NGC6888 bi-colour with Canon 300mm & ASI1600

[thomasv]

Several clear nights in a row, so spent two evenings on this. When I say evenings, with setup and dodging the moon it's about 80min worth of each Ha and Oiii. 

Ha was 4 min subs, Oiii 5mins subs, with ASI1600 set to lowest read noise setting (i think gain=300). Canon 300mm F4 wide open and using Baader 7 and 8.5nm filters. Stacked in Astroart and adjusted in Gimp.

Advice appreciated, I know it's probably too blue, as I was desperately trying to show the blue outer bubble.

Just received today the Baader 'ultra-narrow band' filters that I want to try, but I have to do some hacking as I bought 31mm for availability, but my filter drawers are 36mm, so some 3D printing will be required.

Attached a picture of the portable setup, as I'm just about happy with it, after trying many variations. The picture also shows the extent of light pollution, although it was taken in 'night shot' mode, so not quite as bad as this, but I do have two LED lights just outside my garden.

[alan potts]

I have a 300mm F4 and an F2.8 Canon lenses, the F4 is from 20 years ago but still sharp, how do you connect the lens. I have a 071 and soon a 183mc to play with.

Alan

[thomasv]

Hi, yes they say the older non USM Canon 300m is actually sharper than the latest. I have a geoptik clone EOS to CCD adapter like this one:

https://www.astroshop.eu/dslr-lens-adaptors/omegon-t2-adapter-for-canon-eos-lenses/p,43762

connected to a TS filter drawer unit:

https://www.365astronomy.com/ts-optics-filter-quick-changer-for-36mm-round-unmounted-filters-length-10mm-including-filter-drawer.html

then a spacer that came with the 1600, I just had to shorten it a bit.

You may not need the filter drawer if you don't want to swap filters with your colour cameras, you can put an LP filter inside the EOS to CCD adapter I think. I also have the ZWO EOS to CCD adapter but I found the omegon more solid as its got a ring that you can tighten up against the lens.

 

[AbsolutelyN]

Thanks for the adapter link, not seen that one before. Have used the ZWO/EOS adaptor but I could not get a flat field with my 100-400ii. Does it give a nice flat field or is it fiddly to get spacing right? 

[thomasv]

Hi, I think as it's being used with a lens, the spacing is not super critical as you can adjust focus slightly, as long as it's roughly right and gives you a bit of margin beyond infinity. I did cut the spacer so that it gave me the required 44mm flange to sensor distance.

The posted picture was cropped and stars reduced, I can post a full sized unedited sub later. 

[MartinFransson]

Nice setup 😎 I use the same lens and camera myself (along with other lenses). I have the 300/4L IS version but I would prefer one without the IS. I sometimes have problem getting corner focus right at certain angles. Pretty sure it´s the IS-package hanging in there screwing things up..

That image will be a lot easier to process once you get more data. Looking good already.