I want to increase my DSLR exposure time....

[tingting44]

Hey guys i want to be able to increase my exposure times with my wide field shots using my Canon 7D (1.6x crop) and 18mm focal length = 28.8mm, at the moment im pushing to get 25 seconds without trailing.

So my question is what would be the cheapest way to achieve this? ive looked into making a barn door but do not feel that confident, 1 option would be to get a VERY cheap EQ mount maybe? ive never used an EQ mount so a bit to learn as ive only ever used my AZ goto mount. 

From experience how long does one roughly get a max exposure from a DSLR on an EQ mount (no telescope)?

all the best

Martin

[stelios_t]

I've never used my DSLR without a scope, but at the very low magnifications you are talking about, with a well-aligned EQ mount I think you would be able to go for quite a prolonged period without apparent trailing. Under high magnification the stars would be like short little strings rather than points due to the periodic error, but I don't think it would be visible in the image.

There's nothing inherently complex about an EQ mount, think of it as an Alt-Az but pointed at the pole rather than the zenith. 

[PorkyB]

At that focal length you can expect to get several minutes without trailing.  Why not have a look for a second-hand EQ3 (with polarscope and RA motor).  I put my camera directly onto my EQ5, it works well but you do end up in some very strange positions.  I have modified a red-dot finder to fit in the flash hotshoe to make targetting easier, when I have more time I will make a bracket so I can use my right-angle finder.

[iksose7]

I just got my NEQ6 a couple weeks ago and have managed a 5 minute exposure unguided with a 200mm lens. I would do like Porky B has suggested and get an EQ mount. If you think you will eventually want a scope i would go for the EQ5 to save money in the long run!

[Guy Wells]

Tingting44..I do the same type of photography. Use the Rule of 600 to find the max exposure time. A barndoor would be great. I'll try and knock one up sometime in the future. As has already been mentioned, an EQ mount would be ideal too. I assume your stacking said images?

[tingting44]

At that focal length you can expect to get several minutes without trailing.  Why not have a look for a second-hand EQ3 (with polarscope and RA motor).  I put my camera directly onto my EQ5, it works well but you do end up in some very strange positions.  I have modified a red-dot finder to fit in the flash hotshoe to make targetting easier, when I have more time I will make a bracket so I can use my right-angle finder.

thanks bud ill have a look and see how much EQ3's go for, thats a handy mod you have done with the dslr red dot finder

I've never used my DSLR without a scope, but at the very low magnifications you are talking about, with a well-aligned EQ mount I think you would be able to go for quite a prolonged period without apparent trailing. Under high magnification the stars would be like short little strings rather than points due to the periodic error, but I don't think it would be visible in the image.

There's nothing inherently complex about an EQ mount, think of it as an Alt-Az but pointed at the pole rather than the zenith. 

also sounds good, i think i need an EQ mount lol dont seem to be much on the bay (cheap lol)

I just got my NEQ6 a couple weeks ago and have managed a 5 minute exposure unguided with a 200mm lens. I would do like Porky B has suggested and get an EQ mount. If you think you will eventually want a scope i would go for the EQ5 to save money in the long run!

sounds good, id love to be able to afford an NEQ6 ive all ready got this scope  http://www.firstlightoptics.com/az-goto/skywatcher-explorer-130p-synscan-az-goto.html but i dont hardly use it as im so into widefield shooting at the moment

Tingting44..I do the same type of photography. Use the Rule of 600 to find the max exposure time. A barndoor would be great. I'll try and knock one up sometime in the future. As has already been mentioned, an EQ mount would be ideal too. I assume your stacking said images?

Thanks mate ill look up the rule of 600 im not doing stacking at the moment as im right into my timelapse's at the moment so just want the longer exposures to capture more photons in each image for my timelapse, and also like you say the same timelapse data can also be stacked into 1 single image, so kind of getting 2 birds with one stone which is good

[Scott]

Hi martin,

basically the 600 rule (although I think with a 1.6 crop sensor you should use the 500 rule) is where you divide 600 (or 500) by the focal length of the lens. so with your camera with a 50mm lens I'd divide 500 by 50 giving 10 secs. its only a rough estimate as stars in the south will move further than say, polaris  over a similar period.

At a guess, I'd say that with a 50 mm lens on a driven eq3, well aligned, you'd be more likely to be washhed out by l.p. than star trails causing problems. whatever you decide....good luck and enjoy (it's the name of the game ).

