central bright area...vignetting?

[oopfan]

Joe,

Another note:
Camera orientation will not affect Darks and Dark Flats since the sensor is covered. However, Flats should match the orientation of your Lights. People usually take Flats soon after or before Lights. But you can reuse Flats as long as the camera is in the same orientation. For example, I'll have two sets of Flats for each filter: one for when the camera is oriented in landscape mode, and the other in portrait. Your Hyperstar doesn't allow that since the camera is fixed (at least to my knowledge.) This means that you can capture Flats on a cloudy day. There is no need to waste precious dark skies taking Flats. Just make sure that the camera is attached to the telescope in the same orientation as when you take Lights.

Brian

[psy1280]

Brian,
50 miles north, you must be well out of the NYC light dome. I'm jealous. Thanks for the overview. Yes, I've been aware of all that you write, however, I was intrigued by your comment about re-using flats. That would be amazing to not have to shoot flats every session, unfortunately, I'm not exactly sure how I can ensure camera orientation since the camera screws onto the Hyperstar. I don't believe it would be possible to find the screw threads exactly the same way each time I attach the camera. I'm wondering if this would be possible.

So, with all our discussion on flats, darks, etc., if I can ask for one last conclusion from you, what would be the most likely culprit for the bright middle circle on my image last week? From what you've written, I have to assume it had to do with faulty flats. Whether it was the flat itself or the dark-flat subtraction. Do you concur?

Anyway, looks like another period of clouds for both of us...I can't wait to get out to test things again. Thank you for taking the time to lend a helping hand. Much appreciated.

Joe

[oopfan]

Joe,

Regarding the reuse of Flats, remember that Lights and Flats are captured when the camera is affixed to the telescope. Therefore, you can reuse Flats since the camera orientation is identical from one session to the next. The problem is when you remove the camera to take Darks, you might need to do another set of Flats if you can't return the camera to the same orientation. You can check the orientation by plate solving with SharpCap. Simply point the scope at a star field. The plate solver should report the camera orientation. I'm all right if the orientation is within one degree.

Can you post the image from your last session that shows vignetting? Also, do you have the Raw calibration frames? That is, the Darks, the Flats, and the Dark Flats. It is easier to diagnose problems like this if you had them, instead of guessing. This seems to be a thorny issue that has plagued you for months or longer. If it were me I would go back to basics. Use SharpCap just to capture Lights, Darks, Flats, and Dark Flats of a simple star field. Don't Live Stack. Just use SharpCap's capture tool to capture those frames. Then we can take a look at them. If nothing is obviously wrong, we can process the image with Astro Pixel Processor. The problem could be any number of things: a light leak, incorrect capture of calibration frames, but you will never know by simply guessing. There are too many variables. The chances of guessing the right answer is virtually nil.

Have you tried contacting other members on the forum who have Hyperstar? Several months ago I tried contacting someone who said he had Hyperstar. I sent a PM, but I never received a reply. Some people ask for help but then they are not willing to help others.

Brian

[psy1280]

Well, you've certainly been a help for me Brian.
I shall definitely do some experimenting as soon as the weather cooperates (I work evenings)....You've been a great support. (unfortunately, long story, but I think the processed file is now gone)...let me take a look at the raw images.
Joe

[psy1280]

Brian,
Here's the culprit. Hopefully you'll be able to see the brighter center (the dark blob is probably a cloud or other obstruction, maybe a tree coming into the frame). Curious to see if this offers any additional response from you. Or, as they say, no sense beating a dead horse

Joe

[oopfan]

Hi Joe.

I can't tell much from that. I think we need to go "old school" until we get to the bottom of it. Clear nights are few and far between. But you can do something right now in your free time while you wait:

Question: What gain and exposure did you use for the Light frames?
Answer: For arguments sake, let's call it "G" and "E", respectively.

Then do this:
1. Remove the camera from the scope.
2. Bring your camera into a room away from the living area with a door that can be closed.
3. Do your best to cover the sensor.
4. Connect the camera to your laptop.
5. Start the cooler.
6. Wait 15 minutes.

Capture dark frames:
1. Set the Gain and Exposure in SharpCap, like this:

Gain and Exposure.jpg (33.16 KiB) Viewed 1272 times

2. Capture 30 frames, like this:

Capture Darks.jpg (62.14 KiB) Viewed 1272 times

3. Turn off the lights in the room.
4. Leave the room and shut the door tightly.

Capture bias frames:
1. Keep the Gain the same.
2. Set the Exposure to 1 millisecond.
3. Set the Target Name to "BIAS"
4. Capture 100 frames.
5. Turn off the lights in the room.
6. Leave the room and shut the door tightly.

That's it. We are going to keep it simple and not capture Dark Flats.
Keep the camera off the telescope until we can examine the darks and bias frames.

Joe, do you have a GMAIL account? If so, I can create a folder on my Google Drive, so that you can upload those 130 FITS files.
Let me know when you are done.

Brian

[psy1280]

Brian,
I certainly appreciate the time you took to provide this tutorial...all I can say is thanks!!!
I will get to this first chance. One question, does it matter if I use a gain of 120 (instead of the 100 you suggest)? I always try to accumulate darks at the gain I shoot at.



Yours,
Joe

[oopfan]

Hi Joe,

I sent you an invitation to your email with instructions.

PLEASE DELETE your previous post where you gave us your email address. You don't want unscrupulous people spamming you.

Brian

[oopfan]

Joe,

Sure, use whatever gain. The important thing is to be consistent. All of your calibration files and your Lights MUST use the same gain.

Brian

[psy1280]

I'm about to start the captures...how do you delete a post? Yup, I'm that primitive.