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Very strange problem with meade dsi 2 pro

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#1 neptun2

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Posted 02 February 2013 - 03:57 AM

Hello. I have very strange problem with my meade dsi 2 pro camera. It shows every star as not one but two separate stars. I use it directly with my skywatcher Evostar 120 ED refractor without diagonal and flattener. I tried my DSLRs (sony nex-5n and nikon d90) and everything is ok with them. They show the stars normally so i suppose that there is no problem with the scope itself. My dsi 2 is the monochrome version. I have always used it without any filter because i bought it second hand in this condition but this never caused any problem with my previous scope - 8" newtonian. Is it possible that a luminance filter is needed for proper operation with refractor? Any help is appreciated. Thanks in advance.

#2 jgraham

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Posted 02 February 2013 - 08:07 AM

Odd, I've never seen this, but then again I've never used a Pro without a filter (I have all 3 Pro models). Just for yucks you could try it with any filter that cuts the IR and see if it fixes the problem. If nothing else I like to useva filter to help keep the sensor clean.

#3 neptun2

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Posted 02 February 2013 - 08:32 AM

So in fact the luminance filter is just UV/IR cut filter. If so in fact i made this test using the UV/IR cut filter that was removed during the modification of my nikon d90 dslr. There was no difference in the behavior of dsi 2 with or without the filter.

#4 ccs_hello

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Posted 02 February 2013 - 10:02 AM

Post a picture would be helpful.
Do you see a "comb" like star on both "stars"?

#5 neptun2

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Posted 02 February 2013 - 10:11 AM

I don't have picture but found and old topic with picture in the first post which shows similar problem:

http://www.cloudynig...4776960/Main...

Of course the problem in that topic is caused by guiding but the picture is useful.

#6 jgraham

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Posted 02 February 2013 - 10:30 AM

A couple of quick questions...

How long is the USB cable and what are you connecting the camera to? A laptop, desktop, or hub? The DSIs need a good power source which means no more than 6 feet of unpowered USB line and a powered USB hub is prefered.

How long are the exposures? When using short exposures the interlacing can become visible.

#7 korborh

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Posted 02 February 2013 - 11:30 AM

What software are you using to image? Do you see this same effect with envisage software?

#8 neptun2

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Posted 02 February 2013 - 12:18 PM

The cable is 9 feet long and connected directly to the laptop usb port. I will try with shorter cable and report. I used PHD. Will also try envisage. The strange thing is that it was working 2 months ago with PHD and this cable.

#9 dickbill

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Posted 02 February 2013 - 01:23 PM

How is powered the laptop then?
In the cold the batteries won't stand very long.
If for some raison the dsi revert to a USB1.1 connection, you would get an interline pattern with lines clearly separated with stars looking splitted between two lines.

#10 neptun2

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Posted 03 February 2013 - 11:37 AM

Laptop was powered directly from ac line. I made the last tests in my home. I will check with shorter usb cable and report but this is definitely strange because it was just working 2 months ago when i tested it last time.

#11 neptun2

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Posted 04 February 2013 - 09:20 PM

Well i made more tests today but the problem did not appear again. I don't know what caused it last time but now it is ok. Maybe there was moisture on the dsi chip. I forgot to check this. Thank to all for the help and i hope that thie problem will not happen again. Clear skies to all.

#12 korborh

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Posted 05 February 2013 - 12:08 AM

Good to know the dsi pro 2 self healed. I just acquired this camera recently and so far am quite impressed with it as a guider with my OAG.

#13 neptun2

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Posted 05 February 2013 - 09:14 AM

It is definitely very sensitive camera. I use it now at f7.5 with my refractor and off-axis guider and it never fails fo find guide star at 1 second exposures.

#14 jgraham

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Posted 05 February 2013 - 01:03 PM

Cool! Keep an eye on it, the DSI is very sensitive to power and with your long cable you might be riding the ragged edge. I've never used anything longer than 6 feet with mine.

I used a DSI Pro II for a couple of years as my guide camera and I loved it until I dropped it and it died. Now I'm in a really bad way, I use a DSI Pro III as my guide camera and I'm spoiled big-time. I have a DSI Pro I that I could use, but the large chip in the III is sooooo nice.

#15 astrovienna

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Posted 05 February 2013 - 02:30 PM

A question for you folks guiding with DSI II Pros: how long are your guide exposures, and what mounts are you guiding? My Pro II needs 1.3 seconds to download images (in Win 7). Since I use 1 second exposures to guide my CPC1100, a 1.3 second DL time really didn't make sense. So I guide with my Flea3, which being a video cam has essentially instantaneous downloads. (Anybody want a good Pro II? :))

Kevin

#16 korborh

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Posted 05 February 2013 - 03:16 PM

I am using MaximDL to guide with 0.5-1sec exposures. I use 64x64 pixel subframes which are very fast to download.
Does your guiding software allow sub-frames? I can imagine it would an issue otherwise.

