question regarding mount behavior in different positions

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graywmj5
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question regarding mount behavior in different positions

#1

Post by graywmj5 »


Hi all,

Tonight i was attempting some unguided shots using the LX85 mount and 70MM APO Quad.

With my scope on M51, I took numerous 90 second subs with no star trails, and felt very good about my alignment.
I then moved the scope to M81 and found that even with 10 second subs I had severe star trails.

I would appreciate any ideas on what would cause the differences moving from location to location.

Thanks, Bill
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ram United States of America
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Re: question regarding mount behavior in different positions

#2

Post by ram »


Well, did imaging M81 cause you to point your scope straight at the celestial pole? I think unlikely but usually when you are imaging right near the celestial pole, PA is more sensitive.

Did you go back to M51 and see if you could still do the 90 second subs?

--Ram
Tubes: Celestron 9.25" 235mm f/10 XLT EdgeHD SCT; Meade ETX 80mm f/5 achromat; Coronado SolarMax II 60mm f/6.6 Hα <0.7Å BF10 solar; Stellarvue 70mm f/6 triplet apochromat; Obsession UC18 457mm f/4.2 with Argo Navis & ServoCAT; Takahashi FS128 5" f/8.1 and FC100DF 4" f/7.4 fluorite doublet apochromats. Mounts: AVX; LXD75; Paramount MyT. Eyepieces: 2" Tele Vue Ethos 4.7/13/21mm, Paracorr, 2,4x Powermate; Stellarvue 0.8x, Takahashi 0.7x, 0.66x reducer/corrector. Cameras: ZWO ASI120MC-S; Lodestar X2c; X2m; Canon T7i; QHY163M; QHY247C; QHY294M-Pro. Filters: 1.25" Astrodon 5nm Ha, 3nm O3 and S2; Chroma LRGB.
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JayTee United States of America
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Re: question regarding mount behavior in different positions

#3

Post by JayTee »


Typically when this behavior happens, not being properly balanced is usually the culprit. Were M51 and M81 on different sides of the meridian?

Cheers,
JT
∞ Primary Scopes: #1: Celestron CPC1100 #2: 8" f/7.5 Dob #3: CR150HD f/8 6" frac
∞ AP Scopes: #1: TPO 6" f/9 RC #2: ES 102 f/7 APO #3: ES 80mm f/6 APO
∞ G&G Scopes: #1: Meade 102mm f/7.8 #2: Bresser 102mm f/4.5
∞ Guide Scopes: 70 & 80mm fracs -- The El Cheapo Bros.
∞ Mounts: iOptron CEM70AG, SW EQ6, Celestron AVX, SLT & GT (Alt-Az), Meade DS2000
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∞ EPs: ES 2": 21mm 100° & 30mm 82° Pentax XW: 7, 10, 14, & 20mm 70°

Searching the skies since 1966. "I never met a scope I didn't want to keep."

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graywmj5
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Re: question regarding mount behavior in different positions

#4

Post by graywmj5 »


Thanks for both the responses!

M51 was in the northwest sky and somewhat high. M81 was also in the northwest sky but much lower to the point that it was lower in altitude than Polaris. I did not go back to M51, but that would have been a good excercise. Might do that tonight, conditions permitting.

Thanks!
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