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jgs001

Basic widefield with a Camera and Tripod

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Hi John,

I knew I had forgotten to ask something ...

I'm planning on using APT to control the exposures. What sort of time delay do you recommend between each of the 30 second exposures? Would 10 seconds be ok?

Thanks

Pete

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It's up to you really... 10s is a good value... Although, if you're going to be using a laptop and APT, why not mount the camera on the HEQ5 and capture some 5 minute exposures ?? (I found with 50mm and shorter, guiding is not required)

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Hi John,

Now that is a great idea. I do have an HEQ5 Pro mount but I don't have a dovetail to standard camera mount connector thingy.

I guess I could buy such a thing, or perhaps make one. Could you recommend a site where I could get one from?

Many thanks

Pete

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I can't see your kit list at the mo, but if you got any standard skywatcher tube rings the piggy back bolt is a standard tripod thread. Get a dovetail from FLO and mount a ball head on the dovetail.

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Hi John,

My kit is a 1000D camera with standard zoom kit lens; HEQ5 Pro mount (with SW200 OTA). Also got a 150PL scope and tripod/mount with motors.

Dovetail currently in the post from FLO.

Just thinking ...which is dangerous for me ... why do I need a ball head mount? Couldn't I just use the RA and DEC axes to rotate the mount (and camera) into the required view?

Thanks

Pete

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Hi John,

My 15cm dovetail has just arrived from FLO.

I'm probably being a bit dim but I can't figure out how to attach the camera to the dovetail. I have a spare camera screw that has a wide knurled bit at the end but when screwed into the bottom of the dovetail, it doesn't lie flush with the bottom. The dovetail doesn't sit flush. Should the screw just be a screw?

Thanks

Pete

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You could always leave the knob free of the saddle on the mount. I'm using standard roofing bolts on my tube rings, and they sit proud of the bottom of the dovetail, I just have to adjust the position to the bolt is not in the saddle and balance from there. It might be worth starting another thread, as the rq5 is able to track and this thread is really about using static tripods.

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Good news Pete. We'll look forward to the results

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Thanks for the tutorial, John, I only joined the forum last night and will give this a go when we get some clear nights.

Jim

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Hi John,

Took my first ever set of photos this evening (Canon 1000D on tri-pod, with Canon 50mm f1.8 lens. Exposure controlled using remote release). I took 10 lights at ca. 30 seconds each, and 5 darks at same settings. I've done a quick process in DSS but not sure what to do next. I've saved the DSS image as a TIFF file but it's big at 58MB. I've run it through GIMP played a bit with the 'Curves' (again, no idea what I'm doing) and saved as JPG, attached below.

Looks like 30 seconds was too long an exposure as there are star trails.

Sorry this is a poor image. Any tips or pointers to tutorials as to how to process the files?

Many thanks

Pete

post-11866-0-84368900-1359583523_thumb.j

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I'd start with levels rather than curves. Load in the image and pop up the levels dialog, then move the middle triangular marker under the histogram to the left to bring it close to the main body of the histogram. See how that looks.

James

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Pete, with the Nifty, you're looking at about 8 to 10 seconds before trails set in... As for processing, I posted a few simple examples at the beginning, but that's based on the information MartinB posted (), take a look at that thread. It can take a while to understand exactly what you're looking to do and see , but with practice it becomes easier ;)

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Hi John,

Thank you for your advice. I'll try again but with much shorter exposures (8 seconds). I forgot to mention previously that I had set the aperture to f1.8 and the ISO to 800. Are these settings still ok for such short exposures?

I'll certainly take a look at the thread you mentioned. Thank you.

Just want to say that apart from the Nifty which cost £80 new, the only other expense to use the camera on the tripod was the cable remote at £6.50. I did buy a short dove tail at £12.50 and a two-way 1/4 inch screw at £4.50 but those are for mounting the camera on the HEQ5 mount.

Cheers

Pete

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The nifty at f/1.8 is silly fast, but you get a lot of coma around the edges (egg shaped stars) you really need to stop it down to f/4 for best performance, but that let's in much less light.

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Thanks John, I'll try that and keep exposures relatively short at 8 seconds or so.

By the way, do you happen to know if there is a general guide (or link to a thread) to exposure times versus aperture settings for the nifty, perhaps with different ISO settings. I'm finding all of this very confusing

Cheers

Pete

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Not really... to be honest Pete... ISO seems to be best at about 400 to 800 (800 I think was found to give the least read noise). So go with 800 (or push it to 1600 and see how you get on). Exposure time is going to be dependent on where you're aiming and whether you're tracking or not... On an untracked tripod, 8 to 10 seconds is your limit before trailling sets on. On the HEQ5, 5 minutes should be a doddle. From memory you want to stop down to f/4 as a minimum to deal with some of the problems... things you wouldn't notice under daylight conditions.

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Thanks again John. As a beginner, that's just what I'm looking for.

My plan is to have another go at Orion sometime, may be tonight if it is clear.

Cheers

Pete

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Hi John,

Done a second attempt using a shorter exposure time and F/4.0 aperture. Couple of images posted in the Widefield section.

Pete

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Thanks for the post John, will defo give it a try myself, if I can get Orion ill be a happy camper :)

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Ah.. now that's one of the vagaries of some of the cheaper lenses, they focus past infinity. I cheat and use the liveview and zoom in all the way. Otherwise, if the moon is up, use that with the AF, then switch the lens to manual focus. I've not really got the experience of focusing using other techniques, but I think you're best bet, is to set the lens to the end stop, back off a little, take a test exposure. Zoom in all the way on the preview and check it. Adjust the focus a little, repeat the test, until it's as good as you can get. A bhatinov focus mask would make this much easier to do.

My Nikor 80-200 F2.8 ED lens, older make with 16 glass elements and a long way from being a cheap lens ($3000+ new), always focus's past infinity. It does however come with a focal range window and has an infinity marking. My cheaper lenses don't have this feature and I have to play in daylight to set infinity.

I have a method for doing it, I focus on a distant object using autofocus during daylight, then switch the camera focus switch to manual. WIth the newer lenses (Nikon anyway) they have a manual/auto focus switch on the lens itself. Once I achieve perfect infinite focus, I set the camera switch to manual but leave the lens switch on auto so it won't move if I bump it.

There's always focus lock but that feature won't retain the memory once the camera is turned off and my system (probably used by many but I've just discovered for myself) can be set during daylight then carried to dark skies and my shots are mostly in focus.

There's always going to be the one night though when you're out freezing in the name of getting a great shot but the focus has been moved.....

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