#17 neptun2

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Posted 05 February 2013 - 04:16 PM

I use my dsi 2 pro to guide my heq 5 pro mount. Usually use 1 second exposures. I use it with PHD and frankly i do not see any problems with it like the 1.3 second download time that you mention. It is usb 2.0 camera and with this small resolution i do not see reason why such thing should happen. Are your drivers up to date?

#18 astrovienna

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Posted 05 February 2013 - 05:29 PM

I use it with PHD and frankly i do not see any problems with it like the 1.3 second download time that you mention. It is usb 2.0 camera and with this small resolution i do not see reason why such thing should happen. Are your drivers up to date?


Have you confirmed the guide times in your PHD log? I was completely unaware of the issue until I checked my log, and was astonished to see that it showed guide data only about every 2.4 seconds, versus every 1.1 secs with my video cam, both using 1 second exposures. This was Win 7 - Win XP was slightly better with ~1.9 secs per guide image. I know of one other imager who confirmed these results. The driver is the last one released by Meade.

I am using MaximDL to guide with 0.5-1sec exposures. I use 64x64 pixel subframes which are very fast to download.
Does your guiding software allow sub-frames? I can imagine it would an issue otherwise.


Korborh, AFAIK the DSI (at least the Pro II) doesn't support subframes. I'm guessing it DLs the full frame, but only analyzes the 64x64 block for data. But I really have no idea. Does Maxim's log show you how frequently the guide data gets updated?

Kevin

#19 Mike7Mak

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Posted 05 February 2013 - 05:57 PM

A question for you folks guiding with DSI II Pros: how long are your guide exposures, and what mounts are you guiding?

Depending on seeing I use between 2 and 5 second guide exposures with the DSIpro2 and an LX200gps mount w/OAG. Most often 2.5-3.5 secs with a 1/2 second delay between exposures. I try to find exposure and min motion settings that don't send a guide pulse after every guide exposure.

If PHD is sending guide commands to the mount after every single exposure you're probably chasing the seeing. If you're using 1 second or less exposures you 'can't not' be chasing seeing. :)

#20 astrovienna

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Posted 05 February 2013 - 06:18 PM

Well, exposure time is a trade-off between issuing commands to correct for seeing - which, being impossible, just introduces error - and missing the opportunity to correct tracking errors, which are pretty popular in mid-range mounts like ours. :) Despite reading lots of discussion (as Kissinger said of academic infighting, the disputes are so bitter because the stakes are so small ;)) I've never come across anything convincing that really tells me where to draw the line.

In good seeing, I get stars with an HFR of <1.4 arcsec, so I've haven't messed much with my guiding in a few years. My limited experiments with longer exposures in poor seeing didn't indicate much improvement. Either way, a ~1 second lag time to DL a guide image can't help. I'd like to guide with my DSI - in part because it's more sensitive, but mostly because of the bigger chip - but I get better results with the Flea3. And using an OAG on my C11, I can easily guide on mag 11.5 stars, so I can't really complain.

Kevin

#21 Mike7Mak

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Posted 05 February 2013 - 07:00 PM

I certainly agree with 'ain't broke don't fix' and if something works it works. There's so many variables involved with guiding it's near impossible to make any universal rules, especially as you say, with 'mid-range' mounts (which I think is being kind to the LX200). :)

It wasn't until I ran PemPro that I was able to go beyond 2 seconds. Before that the PE was so ragged it made seeing the least of my problems.

#22 korborh

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Posted 05 February 2013 - 10:13 PM

I just checked my DSI 2 pro downloads and I see no difference between MaximDL subframe and full-frame. They are both almost instantaneous download. So 1.3sec seems odd, unless it is running in USB1 mode.

#23 astrovienna

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Posted 05 February 2013 - 10:51 PM

I just checked my DSI 2 pro downloads and I see no difference between MaximDL subframe and full-frame. They are both almost instantaneous download. So 1.3sec seems odd, unless it is running in USB1 mode.


Does it show you how much time elapses between data points?

#24 korborh

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Posted 05 February 2013 - 11:33 PM

Plotted data points for 1s exposures are ~3s apart. So there is an annoying latency which I always had and not sure where its coming from. My mount is very forgiving though and so this is not an issue for me.

Before getting the dsi 2 pro I was planning to get a video camera for guiding with reduced latency, but deferred the idea until I decide to so planetary imaging.

#25 jgraham

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Posted 06 February 2013 - 12:35 PM

I've used a DSI Pro I, II, and III as well as the DSI III to guide an LXD75 and an Atlas EQ-G. I've also used a guidescope and an off-axis guider. The vast majority of the time I use 1 second exposures. I never use anything shorter, but I have gone as long as 5 seconds. I never paid much attention to the download times.






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