In addition Shawn, I am concerned before buying the Apex ED L reducer flattener if I would get elongated stars in my image and related proper adapters that would be needed to attach my Esprit 120 and the ZWO 2600, besides those adapters included with the camera…your comments please on this would be appreciated. 😊🔭
Pretty solid evidence for why you need to take, and apply, proper calibration frames. Of course, I probably would have deleted the sample boxes in the Pelican 😜
Thanks! Haven't sorted out the BF yet Jim. Seems I errored with my previous calculations and did not account for 6mm on the camera side. I have another adapter/spacer coming. So new spacer would place me right at 58mm based on revised calculations. It will probably arrive when the rain and clouds return! But hopefully I'll be able to do some testing this coming week.
I agree completely with your point on the use of calibration frames - they are absolutely essential for removing vignetting, dust bunnies, etc. I've seen one of your videos before about using DBE with samples just located around the outside of the image, and I've used that for removing gradients from things like light pollution or moon glow, where the gradient is a gradual one from one side or corner of an image to the other, where it works well. I don't think that method can remove residual vignetting though - vignetting is a difference in brightness between the centre and outside of the image, so if you have no sampling of the centre, I'm not sure if it can make an appropriate correction. Adam Block has shown some interesting techniques for the removal of residual vignetting, but that involves using the axial symmetries feature for placing samples and involves a certain amount of trial and error. Like Pompey Monkey, I've always found that decent flats (and maybe I've been lucky in this respect too with my home-made flat panel) work like a charm and I'm then just left with my terrible light pollution to deal with :-(
I’m happy with flats to deal with vignetting, but am also wondering if you’ve found a Backfocus choice that gives good star shapes to aps-c corners. Any joy on this?
Nice tutorial! I think the real issue is the stars quality at corners. I tried last night to adjust the back focus of my Apex 0.65 without success. Vignetting can be solved easily. It is possible to show corners closeup so we can see stars quality? Thank you, Mario
Check out my previous videos on the APEX. I'm working also on getting the BF correct to fix the stars in the corner. This video about vignetting I did because I had complaints that the APEX had bad vignetting. But as I demonstrated it can be removed.
I've heard a lot of people say this reducer is not meant for APS-C sensors when used with the Esprit 100ED. The argument over on cloudy nights is that since you only have a 26mm image circle, the corner stars will ALWAYS be subpar and require cropping. I don't own this reducer myself, but I'm wondering what your honest opinion is on the corner performance with APS-C?
I had the same problem in my svbony triplet . The vignette was enormous (about 20% of frame), not usefull for me... For his sensor ( I think) minor than 1 inch will be not a problem...
Great video Shawn! 👍👍 I have two questions for you: 1. During a long exposure, seeing blurs/enlarges the star images. Has the incorrect spacing between the reducer & the sensor produced abberations that are significantly larger than the typical blurring/enlargement of stars due to seeing during long exposures? 2. Given that vignetting means less signal reaching the edges & corners of the image, but still similar levels of thermal & read noise, I would think that the S/N ratio & the resulting dynamic range would be less along those edges & in the corners (even after applying flats, Dynamic Backround Extraction, and other processing). Have you noticed any signs of the reduced dynamic range when stretching, applying curves & other processing? I guess it would not be terribly problematic when the target subject is centred & doesn't reach the outer part of the field, but in some cases (large object like IC1396, doing mosaics...) I wonder if the vignetting could still become problematic because the outermost part of the field lacks the dynamic range of the inner portion.
I've done flats with t-shirts (even a black one!), handkerchiefs, or no cover at all, illuminated by the sky or a local lamp, and with a dedicated flat field device (Alnitak flip-flat). I've never experienced any issues. They just work. I don't understand how people have problems. Maybe I've just been lucky. Also, as suggested by the masterful (venerable?) Olly Penrice, I've just used the luminance flat master to calibrate my subs, whatever the imaging filter is. Again, it just works. Am I charmed? lol ;)
Thanks for the comment. I usually shoot falts for all filters. As Tim points out, there can be slight differences, such as dust. But interesting approach to just use the lum flat master. If it works for you that's great!
