Huge green bias

[Mike in Rancho]

Well, yes I hadn't thought of that. For sure brings up some new potential issues to figure out.

After a quick google I also found this one with a large Newt and some creative ways needed to take flats: https://wolfcreek.space/index.php/2020/ ... newtonian/

And in fact I know some, even who use refractors, who due to their unique camera and filter situation have had to do something similar - set up a screen, shine indirect lighting at it, and take the flats from a distance away.

So far luckily I seem to have had decent results with my refractor-DSLR flush up against my laptop screen, which has now been replaced with one of those light pad/panel thingys, which I am also doing flush-up.

Good luck!

[patraip1]

I think I am on the right track!!!
The new flats seem to work better!!!
Here is a first stack with all calibration files (and of course the new flats!) of the images I took last night of the North America nebula from my heavily light polluted front yard.200 subs of 15sec @iso200 (I used average instead of intersection in the result tab in stacking settings, all the rest of the settings as per ST recommendations)
https://drive.google.com/file/d/1mV42L3 ... sp=sharing

I think the vingetting is finally GONE!!! .
I dont see enough nebulosity but I have not processed this (or any other nebula) image in ST before , so I dont now if the exposure is short , but first look in autoden I am happy with
I am restacking M31 to see the difference as this is the first time I have shot NGC7000 and mayby it somehow changes the parameters..

[Mike in Rancho]

Well, I hope so!

I thought I still saw vignetting there, but there's so much field rotation and I had to crop so much off, that I can't tell. After the big crop, things seemed even enough however.

NA Neb is a difficult if not impossible target for an umodded Nikon, particularly without major integration time. You got some stars and a couple red areas of the brighter target it seems. But really it needs a modded camera, and even then a filter is immensely helpful.

Will be interesting to see how the new flats procedure works for the brighter targets though.

[patraip1]

Well Mike.... Thanks a LOT for the time and effort you put in helping a begginer like myself. I really appreciate it.
Last night I took 40 subs of m13 and 40 of m57 both at 25 sec while waiting for NGC7000 to come in view from my wind protected front yard location. I then took another 180 subs of NGC7000 this time at 25 sec. (BTW, It seems that for some reason my mount tracked a lot better with the target up in the NW and declining than in the NE and rising. I am suspecting a balance issue. With my setup it is perfectly balanced in mid altitudes, nose heavy towards the horizom and back heavy towards the zenith. I will try to rebalance it the opposite way for NE targets and try M33 again when I get some more time.
Anyway I stacked using intersection this time and all the stacking artifacts from field rotation were gone, although the images came up smaller BUT there was no vingetting in my eyes, just the expected light pollution from the bottom of the image!!!!! I think I got a little more colour this time too in NGC 7000 and was quite happy with m57 and m13 (I will have to ask a friend with a 3d printer to make me a bahtinov mask to be able to focus to perfection... new project!!!)
What would you suggest as appropriate targets for my unmodded NIKON and max 25-30 sec subs???


Thanks again for the help

[Mike in Rancho]

No problem! And good to hear. Hopefully the images pan out nicely.

Yes I typically run intersection mode except for special situations.

I actually have a session running on NA and the Pelican right now. Just a one night stand, awaiting the next monthly target, but a first for me - on the target, on using a camera lens in lieu of the telescope again, but with the modded D5300 and L-eNhance. We'll see if it works or is carnage. A fun experiment to change things up, anyway.

I took a lot of images with my stock D5300 until I picked up my extra one and took the filter out, but avoided most red nebula except for the very very brightest. Plenty out there in the broadband - galaxies and PN's (though they can be small), globs and open clusters, super bright stuff like Orion...

I guess I'd have to look up your framing scale, or review one of the frames you posted already. I typically use Stellarium to check out targets and how I can frame them. There are other planetarium options, even online. All the good ones allow you to plug in the specs of your telescope, camera, and any attachments you are using (flattener, etc.). That'll give you your size limitations.

Then just some research - if it's nebulous look up what the elements are -- reflective, or emission/hydrogen alpha? You might also check out other posted images using a stock Nikon D5300 and up to see what certain target captures look like, and how much integration was needed.

These Nikons are generally a bit worse in the red/Ha line response than similar stock Canons.

Sounds like you are having fun though, which is great. Keep it up!

[patraip1]

Hi mike..
I use skysafari pro to find targets and to see how they will frame in my setup. Right now my problem is that from my backyard I have a window of sky from the NE to S and from my front yard from W to NW ( and a school with huge procection lamps across the street...) My journey to the dark site is postponed (until the strong winds subside) at the moment, but.....
I can officially declare that my new flats are working!! At least that is what I think. I only see a gradient from the bottom of the frame which is to be expected as I take my pictures above city lights. I can remove this with wipe but only with the vingetting option, aggressiveness at 93 and edge at 85 with daf at 4.
Here is the result of 100 15 sec subs @iso200 of m42

orion.jpeg (180.29 KiB) Viewed 5776 times

and 40 subs 25 sec @iso 200 of m13

m13.jpeg (197.82 KiB) Viewed 5776 times

I stacked both with all the suggested settings and just the flats and biases I already had from the other night. No vingetting in either stack!!
Processing was a breeze once I figured out how to remove LP in wipe. Very very happy with Startools!!! The images I produce I am quite happy with and I can show to my family and friends! My wife says I should arrange a photo exhibition at my hospital, LOL

[Mike in Rancho]

Nicely done!

Glad to hear you've worked out the flats and vignetting, that'll make things much nicer for your processing going forward.

Good target choices for an umodded camera. I can even see "the propeller" in your M13 - always a sign you've captured some good detail and pulled it out in processing.

I too have to juggle the mount position a bit. I have one pretty good spot that most things will cross over at zenith, a patch clear to the north and down the other way to a bit past the celestial equator. I placed three flagstones in that spot for the tripod, with little divots, to make PA easy and consistent. For the planets the other night that were lower than that however, I had to set up in the dirt further away. And I even have marks in completely different places for crazy stuff, like when I shot Omega Centauri skimming the southern rooftops.

Have to make due with what the yard gives us.

By the way, did you notice NGC 6207, little tiny galaxy near the bottom of your image?

[patraip1]

Thank you Mike!
I now have noticed the galaxy.... LOL
Cheers

Tryfon