It's Helix nebula season again. I really wanted the outer loops but only got one side. The other side must be very faint! Star shapes are a bit elongated due to me keeping too many trailed subs. I couldn't bring myself to throw that many out.
GSO 10" F4 Newtonian, full spectrum Canon 1100D, Baader Semi-apo filter, 607 x 1 minute subs or 10.1 hours, HEQ5-Pro unguided.
Have you tried a stack with just the good ones? I'm just thinking that if there are too many elongated subs it could play a little havoc with the rejection of fainter nebulosity
You've got some really nice detail so far though.
Have you tried a stack with just the good ones? I'm just thinking that if there are too many elongated subs it could play a little havoc with the rejection of fainter nebulosity
Nah I'll try it again next year when there are (hopefully) less gremlins in the system.
Given the constraints of 1 minute subs, DSLR, and unguided, that's impressive. (Took us 50 hours with a 20" to get the faintest outer chevrons.) You've got a good haul of small galaxies in the image.
The elongated stars are a bit puzzling. The ones at the top left are elongated toward top left, and the ones at top right are elongated toward top right. The ones in the centre are elongated vertically. Those at the bottom left and right corners are much better. That doesn't fit with field rotation, periodic error, or wind buffet. Some combination of camera tilt, mirror flop, and flattener spacing? You'd think that would appear in all subs, not just some, but if there was movement under gravity during the night, it could do it. Out of my depth here, but hoping it might trigger some ideas.
Despite the elongated star question, it's a great image.
Given the constraints of 1 minute subs, DSLR, and unguided, that's impressive. (Took us 50 hours with a 20" to get the faintest outer chevrons.) You've got a good haul of small galaxies in the image.
The elongated stars are a bit puzzling. The ones at the top left are elongated toward top left, and the ones at top right are elongated toward top right. The ones in the centre are elongated vertically. Those at the bottom left and right corners are much better. That doesn't fit with field rotation, periodic error, or wind buffet. Some combination of camera tilt, mirror flop, and flattener spacing? You'd think that would appear in all subs, not just some, but if there was movement under gravity during the night, it could do it. Out of my depth here, but hoping it might trigger some ideas.
Despite the elongated star question, it's a great image.
Best,
Mike
Thanks M&T. It's gremlins. I'll just have to stop feeding them after midnight.
Quote:
Originally Posted by billdan
Looks pretty good Kevin, those outer shells are really hard to pull out.
You can always add more to it it next year.
Bill
Thanks Bill. I guess I can always add to it. Better to start again though I think.
That turned out well Kevin. The elongated stars at the top left and right are consistent with some tilt.
If you are looking at your camera standing behind it the corners to pack out will be the bottom left and the bottom right. it would be a matter of .4mm or less. I got some brass shim from a metal supplier. My filter wheel is a mess of blue tape and taped packers to correct for different scopes!
It looks like the bottom left needs to be packed out a bit more than the bottom left looking at your camera from standing behind it.
Are you using an eyepiece holder to mount your DSLR or a solid screw type adapter? The tilt is likely in the eyepiece holder if that is what you are using.
If you correct for tilt and can't get it any better it may need a touch of collimation.
That turned out well Kevin. The elongated stars at the top left and right are consistent with some tilt.
Are you using an eyepiece holder to mount your DSLR or a solid screw type adapter? The tilt is likely in the eyepiece holder if that is what you are using.
Greg.
Thanks Greg. I'm using A T-ring / M42 adapter on the MPCC MKIII. I see astro shop have focal plane tilt adapters. It might be worthwhile for me to invest in one if I can't otherwise fix it.
Quote:
Originally Posted by traveller
Good effort Kevin.
A f4 light bucket certainly does its job!
Bo
Nice one, Kevin! I don't think I've seen the faint extensions in a RGB image. You might need to go mono/NB... or maybe you'll just amaze us all by doing it with a DSLR
Nice Kevin. How long does it take to stack 607 subs !!.....
I might do a few less subs though.
I stacked in two sets of 302 / 305 subs. Not too long, a couple of hours each.
You can never have too many subs!
Quote:
Originally Posted by RickS
Nice one, Kevin! I don't think I've seen the faint extensions in a RGB image. You might need to go mono/NB... or maybe you'll just amaze us all by doing it with a DSLR
Thanks Rick. I can trace a faint sign of outer extension on the other side but I would need 100 hours to get it more betterer. This image was taken in ideal conditions also. Perfectly clear cloudless sky, cool nights for low noise and high elevation. So yeah without narrow band and a cooled astro cam, it ain't gonna happen with this particular DSLR. It will be my personal benchmark to beat in the future.
i once punched out a 30 minute sub with a Ha filter in front of my uncooled dslr to see if i could nab some more outer extension that the usual loop but the noise levels were way too high.
Thanks Russell. Was thinking of a Ha filter, but the only Ha filter I have is a wide 30nm one and it doesn't do any better than something like a CLS filter cos it's too wide. I'll wait until I get a mono astro cam and narrow band filters.
