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02-27-2020, 12:42 PM   #1
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Astrotracer and large mm lens

Good day. Two years of great success using the Astrotracer on multiple lens/multiple Ap, Shutter and ISO settings -- until now: Sigma 150-500mm...set up all same- all working, and Sigma lens bells/whistles turned off: Shutter I am limited to no more than 30 seconds. If I go straight (True Bulb) this avenue works, but I rather not rely on yet another step (me) to keep consistent accurate shutter time. Any ideas why the 30 second ceiling? I can immediately tack on any other lens; perform the setup and all is great...so the possibility of internal configuration changes is not present.

Thank you.


The answer came to me earlier--backed up by fellow members. Thanks all.


Last edited by OSRags; 02-27-2020 at 02:15 PM.
02-27-2020, 01:35 PM   #2
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QuoteOriginally posted by OSRags Quote
Good day. Two years of great success using the Astrotracer on multiple lens/multiple Ap, Shutter and ISO settings -- until now: Sigma 150-500mm...set up all same- all working, and Sigma lens bells/whistles turned off: Shutter I am limited to no more than 30 seconds. If I go straight (True Bulb) this avenue works, but I rather not rely on yet another step (me) to keep consistent accurate shutter time. Any ideas why the 30 second ceiling? I can immediately tack on any other lens; perform the setup and all is great...so the possibility of internal configuration changes is not present.



Thank you.
If you are using the Sigma at 500mm I wouldn't expect times longer than 30 seconds to be available using Astrotracer. If you use True Bulb then Astrotracer is turned off.

02-27-2020, 01:56 PM - 3 Likes   #3
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I found something curious on Ricoh's website..

Under 'Astrotracer' section it says:
"Telephoto photography is available up to a focal length of 135mm"
PENTAX: The choice for astrophotography / explore | RICOH IMAGING

I've seen images also on Ricoh's website showing the use of a 200mm lens for Astrotracing sample images as well..
ASTROTRACER | GPS UNIT O-GPS1 | RICOH IMAGING

Soooo I don't really know..
02-27-2020, 02:04 PM   #4
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At 500mm, the stars move a long way in 30 seconds and can push the astrotracer system to the motion limits of the IBIS system.

Stupid spinning planet!

02-27-2020, 02:12 PM - 1 Like   #5
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QuoteOriginally posted by slartibartfast01 Quote
If you are using the Sigma at 500mm I wouldn't expect times longer than 30 seconds to be available using Astrotracer. If you use True Bulb then Astrotracer is turned off.
Thanks. Yes, the basics of Sensor and focal length slipped from this mind... age or just anxious...lol.

---------- Post added 02-27-20 at 03:14 PM ----------

QuoteOriginally posted by photoptimist Quote
At 500mm, the stars move a long way in 30 seconds and can push the astrotracer system to the motion limits of the IBIS system.

Stupid spinning planet!
Thanks. Yes, the basics of Sensor and focal length slipped from this mind... age or just anxious...lol.
02-27-2020, 04:45 PM   #6
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Beyond that, you might consider a tracking mount. With such a mount, you'd have considerably longer times for exposures and with ultra-wide lenses, stars stay sharp to the edges (assuming the lens is sharp to begin with). They also work with longer focal lengths though alignment requires more work and photos are more sensitive to drive errors. There are some reasonably priced tracking camera mounts available which fit standard tripods (a good, fairly heavy tripod is recommended). Astrotracer is great for some applications when a mount is unavailable, but it has its limitations. Some astro-mounts (maker and models) are listed below along with their load limits.

iOptron SkyTracker Pro 6.6 lbs.
Sky-Watcher Star Adventurer 10 lbs.
iOptron SkyGuider Pro 11 lbs.
Fornax Mounts LighTrack II 13.2 lbs.
02-27-2020, 08:14 PM - 1 Like   #7
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QuoteOriginally posted by FozzFoster Quote
I found something curious on Ricoh's website..

Under 'Astrotracer' section it says:
"Telephoto photography is available up to a focal length of 135mm"
PENTAX: The choice for astrophotography / explore | RICOH IMAGING

I've seen images also on Ricoh's website showing the use of a 200mm lens for Astrotracing sample images as well..
ASTROTRACER | GPS UNIT O-GPS1 | RICOH IMAGING

Soooo I don't really know..
Wow, I've never seen that link, thanks.
02-28-2020, 06:52 AM   #8
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With good calibration, you can go longer than 135mm. I've seen 200 or 300.
But, exposure times will be pretty short, and the object will track out of the lens field of view after just a couple of shots, requiring repointing the lens.

