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M27 Dumbbell Nebula

Tommohawk

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Tommohawk

Tommohawk

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Well, heres my first effort at M27. I was pretty pleased with this - always room for improvement, but I thought this quite good.

Equipment as signature, using the Canon 550D. 29 lights, 19darks, 20 offsets. ISO 800. 300 second exposures over 2 nights. Focussed using EOS utilites live view with max magnification. (Haven't got round to sorting a Bahtinov)

PHD2 guiding wasnt so accurate as usual - RMS errors were something like 0.35 RA and Dec on average, but quite a lot of variation. I think the balance wasnt great. I turned of Dec as an experiment (whilst not shooting) expecting to see a slow drift on the PHD plot, but it was quite jerky. Seems to suggest that fluctuations/wobbles in the RA transfer to Dec - presumably as theres some Dec backlash. I think the image is not perfectly clear - probably due to guiding issues rather than focus or poor sky.

I stacked the RGB curves in DSS and added 17% saturation. I dont like adding colour, but in fact the final result was pretty close colour wise to the single RAW subs, so not too artificial. I also tweaked the luminosiy curves in Paint.net, which nobody else seems to use!

The Goldilocks variable is absent. I'm sure thats very significant (!) Please feel free to criticise!

RGB stacked+17sat+PNedit_crop.tif

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Tommohawk

Tommohawk

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OK thanks! Havent used PNG before - anyone advise me on the benefit of this format? Got lots of options when saving - dithering etc. Left it as default. Et voila....

post-33831-0-98602300-1406456506_thumb.p

Oh BTW no coma corrector used for these images - have left a hint at home for birthday present!

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PhotoGav

PhotoGav

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Excellent, that looks great! The stars are round and tight, so guiding can't have been too bad! Hopefully the family will pick up on the coma corrector hint as that would definitely improve the edges. Well done!

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O-RICH

O-RICH

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wow, i looked at m27 for the first time the other night through my 200p and it just looked real blurry, nothing like your wonderful pic. Ive wanted to do photography but have no idea how to set the scope up to do it, would you be able to offer any advice? I know the scope has a direct SLR connection but i have no clue how to set it up :(

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ollypenrice

ollypenrice

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A very nice, honest Dumbbell and you are beginning to get a whiff of some of the outer shells there.

A very small adjustment to your background sky might be in order. It's a little high in the red, I think.

Re Dec and PHD, the trick is not to disable Dec altogether but to disable the guide direction (north or south) which you don't need. This reduces oscillation. (Since PA is rarely perfect all your corrections are likely to be in one direction.) Trial and error will find out which you don't need. Not infallible but often useful, this trick.

Olly

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Tommohawk

Tommohawk

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wow, i looked at m27 for the first time the other night through my 200p and it just looked real blurry, nothing like your wonderful pic. Ive wanted to do photography but have no idea how to set the scope up to do it, would you be able to offer any advice? I know the scope has a direct SLR connection but i have no clue how to set it up :(

Well thats a short question with quite a long answer! BTW ta for the compliment on the pic.

You'll need an adapter as you say - the T ring adaptor screws to eyepiece holder. Canon is probably best DSLR simply because they have more astro mods and sofware available.

The main reason photo looks better than direct view is because its long exposure. I think probably 30 seconds would get you a half way decent exposure, but the longer the better  - mine was 5 minutes. You also do multiple exposures and "stack them" ie combine them with software like Deep Sky Stacker to average out data. You also do "dark" pictures with the lens cap on and the software uses these to eliminate random noise. (There are other corrective picture types also - offsets/flats - but dont worry about that yet)

To achieve long exposres you need to drive the mount - assuming its equatorial rather than Alt/Az type - using motors. But even this isnt very accurate so you also have a guiding scope and separate camera atached. The image from this is monitored by guiding sotware - like PHD - which then feeds corrective signals back to the mount. The mount need to have an ST4 port to do this. You can then achieve very long exposures - not sure what the max is - probable more than 10 minutes would give no further benefit.

It s lot to learn - I got started 7 months ago so still a rookie, but have beedn well immersed in it.... or obsessed as my wife would say.

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Tommohawk

Tommohawk

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A very nice, honest Dumbbell and you are beginning to get a whiff of some of the outer shells there.

A very small adjustment to your background sky might be in order. It's a little high in the red, I think.

