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M101 - how to trust what you are seeing?


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Hello all

I'm not sure how to phrase this so please forgive me if it sounds like gibberish!

I recently obtained a 150p flextube and had some great fun taking it to a reasonably rural location over the last couple of weeks. Having tried for some time, I finally managed to tick M51 off my list - twice in two sessions! The view  on the second session was brilliant and I could quite easily make out the two little blobs that make it up.

On the second session I had a go at trying to find M101. I didn't realise until after that this is quite a challenging target in even my 6" scope from relatively good (bortle 4 (maybe even 3) skies). Well it took me nearly 40 minutes but I eventually pinned it down using a straight line of 5 stars as a guide until I was 100% sure I was looking in exactly the right place. It felt pretty close to the limit of what I could see, but over the course of 15 mins it very slowly started to appear and went from a "suspected" to a "found".

All in all I spent about half an hour at it before I took a quick sketch. It was a really weird experience. I would say that because it was at the limit of what I was able to detect it kept drifting in and out of existence and I had to be very patient and wait for a few secs or mins for it to reveal itself again. But it was definitely there. The unusual thing in this case was it felt like it was "moving" occasionally, almost like it was wobbling around. But one thing I very clearly remember that happened a few times was that while the central core remained more or less stable I would very occasionally experience something that I can only describe as someone taking that smudge and twisting it - like a whirlpool or when you add milk to a cup of tea and stir it. But it was so fleeting I couldn't decide whether I'd seen it or not or imagined it or whether it was an artefact. The whirlpool / stirred cup o' tea was also much bigger than the smaller fuzzy patch I was looking at.

So I did a quick sketch and that was that. It was only when I came in for the night and searched for sketches and images that I realised that M101 is actually much bigger than I realised. Much bigger. Additionally it has fairly pronounced spiral arms. To me before this point it was just a name and a location on a map. When I looked on Stellarium I must admit I thought "thats what I saw" - that swirling cup of tea effect was probably the whole galaxy whereas I was just mostly seeing the central core but very occasionally seeing the whole thing. However having done some reading I'm led to believe this is fairly optimistic, I've seen sketches from 16" scopes that don't match the clarity of resolution I subsequently thought I had in those fleeting moments.

So I suppose I'm asking is - for stuff at the limits of seeing, how do you know what you are seeing or not seeing? Having little or no knowledge of M101 before I viewed it I'm confident its not bias, but I'm also confident its unlikely I saw so much detail. So how do you know how much of your own eyes to trust? Particularly with objects that are pretty much "maybe there or not" to start with?  Its certainly something that has stayed with me over the last week.

Below are two sketches - the first is the one I did at the eyepiece. The second is a (slightly exaggerated) view of the "bigger swirlier thing" I thought I saw for a fraction of a second two or three times.

 

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That sounds like the effect of varying seeing / transparency as you were observing and also you "getting your eye in" so to speak. Occasionally you get a piece of optimum atmosphere over you and the detail pops teasingly into view then you blink and it's gone again. Observing for a period of time gives you more chance of catching these moments.

These face on spiral galaxies are usually a lot larger than we can see visually but we might get the occasional glimpse of what our scopes can do if take somewhere truly dark and transparent. Seeing them is one thing, seeing some spiral form in them another and seeing the full extent of their structure something else again.

How do you know what you are seeing and are not seeing ? - I guess that is down to reading the reports of others using similar equipment and practice, practice, practice. Personally I like to be able to repeat an observation of a challenging object at least once before being sure what I've seen. Sometimes the subsequent attempts convince me that I didn't see it the first time and sometimes I get the warm glow of confirmation.

It's those little fleeting moments (and this goes for planetary detail as well) that keeps us "in the game" I reckon :icon_biggrin:

The Horsehead Nebula is probably the most challenging target that I have observed. I guess I'd been preparing and practicing that for a few years before I was finally convinced that I had managed to see it. One of the least impressive objects I've ever observed but still mighty satisfying :icon_biggrin:

Nice sketches - I'm sure they were both accurate at moments during your session :thumbright:

 

 

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Great sketches/observations. Here they are in negative.

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Sketching what you are observing is a great image intensifier, as it focuses your concentration like nothing else I know. One way you can confirm your observations after you've made them is by checking them against the sketches and images of others. Steve Omeara's books on Messier objects and Mallas and Kramer's Messier Album come in handy, but don't worry if you see more than they did as you're just looking for the general feel for the object. You may see much more, or see things differently to them. For example, Omeara tends to draw linear features that don't exist in reality. Your sketches are much more in line with a truthful representation of the visual appearance of M101.

Did you sketch M51 also?

A 6" scope is a fantastic scope for this kind of observing, and if you can shield your eyes from surrounding lights you can go amazingly deep.

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