17 replies to this topic

[DMaury]

I've GOT to have something simple set wrong, as with both the ZWO ASI 120S MM and MC camera, I have to CRANK the exposure time to what you see here to get close to a 50% histogram.  This is with NO filters on the MM camera no barlow on a C14 Edge HD.  I'm running an insanely fast laptop with USB 3.0. put a 4 times barlow on and the image pretty much vanishes except a very high gain and 1 second exposures.  It's got to be something simple I'm just not doing right.  Any tips?

 

 

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[dolphinzilla]

I think something is wrong with the camera - I have a ZWO 120MC-S on my Celestron C8, here is a shot of Saturn from a few nights ago, a 2X Barlow, gain = 62, exposure = 46 ms - 5% of best 200 seconds of video with Autostakkert.  Sat_240615_Gain=62_Exposure=45.9ms_Gamma=50_043238_g3_ap93_conv.bmp   405.12KB   1691 downloads  I am using Firecapture ver 2.4 over USB 3.0

Edited by dolphinzilla, 06 July 2015 - 11:20 PM.

[Merk]

Well i am no expert but your settings with the C8  give better results than mine. I used 95 gain to take 40 ms exposure and 59 % histogram on red channel with my asi 120 mm and edge 8''.

Also i had a 2x barlow. Don't know about your C14, maybe you had moisture on it (Did you use dew shield, or does it need more cooldown or something).

If it was something wrong with your camera it shouldn't work well with your C8 too.

 

Camera=ZWO ASI120MM
Filter=R
Profile=Saturn
Diameter=18.45"
Magnitude=0.04
CMI=251.6° CMIII=221.7°  (during mid of capture)
FocalLength=4500mm
Resolution=0.17"
Filename=2015-05-27-2011_1-R-1.avi
Date=270515
Start=201108.858
Mid=201408.811
End=201708.765
Start(UT)=201108.858
Mid(UT)=201408.812
End(UT)=201708.766
Duration=359.907s
Date_format=ddMMyy
Time_format=HHmmss
LT=UT -4h
Frames captured=8965
File type=AVI
Extended AVI mode=true
Compressed AVI=false
Binning=no
ROI=352x288
ROI(Offset)=0x0
FPS (avg.)=24
Shutter=40.13ms
Gain=95
AutoExposure=off
SoftwareGain=10 (off)
Brightness=0
HighSpeed=on
Gamma=50 (off)
USBTraffic=71
Histogramm(min)=0
Histogramm(max)=152
Histogramm=59%
Noise(avg.deviation)=n/a
Limit=6 Minutes
Sensor temperature=29.0 °C

[james7ca]

If you are using a 4X barlow on a C14 that means you're working at about f/40 which is really too much magnification for the ASI120 camera (3.75 micron pixel size). A 2X barlow will easily give you the critical sampling that you need and that will also result in a two stop decrease in the required exposure times.

 

However, that still doesn't explain (fully) why your exposure times are so long so there must be something else happen here.

 

The other thing that seems a little odd is that there seems to be a lot of flare or haze in the image (screen shot) that you provided. Could it be that you had a very heavy dew on the front corrector of the telescope?

[Kokatha man]

If you are using a 4X barlow on a C14 that means you're working at about f/40 which is really too much magnification for the ASI120 camera (3.75 micron pixel size). A 2X barlow will easily give you the critical sampling that you need and that will also result in a two stop decrease in the required exposure times.
 
However, that still doesn't explain (fully) why your exposure times are so long so there must be something else happen here.
 
The other thing that seems a little odd is that there seems to be a lot of flare or haze in the image (screen shot) that you provided. Could it be that you had a very heavy dew on the front corrector of the telescope?

Yes, f44+ is far too much for the C14 which is an f11 scope at native...thus f44 even if the barlow has no extension between it & the camera sensor: you really need to get down to below 2X with any amplification!

But as James has said that doesn't explain your dilemma tbh - that haze around the planet looks very suspicious! I wouldn't expect to see any haze from a fogged-up corrector - well, we certainly never see this & it happens all the time when we image...the histogram drops off, but no haze etc.

Try looking down at the primary mirror in daylight to see your secondary in the primary mirror's reflections...recently we had a secondary which had become completely dewed over due to moisture getting inside the OTA...that is about all I can suggest atm...

EDIT: ps, you set the gamma at "50" for capturing & you don't need 50% histograms for Saturn with the 120MM...

Edited by Kokatha man, 08 July 2015 - 07:32 AM.

[bunyon]

I believe the screen shot of firecapture in the OP is with NO barlow.  He says then that if he puts a barlow on the image disappears.  DMaury - can you clarify; is the data in the first post without a barlow?  If so, there is no doubt something seriously wrong somewhere.  Either in the scope or in the camera. 

 

I have to ask, was it clear?  It kind of looks like you're imaging through clouds.  I assume not (and am sorry for asking) but it would explain what you see.  Otherwise, check the OTA very carefully and maybe try a daylight image and provide us with exposures/settings for a sunlit field. 

[Kokatha man]

...yes, it appears you're right Paul - "no barlow" - & I guess through pretty heavy clouds that sort of exposure might yield an image like that..!

 

If we're exploring these possibilities I guess we could ask if there's a translucent cap left on, or something else in the imaging train..?

 

Stranger things have happened...& I'm no stranger to doing idiotic things myself!!!

[DMaury]

OK, to clarify some things.