Re Dec and PHD, the trick is not to disable Dec altogether but to disable the guide direction (north or south) which you don't need. This reduces oscillation. (Since PA is rarely perfect all your corrections are likely to be in one direction.) Trial and error will find out which you don't need. Not infallible but often useful, this trick.

Olly

Thanks Olly. Am still only learning the processing stuff, so layers and masks is beyond me just yet.

Ta for the tip regarding Dec disablement - I read about this somewhere but couldn't figure which to disable, N or S. I guess that depends which way youre drifting, ie on the PA error, so expt is the way to go.

BTW with DSLR the live view image is no better that direct viewing - in fact its worse. But  if you rig an OSC CCD, does the live output give a nice live image? I ask because for anyone who's keen to see DSOs but not bothered about photography, this might be the way to go. Maybe not?

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Superdavo

Superdavo

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anyone advise me on the benefit of this format? 

PNGs are good as they perform 'lossless' compression. This means that they are smaller files than uncompressed formats (BMP or TIFF), yet don't lose information in the data (like JPEG, or even worse, GIF). Not sure about the dithering setting though - I leave it as the default as well.

Also, a very nice image!

David

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ollypenrice

ollypenrice

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Thanks Olly. Am still only learning the processing stuff, so layers and masks is beyond me just yet.

Ta for the tip regarding Dec disablement - I read about this somewhere but couldn't figure which to disable, N or S. I guess that depends which way youre drifting, ie on the PA error, so expt is the way to go.

BTW with DSLR the live view image is no better that direct viewing - in fact its worse. But  if you rig an OSC CCD, does the live output give a nice live image? I ask because for anyone who's keen to see DSOs but not bothered about photography, this might be the way to go. Maybe not?

No, OSC CCDs don't output a colour image. (At least Deep Sky ones don't. I don't know about the sensitive fast frame cameras.) The colour info is released in processing when the Bayer Matrix is removed.

Olly

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Tommohawk

Tommohawk

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Thats a shame.

Do CCDs produce a live image at all? I guess they must, cos the guidng CCDs certainly do - but is the image any good... what does the live mono image look like?

I was just thinking that for those with no real interest in photgraphy, there's something to be said for using imaging equipment of one sort or another simply to achieve a better "live" image. I wondered if CCD output might be better than DSLR and allow this. I suppose in practice this would have to be done with some sort of live stacking software, so in effect one would be doing "imaging".

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peroni

peroni

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Well, heres my first effort at M27. I was pretty pleased with this - always room for improvement, but I thought this quite good.

Equipment as signature, using the Canon 550D. 29 lights, 19darks, 20 offsets. ISO 800. 300 second exposures over 2 nights. Focussed using EOS utilites live view with max magnification. (Haven't got round to sorting a Bahtinov)

lol. must read the full post before asking questions  :grin:

It interesting to see the difference in what you've managed to capture with a modded camera. I had a go at that image last year and you definitely caught more of the red areas.

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Davey-T

Davey-T

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BTW with DSLR the live view image is no better that direct viewing - in fact its worse. But  if you rig an OSC CCD, does the live output give a nice live image? I ask because for anyone who's keen to see DSOs but not bothered about photography, this might be the way to go. Maybe not?

You need something like this for live colour.

Dave

http://www.astrophoto.co.uk/

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Tommohawk

Tommohawk

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Thanks. Yes with the 550D.

lol. must read the full post before asking questions  :grin:

It interesting to see the difference in what you've managed to capture with a modded camera. I had a go at that image last year and you definitely caught more of the red areas.

 Double LOL - I should read page 2 before posting!

Re the colour - ideally I would have done more with the Canon before getting it modded, just to see exactly howe much difference it made to the red. But i couldnt face hours of unmodded imaging knowing that I was going to mod it sooner or later so I got it done pretty much at the outset.

You need something like this for live colour.

Dave

http://www.astrophoto.co.uk/

CCD deep sky cameras are not intended to replace the EP view but there are cameras like the Mallincam which are intended for this purpose. I think they are very good. Try the videoa stronomy section.

Olly

Ahh - video. Never thought of that. I cant help but think there must be some market for a "video EP" or similar which just enhances the image by doing a short stack - or something, for those who want to see DSOs but arent bothered about photography. How many times has somebody said, having seen one of your photos, "but it doesnt look like that in my scope"?

Anyhow - looks like a clear cool night - I'm off to grab Cocoon nebula!

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