Oknoder Loc: Western North Dakota

Also known as Messier 31, or NGC 224, is a spiral galaxy approximately 780 kiloparsecs (2.5 million light-years) from Earth. It is the nearest major galaxy to the Milky Way. It received its name from the area of the sky in which it appears, the constellation of Andromeda, which was named after the mythological princess Andromeda. Being approximately 220,000 light years across, it is the largest galaxy of the Local Group, which also contains the Milky Way, the Triangulum Galaxy, and about 44 other smaller galaxies.

This is my 4-5 time imaging this DSO, I rushed through PP and something happened to the stars in the left half of the image since they all turned blue for some reason. Either way this is a stack of 20 300s subs at ISO800 no calibration images applied. I included the original raw only PP was converting to JPG.

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CraigFair Loc: Santa Maria, CA.

Beautiful job of PP Matthew. I to have tried M31 several time and only came out 1/2 as good as your's.
I have only done single images not stacked. Maybe it's time I learned.
Craig

Oknoder Loc: Western North Dakota

Stacking is easy just let whichever program, you decide to use, decide everything. Or decide which program and ask or google. If I can figure it out anyone can.

I don't think there is anything special about my raw, not nearly as good as one of your singles. It's the stacking which reduces the noise and increases the signal to noise ratio .

JimH123 Loc: Morgan Hill, CA

Very nice.

I see the blue effect. I have had this happen to my shots also. But if I really blow up your original image, I see that the left side looks different than the right side. On the left, there appears to be some coma distortion. I also can see some tiny star trails. On the right side, the stars are tiny ovals that are flattened a bit. I wonder if the camera's sensor is exactly perpendicular to the light beam coming from the mirror? I believe you are using a scope that the light exits through a hole in the mirror. If the mirror wasn't perfectly collimated or if the secondary mirror was misadjusted just a tiny bit are possibilities.

Oknoder Loc: Western North Dakota

hmm the scope used was a Williams Optics 70mm refractor the effect may be because of not having a fully flat field. I am using a field flattener but not the one designed for this scope, it is the one for my RC scope. It helps a little bit but the distortion is tamed. Miscollimation is possible since a newer heavier focuser is being used, I guess further testing is required.

Matthew

Oknoder Loc: Western North Dakota

After intensive testing last night, to which I did not get any images worth processing I think I have diagnosed the problem. My setup was working autonomously when this M31 collection of images was taken,after looking through all the raws I have decided it was a branch that was throwing half the image out of sync. I will have to alter my start/stop points that my puter uses to figure out if the image is able to be taken or not. the first couple images were rejected due to leaves blanking out the lower third of the image.

I am hoping this is the issue as the only other possibility is that the sensor in my D800 is off by just a bit and I really do not want to dig into it as it took me two tries tearing apart my D5100 to make it work properly.

Matthew

JimH123 Loc: Morgan Hill, CA

I wouldn't say that is the only possibility left. You are usin a T-ring, and adapter. Is that sitting perfectly flat? And you have a focuser. Is there anything going on with it?

The right side seemed bit out of focus with the ovals. The left side didn't have this problem. It certainly does seem that sensor is not flat to the light source.

Oknoder Loc: Western North Dakota

This is what I tried last night.

Recollinated on Vega but no adjustment needed as per CCDInspector's verdict.

Tested on random starfield no I'll effects on downloaded images.

Tested different cameras five in total. This took the majority of the time since I do not have focus measurements for all my cameras yet. Nothing stuck out as the culprit.

Dejected went looking through the raws to see if I could see anything untoward which is when I noticed that the objects before and after did not experience the same effect. While looking through the raws I noticed the first 5 and last 6 were not used because of leaves in the frame over 30% and the left 60% of the clear images have a brown color cast on the left side of image, which I believe is an unfocused branch from my wife's Aspen tree.

It very well could be something else unthought of but I was tired and hate troubleshooting when I cannot recreate the initial problem.

I see coma issues in all four corners the raws of about equal size and shape is it the raw you were using to evaluate the coma issues, cause the final processed image was cropped from the original.

There maybe an issue with the ring not sitting flush on my D800e that does not exist in my D7000 that I also tested. So if that is the issue it is with my D800e. I wonder how I can check without pushing a caliper into my body to measure distance to flange.

Thanks Jim for all your suggestions maybe I missed something.
Matthew

CraigFair Loc: Santa Maria, CA.

In the first image I'm seeing the distortion in all 4 corners.
It appears to be consistent all the way around.
Could it be you need a Focal Reducer/Flattener???
Craig
PS: I put my faith in my D800E to reproduce exactly what it sees.

Oknoder Loc: Western North Dakota

Well Craig mine has been dropped but pretty sure it is still OK other than autofocus doesn't work. I am using a field flattened but it isn't the one WO suggests, it's the one for my AT6RC I believe it is designated AT22FF. Since this is one of W.O. original premier scopes the field flattened/focal reducer advertised to work best with this unit is hard to come by.

Cheapest I have found is around 300.00. I hate paying MSRP for anything, wife says I'm cheap, I think I'm just being frugal. This is why I'm not allowed to go to the grocery store with her as I'm always trying to haggle. In my defense it is a small mom&pop joint where I have known everyone for years now.
Matthew

CraigFair Loc: Santa Maria, CA.

Take a look at this one Matthew, is this what you need??? It's for the Astro-Tech 2" Refractors.
https://www.astronomics.com/astro-tech-2-inch-field-flattener-astro-tech-tmb-refractors_p17393.aspx
Craig

JimH123 Loc: Morgan Hill, CA

True, the D800E will reproduce exactly what it sees. BUT, if there is something causing the camera & sensor to not sit exactly flat, then it will faithfully reproduce the distortion it sees.

I can also attest as to how important the field flatteners are. And I am sure that each manufacturer's design is specifically designed just for that scope.

JimH123 Loc: Morgan Hill, CA

Matthew, is your AT6RC showing any of this distortion with the same D800e body? Might be able to rule a few things out. I am assuming you are using the same T-ring and T adapter, and if all is well, then the camera and adapters pass. That leaves the scope and the flattener.

Some other differences to consider. The Williams Optics 70mm refractor is F6. The AT6RC is F9. That would make a difference in the flattener.

Also, the D7100 is a crop sensor and the D800e is full frame. The D7100 won't use the light path from the objective all the way to the edges. It will mostly use the center portion of that objective. That alone will make a difference.

Albuqshutterbug Loc: Albuquerque NM

Yours started off with more detail than mine. I plan on shooting another set when the skies clear and I have a free weekend again. I will likely use something other than the Newtonian until I get it collimated. Its the little things that make us pull out what hair we have left.
;)
Nice stacking by the way.
Well done.
:thumbup: :thumbup:

JimH123 Loc: Morgan Hill, CA

One other thing to consider is the distance from the flattener element to the sensor. Different manufacturers may specify a different distance.

What type of fitting is this flattener? Some have 2" threads and screw into the end of the 2" T-adapter barrel.

The SCT type screw onto the back of the scope and then the adapter screws into it.