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Parsec 8300M Sudden Blooming

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#1 Uptmor

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Posted 05 December 2012 - 08:41 AM

OK.. need some help from those more experienced than I..
I recently acquired a Parsec 8300M CCD camera. I've done a number of images with it, including a session of 15 minute images of M42 with no issues. Last night, I went out to do some 45 second exposures. The session started out just fine.. Then, out of the blue, the stars started to saturate and bloom vertically down the image. 'Weird' I thought. So I decreased the exposure time to 1 second. The blooming still occurred. For the heck of it, I unplugged and plugged back in the camera. The blooming went away.
I started my session, which included 45 second images and 3 minute images. It did fine for a while, then bloomed all over the place!
What the heck!? Why would my camera all the sudden do this? It is like the pixels are not discharging between images or something. I have 30 second pause between images too..
I'm running about f6.0 and it happened on all LRGB filters.
Please help! :help:
Thank you, Ryan

#2 Uptmor

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Posted 05 December 2012 - 09:30 AM

One thing I just thought of, one of the only changes I made from my previous 15 minute exposures session (with no blooming), was that I added dithering to my images. Could this be 'streaking' of the bright stars??

#3 rigel123

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Posted 05 December 2012 - 09:31 AM

Can you post an example of what you are seeing so we can determine if it is blooming or trailing?

#4 *skyguy*

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Posted 05 December 2012 - 10:07 AM

I've read about this "sudden blooming problem" happening on other Parsec 8300M cameras. They had to be sent back to Orion for replacement. Here's an example post:

http://tech.groups.y...ras/message/130

Sorry for the bad news ... I hope I'm wrong about your problem and it's something else ... Good Luck.

#5 Uptmor

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Posted 05 December 2012 - 12:13 PM

I will post examples this evening when I get home from work. Thanks guys.

#6 Uptmor

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Posted 05 December 2012 - 06:00 PM

Here is a stretched image of the streaking. After closer inspection, I think I may have something going on with my mount or autoguiding software (MaximDL). It doesn't look like blooming.. More like after a while, my Dec guiding tried to kick in and had stiction or something. I am going to try again tonight and see if I can hear or see what is going on in the observatory.

#7 Uptmor

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Posted 05 December 2012 - 06:01 PM

Here it is:

Attached Files



#8 rigel123

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Posted 05 December 2012 - 07:25 PM

That looks much more like the mount just took off rather than blooming.

#9 Rick J

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Posted 05 December 2012 - 09:09 PM

Looks like the camera is precisely lined up with east at the top and the mount took off rapidly to the west faster than sidereal rate. There is what looks like scintillation along the trails that can't happen with blooming. It's as if it tries to make a guiding correction to the west that never turns off once started. What bothers me is how precisely the camera has to be aligned to the scope axes for this to happen. The trails are exact to the same column (allowing for the back and forth atmospheric scintillation). That is very difficult to achieve but does happen with blooming though true blooming looks very different. Not being familiar with the Parsec 8300M's defect I suppose some weird defect could cause this, sure nothing I've seen before would mimic scintillation this perfectly.

Rick

#10 korborh

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Posted 05 December 2012 - 09:32 PM

How would the mount taking off explain why only some stars are blooming? Something else is perhaps at play here.

#11 Uptmor

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Posted 05 December 2012 - 10:04 PM

I don't really think it is blooming any more after looking at the image further. I think it has something to do with Maxim trying to tell the mount to guide, but something weird happens. I had dither active for the first time. The odd thing is that every photo after this one looked the same. M42 is centered up and the streaks are the same. All this started happening about 30 minutes after the first exposure was taken. This same thing happened again after I disconnected the autoguider and Parsec and started over. It is hazy out right now, but probably ok to try a test..

#12 Rick J

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Posted 06 December 2012 - 01:55 AM

My reaction was the same as korborh's until I applied a severe stretch to the image and found all but the very faint stars had the same streak. With JPG's limitations there is no way to stretch further but I'm quite convinced if you stretch the FITS even those stars will show it.

What does bother me however is that no NEW stars tracked in. I'd have expected some new stars but if this happened right at the end of the exposure that could explain it as there's nothing very bright to move in until it has moved quite a distance. So the move has to be right near the end of the exposure. Or it moved out then back and over precisely the same path. I find that difficult to swallow.

Try a field with plenty of bright stars beyond the FOV and see what happens when the streaks reoccur. Also rotate the camera so it is not aligned with RA and Dec. If it is the mount moving in RA then the streaks will be diagonal. If they still go straight down then there is a very odd camera issue it would appear.

