NGC 3918 'pulsating'

[hotspur]

Finally got a chance to roll the roof back on observatory last night,had a look at 3918,its such along time since I viewed it,I seemed to get brighter,then fade,then do the same again as I viewed-it may have been my averted vision,giving this effect-but it did seem bit different to last time I viewed it,but that was some time ago-so may have been the same.

[mental4astro]

Chris, over what time period was the pulsing happening? As you viewed it, so just over moments? This week's forecast is favourable, so might be good to get a little time in on The Blue Planetary.

[hotspur]

Seemed to be as I was viewing it Alex,it seemed to fade then come bright again.conditions were fairly good.I will not have time to try for image of this blue spot this week due to heavy work load.

Did manage some good imaging on other objects on Saturday night,my auto guiding is going well,and got some nice data on eta,and 5139 and a ten minute sub on 4945 before the fog came in

[gary]

Hi Chris,

I experience this phenomena regularly with NGC 3918 and with NGC 3242.
It is simply caused by the eye flitting around a little and the pulsating comes about
as you go from the cones to the rods and back again as you alluded to.
It is such a powerful illusion that it can seem to take on a life of its own even
when you make a conscious effort to try and not shift your gaze.

[hotspur]

Thanks Gary-I was fairly sure its was something to do with averted vision,great to cross reference your observations-cheers :thumbsup: