Deep sky start

[Nova2000]

Hi all, this is my first post and I hope I am providing sufficient info about what I am referring to. I've done a few time-lapse, star trails constellation shoots. I want to go deeper into astrophotography. I have a low budget unfortunately. I have a Canon 700d  with kit lense. A benro tripod. Can you'll help me out.? 

[ronin]

Possible but not really for DSO's specifically. Wide field Milky way is more applicable.

The simplest way to put it is:

Short focal length ~20mm, fully manual set up so: ISO 800, 20 second exposure, manually focused to infinity, aperture to as wide as possible then back off a half stop or one full stop.

Aim at say Cassiopeia, take 15 to 20 exposures - really need an intervalometer for this. Set intervalometer to 5 second wait at start, then 20 second for the exposure and say 10 second wait after the exposure (this is needed for a bit of sadety). Set to take 15 or 20 exposures.

Head home, reset intervalometer to say 6 to 8 exposures, leave lens cap on camera and put camera and intervalometer in the fridge, Press the go button and close fridge door.

Now you have 15-18 exposures and 6-8 darks. That is your start point for loading the exposures into Deep Sky Stacker.

Bit simplified but will get you going. Without tracking you are limited on length of exposure and number of exposures.

[Nova2000]

Thanks for the info ronin, can you explain to me why do I put the camera in a fridge? Shouldnt the darks and lights be taken in the same temperature. Im not that sure as I've just started deep sky. 2months till the monsoons are over. So I'm doing a bit reading and equipment upgrades.

[Nova2000]

Thanks for the info ronin, can you explain to me why do I put the camera in a fridge? Shouldnt the darks and lights be taken in the same temperature. Im not that sure as I've just started deep sky. 2months till the monsoons are over. So I'm doing a bit reading and equipment upgrades.

[ollypenrice]

In a hot climate an uncooled DSLR is going to struggle and putting the camera in the fridge for the darks is the opposite of what you should be doing. You want the darks and the lights at the same temperature.

What would be far more useful would be getting some freezer packs (as used by physiotherapists) around the camera for taking the lights. On a fixed tripod you will have limited opportunity to take multiple subs because the target will move, but multiple subs will drastically improve your signal to noise ratio and, above all, the colour noise to which DSLRs are prone.

What you need, above all, is a tracking mount. Once you have one you can take multiple exposures of the same target and boost your signal to noise ratio superbly. At a short focal length the mount does not need particularly exotic accuracy. As focal length increases so the tracking accuracy must improve and eventually you will need to guide. But at short focal length very rough equatorial tracking will do fine.

Olly

[wimvb]

Depending on your budget, here are a few options for adding tracking to your setup.

1. Skywatcher star adventurer

2. Skywatcher eq3-2 with RA motor, or goto

3. Barn door tracker, either manual or with motor.

The latter would be a diy project.

Hope this helps

[Nova2000]

OK so, I think I'll go for the star adventurer. It's looks nice and portable. What's autoguideing supposed to be? 

 

[wimvb]

Autoguiding means that you use a second camera with appropriate software to follow a star. The software sees where a certain star is registered on the cameras sensor, then controlls the mount and moves it to keep that star in the exact same location on the camera sensor. When done correctly, this is much more accurate than merely tracking = moving the mount at the same speed but opposite direction of the earths rotation.

Time to refer to this

https://www.firstlightoptics.com/books/making-every-photon-count-steve-richards.html

Good luck

[Dave S]

17 hours ago, ronin said:

Aim at say Cassiopeia, take 15 to 20 exposures - really need an intervalometer for this. Set intervalometer to 5 second wait at start, then 20 second for the exposure and say 10 second wait after the exposure (this is needed for a bit of sadety). Set to take 15 or 20 exposures.

Instead of investing in an intervalometer and if you have a laptop just use the free EOS Utility program which is free and downloadable from the canon support site.  You just need to get hold of the appropriate USB cable to attach the laptop to the camera.  The software then lets you set the camera to set a series of exposures which you can then stack in Deep Sky Stacker (also free).

