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Post by Deleted on Apr 4, 2018 22:52:37 GMT
My LX90 sct's produce very poor images compared to my cheap newts and refractors with all of my cameras and I dont know why . The 8" and 10" LX90 appear to be well collimated and give pretty sharp visuals. I use the optec nexgen ,meade .63 and meade .33 FR's with the zwo 224 and the .63 FR with the ZWO 294 and the results are all bad. I deforked the LX90 8" and put it on the HEQ5 with similar results. My cheap SW ST120 f5 refractor ,GSO f4 newts all produce clear images on EQ mounts. My 12" dob on alt/az is clear as well. Any suggestions ? Paul
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Post by Deleted on Apr 4, 2018 23:32:05 GMT
The mallincam xtreme used to work ok on the LX90, not great like some of the images I used to see online, but ok . I used a .63 meade plus a gso .5 FR but on a 1.25" diagonal. I bought the optec nexgen at about the same time as the 224 .The optec needed a 2" diagonal.Everything has looked terrible ever since.
Maybe the next step is to go back to the 1.25" . That will mean I cant use the 294 on that setup. Paul
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Post by Deleted on Apr 5, 2018 2:37:48 GMT
This is the setup of the FR's with the 2" diagonal On the left and right are the 6.3 and 3.3 meade FR's and in the middle is the Optec with camera I guess the next thing to try is no diagonal. That is ok for the 10" LX90 but the camera doesnt clear the 8" mount at 90 degrees Paul
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Post by ChrisV on Apr 5, 2018 3:26:18 GMT
You could show us some pics of the good, the bad and the ugly - bit I don't think its anything to do with collimation etc.
I think its because the 294 sensor is too big for heavy focal reduction on an SCT. You'll get massive vignetting and distortion which is OK with a really small sensor but not with a bigger one. If you look at the instructions for the meade 3.3 I'm sure its says its only for a 1/3" type sensor (~6mm diagonal) like the 224. The 294 has about 22mm diagonal !!
Maybe start by trying the 6.3 reducer with much shorter 'reducer to sensor' spacing to get lower focal reduction. If it looks better then that's the answer. Then you could try increasing the spacing and see where it becomes unbearable.
Cheers Chris
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Post by Deleted on Apr 5, 2018 6:38:16 GMT
Thanks Chris I only use the 224 on the optec and meade 3.3 but still with bad results. I havent saved any because they are bad.I use the 294 and the 224 on the meade 6.3 which can handle the big sensors but results are still poor.The spacing of the 6.3 is supposed to be about 80 and on an sct I am not sure I can shorten it because the sct adapter comes in one size . I am able to lengthen it. The optec is a fixed spacing of about 57 with no facility for variation at all. I will get rid of the diagonal and see what happens. I will get a few pics as well and post them. Paul
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Post by Dragon Man on Apr 5, 2018 11:27:04 GMT
Paul, it will have something to do with optics mathematics, and that gets complicated. Something about having the correct combination of pixel size and focal length and sensor size (which is what Chris mentioned).
For good to great results it's a bit like a recipe. Too much or not enough of something and the final result tastes bad. For us, get something odd in the mix and it looks bad.
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Post by Deleted on Apr 5, 2018 12:42:53 GMT
Thanks Ken. It is very frustrating and I am over it. I need to get the other scopes out and just enjoy these clear nights. Paul
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Post by ChrisV on Apr 5, 2018 13:47:29 GMT
As usual I didn't read the detail Paul - that it was also poor with the 224. Still a picture would really help, or a description of the problem.
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Post by howie1 on Apr 5, 2018 20:54:23 GMT
Thanks Ken. It is very frustrating and I am over it. I need to get the other scopes out and just enjoy these clear nights. Paul Bingo! I also got far better results just with newts and fracs. Which reminds me I should clear out the two SCT's I have in storage. Dylan in the astro club has won APOD and other astro imaging awards and once we talked about hyperstar and his experiences with reducers on SCT's. He's an SCT man through and through. He said frequently pixels looked oversaturated / blurry with reduced SCT's but weirdly SCT designs with built-in low F Ratio like the RASA SCT's did not and were great to image with. Perhaps as well as finding the "sweet spot" re pixel size to arc secs, the more glass in the system the more aberations creep in also (even if you buy the dear as poison "good" reducers and correctors!). Everything is a compromise, and its hard to find the right combo. In order to keep going I keep telling myself that if it was easy it wouldn't be worth doing. LOL
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Post by Deleted on Apr 6, 2018 5:36:06 GMT
Chris ,the problem is with all the cmos cameras on both LX90's.Having no trouble with the newts and refractors. I removed the 2" diagonal last night and really couldnt even get a focus to get a pic. Have just replaced the 2" with a 1.25 " diagonal . I will use the same configuration as I used with the mallincam Xtreme with a meade 6.3 and prostar .5 fr.and diagonal in between. Paul
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Post by Dragon Man on Apr 6, 2018 13:28:00 GMT
Paul, I remember you using your little SCT here at my place and you had a fantastic detailed view whereas I was struggling that night. Can you remember what camera/combo were you using the night you used your little SCT here?. I think it was the Infinity but I might be wrong.
