Well tonight was the first light for my 5x powermate... and im stoked.. image scale really helps to capture finer detail...
However, I've had this onion ring issue for the last few imaging runs I've had... I've uninstalled the camera drivers/software, reinstalled it all.. set everything to default settings and started from scratch, but im still getting this onion rings...
Only thing other than software I can think of it being is the fact that I've now got a USB extension cable between the webcam and the laptop. I suppose there could be some interference getting in from the mounts power or motors...
the first 3 pics are to show where the onion rings are occurring, the forth image is my usual processing technique without reguard for the rings. the image itself (not withstanding the rings) is actually quite good...
Anyone know what the hell is going on??? its driving me NUTS!
oh, I should mention that the image appears a bit scratchy during capture...
Captured at 15fps, 1/25 shutter speed (tried 1/33 and 1/50 to no avail)
If you're using a ToUcam (which a 900nc is) 15fps is causing compression. Try backing it off to 5 or 10fps.
Also, onion rings are most often the result of underexposure.
What capture software are you using? Make sure you've got a full histogram. If you're not using capture software which gives you a histogram reading or light meter reading pre-capture, download one. I use K3CCDTools...but others are also good.
It's most likely the image looks 'scratchy' because you're having to push the gain, as a result of your settings and the fact you're using a 5x powermate which isn't giving you enough light due to the focal length.
Try 10fps...
A 5x powermate is a fair amount of additional focal length for an 8" instrument.
The seeing would need to be very good to stand that, and it ain't been that good in Bris of late.
I've used a few different capture programs tonight, K3CCD, Virtual Dub, the standard philips capture program...
I'll give 5/10fps a go tomorrow night as I have to work at 6am tomorrow.. so im heading to bed shortly... The gain is usually set less than 1/4, shutter speed at the setting where jupiter appears the brightest in the image preview, saturation @ around 80 - 90% brightness/gamma between 1/3 and 1/2...
The annoyance is that its pretty much the same settings I used previously (mind you at 1/2 the focal length) So perhaps thats causing the loss of light, hence under-exposure, hence onion rings.
Will try a few things out tomorrow night. After that, I suppose I'll just have to add aperture to focal length and get a 10-12" tube...
Here's another tip: Don't touch the brightness slider. Leave it at default...which is 50% (half way). I also leave the gamma alone. Certainly not 1/2 or 1/3.
Only adjust the exp and gain. Try shooting at 10fps...
When you're using KTools, be sure to activate the little light meter and adjust settings to get the reading somewhere between 200 and 225.
Hi Alex, you have got some bad onion rings showing up but apart from that looks like you have captured some nice detail.
First thoughts are that your image looks extremely underexposed. 5x magnification is a lot for an 8" scope meaning that the amount of light falling on the CCD may not be enough to correctly expose the histogram. Always make sure that the histogram is reading around the 250 mark.
cheers Matty... The powermate was a preemptive strike on image scale, as a 10/12" ota is less than a month away...
I cant recall what the histogram was reading during capture, however, as it reads higher the image on the screen appears over-exposed? Ie. without pushing brightness, it can appear as anything between a white disc, and somewhat like the image I've posted...
I've attached a single frame from the AVI to show relative brightness...
cheers Matty... The powermate was a preemptive strike on image scale, as a 10/12" ota is less than a month away...
I cant recall what the histogram was reading during capture, however, as it reads higher the image on the screen appears over-exposed? Ie. without pushing brightness, it can appear as anything between a white disc, and somewhat like the image I've posted...
I've attached a single frame from the AVI to show relative brightness...
Hi Alex, knowing you, I'm sure you will end up with a 12" OTA.
If you have a whiteblob you know the histogram is overexposed. I've learnt to watch what the histogram reads instead of what the live preview image looks like. This way you will always have a correctly exposed image.
i've inquired about a few already.. also a very nice sounding custom made 10"
Im sure a 10" would handle the 5x powermate, and its weight is a key point.. a 12" skywatcher/gso tube weighs in at around 20 ~ 25kg, the 10" is carbon fibre, and weighs in at 12kg... easier to lift, balance etc... takes up less room...
im sure you could get a CF 12" tube made, but the $ figure on carbon fiber goes up exponentially per square inch...... The maker of the optics does 12" ~ 40" mirrors, I suppose you could get a 12" mirror and get a custom made CF tube, but oh so expensive..
