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Astrophotography upgrade advice

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#1 kc1

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Posted 03 June 2013 - 10:13 AM

Hi!

I'm new to this forum and I would like an opinion on upgrading my telescope setup.

Currently I have a CPC 800 telescope (bought in 2005), Canon 7D and 70-200mm f2.8 IS II lens.

The only attempt of DSO astrophotography I have done so far was of M42 with the 200mm lens on a standard tripod in very windy conditions which was obviously very blurry due to the lack of tracking. (I haven't got a piggyback mount for the scope yet)

I tried the 7D at CPC 800 prime, but was quite disappointed as it was very difficult to focus to be of any use. (Maybe I need collimating, or an auto focuser?)


I want to photograph deep sky objects such as M31, M42, M81 etc as a starting point.

There are 4 different ways I could go about this from what I have read.

1) Purchase a Celestron wedge HD, focal reducer and a radial guider to do prime photography. Cost: ~£650 (cons are: quite slow, hard to focus etc)

2) Hyperstar setup. Need to purchase hyper star lens and QHY8. (Very fast imaging, but expensive ~£1400 and may need auto focuser)

3) Purchase a EQ5 Pro Goto mount for 7D and forget about the CPC 800. Cost: ~£550

4) Piggyback mount + wedge HD. Cost: ~£400



Right now, I'm inclined towards option 4 since I already have a great lens and DSLR and it costs the least. For focussing, I heard that you can use the EOS utility to micro focus.

I would greatly appreciate your suggestions.

Thanks!

#2 sg6

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Posted 03 June 2013 - 02:16 PM

If you want to do AP then get an AP setup:
Usually something like a good ED, preferably an apo triplet, around 80mm or there abouts, an HEQ5 or EQ6 with the Synscan option and then attach the DSLR or a ccd.

The Synscan allows the future upgrade to a guided system, with a guide scope and guide camera.

The CPC is probably too long a focal length for DSO AP with or without a wedge. The longer the focal length then the more pronounced are any tracking errors.

Additionally the focal length governs the image size and that governs the brightness - you will get larger but dimmer images of any DSO's so will need a reducer or longer and more exposures.

You will get images with the CPC and the setup you have, but they will not match a system that is specifically intended for the task.

#3 WarmWeatherGuy

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Posted 03 June 2013 - 02:22 PM

I tried the 7D at CPC 800 prime, but was quite disappointed as it was very difficult to focus to be of any use. (Maybe I need collimating, or an auto focuser?)


You don't need anything more than a Bahtinov mask. I went through that learning curve and bought a bunch of expensive focusers. They didn't help because I still didn't know when I was in focus. The Bahtinov mask will let you know when you have perfect focus and you can get that with the crummy stock focuser. Search YouTube for Bahtinov mask to see how simple it is.

#4 frito

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Posted 03 June 2013 - 02:47 PM

OP your best bet to get into imaging is to buy a small ED doublet refractor. they are not expensive, about 300-400 dollars new or used, can be anything from 66mm to 80mm the astro-tech AT72ED's are really popular.

next you will need a mount. CG-5 or similar EQ mounts is a bare minimum really, or get a wedge but the issue with imaging with an SCT is the really long focal length makes tracking extremely important that is why they sell focal reducers for them, it will make imaging with one much easier.

the long and short of imaging is the mount and tracking is the most important thing. the scope is the 2nd most important thing. the shorter the focal length of the scope the wider the field and lower the magnification but the more forgiving the tracking error will be, that is why i'm getting away with what i'm doing on a CG-5 unguided.

here is a shot of M13 i took last night with my 66mm refractor on a CG-5

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#5 frito

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Posted 03 June 2013 - 02:53 PM

I tried the 7D at CPC 800 prime, but was quite disappointed as it was very difficult to focus to be of any use. (Maybe I need collimating, or an auto focuser?)


