Telescope Reviews: Never seen M51 (Whirlpool Galaxy) in binoculars?

M51 is a fine target for binoculars under dark skies, but when Light pollution encroaches, it can become a very difficult target. Neverthless, it is one of the finest galaxies in the sky, so it's definitely worth trying to locate it.

When searching for it in binoculars, it helps a lot to know precisely where M51 is located. If you know that M51 is around 3-4 degrees away from Alkaid in the general direction of Cor Caroli, you may not notice it under borderline viewing conditions.

I find it best to locate Alkaid, and then move towards Cor Coroli and back a bit towards Mizar to locate two relatively bright stars (HIP66385 and 24 Cvn) which should be in the same FOV as Alkaid in most binoculars. These two stars then form a nice pointer to one corner of a trapezoid of 7th mag stars which includes m51. The two pointer stars and the trapezoid that includes M51 is also shown in the overview, so you can be sure to look in the right direction for that pair of pointer stars.

It also helps to know the precise TFOV (True Field of View) of your binoculars so you can accurately gauge the scale of these maps. A typical pair of 10x50 binoculars will have a TFOV of a bit over 5°.

If you have poor skies, it will take some tricks to eke M51 out of the background. Use averted vision to look at any one of the three other stars of the trapezoid and then gently sway the binoculars back and forth. With this star chart, you will now know exactly where M51 is and that should help coax it out of the background.

Under darker skies and at higher magnification, you should be able to see the two separate parts of M51 and also see the orientation. I can just barely make that call with my 18x50 binoculars under SQM 21+ skies. As for smallest binoculars to see M51, I have seen M51 in my 5x32 binoculars under really good dark skies. Cor Coroli is a nice double but too tight for anything but larger binoculars as the separation is only 21".

And if you still find it hopeless from your location with these charts, take it as encouragement to make a sojurn to some really dark skies - you will be amazed at how easy it is to find M51 under those conditions and even if it's a long drive, I'm sure you'll agree it was worth the effort!

Good luck hunting.

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Edited by CESDewar (05/24/08 01:40 AM)

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