Budget Astrophotography: Polarie, Astrotrac, Advanced VX

Gear recommendations, reviews and rants.

Re: Budget Astrophotography: Polarie, Astrotrac, Advanced VX

Postby steve-fung » Sun Jan 17, 2016 10:56 pm

Ed,

That is very interesting you are not getting decent stars even with short exposures. Presently, my wide-field astrophotography exposure time is limited to the 600 rule because I use a fixed tripod. Even then, I notice slight streaking of stars when I zoom into the image. It cannot get worse than that with this mount, can it? Christopher O on Netslyder mentioned that he was able to track at 600 mm focal length for the entire length of a lunar eclipse, which to me is pretty amazing. I do not think I will even attempt that focal length with this mount, maybe 200 mm at most but staying mostly on the 14-24 mm side for wide-field astrophotography. I assume you made sure the polar scope was collimated with the mount axis, rotational direction slide switch was set to "N", and the mode dial was set to celestial tracking (star) and not some other setting (lunar, solar, 0.5-12x). I am very tempted to take you up on your offer, although given the mount's relatively low price (actually less than Polarie and AstroTrac), I will probably order it just to play with it.

Steve
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Re: Budget Astrophotography: Polarie, Astrotrac, Advanced VX

Postby steve-fung » Tue Mar 22, 2016 4:56 am

As a follow up, I recently purchased the Sky-Watcher Star Adventurer Astro Package with optional counterweight and equatorial wedge base (total ~6.85 lbs), which mounts nicely on my Manfrotto 055XPROB tripod. Although the battery and polar scope covers are made of plastic, build quality was better than I thought with relatively sturdy feel and no loose parts. I was glad that I purchased the equatorial wedge, which allows for fine altitudinal and azimuthal adjustments for polar alignment (better than my 410 gear head, which has a bit of slop with axial loading), although the altitudinal clutch lever seems to be made of hard plastic and may someday break with over-tightening. I checked the polar scope alignment during the day and was pleasantly surprised to find it was already aligned with the RA-axis and did not require further calibration.

Instructions that came with the mount for polar alignment were fairly confusing - not sure who actually uses date-time graduation circles to determine orientation of Polaris in the polar scope reticle. My advice is to make sure the mount and tripod are level with the ground by using the attached circular bubble levels and then use a polar alignment program (e.g. Polar Scope Align Pro - see attachment), which calculates the position of Polaris in the polar scope reticle given local time and location (GPS).

Last night, I finally had time to take the setup to a local park for testing. Polar alignment was fairly straightforward with Polar Scope Align Pro on my iPhone. I turned on celestial tracking on the mount, attached the fine-tuning mounting assembly with counterweight, and mounted my camera (Nikon D800 with 70-200 mm f/2.8 lens). I took three 30s exposures at 70 mm focal length, f/2.8, ISO-800 of the Orion constellation. Images were fairly washed out given Houston light pollution, including lights from nearby tennis courts. Moon was also waxing gibbous, which did not help. I did not see any significant streaking of stars when magnified closely, although I should have also taken some pictures zoomed in at 200 mm focal length.

Enclosed images:
(1) Star Adventurer equatorial setup on Manfrotto 055XPROB tripod with attached Nikon D800, 70-200 mm f/2.8 lens, balanced counterweight.
(2) Sample image of Orion constellation taken with three stacked 30 s exposures at 70 mm focal length, f/2.8, ISO-800 (post-processed to remove sky glow from light pollution).
(3) Sample images from Polar Scope Align Pro showing various reticle designs from (a) Orion/Sky-Watcher, (b) Losmandy/Astrotrac/Kenko, (c) Vixen Polar Axis Scope.
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Last edited by steve-fung on Sun Mar 27, 2016 1:54 am, edited 1 time in total.
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Re: Budget Astrophotography: Polarie, Astrotrac, Advanced VX

Postby steve-fung » Sat Mar 26, 2016 11:44 pm

Here is my second attempt at AP using the Sky-Watcher Star Adventurer mount. This time, I took five 30 s exposures at 200 mm focal length, f/4.0, ISO-800 of the Orion Nebula. Again, source images were fairly washed out from Houston light pollution. There was no significant streaking of stars when magnified closely. Mainly, I did this to prove that one can use this very basic mount setup with simple polar alignment for AP even at 200 mm focal length.
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