Ok, I'll ask a question....or three!

Thanks for all the nice accolades on my first light images. I went out again last night, and have a lot of questions. Three in particular are driving me crazy right now.

1) I spent most of last night trying to get the autoguider of my ST8 calibrated with my GM8. I'm using CCDSoft I've tried several times, the 211 guide chip comes up, takes an image, I choose a nice guide star, then select calibrate. It goes through the motions, but each time, it gives me one of three errors. Their wasn't enough movement on one axis or the other, and tells me to increase times (I've done that), Guide star was too close to the edge after the movement, or there was inappropriate movement on one axis or another. I can't tell that the buttons move the mount at all. I'm using an SBIG relay box between the camera and the Losmandy. Am I doing something wrong?

2)I can't figure out how to open the "Curves" dialogue box in Photoshop so I can explore using them.

3)I can't figure out how to keep galaxy cores and bright nebula's from "Whiting Out" before I can expose them long enough to get good luminance detail in the dimmer area's. See the attached images for an example. I've tried moving the white point in the hystogram, and it's just not doing it for me.

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Another image from last night. M-8

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Hi Jim,

I'll try to answer:

1) I don't use CCDSoft but here is something to try. See if CCDSoft will let you switch chips to guide from (Maxim DL allows this). That is, make the "large" chip your guiding chip and then try to re-calibrate. With the large chip you will have a lot more stars to choose from and plenty of room to allow for the calibration. As far as how much mount movement to allow during calibration depends on the focal length your using. If you are using a long f.l. then you may only have to move the mount 5 steps to get your goal of 10 pixels difference. If you use a short f.l. you may need to have the mount move 20 steps or more to get a 10 pixel calibration. Remember, you want at least a 10 pixel movement of the guide star in both RA and DEC during calibration. If the movement is too far however it will move off your guide chip!! After you have done this test switch the chips back and recalibrate using the internal guide chip (so you can image with the large chip).

Using the large chip to test calibration will allow you to make sure the calibration routine is valid. If the calibration routine still is giving you errors then maybe there are relay problems with the SBIG box.

2) In PS choose Image> Adjustment> Curves (if I remember right, I don't have PS of this computer!)

3) During exposure don't worry about burning out the galaxy core -- worry about getting enough signal to overcome sky noise. One way to get a good stretch of your data and un-burn the bright regions is to do a good DDP after you have calibrated, aligned and combined your images.

Hope this helps,

Tom

James,
Does your GM8 have Gemini?