Author Topic: [Theme] Night sky shots  (Read 48551 times)

Øivind Tøien

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Re: [Theme] Night sky shots
« Reply #270 on: November 09, 2021, 23:32:00 »

Thanks for the comment Bruno, and for the tip on comet Leonard. The hope of catching the tail of a comet was what originally inspired me to buy my tracker. I have had lots of fun with it and also captured a number of comets, but none of them had any tails to speak of.

The tracker I have is the iOptron SkyTracker Classic ver. 2 (https://www.ioptron.com/product-p/3302b.htm), which is not produced any longer but might be available on the used market. (The aftercomer, Skytracker Pro probably have about the same accuracy and perhaps a better base, and there is also the more expensive SkyGuider Pro).  It seems to be a bit of a hit and miss how long users can expose with these, as they were probably originally designed for shorter focal lengths than 300mm that I usually use, and there is some variation in tolerances of the parts and how well they are adjusted. It does take some experience to work around imprecisions in the altitude adjustment of the classic version. I also removed an excessive washer from the base to eliminate wobble. Look back in the thread for more information.

What I find important with this tracker is that it allows polar alignment to take place with the camera in position, so it allows small adjustments to polar alignment under ways. It also has a good LED for the polar scope. I highly recommend to adapt a right angle viewfinder for the polar scope if you are at high latitudes like me (hardly use the one I got for the camera's viewfinder any longer after I started using my D500), there are used Nikon versions that can be had on eBay for reasonable amounts. Also, some other trackers come without the base, which can add quite a bit weight if you add a geared head to the package. Here is an image of my setup, probably repeated from earlier in this thread.



Øivind Tøien

Akira

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Re: [Theme] Night sky shots
« Reply #271 on: November 10, 2021, 12:05:54 »
Beautiful meteor image, Øivind!  I love the way the transitional colors of the trails of the meteors are rendered.
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Bruno Schroder

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Re: [Theme] Night sky shots
« Reply #272 on: November 10, 2021, 22:41:41 »
Thanks a lot for the detailed info, Øivind. It is very helpful. I would use the 500/5.6 PF which is 700gr heavier than the 300 PF.  Do you think it would work with the extra 700gr?

Thanks
Bruno Schröder

Akira

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Re: [Theme] Night sky shots
« Reply #273 on: November 11, 2021, 01:26:44 »
A while ago, I bumped into this Kickstarter project by Benro.  A tripod head with the built-in GPS, compass and astromatps:

https://www.kickstarter.com/projects/benropolaris/polaris-smart-electric-tripod-head?ref=6tba32


One of the problem I found in the astrophotography is that you had to place your tripod where you can see the Polaris to align the rotation of the tracker.  But here in Tokyo, you are not guaranteed to see the Polaris from the place you want to shoot, because of the bristling buildings.

A tripod head like this one by Benro can solve the problem.
"The eye is blind if the mind is absent." - Confucius

"Limitation is inspiration." - Akira

Øivind Tøien

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Re: [Theme] Night sky shots
« Reply #274 on: November 11, 2021, 06:40:25 »
Thanks for the comment Akira. Yes the colors of meteors with their transitions can be beautiful, and that is one of the things that makes it easy to distinguish them from satellite tracks beyond that the latter typically appear in more than one frame. Too bad the second meteor was cut off by the end of the exposure, but I think that one would mostly have displayed just the same warm color as the visible section.

Thanks a lot for the detailed info, Øivind. It is very helpful. I would use the 500/5.6 PF which is 700gr heavier than the 300 PF.  Do you think it would work with the extra 700gr?

Thanks

I have successfully used my Skytracker with the old AF 300mm f/4 ED, which is about the same weight as the 500/5.6 PF, so I do not think the weight is a problem if you are not at too low latitudes so that the polar alignment is more horizontal. It is important to balance the camera so that the weight is working slightly against the rotation. If it balancing at the tipping point slack in the gears can cause bad tracking. However although I have been able to successfully track with TC-14E added to the 300 PF, I feel that the 420mm focal length is stretching it and can be more of a hit and miss. (There is also the issue of bad seeing around here which often limits resolution.) If you could get hold of a very cheap used Skytracker classic, it would not hurt to try it out though. 

I have seen a number of very nice results from the 500/5.6 PF, but then usually on a sturdier more expensive tracker with a very low periodic error, the Fornax LightTrack II  https://fornaxmounts.com/products/lightrack-ii-mount/. It is not quite as compact as the smaller trackers, but still quite portable. It will have the disadvantage that it has to be reset during a session once the range of the arm has been fully utilized. Note that a base or extra tripod head is needed in addition to what is seen in the link.

It is also possible that the more expensive iOptron model above or the StarAdventurer could do, but then with guiding (requiring a computer setup) which will reduce the much larger periodic errors of these trackers.

I believe the tracker listed by Akira would be more oriented toward wide angle use and time lapse panning. For high accuracy one really need a polar aligned tracker, not an alt-azimuth oriented one. Also there is the risk of crowdsourcing. I have seen a number of nice results from the built in Pentax Astrotracer that is also based on GPS orientation, but then based on (limited) sensor shifts instead of moving the whole rig.
Øivind Tøien

Akira

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Re: [Theme] Night sky shots
« Reply #275 on: November 13, 2021, 23:30:59 »
Thanks for the comment Akira. Yes the colors of meteors with their transitions can be beautiful, and that is one of the things that makes it easy to distinguish them from satellite tracks beyond that the latter typically appear in more than one frame. Too bad the second meteor was cut off by the end of the exposure, but I think that one would mostly have displayed just the same warm color as the visible section.

I believe the tracker listed by Akira would be more oriented toward wide angle use and time lapse panning. For high accuracy one really need a polar aligned tracker, not an alt-azimuth oriented one. Also there is the risk of crowdsourcing. I have seen a number of nice results from the built in Pentax Astrotracer that is also based on GPS orientation, but then based on (limited) sensor shifts instead of moving the whole rig.

Thank you for the details of the meteors.  And your assessment for the tracker/tripod head makes sense.
"The eye is blind if the mind is absent." - Confucius

"Limitation is inspiration." - Akira