Would love some advice on using an iOptron SkyTracker - Christmas gift.

Advise not waiting until your upcoming possible Clear Sky opportunity to Start Practicing with your Newbee Equipment . . . Even a few Dry Runs will give you the Familiarity You'll NEED in the field.

Have FUN & Enjoy Your Holiday Season . . .

Congrats on the SkyTracker! I think it's a great tacker and a great value for the money.

Have you done any AP yet? If not you may want to spend some time with your camera on a tripod and practice focusing and taking shots of the night sky. Focusing can be a real challenge. Use focus zooming and zoom in on a bright star to focus. The peak level focusing feature will help too. That will be good enough with the wide lenses you have. To determine the maximum exposure you can take without any star trails use 500/FL. Since your A7rII is FF the formula works as is (you have to adjust by the crop factor if not FF.) So, for example, with your 24mm it would be 500/24 = 20.8 so 20 seconds max. ISO settings are a topic of great debate (as is most stuff in AP) but I'd start at 800 and see what you get. Try different settings as different cameras will produce different results.

For the SkyTracker I'd (1) read the manual, (2) re-read the manual and (3) download the iOptron polar scope app. It makes polar alignment really easy. IMHO it should be free but it's $1.99 the last time I checked. Still, WELL worth the money. Once you're ready to try it out make sure it's on a good and steady tripod.

If you plan on taking multiple shots on the SkyTracker (that's basically what it's for) you'll need a way to control the exposure and shots. There are several ways to do this but I use an intervalometer. Yes, it's an extra piece of equipment but it basically bullet-proof. Another way is with computer control using something like BYE. And if you're doing this you'll need software to stack the shots. DSS is free for PCs and a good way to start. I use a Mac so I had to find a different solution. Nebulosity isn't free but besides stacking it has some decent PP functionality.

Also check out:


Lots of good information there.

Hope this helps!

Thanks Orion12 - good advice. I have started the dry run process and have watched videos on YouTube regarding setting up the SkyTracker.

Thanks Rokaroka! I have done some minor AP work by just setting on camera on the tripod and following the steps that you suggested. Also got some great Northern Light shots this past November in Churchill, Manitoba, Canada.

i did also get an Intervalometer for Christmas, so I can use that for multiple shots. But I'm not sure what stacking multiple exposures gets me over single longer exposures. And I'm not sure if I should close my aperture down a bit since I now have a star tracker and how long I can and should keep the exposure going. Another thing is that it is going to be cold as heck (low teens or even single digits), so I'm not going to want to be outside for too long.

Thanks for your excellent response to my question!

The i-Optron SkyTracker is a great value for money and a good tracker. You will need a sturdy tripod and a good ballhead to go along with it. I just bot the SkyTracker about a month ago and it has helped me get some great pictures. A few comments:

1. The rule of 500 is applicable only to UNtracked imaging sessions, that is for camera on a static tripod and NOT for the SkyTracker. So, with a 24 mm lens, 20 seconds is close to max longest exposure you can take,
2. Reason for going to longer exposures is to catch more photons. Increasing ISO does NOT increase # of photons caught, but ISO just amplifies the in the image, so it also amplifies noise. So ISOs of 1600 or less are considered good, but with the limitation on exposure time due to 500 rule on untracked images, those images do not catch enough light photons.
3. With the SkyTracker, you might be able to get 2 to 4 minute (or longer) exposures on wideangle lenses, IF your polar alignment is correct. Do get the polar alignment app. It will make polar alignment process easier AND more accurate,
4. Lastly, many newer cameras like yours may have an intervalometer built in (mine does). It is usually good for max exposure time of 30 seconds. So, bulb mode (longer than 30 sec exposures will need the use of either BYE software mentioned or a physical device that remotely controls the interval duration, # of exposures and exposure time. There many reasonably priced ones avaialble on the market.
5. You will need to stack the multiple exposures in a stacking program The are a number of them available, but DSS (Deep Sky Stacker) is free and reasonably easy to use.
6. Stacking multiple individual pictures is very important to reduce digital noise inherent in all sensors (the random greyness). Noise reduces by the square root of the number of images. Meaning if you take 9 images, signal (desired objects) to noise ratio improves by a factor of 3 (sq rt of 9). Another way to say this is the noise gets dimmer as you stack more images (after you boost the stacked image in post processing).

I would also suggest using the camera on a static tripod first to get the focussing right and trying to get the exposure correct. Many newbies (including yours truly), make the mistake of taking individual images that have dark background sky. However, usually for stacking and added post-processing, one needs to have individual images looking a little blown out. The most important criteria for good indiv frames is that the histogram peak should be between 1/4 to 1/3 away from the left edge. This allows enough room for pulling & pushing (stretching) the final stacked image in PP (post-processing) software like Photoshop etc.

So, my suggestion would be to get a good handle on stacking and PP so you get a good final result. Go out before your trip and try various settings and see what works. Reason is that settings are also dependent on location (light pollution levels, humidity, temps, seeing conditions like air-turbulence, wind etc). Best luck and have FUN! ...... Anil

rokaroka said:

Also check out:

http://www.lonelyspeck.com

Lots of good information there.

Click to expand...

Yes, except his post processing doesn't understand the basics of multiply versus subtract, resulting in unnatural color and color balance changing with image intensity.

