First Astro Image

[KenMiller]

I took my first astro image last night. Here it is: NGC 7789, an open cluster in Cassiopeia.

Canon Digital Rebel xTi through a TOA-130. Ten 30 second images combined using Maxim DSLR.

I've got a lot to learn in the processing department but I think this turned out OK for only doing darks.

[BT Technologies]

Hello Ken.. That is an AWESOME first shot image!! Excellent tracking and focus...

I can't wait to see some of your other shots as well!! Keep them coming...

[KenMiller]

There are artifacts in the original image I removed in processing that I'm curious about.

I've attached two small images that show them.

The first image is from the upper left corner and the second is from the lower right corner.

Notice that the stars are elongated toward the center of the image. the stars in the center do not exhibit this elongation.

Is this a well known phenomenon?

[BT Technologies]

Ken, can you post a full frame image of this rather than the small thubnail?

[KenMiller]

Here's a link to a full image.

http://www.astrobeginner.com/images/img_0014.jpg

[BT Technologies]

Ahhhh, much better... It appears that your tracking is a bit off so a more careful polar alignment/drift alignment would be in order. You can see a tiny bit of tracking error on the stars in the center of your image.

As far as the extreme corners, you are seeing a bit of field curvature. This is the reason that Takahashi has the flatteners available for the scope. With the flattener you would not get this phenomenon. Don't forget that you are using a large ccd array with your camera. If you were using a smaller sized detector you would never see it.

Originally Posted by KenMiller

Here's a link to a full image.

http://www.astrobeginner.com/images/img_0014.jpg

[KenMiller]

OK. Better alignment doesn't surprise me, but the field curvature does.

This was with the relatively small sensor of the Canon Rebel XTi at a 22.2 x 14.8 mm.

I'm guessing it's going to be considerably worse with a 35mm sensor?

[BT Technologies]

It depends on the positioning of the camera to the scope. This is why they make a special adapter to put a specific camera at the correct "metal back" distance to the ccd detector for a specific scope. If you stray too far from this perfect distance then field curvature and other anomalies will result.

How did you attach the camera to the scope Ken?

Originally Posted by KenMiller

OK. Better alignment doesn't surprise me, but the field curvature does.

This was with the relatively small sensor of the Canon Rebel XTi at a 22.2 x 14.8 mm.

I'm guessing it's going to be considerably worse with a 35mm sensor?

[KenMiller]

I used a Takahashi Canon EOS adapter.

I suppose there is a possibility that I mixed up the adapter for the E-180 with the one for the TOA-130. I still have one in a box (which I think is for the E-180) with the part number TMW004.

So, the one I used with the 130 was not the TMW004.

Did I use the wrong one?

[BT Technologies]

I will have to check for you tomorrow Ken which adapter is which. Did you try to use your 5d with the TOA-130 yet? I would really be interested in seeing some images taken with that camera with the larger ccd detector.

Originally Posted by KenMiller

I used a Takahashi Canon EOS adapter.

I suppose there is a possibility that I mixed up the adapter for the E-180 with the one for the TOA-130. I still have one in a box (which I think is for the E-180) with the part number TMW004.

So, the one I used with the 130 was not the TMW004.

Did I use the wrong one?