hey gang, a quick question regarding video astronomy. I have a samsung sdc435 i bought with the intentions of doing video astronomy but never got around to it a couple of years ago. now that i have a bit more motivation, i'm looking to really get in to it. I have all the necessary stuff to get it started (heq5, portable tv, power supply) but i'm in between scopes to mount on the heq5. I have a couple of choices here, should I go for a large achromatic refractor or a decent sized newt (prob gonna limit to 8" for the sake of the mount) or an ed80
Fast refractor. F6.5 or shorter. Get a 1.25" 0.5 reducer to make it even faster. A balance between aperture and optical system speed is the key here.
I think a 6" F4 newt might be good too for imaging with an EQ5.
But, I think a relatively fast refractor might be in order.
I sometimes use an 8" f/4 Newt for video - very nice So a 6" f/4 Newt is no problem.
Be aware though that the 1.25" 0.5x focal reducers are not for Newts. These are designed for use with convex focal planes, such as those produced by refractors SCTs and Maks, not concave focal plane produced by Newts. From what I've been able to see, there is one focal reducer for Newts, and it is available Mallincam. I don't have one, and all about them is from reading reports about these, and I am considering one.
+1 with what everyone else has said. And the HEQ5 will be brilliant for video. Howie up near Brisbane does does beautiful video with an 8" F5 newt on an HEQ5. He does single 30-60sec shots with a dslr. Here's an example: http://astrovideoforum.proboards.com...ec-frame-night.
All the scopes you mentioned would be good (prefer the newts and ed80 rather than the achromat). I'm now using a GSO 8" F5 and an 80mm F5.9 triplet. They complement each other - one larger, one smaller FOV. I got those second hand here. The 8" F4 would be really fast - even better for video, and many people use 6" newts - I'd be interested to see how you go with them.
I don't know the samsung you have, but they have been used in the past. Give it a go, but it might be a bit underwhelming? You can always bang a 1.25" 0.5x reducer. We are live-viewing not imaging. So don't mind a bit of coma.
Have a go on stellarium (or something) and see how big the FOV is for differ scope/reducer combinations on a 1/3" camera for a few objects you want to look at.
One thing about these reducers, as you increase the distance between the camera's chip and the reducer lens you further reduce the scope's effective focal length - that is you make the focal ratio faster. Down side is you also increase the in-travel of the drawtube. With a refractor instead of using a 2" diagonal, a 1.25" diagonal will afford you a little more in-travel. This is more problematic with a Newt.
Its so cheap its worth a go. But it might be a bit severe on an ED80. As Alex says, if you can reduce the sensor-reducer distance it will be less severe. And you won't be able to go much above a 1/3" camera sensor as you'll get bad vignetting & coma. I've used meade & celestron F6.3 & 3.3 SCT reducers on my refractor - shifting it from F5.9 down to 3.5 before I ran out of in-travel. The coma got pretty bad though.
I posted this question on the astrovideoforum (thanks chris!) but I thought i might as well post it here as well. I've read articles that said removing the in built IR filter would improve the image but I can't get to it as one of the screws on the case has stripped basically clean. How much would this affect the image, and any tips on how to remove a stripped screw?
EDIT - got the ir filter after stripping the tips of my fingers clean.
I was surprised at how much magnification it was. Omega Centauri was a neat sight through the ED80/SDC485 combo. Jupiter was meh cos I couldn't find the right exposure . Eta carina was prob the best in my opinion. The screen cap I took doesn't do it justice
So my focal reducer and barlow arrived from bintel today. I ordered the 1.25" but received the 2". I didnt even know they sold these (couldnt find them on the website). My question is should i return this and get it replaced with the 1.25"? The samsung has a 1.25" nosepiece and so does my canon m10. I hear putting the focal reducer further into the tube will decrease image quality
Boy, posts are few and far between on this thread! Guess not many have gotten into EAA that much in Oz? Or everyone is out there having a blast and don't need to post?
Re focusing ... that video in the last post was one of mine, but doesnt really show focusing. Here's one I made quite a while back which shows a home made bahtinov mask which works a treat, and it shows it in use. And another which shows you really don't need a full size mask with a cutout when using a SCT ... a smaller one hung around the edges works just as well. That tip is especially useful if one is using a hyperstar on a SCT. BTW those flyscreen ones are much easier to make nice and small to allow focus using a DSLR lens. Having said that, if you either don't wish to make one, nor buy a commercial mask, then zooming in the liveview (if your Canon has that liveview) and moving the focuser of OTA or lens until the zoomed image looks as small as you can get works well too. https://youtu.be/IeUs7pFwMJw
and ... https://youtu.be/r9HPXvhw6ZQ
cheers
Last edited by Howard; 08-05-2018 at 12:27 PM.
Reason: Added the bit about hyperstar
So a 6" f/4 Newt is no problem.
