My first real attempt at a widefield - Help

[SniffTheGlove]

This is my first real attempt at widefiled after doing lots of other fiddly things over the last few months like putting in a pier, modding the Canon 350D and buying the nifty fifty.

My image is NOT perfect but I am not sure something is going correctly. I know we are not in astro dark conditions.

This image is of Megrez http://nova.astromet...er_images/53254

Taken at 00:03 during the early hours of this morning 26th May 2013.

Canon 350D modded (Filter Removed)

Canon EF 50mm 1.8 II Lens with B+W 486 IR Filter

30 second exposure

Aperture 1.8

ISO 800

RAW Format taken with APT

EQ6 Pro Mount guided by QHY5 PHD via EQMOD

Now my reason for posting is as you can see is that it is very light and purple. I know there will be some colour correction needed due to filter removal and the use of the B+W486 filter but is this image totally wrong do I need to do something else to get a darker background.

Thanks

[Aenima]

Sorry slightly beyond my skill level but I noticed the zero replies and looked anyway.

Recently I had the filter removed from my 300D, and although it means only using it on a Newtonian, preferably with IR/UV block (not tried this yet) and the subs come out pink, when stacked in DSS (even only 3 or 4 ) the software resets the white balance and seems to rectify the 'light' background (especially those exposures taken after 2.00am).

So my best suggestion would be to take a couple exposures and run them through deepskystacker with maybe some darks...?

I'm sure someone more knowledgeable will pick up on this thread (even a unhelpful answer can help by bumping the question back up the forum )

Best of luck,

Regards

Aenima

[SniffTheGlove]

Thanks,

I gave up mid week as I just could not get a good focus when using the 350D with my lens. I had improved the focus buy hot gluing a 37mm UV filter glass in front of the mirror in the 350D body but still could not get focus on the 50mm Prime. So until I can afford a >=500d or >=1100d with it reshimed correctly for autofocus to work I have put the 350d onto my only scope at the moment with is the ST80. Not good but again saving up for an APO.

Still with the 350d on the ST80 I am still getting a lot of purple backgrounds but not actually tried stacking anthing yet as you have suggest so will give it a go. Thanks

[Aenima]

Yeah I cant promise much but always noticed that DSS deals pretty well with the white balance and background when stacking a number of not-so-good subs, and with widefield I see no reason why several frames cant be stacked to improve contrast and detail. Might even help with trails by allowing a few shorter exposures to be stacked giving similar results to one longer exposure.

Hope you get it sorted,

Regards

Aenima

[nmoushon]

Also try taking new flats. Thats how I counter act the blueing that CLS filters add to my 350D (unmodded though). Try taking several exposures and stacking them together with the flats like Aenima suggested.

[Aenima]

Thanks,

I gave up mid week as I just could not get a good focus when using the 350D with my lens. I had improved the focus buy hot gluing a 37mm UV filter glass in front of the mirror in the 350D body but still could not get focus on the 50mm Prime. So until I can afford a >=500d or >=1100d with it reshimed correctly for autofocus to work I have put the 350d onto my only scope at the moment with is the ST80. Not good but again saving up for an APO.

Still with the 350d on the ST80 I am still getting a lot of purple backgrounds but not actually tried stacking anthing yet as you have suggest so will give it a go. Thanks

I dont know if you have already done this but with modded dslr's a custom white balance is needed to tell the camera what White is again. You'll not regain the sharpness in focussing with lenses after filter removal unless the filter was replaced with another identical in thickness, but you can restore normal colour by taking a picture of a pure white surface, like a bit of card, and go into menu to select 'custom white balance' and when asked for an image give it the white card one (which will look pink due to the mod, but the camera will then see that as white and the balance is resored).

Hope this is of some help.

Regards

Aenima

[SniffTheGlove]

Thanks for the info.

Taking flats is a bit difficult as the moment as I don't have an EP panel and waiting for dawn for a light sky is too long a wait. Thinking of (well read) of using my FTF screen on my HP Mini whilst running notepad full screen in white.

Will do the white balance.

I have runs some photos through DSS with a lit lucj but if I save as TIFF the it look completely dark as compared to the image in DSS, also if it saves as FIT what can worj with FIT files?

