Society for Popular Astronomy

newbie to astrophotography
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Author:  ianb001 [ Mon Feb 06, 2012 12:19 pm ]
Post subject:  newbie to astrophotography

Hi Astronomer's, today 05/02/12 i got my 1st ever image onto a laptop using a cheap webcam fitted with an M12 x 1.25" adaptor, using no astronomical software simply what came with the webcam and a few mouse clicks later i had the images, it was of an overcast moon but to my shock the image was too powerful, more powerful than my 6mm lens , i have a celestron 127 nexstar 1500mm focal length, is it possible to reduce the power to enable more of the moon to be seen. also will i need any filters i've noted people recomending I/R filters and moon filters......... can anyone offer me advice please ianb001

Author:  Brian [ Mon Feb 06, 2012 10:29 pm ]
Post subject: 

Hi, Ian, and welcome to the Forum!

To get you started it's not necessary to use an IR-cut filter (it screws onto the nosepiece/adapter) but as you make progress you will find that the filter will improve your images. One extra advantage of a filter is that it helps keep your imaging chip clean. Dust on the chip can give "doughnut" rings or dark blobs on the image, especially with very bright targets like the Moon.

How much of the Moon you can get onto your imaging chip (CCD) depends on two things :
- the size of the chip (normally 1/4 inch diagonal for a 640x480 pixel CCD)
- the focal length of your telescope. The larger the focal length, the larger the image formed on the CCD.

Now as a rule of thumb, to get the whole image of the Full Moon onto our 1/4 inch CCD at prime focus we can't exceed a focal length of approximately 300mm. With 1500mm focal length you will need to take a series of images to cover the visible surface, then stitch them into a mosaic using software such as MS Ice, Imerge and others.

Personally I don't use moon filters for imaging. I use my webcams in manual mode (not auto) and reduce the image brightness by using lower gain and faster shutter speeds which freezes the seeing "wobbles". Can you get manual control of your webcam? Which webcam BTW? :)

HTH a bit. Ask away :D

Author:  ianb001 [ Wed Feb 08, 2012 1:17 pm ]
Post subject:  Newbie to astrophotography

Hi Brian, thanks for the help, firstly i estimate i can only see less than 5% of the moons surface, and the webcam is a cheap n cheerful 'Trust' webcam pretty basic which had a manual focus , untill i removed the lens, I haven't a clue now, but the image stays in focus when i use the telescopes focusing knob.
I have a partially sighted wife, and i would love her to see planets and greater and more detail of the moon in view on the laptop to aid her viewing. She cannot cope with her eyes up to the lens of a telescope , if I'm right would need 2 reducers to get down to approx 375 focal length 1500 x 0.5 x o.5 +375, but that would set me back best part of a proper ccd camera and software package. I'm open to suggestions, i even have another webcam i could open up screw in the adapter in and try that but by the sounds of it the focal length is the issue and i would still have too great an image to contend with regards Ian

Author:  Brian [ Wed Feb 08, 2012 8:47 pm ]
Post subject: 

Hi Ian. Sounds as if your webcam is one of those with a very small (352x288 pixel?) CCD. It may be worth thinking of getting one of the Trust webcams with a larger CCD, for instance the Trust Megapixel USB2 Webcam Live WB-6250X which I think Amazon is selling for about £14. I think Trust make a number of similar megapixel webcams, cost varies.

I don't think doubling up focal reducers will do what you want. One on it's own might be useful though, especially with a megapixel webcam used on the Moon. Unfortunately I can't recommend those webcams for viewing planets - in fact I don't know of any webcam that gives good clear live video of planets. The images you see posted are made by stacking many hundreds of video frames in software to bring out detail and reduce atmospheric blurring at the same time.

As an example of what you might see of the Moon under superb seeing conditions using a standard 640x480 pixel webcam with a telescope of 60mm aperture and 300mm focal length:


Bear in mind this image is not a single video frame, but many stacked and processed, so you would be very lucky to see them so clearly on-screen in real-time,


Author:  ianb001 [ Thu Feb 09, 2012 1:06 pm ]
Post subject: 

Hi Brian, that image of the moon is more like what i'm after achieving, btw I've had 2 stockists trying to flog me ccd cameras, the first one is this ... 10_0_50_87 at £149 and ... +Imager+IV at £85 approx, however the latter has just now informed me by email that the focal length of my telescope is too great and that his ccd camera would be of no use for what i'm after, now isnt that refreshing in this day and age he's not trying to sell it to me anyway lol, i'm going to have a re think of what to do, i still haven't tinkered with that 2nd webcam yet but i will get round to it and i'll check the size of the webcams out there against cost, i read a past comment of yours about a flashed philips webcam folloed the link only to find sold out of stock but, i clicked the email me when back in stock button, I will let you know how i progress in due course and thanks very much it's nice to know there is help out there, bye for now Ian

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