Observing Report 12th May 2010

[Moonshane]

Observing Report 12th May 2010

Location Stockport, England Latitude: +53.42 (53°25'12"N)

Longitude: -2.17 (2°10'12"W)

Equipment – f5.3 300mm Orion Optics UK Dobsonian, TV Radian and Panoptic /Powermate / WO 33mm SWAN

Main Target: Test new Cheap (£7) Zoom against my existing eyepieces.

This was the first clear night after the impulse purchase of a very cheap 10mm-20mm (apparently) zoom eyepiece from the Astroboot of Scopes N Skies website. I bought this partly with my neighbour in mind who said he was after a zoom and likes a bargain – BUT with the view that for £7 it would be good if I ever do a public session which is possible. As a real challenge I thought I’d test it against my ‘premium’ eyepieces per my signature.

Although clear there seemed to be some high thin cloud and therefore the seeing restricted anything above about 160x but this gave me enough magnification to test the zoom so I was quite happy.

My first target (as usual) was Saturn. Trying the zoom first, I was actually very surprised at how good the observable detail was. For £7 I expected all sorts of chromatic aberration, and a poor general image quality. This was not the case. At the minimum focal length (approx. 10mm) Saturn gave up some good detail with banding seen on the disc and just a hint of Cassini visible. I managed to see four moons (Rhea, Dione, Tethys and Titan) and in all it was very surprisingly good. OK the zooming action was a little stiff in the scope but this was fine once the set screw / compression ring was tightened a little more than usual.

I then turned to my ‘comparable’ Televue eyepiece, a 24mm Panoptic in the 2.5x Powermate; this gives a focal length of around 10mm. One definite advantage of the zoom is that it’s both extremely light and extremely small (as well as extremely cheap of course – did I say it was cheap?) compared with the TV combination. I have to say that although the view through the Panoptic was certainly sharper, with a wider field and just ‘easier’ on the eye (I mean functionally not cosmetically) the difference was not £250+ of a difference, especially in the central area of view. I could pick out no additional moons around Saturn.

Turning to Leo, I then thought about how a double star would equate in performance terms. I pointed to Gamma Leonis (Algieba) as this is bright, quite close and easily accessible. This showed the differences a little more as although it was easily split in both, the sharpness of the image was much less in the zoom – a split’s a split though when it comes to doubles. I also managed to see a definite split when looking at Epsilon Lyrae (the Double Double), albeit not quite as sharp as in the Panoptic Powermate pairing. The colours were identical in both scopes.

Also in Leo I located M65 and M66 with the Panoptic and they showed as faint whiffs of cloud as usual. In the zoom, the main ‘fault’ showed itself on these targets. The very narrow field of view was quite claustrophobic after the Panoptic and I think I’d have struggled to find them with the zoom had I not already done so with the Panoptic. If you are used to plossls, this might not be an issue though. The detail visible was similar but I’d say a little darker in the zoom – this may have been due to the 20mm focal length versus 24mm.

To compare further targets I then moved across to Hercules and looked at M13, the best globular cluster we can see in the UK in my view (so far!). Again there were differences but they were really quite minor and the zoom had the advantage of being able to vary the focal length to suit. There were not quite as many stars resolved but the image was respectable with the zoom. The same comments apply to M3, which was viewed through both eyepieces slightly later in the evening.

In summary then, the zoom is not going to make me sell my Televues but if you are on a very tight budget or want a cheap public session eyepiece, this will be a great one to have in your case. It’s definitely one that gives a respectable image over a reasonable range of magnifications.

My curiosity satisfied, I then decided to have a look around Ursa Major to try and locate some galaxies not seen previously; unfortunately I failed! I used M81 and M82 as a test as always and they were located with the usual relative ease. Unfortunately I could not find M101 and M40 at all. I think I picked out a little ‘vapour’ that may have been M108 but I really could not be sure. I’ll try again at another site or possibly next winter/autumn when it’s darker at night.

As Cassiopeia was just about in view from my garden I had a go at a couple of the open clusters, M103 and M52. On the night I was quite happy that I found them but unfortunately I have since read that there are around two dozen open clusters around this asterism and therefore I have decided to try again and ensure I was looking at the right ones. Turn Left at Orion has a good summary and I’ll use this next time!

My final target was the Globular Cluster M12 in Ophiuchus. This constellation is just becoming visible from my site but unfortunately a lot of the asterism is still behind trees. Thankfully, M12 was visible and I managed to locate it eventually. It is really quite a dim globular compared with say M13 and appears slightly less concentrated than other globulars I have observed. Hopefully I can compare this one with M10 once this rises a little more.

Best wishes

Shane

[DarkerSky]

Sounds like you picked up a bargain there Shane with that zoom eyepiece. A good find.

I was on M12 the same night. Got some partial resolution of stars in the globuar with my 16" - chains of stars working N-S. But you are right, it is pretty dim

[Moonshane]

cheers Seb, it's always a relief when someone agrees with me!

I REALLY want to get to a dark site with this dob as I have never experienced this with any scope. I cannot wait.