[Aenima]

Thanks for the info.

Taking flats is a bit difficult as the moment as I don't have an EP panel and waiting for dawn for a light sky is too long a wait. Thinking of (well read) of using my FTF screen on my HP Mini whilst running notepad full screen in white.

Will do the white balance.

I have runs some photos through DSS with a lit lucj but if I save as TIFF the it look completely dark as compared to the image in DSS, also if it saves as FIT what can worj with FIT files?

Best to work with TIFF as I believe its a bit more straightforward and compatible. As for processing after DSS, you should be able to restore a lot of the brightness using levels or curves, or even just brightness itself, as for when your in deepskystacker and after the stacking process you need to be in the processing window and align RGB and set a 'S' curve in luminance using the sliders and hopefully it'll give you something to work with when you open in your editing program.

First thing is to get the hang of DSS as best you can, the 'save file to disk' for further processing. Sorry if you know this stuff already, just trying to cover everything

Best o' luck,

Regards

Aenima

[tferrari]

The overall cast is from light pollution. The strange color is from white balance issues. You can manually align your color channels for your image (or stack) in Photoshop (or perhaps Gimp, for that matter) or you can read about setting white balance for modded DSLRs. There is a lot of info about this floating around the forums/Google.

[nmoushon]

Thanks for the info.

Taking flats is a bit difficult as the moment as I don't have an EP panel and waiting for dawn for a light sky is too long a wait. Thinking of (well read) of using my FTF screen on my HP Mini whilst running notepad full screen in white.

Will do the white balance.

I have runs some photos through DSS with a lit lucj but if I save as TIFF the it look completely dark as compared to the image in DSS, also if it saves as FIT what can worj with FIT files?

Dont need an EP panel. I use my laptop screen opened up to notepad. Works perfect for me.

[russellhq]

Have you tried lowering your exposure time or ISO? I had a look at the histogram for your image and the blue channel's peak is hard against the right hand side meaning your image is over-exposed. Ideally you should keep your histogram peak to less than 50% of the way along the histogram x-axis.

[SniffTheGlove]

Not really had to chance to play with the Canon350d yet due to clouds etc.

But will try these newer settings once I can get a clear couple of hours. Anyway I am in the hopeful process of an upgrade soon if I am allowed to? I sold my 250mm F7 OTA pre-xmas to help fund a newer scope but that money disappeard quickly from everyone in the house using my secret stash as the family cashpoint

Anyway in the next few months hopefully before the main winter session will start I hope to get a better camera, either a Canon 1100D or a CCD of the same price point, along with an 80ED with flattener/Reducer as currently I am just using my ST80 which is not ideal with my modded 350d. Going to another camera will allow me to use one less cable going to the camera (350d has the usb plus a Opto-LX cable).

I just did not realise that modding the 350d would produce more complicted image processing and as I am a good programmer I am useless with graphic application. Photoshop is so complicated but just need a "good monkey see monkey do" tutorial on processing modded camera images.

[Aenima]

Hi Sean,

I dont know how far along you are with solutions to the mentioned problems, but after reading a different post regarding restoring custom white balance it was said the card should be 18% grey rather than pure white - unsure on technicals but wanted to pass on the info

Also in DSS in the settings tabs under 'output' you can tick the box #TIFF instead of #FITS for the final saving to disk.

Good luck with the imaging.

Regards

Aenima

[sgazer]

When you mod'd the 350d, did you replace the filter with another piece of glass or filter? If not, the light path between the lens and sensor will have changed, hence you won't be able to reach infinity focus with the 50mm. Adding an EOS clip filter (between the lens and sensor) will help as it's adding 'glass' but I remember they were not quite as thick as the filter which was removed, so still an issue. Regarding the image itself, you need to take a few (eg 16) and stack in DSS to get the noise down. DSS also has settings to set the white balance correctly to get rid of that pink hue. Then process in PS or GIMP to darken the background and extract the detail. Your skies seem light polluted, so some kind of UHC filter would be good. And you definitely need flats, I've never used an EP panel, but had plenty of success with an evenly illuminated painted wall or door (don't need to be white), sheet of paper on the wall, white T-shirt etc. Just move the scope around a bit to average out any spots. Hope that helps.