting over a diagonal to get a good eyepiece position while seated, but the Newtonian eyepiece position turned out to be quite comfortable despite my previous concerns. I had to stand throughout the session but the eyepiece was mostly well positioned at standing height as I’d adjusted the rings so that I was looking down into the eyepiece. Standing rather than sitting does make it harder to keep still, and for longer periods. At high altitudes the eyepiece is nearer the horizontal meaning I had to stoop, but the mount cannot exceed 70° altitude with this scope anyway. I needed to clear space to be able to stand right around the scope as there is no adjusting the eyepiece orientation as I can with the Mak and Apo.

This scope is right on the 5kg weight limit of the Sky-Watcher SynScan AZ GOTO Mount, even without an eyepiece, but the mount coped very well with the larger scope. There was no issue with alignment or finding targets and the only issue was a much longer time to stop wobbling (about six seconds). This was only a problem when I nudged the eyepiece, and particularly the Binoviewer as it sits across the nose and is easy to nudge.

Moon

This was the main target for the session. It was too bright for single eyepieces without a filter but interestingly the Baader Blue filter seemed to be better than the Baader Yellow filter which is my usual choice for the Moon. The Seas looked particularly clear with the blue filter.

The Langrenus crater was very distinctive and I could clearly see the crater walls, as was Copernicus and the rays of debris emanating from it.

I could just see the whole of the Moon’s disc with the ES82 8.8mm and the ES82 4.7mm gave a more detailed view. The BCO 10mm also showed the whole disc and more detail with the x2.25 Barlow Lens. I compared the two ES eyepieces with the BCO 10mm with and without the x2.25 Barlow Lens. Without filters the BCO was slightly clearer than the ES but with the blue filter there was no difference. It may be that at F5, being my fastest scope, the Explorer 150PDS is pushing the limits of the ES eyepieces. The ES eyepieces gave a wider field of view than the BCO 10mm though, and they are easier on the eye.

The best view of the Moon by far thought was with the Binoviewer with x2.25 Barlow Lens and the WO 20mm eyepieces. The detail through this was amazing and it completely blew away all of the single eyepieces. I could make out the smaller craters and much more detail throughout. This was all without filters which didn’t seem to be needed with the Binoviewer and which in any case I can’t use (in the filter wheel) because of the limited back focus.

I had a quick look at other targets to check that the scope was working but the views were not great.

M3 / M13 / M94

With the ES82 6.7mm these were faint fuzzy round blobs.

M44

This was nicely framed with the ES68 24mm, showing an open cluster of bright stars clearly distinct from the surroundings, but the background sky was quite bright with Moonlight.

M81 / M82

According to Stellarium I should have been able to see both of these in the same field of view, which is one of my favourite targets, but I could only see M81 (the brighter of the two) and then only as a faint fuzzy round blob.

I'm looking forward to using the Explorer 150PDS now on a Moonless night!