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Post by Deleted on Apr 6, 2018 14:19:29 GMT
That was the 6SE with hyperstar and the 290 or 224.It is my grab and go kit and works well.The Infinity is a big brick sitting on the hyperstar so I dont tend to use it on the 6SE. Had another attempt at different combinations of FRs and spacing with the LX90 tonight. Still getting rubbish pics. Time to give the other scopes a go while we still have these fantastic clear nights
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Post by Deleted on Apr 6, 2018 14:39:07 GMT
Howie I saw some of Dylans pics in Sky and Telescope with the RASA SCT. It is reassuring that he is an SCT man. There must be some combination of camera reducer that works on my SCTs but it is too hard basket at the moment. Time to get the newts and fracs out
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Post by Deleted on Apr 10, 2018 4:50:50 GMT
I removed the diagonal and things improved a bit. ZWO 224 + prostar .5 FR and Meade 6.3 FR . LX90 8" M65 30sec
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Post by Deleted on Apr 12, 2018 12:35:30 GMT
This is M65 30s with LX90 8" on Sharpcap ZWO 294 with Meade 6.3 and Altair .6 FR together. Lot of trouble out at the edges but it is possible to use 2 FR's together with the big 294 sensor When I just used the Meade 6.3 and no Altair, the 30s exposure was very dim. At least I can now see the DSO With a 45s exposure, the stars begin to elongate and with a 5 x 30s stack the pic becomes quite blurred. Certainly limited to 30s with the Alt/Az
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Post by Dragon Man on Apr 12, 2018 15:06:47 GMT
Fantastic result Paul
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Post by Deleted on Apr 13, 2018 3:43:25 GMT
Have deforked the LX90 8" and will give it another crack on the HEQ5 now that I can get a focused pic at 30 secs. Will get a DSO on the 8" f4 newt for comparison. Paul
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Post by howie1 on Apr 13, 2018 5:01:05 GMT
This is M65 30s with LX90 8" on Sharpcap ZWO 294 with Meade 6.3 and Altair .6 FR together. Lot of trouble out at the edges but it is possible to use 2 FR's together with the big 294 sensor When I just used the Meade 6.3 and no Altair, the 30s exposure was very dim. At least I can now see the DSO With a 45s exposure, the stars begin to elongate and with a 5 x 30s stack the pic becomes quite blurred. Certainly limited to 30s with the Alt/Az Hi Paul, if a single 30sec image is sharp, then it is very odd that a stack is blurred. Check if the "Align frames" checkbox in Sharpcap is selected. I suspect when you started M65 was in a part of the sky where 30 sec frames did not show any field rotation. Hence the shot was sharp. I think you then may have started trying out 45 s and so on and then later on decided 30 sec worked so you set 30 sec and started a stack of 5? Was that the case? Because within half an hour the object has moved more towards North and higher in Alt and is then in a part of the sky where even a 25 sec frame shows field rotation ... hence every frame would have blurred stars. If you stack blurred frames then you'll get a blurred final image. And of course conversely ... if you stack sharp images then you'll get a sharp final image. You're latitude 37 in Bendigo. Table is for MAX exp times before field rotation effects at lat 40 (but it doesnt have to be exact so it will work fine for you). And really important to note ... 1. all the times in the table are for the MAX poss single exposure time ... underline the word MAX!! If your mount is low-end then the gear sets, motor pulses, track speed are all much less refined than high end Alt Az mounts (like the evolution which I know exceeds the MAX times in my AltAz exp times tables attached). So you mount might never get those MAX times, but it will get close. So use the table as a guide. 2. all times over 45 to 50 secs are NOT possible ... underline the word NOT!! Unless as above using Evolution AltAz which I've seen go 65 secs in some parts of the sky. cheers
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Post by Deleted on Apr 13, 2018 7:39:45 GMT
Thanks for your input Howie You are correct. That is about how I did it. I often turn Align Frames off if Sharpcap starts ignoring frames because there is no alignment
I have just now deforked the 8" and mounted it on the HEQ5 hopeing for clear skies tonight, but that is not going to happen. I still have the 10" on Alt/Az forks. I have generally accepted that 30 secs will be max on the alt/az and if I stack ,I try 12 to 15 secs x 5 and try and keep the total round about a minute .
You have posted that table before and I have been amazed at those max times at lower altitudes and 90 and 270 az. I now realize I should have been taking better note of the max times at high alt which is more relevant to my 30 sec rule. There is a lot of sky that wont handle 30 secs in alt/az so I need to be more aware of that in future.
Now that I am fairly comfortable with EQ mounts, my alt/az mounts will mainly be used for grab and go with the C6 or when using the Dob. Paul
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Post by Dragon Man on Apr 13, 2018 13:18:30 GMT
. . . hopeing for clear skies tonight, but that is not going to happen. Paul Correct. Cloud, rain, and damaging winds for all of us tonight and tomorrow Paul
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