High temps & DSLR Noise! - M23 Cluster

[SimmoW]

'high' resolution, if you can call it that (https://www.flickr.com/photos/48232585@N00/15387722412/)

Here's an image from Sat night, it was balmy and around 22c outside, so comfy for imaging but not so good for my DSLR sensor! Pretty disappointed with the end result, so noisy if you zoom in close, but it's the best I could do, with 10 shots of 5 mins each. Attached is one of the flats, you can see how bleached out the image is in Melbourne at 5 mins, but a surprising amount of detail available once you stretch. Maybe I should try fewer minutes to lessen the noise?

Also attached is one of the darks I took on the night, I can't believe any image is possible with that amt of noise! yowser. A testament to Pixinsight's abilities to resurrect an image.

[Mosc_007]

I think you will find all the Back Ground color is Sky Glow. I found in the western suburbs of Sydney I can only do about 30 second exposures before the sky glow is bad.

A CLS Filter will help to remove a Lot of the sky glow. But only really useful for Nebula Images. It will dim the stars too.


Charles

[rustigsmed]

hi Simon,

nice processing!
I get similar results, it looks like you may need to wind back the sub length and or grab a light pollution filter.
I don't think my dslr will be getting much use over the warmer months ...

cheers

[SimmoW]

Thanks Russell, ha yes I already have a LP filter Per my signature. Without it I wouldn't break 1 min!

I'll have to meet with the BOW bank (Bank of Wife) to discuss any possibility of getting a cooled CCD! Sheesh this hobby is a money pit...

[raymo]

Forgive my ignorance, but what exactly is the first image that SimmoW
calls a flat? I have not yet used flats, but I thought that they were
plain white evenly illuminated pics of nothing.
raymo

[SimmoW]

Sorry Raymo, I meant Lights, not flats.

[rustigsmed]

indeed, there is a QHY8 cooled colour in the classifieds.
i'm going to try and by-pass going for cooled colour and aim for the QHY9 with new 7x 36 filter wheels... we'll see though!

[raymo]

Now I'm really confused; after looking through all my AP books, it
seems that flat field frames and light frames are the same thing, a plain white field. Your image looks like what I get from DSS before doing any
processing. Sorry to be a nuisance.
raymo

[SimmoW]

Same here Russell, I almost bid on the 8 but decided I'd wait and go mono.

Raymo, here's a 'Flat' of mine, accentuated to highlight the details, the vignetting and dust spots aren't really that bad. If you start to get spots/marks on your images or vignetting, that's when flats are important. As my scope is very bright (F3.3) it's got some noticeable vignetting that's easily removed with some flats.

[SimmoW]

no you ain't no nuisance Raymo! I must be since I called the Flat the wrong name...

Flats may look very flat, but again, if you up the contrast, you might notice some vignetting or the dreaded dust mote (you'll see I have at least 3 and growing...).

It's easy to take flats early on in the evening, take a pic of some clear sky before it gets dark, I've been told to take around 20-30, make sure you keep your camera in the same position as you'll be using it in the night. Just set your cam to automatic, or shutter speed priority, around 1/60th a sec might suffice, or faster.

Light frames are just the raw images you take, of the pretty space thingies :D

[raymo]

Thanks for the explanation.
raymo

[Mosc_007]

If you are in the Subs of Melbourne you will have the same problem with a Cooled CCD. Most of that is Sky Glow, Not Cmos Noise.. And even with a Sky Glow (CLS) filter the best I can do in the Subs of Sydney is about 30 seconds before sky glow appears.

Up at Linden were the sky is very dark I can do 10 Min subs with a stock canon 100D. No Filter at all, and the Sky glow is minimal.


Charles