See: http://www.clarkvision.com/articles/nightsky-natural-color-vs-bad-post-processing/

coloradosnowman said:

Thanks Rokaroka! I have done some minor AP work by just setting on camera on the tripod and following the steps that you suggested. Also got some great Northern Light shots this past November in Churchill, Manitoba, Canada.

i did also get an Intervalometer for Christmas, so I can use that for multiple shots. But I'm not sure what stacking multiple exposures gets me over single longer exposures. And I'm not sure if I should close my aperture down a bit since I now have a star tracker and how long I can and should keep the exposure going. Another thing is that it is going to be cold as heck (low teens or even single digits), so I'm not going to want to be outside for too long.

Thanks for your excellent response to my question!

Click to expand...

Stacking multiple exposures reduces noise and increases detail. One long exposure increases noise. Refer to the processing tips at clarkvision.com for detailed explanations on this.

After using mine for a while I did learn a few tricks. First get a rough polar align then compose and focus your shot. Then go back and dial in your polar alignment, it will shift around and you want it to be the last thing you check before you start shooting.

Have fun....

#1 Practice setting everything up until you can do it in the dark without thinking. You can down load the polar alignment utility for free but make sure you know how to use it, because that is what will largely determine how accurately your camera can track.

#2 Practice focusing. AF is useless in the dark and relying on the infinity stop or mark on the lens barrel is a recipe for disaster. You'll have to use LiveView at 100% to make sure your stars are in focus. Then take a couple of 10-20 sec test shots and review them at 100% as well. Check and double check that your focus is perfect, before committing to a long series of subs.

#3 You may or may not be able to shoot wide open. While examining your "focus- check test photo", also check the corners for lens aberrations and stop down accordingly to get corner to corner sharp stars. Stars are the most brutal test for lens' there is.

#4 I'd start with ISO 1600 for your first time out and 30 sec exposures. Estes Park is not as "AP dark" as you think , with all of the light domes of the conjoined suburbs and their 3 million residents sprawled at your feet a few miles away. Check your BOC histogram. You want the peak to be ~ 1/4-1/3 of the left side. If your histo is too close to the left edge @ 30 sec. then go ahead and try 1 min. exposures.

#5 Enjoy your new "toy" !!! Learn from your mistakes and keep at it ! I'm likely going to be out as well, but further east, out on the Pawnee Grasslands to be able to shoot 3-4 hours towards Orion, before it gets swallowed by the Fort-Denver-Springs megalopolis light dome.

Great advice in this thread. If your iOptron is like mine, getting the battery holder in and out with batteries loaded (4 of them) is a real chore and will wear out the wires. So I bought an external battery holder. Another advantage of the external holder is you can unplug the battery holder so you won't accidentally leave the thing on while in transport and run down the batteries. I bought 2 external holders so I am ready for a quick switch when one set dies.

Roger

rnclark said:

Great advice in this thread. If your iOptron is like mine, getting the battery holder in and out with batteries loaded (4 of them) is a real chore and will wear out the wires. So I bought an external battery holder. Another advantage of the external holder is you can unplug the battery holder so you won't accidentally leave the thing on while in transport and run down the batteries. I bought 2 external holders so I am ready for a quick switch when one set dies.

Roger

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+1


The stock battery holder is a royal PITA !! I wouldn't worry about getting two holders, however. I can normally get two entire nights on one set of good NiMH batteries.

Thanks for the explanation. And I'll check out the Clark site for further details.

Thanks Anil! Awesome advice.

Roger, you are correct. This is an informative thread that newbies like me can fall back on over and over again. I'll be sure to review your site. Regards, Dean

Thanks for the suggestions. Great information for me! Are you going out to the Pawnee Grasslands this week? If so, stay warm. It's going to be cold out there after dark! Regards Dean

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Operator error on that empty post.

Thanks Okiedrifter! I've now got a lot to try to remember.

rnclark said:

Great advice in this thread. If your iOptron is like mine, getting the battery holder in and out with batteries loaded (4 of them) is a real chore and will wear out the wires. So I bought an external battery holder. Another advantage of the external holder is you can unplug the battery holder so you won't accidentally leave the thing on while in transport and run down the batteries. I bought 2 external holders so I am ready for a quick switch when one set dies.

Roger

Click to expand...

I use an external 8 AA battery holder actually made for use with the Astrotrac TT A320 unit. The plug exactly fits the iOptron so no assembly is required. Order the battery pack, insert batteries and plug it in. The wires from the battery pack to plug are long enough so the battery pack can be placed on the ground.

Here is a link: http://www.optcorp.com/telescope-ac...tteries-cords/at-bh8aa-aa-battery-holder.html

Good luck whatever you decide on.

I am finding very little on the internet regarding how to use the iOptron Polar Scope app. The app seems to be able to calculate my Latitude & Longitude fairly well. Am I better off just using the Latitude & Longitude calculated by the app? Or should I be manually entering in Lat/Long values found on the internet for the location that I am at (Estes Park, CO)? Based on proper Lat/Long values for my location, is the key to place the polaris star in my iOptron Polar Scope at the same location as it shows up as the green dot in my Polar Scope app? And not in the tiny center circle of the scope like I originally thought? Thanks, Dean