michaelmorris

Simple and functional.

Two extra tips for DSO imaging I have picked. Dithering - this really helps with reducing fixed pattern noise and hot pixels. Dark Master software. Helps match your darks to your light frames before bunging them into DSS.

Thanks

The Geoptik adaptor has two threaded sockets built in to it. If you use these to add their Base plate for finders / guiding scopes https://www.rothervalleyoptics.co.uk/geoptik-finderscope-adaptor-for-slr-ccd-adaptors.html You could mount a finder/guidescope on that.

About 18 months ago I made my first foray into CCD imaging when I bought an Atik 460EX mono CCD camera and a set of RGB and narrow band filters to use with it in an electronic filter wheel. This was supposed to largely replace the Astro-modified Canon 1100D I had used up until then. I live in the relatively light polluted suburbs of Worcester with an observatory in the back garden. The observatory consists of an EQ8 mount carrying a Celestron C9.25 SCT, Skywatcher 80ED and a Revelation 66ED. The scopes fulfil the following functions Revelation 66ED · Guidescope · Ha telescope (with Coronado Etalon and BF10 blocking filter) · Wide field CCD imaging with Atik 460 (with WO Type II FF/FR) Skywatcher 80ED · CCD imaging with Atik 460 (with SW FF/FR) Celestron C9.25 · Main visual scope for double star observing · Visual and imaging of planets and Moon · Main visual scope for DSOs I have ambitions to start doing DSO imaging with the C9.25 (with 0.63 x FR) with an off axis guider Because of the light pollution at home, in the days of having just the DSLR, almost all my DSO imaging used to be done at star parties. Buying the Atik 460 has changed my life significantly allowing me to do narrowband imaging of DSOs from my light polluted back garden. My plan has always been to reserve star parties for taking full advantage of the darker skies to concentrate on RGB imaging using my HEQ5Pro mount, either on purely RGB subjects or for collecting RGB data for star colour in narrow band images. After a year of trying to achieve this I realise that my present limited time at star parties just doesn’t give me the time I need to achieve the RGB imaging time I’m after. At Kelling Heath this year the one decent night we had gave me time to get about 10 x 5 minute decent subs for each R, G and B channels on IC1396. I took many more, but intermittent cloud made many subs relatively poor in quality. I tandem with this, I’d like to try my hand at taking RGB images of galaxies through the C9.25 (with x 0.63 FF/FR fitted). Even using the EQ8 and using an OAG I’m anticipating loosing quite a few subs due to poor guiding. So here is one possible solution to both the issues of too little time to collect RGB data at star parties and the desirability of having a very sensitive camera to allow me to use short sub lengths for DSO imaging of predominately RGB targets through the C9.25 - a CMOS-chipped One Shot Colour (OSC) camera. I have done a fair bit of reading up on this subject and it strikes me that with one of the new generation of cooled CMOS OSC cameras, with their very sensitive chips and very low read noise I could potentially solve both problems at once at a (relatively) low financial outlay of around £1000. There is also the tantalising possibility of running the Atik 460 taking narrow band images through the 66ED and the OSC colour camera colour subs through the 80ED simultaneously! I am considering one of two ZWO cameras, the ASI 1600MC Pro or the new ASI 294 MC. I would greatly appreciate hearing the views of forum members who · have used either of these cameras, · use OSC CMOS cameras on SCT scopes · use or have tried using OSC colour cameras for producing RGB data for narrowband images Thanks

What he said.

Hi John The answer to your first question is, it depends on the camera!! ISO in DSLRs is NOT directly analagous to ISO in film cameras. Noise drops with ISO setting, but on DSLRs this doesn't tend to be a straight line or even a smooth curve. In many cameras there tends to be cliff where as ISO rises, noise suddenly increases. On the 1000D the sweet spot between sensitivity and noise seems to be around ISO 800. In some more modern cameras this sweet spot can to be at 1600 or even 3200. As far as the length of sub exposure goes, the longer the better, but in reality this has a number of limitations light pollution length of accurate tracking of your mount the amount of noise from the camera the amount of background noise from thermal signal Whilst this might make it seem that taking lots of short exposures is the answer, unfortunately every time a camera chip downloads the image to memory, this process introduces noise (known as 'bias' or 'shot noise'). The net result of this combination of factors is that the sweet spot for exposure length under a dark sky with a 1000D is going to be around 300 seconds. Take 20 or so of them with darks, flats and bias calibration frames chuck the whole lot into Deepskystacker and you should be able to get some nice images. I know, this imaging lark can get pretty confusing, but it all starts to make sense eventually (so I'm told). I thoroughly recommend you look at Astropix.com for more information.

Image calibration will help take out hot and cold pixels and other fixed pattern noise and the signal generated by IR photons caused by the internal electronics of the camera (i.e. amp glow), but as far as I understand it, not the relatively random noise generated by ambient heat (i.e. IR photons). That is why astro cameras are cooled.

Giving the quiz master grief on quiz night = points deduction (unless the heckling is funny).

Here is my meagre effort.

Oh - shiny things, shiny new things, nice new shiny new things. (rubs hands like Gollum)

The cooler will be available for collection at the SGL Star Party if you wish.

What about observing planetary nebulae?

No apologies needed, a cold finger direct onto the back of the chip is always going to be more effective than a cool box. The advantage of the cool box is that you don't have to dismember the camera first, so much better for techo-numpties like me!

Saw him at Kelling Heath last week. He said he wasn't coming to SGL this year.