M16 15nm Ha with a 40D

Bassnut (Fred) · #1 23-07-2009, 08:12 PM

Hi Guys

Ive been trying my modded 40D out whilst my CCD was away being fixed, its back, so the 40D will retire for a while. Im happy with the 40D Ha performance, a bit of a struggle to find the right settings, and it does take longer in many respects to try and match CCD pics, but then that wasnt suprising, given its a fraction of the cost of an astro CCD (well, you dont get next to anything for next to nothin

).

I must say, on bright objects, and some dedication, excellent results can be had on a 40D, but I do find the ST10 actually easier to use, for a given result. At long focal lengths, the higher resolution of the 40D is mute IMO.

Anyway, here is the pic, 200mins of 15nm Ha with 10min subs with seperate darks, no flats. Ran out of time for RGB.

Hagar (Doug) · #2 23-07-2009, 09:21 PM

Nice Fred. Youve picked up plenty of detail in the pillars. Contrast looks good and adds apparent depth to the image. Well done. I didn't know how a DSLR would handle the Ha filter.

lesbehrens (Les) · #3 23-07-2009, 09:22 PM

very nice

Omaroo (Chris Malikoff) · #4 23-07-2009, 09:37 PM

Nice image there Fred

Interesting result from asking a 20D to suck light through 12nm Ha. Worked well I think!

renormalised (Carl) · #5 23-07-2009, 09:54 PM

Nice image there, Fred. Lots of detail in them thar pillars

Alchemy (Clive) · #6 23-07-2009, 10:18 PM

nice detail fred, im just doing a run on the same object at the moment, i wouldnt mind the tighter stars you have there.

Bassnut (Fred) · #7 24-07-2009, 08:39 AM

Thanks Doug,Les,Chris, Carl and Clive. All of the exposure was taken with moon up, so along with smaller stars and more detail, the Ha filter was a handy and worthwhile purchase.

Omaroo (Chris Malikoff) · #8 24-07-2009, 08:48 AM

Quote:

Originally Posted by Bassnut

All of the exposure was taken with moon up, so along with smaller stars and more detail, the Ha filter was a handy and worthwhile purchase.

I've just taken delivery (yesterday) of my own 2" 7nm Ha filter Fred - and you've hit it on the head - being able to perform a meaningful imaging session with the moon up is going to be a real treat. It gives one sooooooo much more time out there. Can't wait.

marc4darkskies (Marcus) · #9 24-07-2009, 10:13 AM

Not bad at all for a DSLR!! Tons of detail & quite smooth. Nice job Fred!

Interesting you say the CCD is easier to use - how so?

Cheers, Marcus

telecasterguru (Frank) · #10 24-07-2009, 10:56 AM

DSLR with ha filter looks very interesting indeed. Fantastic image.

Frank

Bassnut (Fred) · #11 24-07-2009, 11:57 AM

Chris. Thats the killer with Ha, the time available to image, projects dont just stop when the moon appears.

Marcus. It took longer for me initially working out the best iso/exposure times etc. After that, it was the need to make more darks if the temp changed (Ive used the same library for a year on the CCD), the more subs required at a max of 10min ea (the CCD has 80% QE, and I can take far longer subs with it, for overall less exposure time), difficulty in composing without removing the Ha filter 1st, I needed 2-5min subs to see the image to compose, on the CCD I just flick to the Lum filter and bin 3 for continouse 5-20sec exposures to allow fine composure tweaking.

RGB is sort of quicker on the 40d, but given the lower QE, you need more subs, although for bright objects the 40D would win with acceptable results.

And handling large numbers of huge subs took much longer to process (the CCD is only 3.2 mpx). PS was slow too with the huge images. I reduced them 1st in the end, but that kind of lost the res advantage of the 40D (not that it mattered much at long FL).

IP did a great job without trouble processing from disk, but I prefer CCD stacks interface, more contol you can see. CCD stack just died tring to us it with the 40D subs, id need a much faster PC and huge ram to make it sing with the 40D subs.

The CCD allows very fast autofocus on my rig, although the live view on the 40D is magic and also fast, but manual, and I needed to slew to a bright star to focus through the Ha filter (which works well BTW), so the 40D takes longer to focus given its manual and the need to slew to a bright star.

Frank, yep, Ha is an essential tool IMO, use it all the time on Nebs, no good for galaxies though (ie broadband scources).

RobF (Rob) · #12 24-07-2009, 09:00 PM

Just to confirm Fred, you're talking about an umodded 40D here? Would it be worth my while to invest in a Ha for my (unmodded) 450D if I ever scrounge up the cash? I think they're a bit less sensitive, particularly out in the longer red wavelengths?

Love your pic too, and fascinating to hear such a detailed breakdown on the pros and conds of CCD vs DSLR....

Ta,
Rob

Bassnut (Fred) · #13 24-07-2009, 09:04 PM

Rob

No, mine is modded. Forget an Ha filter with an unmodded cam, the internal filter cuts Ha off, wont work.

RobF (Rob) · #14 24-07-2009, 09:09 PM

Quote:

Originally Posted by Bassnut

Rob

No, mine is modded. Forget an Ha filter with an unmodded cam, the internal filter cuts Ha off, wont work.

D'oh! Just re-read the first line of your original post!

Sorry Fred.

(Whew - I can feel my wallet cooling down in my hip pocket....)

Tamtarn · #15 24-07-2009, 09:32 PM

That's an excellent image Fred, the depth of detail and contrast you have got from the 40D is outstanding.