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Astrophotography and Sketching >> DSLR & Digital Camera Astro Imaging & Processing

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BenB85
member
*****

Reged: 02/17/13

Loc: Colorado and Alaska USA
M51 issues
      #5777003 - 04/04/13 04:30 AM Attachment (41 downloads)

Can anyone give me some advice.

This is the second time I have been out imaging and cant seem to get the gear to work right.

For some reason the scope seemed to drift even though polar alignment was good, at least I think. It was a dark sky site and low to no wind.

First image details:

ES 127mm APO f7.5 952mm fl
Canon 1000d modified ISO 800
1 x 120 second exposure
Guiding with Orion ST80 400mm fl using PHD guide with SSAG was calibrated and enabled.
Atlas Mount

Second image details:

ES 127mm APO f7.5 952mm fl
Canon 1000d modified ISO 800
1 x 600 second exposure
Guiding with Orion ST80 400mm fl using PHD guide with SSAG was calibrated and enabled.
Atlas Mount

One thing to note, slowly, over about 2 minutes the guide star would start to drift down the screen, and PHD guide would start to flash and say "lost star" or similar and stop guiding.

Also, how much difficulty have you all had finding a guide star? I used 1 second capturing with a gain of 95% and I have to move the scope all over to just find one star, and when I do, I can barely see the one star in the field of view, and sometimes two but even then they are extremely faint. They are much more faint than the stars in the live view mode on the Canon.


Thank you all for your help.
This is a much more difficult endeavor than I thought.


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BenB85
member
*****

Reged: 02/17/13

Loc: Colorado and Alaska USA
Re: M51 issues new [Re: BenB85]
      #5777006 - 04/04/13 04:35 AM Attachment (31 downloads)

Here is the 600 second pic, notice the bizzare trailing.

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snowcrow
sage


Reged: 10/21/12

Loc: Vermont
Re: M51 issues new [Re: BenB85]
      #5777017 - 04/04/13 05:24 AM

What mount are you using?

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BenB85
member
*****

Reged: 02/17/13

Loc: Colorado and Alaska USA
Re: M51 issues new [Re: snowcrow]
      #5777021 - 04/04/13 05:31 AM

Sorry

Atlas mount


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jambroseus
professor emeritus


Reged: 04/05/07

Loc: Mount Laurel, New Jersey
Re: M51 issues new [Re: BenB85]
      #5777202 - 04/04/13 09:12 AM Attachment (15 downloads)

I think your PHD settings need adjustment, especially the DEC step size. It is not stepping far enough to keep up. Here are my settings (am using a 50mm guide scope).

Good luck,
John


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rflinn68
Carpal Tunnel


Reged: 03/09/12

Loc: Arkansas
Re: M51 issues new [Re: jambroseus]
      #5777522 - 04/04/13 12:07 PM

Were they all like this? Every once in a while I'll get one like this but then it acts fine. Are you positive you had a good polar alignment? As for the dim stars, have you tried adjusting the gain? Taking a dark frame with the guidescope will also help show guide stars better.

EDIT: I see now you had the gain at 95%. Did you try "force calibration"? I also force calibration if I move to west of meridian from east of meridian. 1 second capturing works well for me. Sounds like you are having the exact same trouble I had when I first started using the SSAG.

Edited by rflinn68 (04/04/13 12:15 PM)


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Tom and Beth
Post Laureate


Reged: 01/08/07

Loc: Tucson, AZ
Re: M51 issues new [Re: BenB85]
      #5777866 - 04/04/13 02:30 PM

Besides the PHD guiding suggestions jambroseus listed, you might need to increase the time PHD is accumulating Photons. This raises the sensitivity of the tracker which gives you a fighting chance of PHD staying locked on. Click on the 1 second window and you can choose up to 10 seconds, although I look for another guide star if I need more than 4.

Another thing. If your guiding scope is flexing relative to the main scope, PHD won't fix that.

Edited by Tom and Beth (04/04/13 02:31 PM)


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Skipsabn
journeyman


Reged: 11/03/09

Loc: Newbury Park, CA
Re: M51 issues new [Re: Tom and Beth]
      #5778135 - 04/04/13 05:01 PM

It looks like typical Periodic Error + Drift on your 600s image (possibly even imaging while it's calibrating?). Forgive the obvious but it sounds like either PHD is not communicating with your mount and/or your Polar Alignment is not what you think it is. That and the flexure scenario above.

For whatever it's worth I did this comparison of where I started to where I was roughly 4 years later! Worst case, know there is hope!

http://farm7.staticflickr.com/6144/5989468700_9c97994fae_b.jpg


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Dustin S
sage


Reged: 10/27/11

Loc: Michigan
Re: M51 issues new [Re: Skipsabn]
      #5778395 - 04/04/13 07:17 PM

is your mount on the ground or on a wooden tech or some other construct that could vibrate as you walk around it?

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Falcon-
Post Laureate
*****

Reged: 09/11/09

Loc: Gambier Island, BC, Canada
Re: M51 issues new [Re: Dustin S]
      #5778404 - 04/04/13 07:24 PM

BTW - "Lost Star" from PHD simply indicates that the star has drifted too far from it's original position (drifted outside of the green box).

My first suspicion, given the look of the 600s exposure would be, as others have mentioned, that the guide commands from PHD are not actually reaching the mount.

When you do the Calibration how many steps does it take to get calibrated? If it takes a REALLY long time to calibrate it could indicate either the step settings are too small or the correction commands are not actually getting to the mount.


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