You won't be able to go for DSO's but with just the tripod you'll be able to get some nice wide-field shots. And it'll keep you in the running till you get your Star Adventurer.

Dave...

 

[Nova2000]

Thank you Dave, wimvb and ollypenrice. I got the eos software with my camera. Does anyone know how much zoom can I use on the star adventurer? I. E 200mm,300mm. I'm asking this cause I heard about trailing effects. 

[Dave S]

I'm no expert on the adventurer but trailing isn't an issue with tracked mounts so long as it's aligned correctly. But for really accurate imaging most use some form of additional guiding where a second scope coupled with a guiding camera locks on a star and corrects the tracking for innacuracies.

For static (i.e on a tripod with no tracking) there is the rule of 500.

That is 500 divided by the focal length in mm equals the maximum exposure time without showing star trails.

so for a 55mm lens 500/55 = 9 secs  it's not absolute but gives a guide for experimentation.

Dave...

I've just got back into things recently with a new camera so I'm in pretty much the same boat as you.

I just posted this this morning.

 

[Nova2000]

I tried mounting my camera on my skywatcher mount (not motorized) and tried manual tracking. Got a few shots of the moon. Little blur tho some were bad with trails. 

[Dave S]

3 minutes ago, Nova2000 said:

I tried mounting my camera on my skywatcher mount (not motorized) and tried manual tracking. Got a few shots of the moon. Little blur tho some were bad with trails. 

What exposure time did you use?  THe moon is very bright and only needs a very short exposure like 1/10 or 1/4 sec which may cut out the blur.

[wimvb]

Do the test. Assuming you use a tracking mount, start with polar aligning as accurately as you can. Then use the longest fl you plan to use. Do an exposure at, say, 30 seconds. Double this until star trails start to become annoying (it's your preference that says when enough is enough). Then back off from this value.

Spend a night experimenting, so you get to know your equipment and its limitations. This way you won't have to experiment when you are about to do some "real" photography.

Also, redo the polar alignment and reshoot the longest time. There's nothing more frustrating than finding out that you can't reproduce your results when it counts.

These tests can also help you determine the best exposure time to limit light pollution.

Hope this helps.

[alacant]

17 hours ago, ollypenrice said:

freezer packs

Ahhggh, no! Bitter August experience, keep those for the beer. In fact look what happens to a cool beer in the heat. Condensation everywhere. Lens, shutter, mirror... Whole session ruined within 30 seconds. Nice idea and of course YMMV but for me, never again! HTH.

[ollypenrice]

8 minutes ago, alacant said:

Ahhggh, no! Bitter August experience, keep those for the beer. In fact look what happens to a cool beer in the heat. Condensation everywhere. Lens, shutter, mirror... Whole session ruined within 30 seconds. Nice idea and of course YMMV but for me, never again! HTH.

It's a technique used routinely here by experienced DSLR imagers. I've never seen it cause a problem. They put them round the rear of the camera body and nowhere near the lens. It's the chip that needs to be cool.

Olly

[Nova2000]

I shot at 1/100 I think it was movement of the tripod on my terrace. I'll be placing my order for the star adventurer tomorrow. Will spend a few nights experimenting different focal lengths and shutter speeds. I'm trying to find apps for polar alignment. 

[alacant]

2 hours ago, ollypenrice said:

experienced DSLR imagers

Inexperienced dslr user here on the getting started section. Very! 

[RSM]

On 12 October 2016 at 13:31, Nova2000 said:

I shot at 1/100 I think it was movement of the tripod on my terrace. I'll be placing my order for the star adventurer tomorrow. Will spend a few nights experimenting different focal lengths and shutter speeds. I'm trying to find apps for polar alignment. 

I use Polar Align 6.1 by George Varros for my PA on my iPhone. Very simple and gives you what you need for your location.