You don't need anything more than a Bahtinov mask. I went through that learning curve and bought a bunch of expensive focusers. They didn't help because I still didn't know when I was in focus. The Bahtinov mask will let you know when you have perfect focus and you can get that with the crummy stock focuser. Search YouTube for Bahtinov mask to see how simple it is.


i ordered a Bahtinov mask yesterday and after using BackyardEOS last night for the first time i'm starting to think i don't need the Bahtinov mask because it makes focusing much easier esp with a DSLR like mine that does not have live view. i would say that having a good dual speed focuser like my WO 66SD has on it that is graduated also helps because i know exactly the right area i need to have the focuser in to get close and then i simply use the fine adjust along with BYEOS and watch my netbook's screen to see the FWHM numbers go up or down until i get it to the lowest I can then I lock it.

#6 orlyandico

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Posted 03 June 2013 - 10:23 PM

I think the advice to go out buy an EQ mount may be overly hasty.

The CPC can do well enough on a wedge. Piggyback the refractor on it. This guy has some pretty good images -

http://www.johnmiran...m/telescope.htm

most of them are with Hyperstar, but the smaller galaxies were through the 1100 with a 6.3 reducer.

#7 frito

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Posted 04 June 2013 - 12:05 AM

you are correct, one can image with a wedge and a fork mount, its a bit more limited than an GEM and you would likely want to start off with the hyperstar to as it will be more forgiving at first, I had no idea they made a focal reducer that extreme for them :)

#8 frito

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Posted 04 June 2013 - 12:10 AM

what i do read however is that polar aligning wedges is a real pain, by that i take it drift alignment is the only good way.

GEM's are still the way to go if you can because one of their best features in my opinion is their flexibility in not being stuck with one main OTA to use on one and every type of scope minus newtonian designs are pretty easy to use on a GEM for the most part except for perhaps looking at zenith with a long refractor but that only matters for visual use.

#9 kc1

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Posted 04 June 2013 - 02:17 PM

Thanks for the advice. I will go the piggyback route to get started for now I think.

#10 Tom and Beth

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Posted 04 June 2013 - 03:29 PM

It seems the best NEXT step for you is be comfortable with your Cam control. Might I suggest BYEOS? It will work with your camera lens and using the camera behind the scope. With it, you can focus the Zoom lens you have while getting feedback on when your focus is close to perfect. This skill will help you learn how to do it with the 2 meter FL of your scope.

After that. You should have a secure way of attaching the telescope and the camera. IIRC the 7D has the big sensor, so look for the 2 inch to EOS adapter as one piece. Baader is a good choice.

Then you should tackle Polar Alignment. Maybe add a 50MM Finder/Tracker and PHD to guide with.

I'd avoid spending money on anything that isn't capable of moving from scope to scope at this stage.

#11 cn register 5

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Posted 04 June 2013 - 04:50 PM

A CPC mount on a wedge can be polar aligned using the AllStar polar align method, just as a GEM can be. It will be easily good enough for piggy back photography.
Chris

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#12 frito

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Posted 04 June 2013 - 06:02 PM

A CPC mount on a wedge can be polar aligned using the AllStar polar align method, just as a GEM can be. It will be easily good enough for piggy back photography.
Chris

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oh thats good, then if you can ASPA on a wedge mounted celestron then it will make things much easier. that ASPA is probably one of the best features of my CG-5. hasn't failed me once yet for polar aligning because i do my part.

#13 groz

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Posted 07 June 2013 - 04:22 PM

I want to photograph deep sky objects such as M31, M42, M81 etc as a starting point.


M31 and M42 are HUGE, 81 is comparatively very small.

Before you get to caught up in various recomendations, I would suggest you sit down and look at the relative size of things you would like to shoot photos of, then look at the field of view for your camera / telescope combinations you are contemplating. If you have a combination that can encompass the whole of M31, then something like M81 is just going to be a small smudge in the center of that huge frame, and you'll find a few more galaxies, even smaller smudges, in that same frame. You will not find a single combination that fits everything.






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