Looks good Marc!
Two questions if I may-
Are you suggesting that more subs = less noise doesn't work with the moon about?
Do you also experience gradient problems imaging in Ha when the moon is out?
Looks good Marc!
Two questions if I may-
Are you suggesting that more subs = less noise doesn't work with the moon about?
Do you also experience gradient problems imaging in Ha when the moon is out?
Cheers
Andy
Thanks Andy. Yes, more subs = less noise. Always. Moon or not. If your sky background is bright it's harder to get your contrast back so by processing out the glow to compensate to get more contrast you'll bring more noise into your final pic. That's what I tend to do when processing "flat" pictures. Boost contrast more and that comes with noise in the shadows and lower mid tones..
You can get gradients and all sort of other reflections, etc... if the moon shines close to the aperture of the fov as well.
I guess it depends on the FL and scope you use as well.
Finally if your filter bandpass is narrower you'll get more contrast. Mine is 7nm. I suspect I'd get better results with a 3nm? But they're expensive and I can't justify the dow for the level of improvement.
Having said that, my 8nm Sii and Oiii are close to useless under my light polluted skies. Then again maybe I don't try hard enough.
Thanks Andy. Yes, more subs = less noise. Always. Moon or not. If your sky background is bright it's harder to get your contrast back so by processing out the glow to compensate to get more contrast you'll bring more noise into your final pic. That's what I tend to do when processing "flat" pictures. Boost contrast more and that comes with noise in the shadows and lower mid tones..
You can get gradients and all sort of other reflections, etc... if the moon shines close to the aperture of the fov as well.
I guess it depends on the FL and scope you use as well.
Finally if your filter bandpass is narrower you'll get more contrast. Mine is 7nm. I suspect I'd get better results with a 3nm? But they're expensive and I can't justify the dow for the level of improvement.
Having said that, my 8nm Sii and Oiii are close to useless under my light polluted skies. Then again maybe I don't try hard enough.
Using a 3nm Ha would make a big difference with the moon light.
Marc, I’m amazed at the quality of the stars across the field with a GSO 8 inch f/4 scope. These are very cheap scopes but seem to deliver amazing performance. I assume that you are using a Baader coma corrector or similar?
Marc, I’m amazed at the quality of the stars across the field with a GSO 8 inch f/4 scope. These are very cheap scopes but seem to deliver amazing performance. I assume that you are using a Baader coma corrector or similar?
Thanks Murray. TBH, they're not crash hot mechanically with the standard bog focuser, spider vanes, etc... even the primary cell is chonky. The good things about this one are the optics and the CF tube. Now I did a lot of work on it.
Modified the primary cell mirror mounting, changed the spider vanes to stronger ones, the focuser is a low profile moonlite, I also have David's excellent digital focuser control. At F/4 you need it. Even with the CF tube this thing will go out of focus pretty quickly for every degree drop in temperature.
Now for the flat field. Well, it's pretty curved (20%) and also comes with coma, no astigmatism. I'm now about 90% there with my spacing. Still some coma on the extreme corners. Only on one side now thought so just residual tilt to sort out to center the field. Good news is that collimation is rock solid. Doesn't budge in different parts of the sky and that's what matters. The rest of the corner stars, well I crop out or I fix with startools for now.
On axis is pretty damn good. Ray (Shiraz) will tell you the same thing.
MPCC Mark III yeah, although I sold my Mark I a while ago. Honestly I couldn't tell the difference between the two.
PS: forgot to add, all the plastic light baffles inside the tube were lose and not even aligned so I had to reposition them all and glue them. I was getting oblong stars because the aperture wasn't circular. So, yeah, as I say mechanically there's not much QA process when they put them together.
Thanks Andy. Yes, more subs = less noise. Always. Moon or not. If your sky background is bright it's harder to get your contrast back so by processing out the glow to compensate to get more contrast you'll bring more noise into your final pic. That's what I tend to do when processing "flat" pictures. Boost contrast more and that comes with noise in the shadows and lower mid tones..
You can get gradients and all sort of other reflections, etc... if the moon shines close to the aperture of the fov as well.
I guess it depends on the FL and scope you use as well.
Finally if your filter bandpass is narrower you'll get more contrast. Mine is 7nm. I suspect I'd get better results with a 3nm? But they're expensive and I can't justify the dow for the level of improvement.
Having said that, my 8nm Sii and Oiii are close to useless under my light polluted skies. Then again maybe I don't try hard enough.
Thanks Marc, that all makes sense!
I have 5nm Astrodons and a 110mm/ 660ml refractor. I have often imaged from my Melbourne suburban backyard in NB under both LP & Moonlight.
I recently experienced poor results on a recent attempt at the Cat's Paw with the moon close to the nebula. Three night's data was collected but an unresolved, incomplete image, dreadful gradients and nightmare processing were the result - I'm a bit gunshy of shooting under the moon now!
Maybe it's best to choose targets at least 90degrees away from the moon
Thanks Marc, that all makes sense!
I have 5nm Astrodons and a 110mm/ 660ml refractor. I have often imaged from my Melbourne suburban backyard in NB under both LP & Moonlight.
I recently experienced poor results on a recent attempt at the Cat's Paw with the moon close to the nebula. Three night's data was collected but an unresolved, incomplete image, dreadful gradients and nightmare processing were the result - I'm a bit gunshy of shooting under the moon now!
Maybe it's best to choose targets at least 90degrees away from the moon
5nm is very good. Problem with moon glow is that if you have a wet night and the sky is a little hazy as a result then there's nothing you can do about it. It'll catch everything. If it's cold and crisp doesn't matter if the moon is even only a few degrees of your field. The only issue is light bouncing on metallic parts of the aperture, vanes or lens holders, filter edges, etc... there are so many parts scattered and stray light can enter your imaging path. Even the back of my primary is not light proof. I just stick a shower cup on it and flock the hell out of everything else. I think Greg Bradley even runs a black marker on the edges of his filters to stop light bouncing. Whatever works.
Nice HD image Marc. Looks pretty smooth to me and a similar field of view to what I got with my refractor. I reckon your could just do a bit more contrast work yet though. Though that is personal taste.
I totally agree about your comments regarding how these scopes are made, but the important thing as you point out is the quality of the optics. Every GSO scope I have looked through produces very good results optically. It is the crap focusor and minor parts that can let the side down.
Nice HD image Marc. Looks pretty smooth to me and a similar field of view to what I got with my refractor. I reckon your could just do a bit more contrast work yet though. Though that is personal taste.
I totally agree about your comments regarding how these scopes are made, but the important thing as you point out is the quality of the optics. Every GSO scope I have looked through produces very good results optically. It is the crap focusor and minor parts that can let the side down.
Nice work.
Thanks Paul. Yeah, they aren't bad in all. Just a bit of tlc, but usually more than people are willing to give.
