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M74


Freedom2099

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Yesterday I tried with M74... for the first time I tried as well taking the bias, dark and flat frames and combine them... but I did not see any difference in the final result (maybe a little bit better but the improvement was negligible). I guess I'm doing something wrong  :embarrassed:

I'm still amazed by the result though... this is the result of a 50 x 15s:

 post-38546-0-89587900-1447843232.png

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"I guess I'm doing something wrong"

To get DSO images you really need an EQ mount so that you can take long exposures. Rather than 15sec exposures you need maybe 5 -10 mins or more exposures. Your scope will be good for planetary imaging though.

Peter

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"I guess I'm doing something wrong"

To get DSO images you really need an EQ mount so that you can take long exposures. Rather than 15sec exposures you need maybe 5 -10 mins or more exposures. Your scope will be good for planetary imaging though.

Peter

I have the EQ Wedge... guess I'll have to start using it. 

I do have a question... is there a big difference between the length of each shot? I mean... is 3x1m equals to 12x15s? In general I'd say it depends from the sensitivity of the camera... meaning that with shorter exposure some info might never appear at all even if I took hundreds of shots.... but is just a guess.

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It's all to do with Signal to Noise - with longer shots you will get detail that you will never see if you just take short exposures.

Use the wedge by all means but you may find that guiding is a bit "challenging" with that scope and you would probably need an off axis guider (OAG). For DSO imaging a short focal length scope is the easier way to go. That's why I do all my DSO imaging with my ED80 or ED120. I use the C9.25 for planetary imaging for which it excels.

Peter

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The problem with the 15 second sub. Signal increases far faster than noise but initially they are almost linear i.e. noise matching the level of signal. After a few more seconds the signal rapidly increases leaving the noise behind. You are taking short exposures therefore your noise nearly matches the level of signal thus your frames are noisy. The thing you must do is to increase exposure length thus pulling the desired signal away from the undesired noise. Get a copy of the book the Deep Sky Primer (Bracken) this little book is a goldmine of information & will explain the concepts to you.

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that target is *extremely* faint, given you only have 15 second exposures is pretty cool you caught any noticeable structure at all

Give yourself a pat on the back when you take everything into consideration, you find the right place in the sky it's pretty well centred so onwards an upwards.

Les

ps every sub  Contains data whatever sizes 10 x 100  or 100 x 10 still the same .

this statement isn't entirely true, it's all about signal to noise ratio. For faint DSOs a high volume of short exposures will not equal a small number of long exposures with equal integration time - the shorter exposures have more noise, and will need significantly more short exposures (and ultimately integrated time) to get enough usable signal

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