 

No, the glass was not fogged; checked that and had a large dew heater going.  The haziness and brightness you are seeing is that I had it set up in the parking lot of my office as it's the closest place I can set it up and run power to it and get a shot of Jupiter with it this low in the horizon.  I just slewed it to Saturn to get the screen cap as by then clouds had obscured Jupiter.  Saturn happened to be a few degrees above the eave of the office and a bright security light; so you are seeing that blasting into the C14.

 

Interestingly enough I set up Firecapture on an older windows 7 laptop, ran it via USB 2 and got some fairly good fps rates (but still haven't been able to set how bright Saturn or Jupiter looks through a scope with the camera yet)  So I removed and installed a fresh copy of FC on the new laptop, have the high speed box and 100% USB traffic set and I seem to be getting near max fps transfers with the camera off a scope.  Hopefully it as some setting that glitched in FC.  I'll update tonight, as even if I can't get Jupiter, I will shoot Saturn from my house where there will be no lighting interference.

 

Also correct; that image was without any barlows (would use a Televue 2X; just tried the 4X to see what would happen), nor were there any filters in place for that shot. 

 

I would also find it hard to believe I have TWO bad ZWO cameras (remember I am getting the same need for long exposure to see the planets in both the monochrome camera and the color camera.)

[bunyon]

Hopefully the flare is from shooting right over a streetlight.  If there were clouds covering Jupiter and if Saturn wasn't very high, it's also quite possible that there was enough haze/thin cloud in the area you couldn't see to dim the image.  Try it again with the moon or planets on a night that you know, absolutely, is clear (transparent - no haze, think clouds, etc.).  And away from streetlights.

 

I'm still not convinced that haze/streetlights were the problem but you need to rule them out before moving on.

[Fossil Light]

_{Looks to me much like fogging much closer to the focal plane like fogging of the protection window, which would then cause a local halo. Let us know if you see it again.}

 

_{Very unlikely you have two defective cameras.  Can you try your camera on someone else's set up to help you troubleshoot this problem?}

 

 

_{As another reference point, last year at f18 I had an exposure of 23msec at a gain of 80 on my ASI120MM with no filters on Saturn to give a histogram level of 70-80%. That was for a 222mm scope not that that will affect the exposure its the fratio that is important.}

 

_Martin

[james7ca]

I think FireCapture recommends a maximum of 80% USB traffic for the ZWO ASI cameras (you said you were running at 100%?). That shouldn't cause any issues like you are seeing but it may affect the stability of the application/driver itself.

[phileefan]

DMaury,

 

It looks to me from your screenshot, in your capture settings box you're using Jupiter properties not Saturn. I would also change the filter from L to either R or none. I think you'll see a difference with this. If I'm not doing an image in RGB, I'll just select the R filter setting even though I'm not using this filter. Below is a Saturn non RGB image I captured the end of April at 30 degrees. If you have your log from that capture can you post it.

 

 

 

[phileefan]

Here is my capture log from the above pic.

 

Scope=Celestron CPC 1100 GPS
Camera=ZWO ASI120MM
Filter=R
Profile=Saturn
Diameter=18.28"
Magnitude=0.15
CMI=166.7° CMIII=17.3°  (during mid of capture)
FocalLength=8400mm
Resolution=0.09"
Filename=2015-04-29-0414_8-MB-R-1.avi
Date=042915
Start=041450.623
Mid=041550.629
End=041650.635
Start(UT)=041450.623
Mid(UT)=041550.629
End(UT)=041650.635
Duration=120.012s
Date_format=MMddyy
Time_format=HHmmss
LT=UT -5h
Frames captured=6007
File type=AVI
Extended AVI mode=true
Compressed AVI=false
Binning=no
ROI=512x440
ROI(Offset)=0x0
FPS (avg.)=50
Shutter=19.98ms
Gain=98
HighSpeed=on
Gamma=50 (off)
Brightness=0
SoftwareGain=10 (off)
USBTraffic=80
AutoExposure=off
Histogramm(min)=0
Histogramm(max)=130
Histogramm=50%
Noise(avg.deviation)=n/a
Limit=120 Seconds
Sensor temperature=65.3 °F

 

[GenevaBrown]

DMaury, just wanted to say that you are not alone.

My images of Saturn, with the same set up as you, look just as bad. And I am mystified. Tried on 3 separate occasions - the result is more-or-less always the same.

I think that the collimation is OK, and I thought that the seeing was reasonable. Is it just down to the current low elevation of Saturn? I tell myself this because my visual observation of Saturn is pretty poor too. What is yours like?

 

P.S. I thought that the filter settings in FireCapture were there just so that you had a record of any filters that you used, and that they didn't actually make any difference to the capture process. Am I wrong?

[james7ca]

...P.S. I thought that the filter settings in FireCapture were there just so that you had a record of any filters that you used, and that they didn't actually make any difference to the capture process. Am I wrong?

When you change filters FC will also automatically change the exposure settings to match the last values you set for that particular filter. Other than this and to record what filter is in use I don't think it makes any other difference (but I could be wrong). 

[DMaury]

I was going through old emails and realized I never replied to this post with the solution.  Something became corrupted with the two versions of Firecapture installed at the same time.  I uninstalled both, reinstalled only one fully updated copy and was able to run both cameras as they should.  This was the Saturn I was able to get that night when it worked. Thanks for all the help!

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[HowardK]

Well done for updating

 

i hate when threads do not conclude

[james7ca]

Yes, thanks for the update and your Saturn image is looking very nice.