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Star adventurer

gary1968

By gary1968
in Discussions - Mounts

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dph1nm

dph1nm

Posted
Posted
This is an animated GIF of Capella two 10min images taken 10min apart, the star movement is in RA caused by the mount not keeping up with the stars.

Looking around the web, the periodic error seems to around 20-30" peak-to-peak.  So I would expect 10mins at 300mm to show trailing in RA. You might get away with 2mins I guess.

NigelM

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  • 2 weeks later...
Davey-T

Davey-T

Posted
Posted

Just got replacement SW SA head from FLO, their usual excellent service, no clear sky so I've set it up on the dining room table with a laser level on the dovetail, leaving it running for 24hrs to see how accurate a full sidereal rotation is just to get some idea, couldn't keep up with stars for more than 60 secs before.

Dave

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hobsey

hobsey

Posted
Posted

Good luck with it.

Managed to have a proper go with mine the other night, managed 2 minute subs, unguided at 200mm. 

Just a shame the lens was much good, bloated the stars and couldn't focus to infinity with the lens adapter.

bloatedstars.jpg

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lensman57

lensman57

Posted
Posted

Good luck with it.

Managed to have a proper go with mine the other night, managed 2 minute subs, unguided at 200mm. 

Just a shame the lens was much good, bloated the stars and couldn't focus to infinity with the lens adapter.

bloatedstars.jpg

I think that you maybe expecting too much from this little thing. An Astrotrac, probably more accurate, has a maximum recommended sub length of 300s with a relatively widefield lens, about 70mm of FL,  if the PA is absolutely spot on and about 2 or 3  minutes with a 300mm lens . I have a feeling that these were really designed for true ultra wide field imaging and their strength is the portability. I am sure that these were never intended to replace a proper tracking mount. Whatever the claimed maximum payload is divide it by 2 and you get close to the real capacity.

A.G

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Tinker1947

Tinker1947

Posted
Posted

Very interested in this thread, i'm thinking about buying one and have order all the bits to make a 5v stable PSU, running from 8 rechargeable (9.6v into a 7805) hoping this drives it ok, i have a Sigma 150mm 2.8 and a 5200D DSLR, so just waiting on the after Xmas testing to see how it tracks, good luck and merry Xmas.

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hobsey

hobsey

Posted
Posted

just waiting on the after Xmas testing to see how it tracks, good luck and merry Xmas.

Personally, I think it tracks very well.

The above image is with my first proper attempt at polar alignment and as a newbie to imaging I'm happy with the results.

I don't intend to go above 200mm and with the 2.8 I can shorten the exposure times eliminating trailing due to poor alignment.

Only with practice will I get better.

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Davey-T

Davey-T

Posted
Posted

Here's the result of my 24Hr test with new SW SA Head, laser level mounted in dovetail projecting a starting point on the wall marked with pen and the laser red dot showing the position after 24Hrs. Not particularly rigorous scientific test but looks pretty good for 3min subs.

Might even get to try it tonight :)

Dave

post-21198-0-75242900-1419440792_thumb.j  post-21198-0-24978500-1419440794_thumb.j

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hobsey

hobsey

Posted
Posted

Good luck and clear skies, look forward to seeing your results if it stays clear for you.

I was going to have another go this evening but looking a bit iffy.

I was laying off the beer just in case I went out as I have to drive but I think I will give in and crack a bottle open and leave it for another night.

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Davey-T

Davey-T

Posted
Posted

Set up outside but getting cloudier by the minute, forecast says clear ?.

Polar scope is not perfectly aligned, unlike the first mount which was spot on, but not going to mess with it tonight, just left it running to see if Polaris tracks nicely round the reticle like the last one did, will then try some pics if I can still see some stars, just found the camera battery is nearly flat so have to wait for it to charge now.

Good excuse to have a scotch as it's a bit chilly out.

Dave

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Davey-T

Davey-T

Posted
Posted

Orion and Hyades through cloud.

Canon 60da, Canon 20mm 2.8, 240secs

Started with my widest angle fixed lens and will work my way up to 300mm, stars look nice and round so far and the PA wasn't spot on, given up now, too cloudy.

Dave

post-21198-0-06310900-1419460896_thumb.j

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Davey-T

Davey-T

Posted
Posted

Got the replacement SW SA set up last night for Comet Lovejoy, definitely tracks better than the first one.

10x60secs 60Da, ISO 800, 300mm f/4

Faint suspicion of a tail in the original but disappeared on upload

Dave

post-21198-0-03461000-1419860345.jpg

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