Scott 

[tingting44]

Hi martin,

basically the 600 rule (although I think with a 1.6 crop sensor you should use the 500 rule) is where you divide 600 (or 500) by the focal length of the lens. so with your camera with a 50mm lens I'd divide 500 by 50 giving 10 secs. its only a rough estimate as stars in the south will move further than say, polaris  over a similar period.

At a guess, I'd say that with a 50 mm lens on a driven eq3, well aligned, you'd be more likely to be washhed out by l.p. than star trails causing problems. whatever you decide....good luck and enjoy (it's the name of the game ).

Scott 

Hi Scott

ah nice so at say 18mm id be looking at an exposure of 27 seconds which does add up with my max exposure of around 25'ish seconds thanks for that, handy to know light pollution is pretty good at the spot we go in the forest, its a real nice spot, can easily see the milky way with the naked eye and a lot of fuzzies

thanks bud will keep you posted on how this pans out

[Jammy]

I've used my dslr directly fitted to my mount, but find it difficult to get exposures over 30 sec.  Stars start to trail, but the main problem here is light pollution.  Wide angle shots overhead are usually the best.  Try stacking in Deep Sky Stacker - you only need a few exposures to notice the difference.  Once you've tried a few, you will want to try many more.  Have fun!

[glowingturnip]

I've managed 3 minutes without a hint of trailing with a  DLSR at 18mm  (ISO800, f3.5, stacked, darks, flats) piggybacked on a goto mount which was sidereal tracking but not guided, result here - http://www.flickr.com/photos/glowingturnip/9328004384/

I think the rule of 600 would only apply to a stationary camera ?

[Scott]

I've managed 3 minutes without a hint of trailing with a  DLSR at 18mm  (ISO800, f3.5, stacked, darks, flats) piggybacked on a goto mount which was sidereal tracking but not guided, result here - http://www.flickr.com/photos/glowingturnip/9328004384/

I think the rule of 600 would only apply to a stationary camera ?

Yes, this is right. 600 rule is for camera tripod (stationary camera).

Edit:- Nice milky way by the way 

[idigitize]

I thought this might be good to try... http://www.firstlightoptics.com/skywatcher-mounts/skywatcher-tabletop-eq1-geq-mount-with-ra-drive-and-multi-speed-hand-controller.html. But actually discontinued it seems, great for the camera bag though if steady enough.

[tingting44]

I thought this might be good to try... http://www.firstlightoptics.com/skywatcher-mounts/skywatcher-tabletop-eq1-geq-mount-with-ra-drive-and-multi-speed-hand-controller.html. But actually discontinued it seems, great for the camera bag though if steady enough.

Well that is an interesting find!!! i like it a lot, found one in stock here

http://www.365astronomy.com/tabletop-eq1-equatorial-mount-p-2224.html

[idigitize]

Yep, looks good! No motor on that one, which I think is an extra £25 ish. Think would be good for the car roof or 'a table I guess' with a wide ish angle lens

[tingting44]

Yep, looks good! No motor on that one, which I think is an extra £25 ish. Think would be good for the car roof or 'a table I guess' with a wide ish angle lens

yeah was thinking of the top of the car ohh im excited now lol, wonder if anyone on here has tried them...

[idigitize]

I'm sure I read about one in a thread connected to the st80 version, have a search ,

[Leveye]

I love my iOptron ZEQ25GT and my SmartEQPro mounts both can run on battery power and are quite affordable for what they can accomplish. 

With just a camera and lens and a great polar alignment I can get about 2 minutes no trailing. I have used 12mm up to 300mm.

[jgs001]

On a well setup EQ1 with a reasonable polar alignment, I was able to achieve a couple of minutes at 18mm. With my HEQ5, I've been able to hit 5 minutes with 50mm without the mount breaking a sweat, no need for guiding. The Astrotrac provides the same level of tracking accuracy. I've yet to push it beyond 50mm to see what I can achieve, but I have a plan for using a longer lens. Why don't you just mount the SLR to that AZ goto mount ? You'll be good for exposures of 30-40 seconds overheard, increasing to 2 minutes low in the east and west, and focal length does not affect those times. Focal Length and weight will affect the tracking accuracy though. If you've not tried it, certainly give it a try, it's not ideal, but it's all good fun.