25x100s 21st Sep

[Tweedledee]

Had first light with the new bins in the backyard tonight.

Not much to report since the sky in Mansfield was not dark at all, with the moon up and only just passed full, and some thin hazy cloud before becoming completely overcast.

Despite the poor skies that would not even show me the Milky Way after good dark adaptation, I saw enough to tell me that these big Celestron Skymasters are going to be an absolute joy at a dark site on a clear moonless night. Looked at all the usual bright DSOs and saw them large and full of detail looking much more like I'd expect to see them through a telescope than binoculars. But of course these are two 4" scopes.

The collimation was spot on, which is always a worry with secondhand bins as it is less easy to detect if checking in daylight, so I was very pleased not to be seeing double stars everywhere.

These are the first bins I have had with individually focused eyepieces, and I noticed that I seem to get on better with this method than the combined focusing on my other bins. My eyes seem to change focus very slightly over time, and require some tweaking relative to each other, so individual focus makes this easier to adjust for.

The substantial improvement from 15x70s to 25x100s is a very similar jump as going from 10x50s to 15x70s and is more pronounced than I would have expected. Therefore I'm glad I did not bother with the 20x80s and have now answered my own query in post #16 in this thread...
http://www.eastmidlandsstargazers.org.uk/topic/5283-celestron-15-x-70-skymaster-binocular/

 

This is how the 15x70s impressed me recently...
http://www.eastmidlandsstargazers.org.uk/topic/5820-15x70s-2nd-september/#entry66102

These 25x100s are specified as having a 3 degree field of view, but most of the internet reports I have seen, suggest that this is optimistic and the actual field is nearer 2.5 degrees. I shall verify this on another night, but either way, what this means in practice is that they are not so easy to align on the required target having such a small field. Graham already has some details to make me a finder bracket that will clamp onto the chrome mounting bar and will enable any finder with a Skywatcher dovetail to be used with the bins. I will try both an RDF and laser to help point them.

My camera tripod with pan and tilt head would not let me see Cygnus overhead, so I ended up lying on my back in the garden with the tripod horizontal. This method provided ample stability and comfort for the 25 magnification. Cygnus was a little less rich with stars than usual, suffering from the brightness of the background sky tonight.

Saw lots of colour in the stars and Albireo looked gorgeous. Picked out some nice orange stars in and around the very nicely spread out double cluster.
To my surprise, I accidentally came across an asterism which although very small in the bins, I recognised the shape instantly as O'Meara 3 or Alessi J20053+4732. This is a tiny, virtually unknown asterism about one and a half degrees west of Omicron 1 and 2 Cygni. This unassociated group of stars stands out from its surroundings as a compact cluster. I first saw this last year in the 10" after reading about it in a book called "The Secret Deep" by Stephen James O'Meara, who found Alessi's grouping of stars independently in September 2009 and put his own name to it (O'Meara 3) as he has done with several other finds. The obscure Alessi catalog contains 41 clusters and asterisms found by Brazilian amateur Bruno Alessi in 1997/8.
The ring nebula was so easy to pick out and the Owl Cluster in Cassiopeia was well resolved into its characteristic shape. Clusters M39 amd M34 looked large in the field of view.

Looking forward to using these under a much darker sky.

[BAZ]

It looks like you will be hard to part from those Bino's in the future. A nice read as usual Pete, thanks.

[Doc]

I agree a cracking read and a very nice observing session you had.

[Tweedledee]

Thanks Martyn and Mick.

I was disappointed with the sky, but know these bins will give some really exciting views under the right conditions.