| What exposure time do you use? | |
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| 10 Seconds | |
| 20 Seconds | |
| 30 Seconds | |
| Other (If you use Seestar_ALP) | |
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Given the recently added update for support of equatorially mounting the Seestar, I would like to know the exposure times that you use, along with why. I am currently doing my own comparison between 10s, 20s, 30s, and would like to see the advantages of each.
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I used to use 10 s and tried 20s, depending on the target image. Last night with the Seestar S50 in EQ mode I used 30 sec. the first time, but I am not convinced as the stars are blown too much and not round anymore The roundness could also be a problem with EQ mount adjustments , but I was in all green (< 0.2) when doing the polar alignment befor imaging https://www.astrobin.com/uufkf6/E/?nc=collection&nce=45615 |
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This photo took 50 mins @ 10 sec with mosaic mode in Nov 2024.
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I have also used 10s on all my photos till date. Sadly my frame success rate has always been around 50-70 %. This despite the level being between 0.2 and 0.4. I observe that the level gets worse after a while and I always have to stop, re-Level, and go again. My wedge should arrive soon. I will try 20s or 30 s subs in the EQ mode over Easter. From what I have seen on YouTube along with comments here on Astrobin , 20s seems to be the sweet spot. Let’s see.
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I have used till now allways 10 seconds en do not change this. There has been on YouTube already a test that it does not matter. Besides to get rid of bad images it is a minor loss . Think of Plaines, satellites. The loss of images depends highly on the calibrating . You have to do ALL the calibrating options. Also in the EQ mode. Once done the loss is minimal. Maybe one or two an hour.
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In AltAz mode, without using the livestacking, and hence saving ALL the frames without exception and then stacking them offline, I get 60% useful subs at 30s, about 75-80% at 20s and about 95% at 10s. In EQ mode the results have varied a bit, and of course they vary depending on the position of the object in the sky, so far I have struggled to get consistent results even at 20s, so I wonder if it is worth the added effort. Moreover I have noticed that my S50 has a rather consistent periodic error. My latitude is 45, people at higher latitudes and/or with better specimens of S50 may get better results. I plan to buy also a S30 and try the EQ mode with it too. Main reason would be to get rid of field rotation, but since my balcony looks to the West, often I have just a reduced amount of field rotation. |
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Didn't see the ALP note for "Other" in the survey……….I do not use ALP. I expose for 10 sec when in Alt Az mode, and for 20 sec when in EQ mode. |
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I've had mixed results with EQ mode and 30 s. Last night a lot of frames "failed". Maybe 40% of them. A few days ago I used the Seastar_alp interface to have the device save and label failed frames. Upon review, all of them last night were due to smudges/streaks of stars like one would get on a windy evening, but it wasn't windy. One previous session since I had the scope save and label failed frames showed only 2 fail out of about 250. I think the main advantage of 30 sec is less .fit files to process in PixInsight. I'm going to try 20 s exposures next to see if things improve. My gut feeling is shorter exposures and more frames could help eliminate sensor noise. And maybe provide more dithering the scope seems to be doing as well. |
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I push the longest exposure I can for more detail. Last night I was able to get 60s on M101, so I shot 60s. I can get 60s on M81 as well. I could only get 45s on M51 though. I shoot the longest exposure I can and hope for 80% efficiency, but sometimes I settle for 70% efficiency. I could shoot 30s for near 100% efficiency if I wanted.
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I get elongation of smaller stars in EQ mode when I use anything more than 10 secs. The Seestar stacking program seems to accept them but since it was so noticeable I haven't tried it in Pixinsight yet.
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I got in a few hours EQ mode testing last night . 2:40 of 20s subs on part of Antlia while it transitioned from high 60’s E through 88 degrees N to low 80’s W. Very few subs failed on S50. Another 2+ hours were shot as 30 sec subs of the Antenna galaxy. Few of those failed as well. I was much more attentive to leveling the skywatcher wedge with the three wheel thing between tripod and wedge. I hadn’t used that on previous session which had so many bad 30 subs (just had made the tripod bubble as centered as possible). I’ve seen a comment leveling the wedge isn’t so critical when establishing good polar alignment, but maybe it is. Maybe more so when shooting objects lower in sky after the adjustments have have been made off high solved frames? |
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I tried 20 sec for some time but the results were the best with 10 sec. In 20 sec the no of frame drops were higher due to trails and other reason.
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I had one good 30s exposures session in Eq mode, then two bad sessions at that exp that had non-round stars, so I am now using 20s in EQ mode and it seems to be working mostly at that. Pretty much always 10s in AltAz mode.
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What I am thinking could be the problem : The Seestar fastening on the mount, it could be even worse in EQ mode. Is there a sweet spot ? How many turns? I had similar experiences of elongated stars, getting worse on longer exposure. Now I try to keep the same number of turns and remember the final position C.S. Wanni |
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I've had nothing but clouds to shoot through for a week or more, bah humbug. But I'm encouraged in a discouraging sort of way that the ovaloid stars I've seen in EQ mode are not unique to my S50. It suffered a fault of jamming itself trying to close the wrong way shortly after the release of EQ mode. The resultant grinding of the stepper motor during the period it took me to sort out how to "fix" the problem had me very worried its ability to line up and track things would be compromised. Back to exposure times. It seems pretty clear there are issues with longer times. And on the flip side, I read of beta-testers for the S50 playing with 5 sec exposures, which may apparently be coming in future versions of the software. I'm pretty vague about what other advantages 5 sec exposures would offer other than avoiding tracking issues, but apparently there are some. Anyone here know more about that than I do (which shouldn't be hard)? I can only think of disadvantages having to do with what I perceive as the time the S50 must spend doing real-time stacking. I imagine this processing gets in the way of simply making exposures. One thing I'd love to see is a mode where, after two or three exposures stacked to give visual verification one is on target, the device simply starts shooting subs and storing them as fast as it can, with time lost only to needed dithering movements. I have learned from a few sessions after having used the seestar_alp web interface to have it store failed subs, that it doesn't always fail the ones I or PixInsight would. I'm less trusting of the internal real time stacking abilities of the unit now and I prefer to do my own stacking. -Jeff |
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Jeff Parke: Live stacking also uses quite a bit of the S50’s resources, which someone had suggested I turn off live to combat against it bogging down the processing. While it does continuously shoot exposures without stopping and waiting to stack them, I wholeheartedly agree that there should at least be an option where the user can put the amount of subs that the Seestar should stack when that number is reached; be it every 50,100,200 subs etc. Skye |
