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Thread: Equatorial Wedges

  1. #11
    Pauls72's Avatar
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    Default Re: Equatorial Wedges



    A long focal length scope like an SCT is ideal for imaging very bright objects like the moon and planets. Most people take video images and then stack the hundreds of frames and throw away the bad ones. This type of imaging can be easily done with your LX200. You might be able to get a few very bright objects like M42 and M45 too.

    DSO imaging is a totally different beast. A small, fast, Refractor (preferably a triplet APO) on a GEM mount is the easiest way to go. Can you do DSO imaging with a long focal length scope like an SCT on an Alt/Az mount with a wedge? Sure you can, but it's going to take a quite a bit longer to lean and generate tons of frustration and lots of garbage images. DSO AP is a challenge and has so many other skills to learn, most people want to make whatever they can easier.

    With a short focal length scope, any guiding or tracking errors will be much less visible. Here is another thing at f/10 it takes roughly 4 times the length of time for an image to gather the same amount of light as at f/5. That highly increases your odds of having a tracking issue, a gust of wind move your scope, vibrations from anything causing a small amount of movement, a plane or satellite crossing your field of view and ruining a sub. SCT's are notorious for having mirror flop, this is another reason too stay away from them when doing DSO AP. You may want to even consider taking some images just with a DSLR and regular lens on a GEM mount.

    I would recommend you get these 2 books and read them first:
    The Deep-sky Imaging Primer by Charles Bracken
    https://www.amazon.com/Deep-sky-Imag...harles+bracken

    Beginners Guide to DSLR Astrophotography
    Catching the Light - Astrophotography by Jerry Lodriguss
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    Default Re: Equatorial Wedges

    Hi and thanks so much for the info

    I have been looking at a variety of cameras (mostly CMOS due to budget constraints) but have not made any decisions yet. I am nased in SA and thus getting some of these models become expensive as most need to be imported and the ones already here are double to price of those in the USA... I think I will have to save a little for this but I am getting a T-adapter (I have the ring already) for my Nikon and maybe a 2x Barlow to play with images of the Moon and Planets. With a standard DSLR however I am concerned that I will be unable to get good images of the planets due to exposure times forced by the mirror flop and field rotation issues you mentioned. My camera is a D7000 and thus does not have a full frame sensor. Is this a futile exercise??

  3. #13
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    Default Re: Equatorial Wedges

    you would be fine with what you have for the planets, although the images taken will be too small, mars will be a pixel, etc. Field rotation isn't an issue as your exposure times will be less than a second. your moon shots would be great. A 2x barlow won't make much of a difference for the pictures. But the barlow would be great for your eyepieces. i have'nt tried, but a ccd or cmos, is supposedly much better for planets. your current scope with dslr and alt/z mount will take pictures of dso's at 10 sec exposures, so try that. you'll get some images. A focusing mask is a must have and cheap, to help you focus dslr. mounting a sct on a equatorial tripod can be expensive due to weight, that's why everyone suggests an equatorial mount with a low weight refractor for photos, other factors make a refractor a better imaging system than the sct anyways. also you can use the sct as is for viewing and while take photos at the same time, if you have the two separate telescopes! have fun and clear skies.

    buy a bahtinov mask(low cost) when you get the t-adaptor(also low cost) and try some 10 sec exposures on some dso's. i won't be futile. but you'll be dissapointed with the planet photos. you'll like the dso images.
    -Herman
    ETX60. Meade 10" LX90GPS, 10x50, 15x70, zoom12-100x70 binoculars, Canon 3Ti, Meade infinity 102mm.

  4. #14
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    Default Re: Equatorial Wedges

    Quote Originally Posted by bencoley2 View Post
    With a standard DSLR however I am concerned that I will be unable to get good images of the planets due to exposure times forced by the mirror flop and field rotation issues you mentioned. My camera is a D7000 and thus does not have a full frame sensor. Is this a futile exercise??
    For planets, you should be shooting video, not doing long exposures. With video, field rotation is not an issue. Neither is mirror flop in the scope or mirror lockup vibration in the camera. You might lose a few frames here and there, but you should shoot thousands of frames on one subject, so you can afford to lose 80% of them and still get a good image.

    Similarly, sensor frame size is not an issue for planets. For the Moon, perhaps. The planets will be so small that all the cropped frame sensor crops is black sky anyway.
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    Default Re: Equatorial Wedges

    i should also add, that to make the sct f/10 to f/6 a focal reducer is used. The focal reducer certainly helps, but it isn't cheap. about $100 USdollars. I have one, it does help, a work around is using photoshop to increase exposure otherwise your dso images will not be visible(or very dark), this is normal, and part of the limitations of what you have. i don't use it much now, because i use a refractor with my camera, but i do use it occasionally when i want to make use of the larger aperture of the sct.
    Last edited by Chinaman4u; 02-13-2018 at 04:33 PM.
    -Herman
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