Thinking about mono...

[Whistlin Bob]

I've been imaging with a DSLR for the last couple of years and having a ball. At the beginning of the summer I picked up a 2nd hand Canon 550d with a home built Peltier Cooler which works very nicely and until this past week I was confident this would see me through a few seasons at least.

What's happened this week:
- Last weekend I did some Bi-colour imaging on the Heart and Elephant Trunk nebulae. Pretty pleased with the Heart, but the camera seems pretty poor at picking up faint Oiii (I know it's almost always fainter than Ha) and it got almost nothing out of the Elephant Trunk.
- I just got a bonus at work which I really wasn't expecting.
- My wife said "It's Christmas- you should have one of those cameras you keep looking at" (I knew there was a reason I married her!!!)

- I saw that ZWO have a sale on- thinking about 183mm Pro or 1600mm Pro.

So, if you don't mind, a few questions to the knowledgeable...

- Have any of you gone from a One Shot Colour camera to Mono, decided you didn't like it, and then gone back again?
- My first love is observing. I'm lucky to have a shed with a permanent setup in it so a perfect astro evening for me is setting the rig running and leaving it to it whilst I get the dob out. I know filters would need to be changed now and again- but does it take very long? Are the filters really parfocal? Would my approach be any less viable with mono than OSC?
- My local council installed very bright LED streetlights last year. I was only able to carry on RGB imaging with an IDAS D2 filter. Would I still need to use it as well as the RGB filters on a mono setup?
- I've posted my Heart below- the Oiii in this I fed into the Blue and Green channels (with emphasis on blue 'coz I like purple!) and comes from 14x 10 min subs with a Baader 8nm filter. Could I expect a much stronger signal from 140 mins mono integration time or have I just got kit acquisition fever?

 

[DaveS]

Probably the best thing I ever did was go from a DSLR (Un-modded 550D) to mono CCD. Between the ASI183 and 1600, it's not an easy decision, I would tend to go with the 1600 for the FoV and less processor intensive data crunching, those 40 MB subs add up quickly. Also I found the 183 to be much more fussy about Dark Frames to kill the horrendous amp glow.

As for filters, get an electronic filter wheel and your capture software will change the filters for you. Filters from any one manufacturer will be physically parfocal, whether your 'scope will be sufficiently apochromatic to put all wavelengths to the same focus, only you can determine.

I would keep an IDAS D2 for your Luminance filter in an LRGB set. This may be a slight complication as they don't do it in the most affordable 1.25" size, and 2" filters tend to be expensive.

With mono you can use NB filters to their fullest extent (I have my doubts about fancy multiband filters for OSC cameras), to give proper separation between hydrogen, sulphur and oxygen wavelengths (You cannot separate hydrogen and sulphur in an OSC system since both are red.

Hope this gives you some pointers.

[Whistlin Bob]

Thanks @DaveS, that's really helpful- especially your comments on the 183 amp glow- that has me leaning towards the 1600