PA with a dobsonian

Using SharpCap's Polar Alignment feature
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Tiago Ferreira
Posts: 143
Joined: Sun Mar 21, 2021 10:50 pm

Re: PA with a dobsonian

#21

Post by Tiago Ferreira »

DanK wrote: Tue Aug 17, 2021 5:16 pm This is great Tiago and Robin! Exactly what I needed

Dan Kahraman
I'm still testing every night and couldn't figure yet what variable made the change from consistent to inconsistent results.
It was since i've changed the weight of my set up. It was not the springs or loosen objects. I tend to think that i had a certain weight that when resetting the platform didn't move anything and now that is lighter when i reset the platform it stops at "zero/start" abruptly and change mainly on latitude consistency readings. Anyway, today i had to change again the scope to install an auto focuser and again i increased the weight a bit so i will see if it has any impact. Could also be the need to rebalance. I have no solid conclusion yet and i'm doing my best to make this work for me and everybody. I use drift alignment successfully but it's boring. It could help someone to try and post here the feedback to compare. Who knows if the issue is from my set up and we are loosing the opportunity to make this simple tool work well with a dobsonian in an eq platform? Try it.
Youtube channel: https://youtube.com/@DobsonianPower

12" f/5 Dobsonian GSO
8" f/6 Dobsonian GSO
6" f/5 Dobsonian Go-To Virtuoso Gti
Dwarf II Smart Telescope
Geoptik Eartha Eq Platform
ZWO ASI224MC + ZWO ASI294MC
User avatar
Tiago Ferreira
Posts: 143
Joined: Sun Mar 21, 2021 10:50 pm

Re: PA with a dobsonian

#22

Post by Tiago Ferreira »

Unfortunately i suspended this experience a week ago. I have my setup polar aligned by the drift method and using the sharpcap PA feature keeps returning nonsense results. I tried everything i could think but it just can't have consistent readings even knowing i have it aligned. So i give up.
I'm not sure but i think the problem is that my eq platform reset button do the reset fast and with strength and the telescope always bump after reset. Although this doesn't affect the alignment at all and it's comfortable not to wait for the reset too long, it will affect a precision measure from point A to point B as sharpcap do so this can't be done with my setup. It's a beast.
Thus in my situation the drift method using sharpcap live stacking still the best method for me to fine tune, simple and easy, although require time to watch and correct the drift and that's why i put an effort in sharpcap PA feature to work.
At least we've tried, thank you Robin to support this experiment, and the door is open because i believe that this still can be done with a different dobsonian set up. May be someone in the future can make it work and worth...
Youtube channel: https://youtube.com/@DobsonianPower

12" f/5 Dobsonian GSO
8" f/6 Dobsonian GSO
6" f/5 Dobsonian Go-To Virtuoso Gti
Dwarf II Smart Telescope
Geoptik Eartha Eq Platform
ZWO ASI224MC + ZWO ASI294MC
MikeHuerto
Posts: 75
Joined: Thu Jan 21, 2021 12:05 pm
Location: Spain

Re: PA with a dobsonian

#23

Post by MikeHuerto »

timh wrote: Sun Jun 27, 2021 9:56 pm Hi,
Can you explain in very simple terms what it is that you have done here? I also have a Dobsonian mounted scope but I don't understand what it would mean to polar align such a set up other than by changing the mount so that it was turned into an Equatorial? Is it that you have tilted and clamped the base so that the Zenith position is now aligned with the pole. In my case - to achieve something similar - I removed the scope entirely from its Dobsonian mount, put tube rings and a dovetail on an remounted it on an Equatorial mount. Thanks..it seems intriguing.

I couldn't get the link to work?

TimH

PS Apologies for the question..I just found the Geoptik platform on google. How ingenious!
@ Tim,

So looking at your fantastic Astrobin images recently, can I assume that you eventually purchased a 200 Netwonian OTA to put on the equitorial mount. I am just curious as to why the the Dobson OTA plus rings and dovetails did not work out for you. Too much tube flex perhaps? I assume Dobson tubes are not designed to pivot on an EQ mount.

@Tiago, thanks for sharing your experience, Very interesting and useful for others attempting this

Mike
Bortle 5
Skywatcher GOTO Synscan 14" Dobson
Skywatcher 130PDS on HEQ5
ZWOASI224MC and ASI294MCPro
Laptop = Lenovo Legion 5 FullHD 144Hz (Intel Core i7-10750H, 16GB RAM, 512GB SSD, NVIDIA RTX2060-6GB, Windows 10
timh
Posts: 515
Joined: Mon Aug 26, 2019 5:50 pm

Re: PA with a dobsonian

#24

Post by timh »

Hi Mike,

Many thanks for your kind comments on my Astrobin efforts.

Although I really liked the Synscan 250 as an ideal goto visual and EEA scope I ended up selling it. With two tube rings, a top bar and a f = 400mm finder scope on top it was pushing the weight on the CEM70 mount. The set up did in fact nevertheless work OK - but there was - exactly as you suggest- a bit of tube flex and the focuser I had on it just wasn't good enough for high quality astrophotography with the camera weight.

So, I decided to sell in order to part pay for the purchase of an aluminium tube Orion Optics VX12 (300 mm F =4) which, although bigger diameter, is in fact lighter than the 250 Synscan. I don't have that yet but am looking forward to its delivery - we will see how that goes. I was fortunate to already have the SW200PDS which - with a Baader focuser and Pegasus focus controller - really has performed better than I had any right to expect for what is really not very expensive scope.

best wishes
Tim
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