Rick

#13 krneki

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Posted 06 December 2012 - 04:04 AM

It looks like the shutter was not closed while the sensor was being read.

#14 Uptmor

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Posted 06 December 2012 - 08:58 AM

Well, I did some imaging last night and the issue presented itself again in the exact same way with the dithering off and the autoguider settings the same as when I got successful images. krneki, I had the same thought about the shutter not closing all the way while being read. While it is cloudy out, I will take off the camera and see if the shutter is closing correctly. I will then remount it at a 45 degree angle to do a test relative to the mount.

#15 korborh

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Posted 06 December 2012 - 09:27 AM

Rick, that makes sense.
There is also a small wiggle in the vertical lines which would be consistent with mount moving while blooming would be straight columns.
I am also curious to see experiment with rotating the camera and see if the lines rotate.

#16 Uptmor

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Posted 06 December 2012 - 10:19 AM

The thing that really confuses me (not that this whole thing doesn't) is the dots above the brightest stars. Maybe there is something odd going on with the mount. Not sure what would cause those dots other than maybe a mount that is 'sticking' and then the autoguider kicks in and corrects it? That seems odd though. I will rotate the camera and see what happens. The skies look like they may be bad the next couple nights unfortunately. Maybe the clouds will hold off just enough to grab an image with the camera orientation changed. I will let you all know. Thank you again.

#17 Uptmor

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Posted 06 December 2012 - 10:49 AM

My theory is this using everyone's input.. I believe the mount is moving during the exposure. This could be due to some sort of 'stiction' or commanded movement via the autoguider or both. We are using the Orion Awesome Autoguider, which we have had issues with the USB cable not remaining connected due to a cruddy design. This has caused weird movement in the past. However, due to the consistency of the issue at every exposure (and the fact that I only see one streak per exposure), it could be a weird Maxim command. Also, when I disconnected the cameras and reconnected them, the problem temporarily went away.
So, here will be my troubleshooting procedure:
1) recreate the problem with the same settings as before
2) Turn off autoguiding and see what happens. If the issue goes away, troubleshoot software and cabling (try PHD/look through wiring)
3) If issue persists, rotate the camera and see if the streaks rotate with it. If so, there is something weird wrong with the camera.
I will keep you informed. Thank you again!
Ryan

#18 Paramount

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Posted 06 December 2012 - 05:16 PM

Have a check to see that your shutter is set to the closed position in the settings prior to doing any exposures. A while back I opened the shutter to examine the sensor and forgot to close it and I got exactly the same effect that you are getting, so I would check this.
Best wishes
Gordon

#19 Uptmor

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Posted 06 December 2012 - 05:26 PM

How do I set the shutter position? Is it in maxim?

#20 Paramount

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Posted 07 December 2012 - 01:03 AM

Yes, within the settings you can open the shutter but remember to close it after, the easiest way to check is to choose a luminance filter and then look straight down the tube assembly at the chip of the camera, you can see if the shutter is open or closed, it should be closed

#21 shams42

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Posted 09 December 2012 - 01:31 PM

I once had a QHY9 with a shutter problem -- it looked very much like this. The "blooms" weren't perfectly straight. I think it's a problem with the camera.

#22 Uptmor

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Posted 10 December 2012 - 08:47 AM

Looks like it will be clear tonight (and the next couple nights). Will try to troubleshoot and report what happens.

#23 Jared

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Posted 10 December 2012 - 12:53 PM

Bound to be a shutter problem. The odds of the mount being the issue seem very low to me--how would you get the perfect, vertical orientation of the "blooms"? I suspect your shutter is just sticking open sometimes, and since the 8300 is a full frame chip (no electronic shutter), as the rows are read out and charge is transferred to the next row, you keep accumulating light in each row during the download period.

#24 Alfredo Beltran

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Posted 10 December 2012 - 01:10 PM

Does anybody kno what kind of shutter does the Parsec have? Is it an even illumination shutter as in the Sbig and QSI, or an iris shutter?

Best regards

Alfredo

#25 Uptmor

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Posted 12 December 2012 - 03:18 PM

Well, it looks like the issue may have been caused by a 'jumping' mount. We have a CGE-Pro and the RA axis seems to be very sensitive to the amount of tension in the clutch knobs. They need to be just barely finger tight, or the RA 'ticks' and throws off the image. The tighter they are, the worse the jump. As the temperature goes down, the bolts will actually tighten up and it will start to jump. If I slightly loosen them, the problem goes away. From the forums I have read, it may be an issue with the motor to worm gear pressure (too tight). We will open up the mount and take a look when the weather warms up....






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