Basically if you're trying to do a lot of imaging using a lens longer than 250 or so, you're probably better off getting a tracking mount.

02-28-2020, 07:34 AM - 1 Like   #9
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QuoteOriginally posted by OSRags Quote
Shutter I am limited to no more than 30 seconds.
When you say limited to 30 seconds do you mean you can't set astrotracer to take a shot longer than 30 seconds or that you get garbage results beyond 30 seconds. If it is the first it sounds like something is wrong with your setup if it is the later then it seems normal. I regularly shoot with astrotracer and a 400mm lens but am limited to about 20 seconds before I start getting bad results (unacceptable to me) and I will run a 300mm lens at 30 seconds. Here is a single shot I captured with my 400mm and astro tracer at 20 seconds. This was a throwaway shot as it was the first one I took right after getting everything setup to check calibration and find out where the lens was at cooling down. This lens takes a long time to come into thermal equilibrium and until it does it shows really bad coma which it is doing here and this was also shot wide open instead of stopped down 2/3 of a stop.

At 500mm I think I would be hard pressed to get even a 20 seconds shot I would consider a keeper.

QuoteOriginally posted by SteveinSLC Quote
Basically if you're trying to do a lot of imaging using a lens longer than 250 or so, you're probably better off getting a tracking mount.
In the long run if one gets serious about astro imaging yes, but for someone just getting started or as a stepping stone it works well enough with longer glass. Although I would say that the 500-600mm range is probably the upper limit of what one could reasonably expect any decent results.

As far as setting expectations of what one can accomplish with longer glass here is a processed stack I that was captured with my 400mm, K-3, and O-GPS1 with astrotracer. At present I do want to move up to an equatorial mount but it will have to be a bigger one and not one of those little ones as the lens I use alone would exceed their maximum capacity and to ensure smooth operation really need one with a capacity of 30+ LBS.
02-28-2020, 09:32 AM   #10
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Iíve managed 50sec with a 200mm lens, donít know what went wrong - never managed to achieved it again.
1x50sec, K-70, M200 f4, Whirlpool Galaxy


18x50sec, K-70, M200 f4, Whirlpool Galaxy heavily cropped


35x10sec @ISO1600, K-70/DA*300mm
02-28-2020, 05:42 PM   #11
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QuoteOriginally posted by DrawsACircle Quote
I’ve managed 50sec with a 200mm lens, don’t know what went wrong - never managed to achieved it again.
By chance did you sacrifice a chicken before hand?
In all seriousness astrotracer is rather finicky but with experience one can get good to pretty good results consistently with a few outstanding ones every now and then.

I should start chasing the whirlpool again next month when it gets above the ravine walls and trees where I like to shoot in the nearby dark area. Now I need to figure out how to get it in frame with my 400.
02-29-2020, 08:31 AM   #12
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QuoteOriginally posted by MossyRocks Quote
By chance did you sacrifice a chicken before hand?
In all seriousness astrotracer is rather finicky but with experience one can get good to pretty good results consistently with a few outstanding ones every now and then.

I should start chasing the whirlpool again next month when it gets above the ravine walls and trees where I like to shoot in the nearby dark area. Now I need to figure out how to get it in frame with my 400.
My neighbour couldn't find one of his the day after - I think you need more than one chicken to get the Whirlpool Galaxy in the FoV on your 400mm lens
Next you need to keep it there, that's also a nightmare. I used a faint star, tried to keep it in the same area in liveview.
You only need a mouse farting in the neighborhood and the Whirlpool is gone.

Last edited by DrawsACircle; 02-29-2020 at 08:42 AM.
03-01-2020, 07:52 PM   #13
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QuoteOriginally posted by DrawsACircle Quote
I think you need more than one chicken to get the Whirlpool Galaxy in the FoV on your 400mm lensNext you need to keep it there, that's also a nightmare. I used a faint star, tried to keep it in the same area in liveview.You only need a mouse farting in the neighborhood and the Whirlpool is gone.
That 2.8 makes a lot of things visible through the viewfinder. Even in my backyard I can make out some the M31's disk.


With my 300mm once I would get it in the view finder I would keep a guide star in the correct general position. I actually got really good at getting it in the frame with that 300 when I went after it 2 summers ago. As far as a mouse farting knocking things off I'm not too worried with the tripod I stick things on.
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