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M27 Dumbell Neb Unguided

jnc71106

By jnc71106
in Imaging - Deep Sky

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jnc71106

jnc71106

Posted
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first attempt at this one unguided as well

20x lights 60sec iso800

10x darks 60sec iso800

10x bias 1/4000 iso800

flats er still not sure how to do them

taken with the bits in my sig

all comments welcome the clouds rolled in and stopped me getting more subs

post-24512-133877606548_thumb.jpg

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jnc71106

jnc71106

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Focus isn't a mile out, I don't think. Getting your target dead centre is important because off axis coma soon sets in with a Newt.

Flats can be a pig but an EL panel makes it easier.

Olly

How does the pointing the scope at the laptop with notepad open flats work

How long do i do the exposures ? Do I keep the same iso settings ? And do i literally hold the laptop up to the front of the telescope ?

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jnc71106

jnc71106

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Might have another go at this tonight if my weather holds up.

I have my guiding setup now so I will have a go at working all that out

Have taken a few 2 min unguided subs and they had a tiny bit of star trails but the clouds came over so I had to stop

Hopefully with the guiding I can then get my pics past the 2 min exposure

Well I will have a go anyway

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ollypenrice

ollypenrice

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I'd have thought that your aperture was on the big side for a PC screen but I don't know.

Don't try and hold the screen. Slew the scope to horizontal and contrive some kind of table or whotnot to put the PC on so that the screen is in front of it. It needs to be pretty orthogonal (square on to the scope) or the inverse square law will get you and your 'flats' will have a gradient. The vignetting in your first image is very evident so flats are not a 'maybe' but are a 'must.' In fact they always are, TBH.

Olly

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jnc71106

jnc71106

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How about the camera setting do i use the same setting as I did for the lights as in exp time iso etc ?

Can I bring the telescope inside place the OTA on a table and put the screen on the table in front of it ?

Does the screen need to be a certain distance from the OTA ?

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Sparrow

Sparrow

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I'm no expert or authority on flats, but just to let you know that I take mine by putting a piece of ordinary A4 printer paper in front of the scope and pointing it at a bright sky to take flats. It seems to work pretty well - as a starting point I think mine were something like 1/120 second at ISO 100 but that was with teh LP filter on - without a filter it would probably need a faster shutter speed.

Flats will definately improve your image by substantially removing the vignetting.

Regards

John

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fatwoul

fatwoul

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Heh. I have an embarrassing confession to make. At some point I got it into my head that flats had to be identical to the lights in every respect except of uniform field of light; not just focus and orientation of camera, but also shutter speed. This has become such a habit that I was sure it was in MEPC, but upon re-reading, I realise it isn't. This might explain my own vignetting problem. :eek:

As for the method for generating the flats, I used to have this complicated light box thing, but I ditched it. Boxes of foamboard come with a thin sheet of packing material inside front and back, which happens to be thin enough to be translucent, and looks fairly uniform. I now just switch the mount off, point the scope at zenith and place a piece of this material on the front of the OTA.

The problem with this material is that it is very delicate. I'm looking into getting a piece thin white perspex cut to do the job instead.

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ollypenrice

ollypenrice

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Focus must not change. Orientation of camera in scope must not change. Camera settings can change as much as you like and will have to, to get the right level of exposure, which is something like the peak being about half way up. But half way, one third, two thirds... who cares? That is the ball park figure that will give you a result.

By taking the OTA inside with the camera and focus unchanged you can do them 'tomorrow' or 'yesterday' entirely as you wish. I have used the shower room wall, lit evenly, before I got a panel that worked perfectly.

Olly

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RikM

RikM

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I use the 'stick a white t-shirt over the end of the scope, set it to Av mode and point it at the sky' method. That gives me the best results.

I have also hung an EL light box (for viewing film negatives) at the back of the shed and point the scope at that. Sometimes works, sometimes not, don't know why. I also tried pointing the scope straight up and sticking the EL panel directly on the scope, but that was hopeless, I ended up with all sorts of strange colours???

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fatwoul

fatwoul

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Focus must not change. Orientation of camera in scope must not change. Camera settings can change as much as you like and will have to, to get the right level of exposure, which is something like the peak being about half way up. But half way, one third, two thirds... who cares? That is the ball park figure that will give you a result...

Of course I see that now. I should have probably tried thinking about what flat frames are for. About 10 months ago would have been good. :eek:

I seem to recall Mr Richards stating the same thing; that the wells should be no more than 50% full for flats.

By taking the OTA inside with the camera and focus unchanged you can do them 'tomorrow' or 'yesterday' entirely as you wish. I have used the shower room wall, lit evenly, before I got a panel that worked perfectly...

I have a couple of walls I could try that with. Unfortunately, carrying an MN190 with a D3 hanging off the side of it makes me shudder at the thought!

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