M27 Dumbell Nebula 15.7.13

Thanks Dave, that does help- I'd always been concerned about my flats as I take the full imaging rig off the telescope each night and assumed I'd need new sets every session. I haven't used dark calibration frames in any of the images I've posted recently as I'm using the new Sony 694AQG chip and they say that darks are not required for most objects and in fact can introduce further noise if subtracted. This is my first CCD and I don't have any frame of reference but certainly compared to my 450D there is simply no comparison with how little noise this chip creates even after some severe heavy handed stretching in PS!

The acid test for darks would be to try imaging without and then with them and see if there is any discernable difference. If there is none then you can safely ditch them altogether. I'd always be wary of manufacturer's claims and would prefer to have direct evidence. It shouldn't take long to take a few darks, take a few shots, process them and see if there is a significant difference. Of course, since we have so little imaging time here in Ireland, time is of a premium and if you are happy enough at it is, don't go to the bother unless you find yourself looking for a project to take on.

As regards flats, if the imaging train is coming off but going back on in much the same orientation etc., you should be able to use them over and over. Again, one way of seeing if there is a need to take them each time is to take flats one night and take them again a second night. Process them to a master flat for each night then minus one from the other. The resulting image will show if there are any significant differences.

Out of interest, can you list out your full optical and imaging system? And what kind of imaging do you like doing? And where are you?

Cheers

Dave

Starlight Xpress usually go for low dark signal noise chips so most users ditch the need to take them. Flats and bias usually suffice and any residual effects can be taken out with a hot/dead pixel removal.

dmcdona wrote: can you list out your full optical and imaging system?

I'll update my signature but I'm currently using,

Televue NP101 & NEQ6 Pro w/Pier
Starlight Xpress SXVR-H694C
Lodestar & SX OAG
Televue NPR1073 .8x Reducer
2" IDAS LPS-P2
Nebulosity / PHD / EQMOD / CdC / PS CS2

dmcdona wrote: what kind of imaging do you like doing?

Really going through a Nebula phase at the moment - spending my time in Cygnus, Cepheus, Cassiopeia etc. getting to grips with my SX694C that I bought in June after using a 450D for a few months. I spent ages trawling the sites on the mono/OSC debate and had fully decided to go for the Atik 460EX Mono, then a Starlight Xpress H694 OSC camera with the same chip came up for sale 2nd hand at a massive discount and I haven't looked back.

Just for the record, if anyone is considering moving from a modded DSLR to a CCD, I couldn't recommend a One Shot Colour enough. Almost all of the forums will tell you to go mono and buy filters, filter wheels etc. and I was convinced to go that route myself until the SX came up in the classifieds and I took a chance. I accept that better detail will ultimately be extracted from LRGB imaging if you have the skills to take advantage of it, but at my level a OSC is more than enough for me to produce images that I'm pleased with. One of my concerns with the OSC was that it would be a bit of a sideways move from the DSLR but in fact it is a HUGE jump up in quality and there really is no comparison, particularly with these new Sony chips.

dmcdona wrote: And where are you?

Dundrum!

I'm not sure how Dundrum measures up for light pollution but it doesn't seem to have had any major effect on your images. I'm in Celbridge and its OK as long as I don't image toward the East and Dublin...

That seems a really neat setup for the nebula line of work. I'm too lazy to calculate your field of view but I'd imagine its big enough.

Did you keep the ATIK? The reason I ask is that if you ever wanted to get into science stuff, mono is probably best. That said, I'm sure OSC is good enough for astrometry. Of course, for 'pretty pictures', an OSC removes the complications (and expense) of filters and filter wheels as you say. And the quality of the imagers keeps getting better and better with some pretty stunning images coming out of them.

For now though, keep at the nebula's and keep posting.

Cheers
Dave

dmcdona wrote: Did you keep the ATIK?

I never actually purchased the Atik Mono, I was about to and it was my preferred manufacturer (mainly because I'd heard such good things about Artemis) but the SX Colour version came up and I went for it. Best laid plans and all that!

Just on the FOV- @ Native I'm getting 1.32 x 1.06deg and 1.73arcsecs /pixel. With the 8x reducer it's giving me 1.66 x 1.32 and 2.17 /pixel @ f/4.3