"I've just used the luminance flat master to calibrate my subs, whatever the imaging filter is. Again, it just works." I believe that would only work if your filters are spotlessly clean. Generally you should take flats on a per-filter basis.
Did you ever tried the TSRED379 with that scope? I am waiting for clear nights to test out this combination. It is not reducing that strong and should give less vignetting and better stars at the edge. Maybe ;)
@@VisibledarkAstro Yes, I am using the ESPRIT 100. I got an adapter from TS that is specifically made for connecting this reducer to the Skywatcher focuser. I also own the QHY268C. Can't test full frame but APS-C.
Yes but the point I wanted to make is that the vignetting can be dealt with and obtain a good result. Some people complain about the vignetting. I wouldn't use larger than APS-C with the Apex. Rumour is they are developing one for larger sensors.
@@VisibledarkAstro Better to use a sensor that is the right size if your image goes all the way to the edges. Otherwise you are just stretching the edges more and creating more noise there. Why spend extra $$$ on a larger sensor if it just means it knocks you back a stop.
@@TheNarrowbandChannel this wasn't about buying larger sensors. And most aren't using small sensors anymore for deepsky. Was demonstrating how the vignetting could be addressed with it.
@@VisibledarkAstro Yes I see that. Just saying an even easier solution is just to go with a smaller sensor. Then you do not loos the speed that you gain with a focal reducer. It is like sampling. You do not want to buy a sensor that is over or under sampled. Also bear in mind that larger sensors have mainly older technology in them. The smaller ones ie Cell phone sensor have like 4-5years newer technology in them.
@@VisibledarkAstro if I can offer a suggestion - wait to switch between paragraphs, not just sentences? It's a lot less jarring if it's in the middle of a longer pause (and less frequent) if I compare to other YT channels.
@@OlliesSpace Thank you. I appreciate your positive comment. A lot of time, money and knowledge go into making the videos and keeping the channel going for the benefit and help of the astro community. Thanks again.
Thanks Shawn, I love your approach in presenting the perceived issues, analysis and approach to resolving.
Keep up the good work
Much appreciated!
Hi Shawn , what was the sensor size of your camera, in this case?
Thanks Shawn I'm pretty new to Pixinsight so some good tips here. Cheers.
You're welcome! Thanks for watching.
In addition Shawn, I am concerned before buying the Apex ED L reducer flattener if I would get elongated stars in my image and related proper adapters that would be needed to attach my Esprit 120 and the ZWO 2600, besides those adapters included with the camera…your comments please on this would be appreciated. 😊🔭
Pretty solid evidence for why you need to take, and apply, proper calibration frames. Of course, I probably would have deleted the sample boxes in the Pelican 😜
Good video. What backfocus are you using?
Thanks! Haven't sorted out the BF yet Jim. Seems I errored with my previous calculations and did not account for 6mm on the camera side. I have another adapter/spacer coming. So new spacer would place me right at 58mm based on revised calculations. It will probably arrive when the rain and clouds return! But hopefully I'll be able to do some testing this coming week.
I agree completely with your point on the use of calibration frames - they are absolutely essential for removing vignetting, dust bunnies, etc. I've seen one of your videos before about using DBE with samples just located around the outside of the image, and I've used that for removing gradients from things like light pollution or moon glow, where the gradient is a gradual one from one side or corner of an image to the other, where it works well. I don't think that method can remove residual vignetting though - vignetting is a difference in brightness between the centre and outside of the image, so if you have no sampling of the centre, I'm not sure if it can make an appropriate correction. Adam Block has shown some interesting techniques for the removal of residual vignetting, but that involves using the axial symmetries feature for placing samples and involves a certain amount of trial and error. Like Pompey Monkey, I've always found that decent flats (and maybe I've been lucky in this respect too with my home-made flat panel) work like a charm and I'm then just left with my terrible light pollution to deal with :-(
Thanks for the detailed comment!
I’m happy with flats to deal with vignetting, but am also wondering if you’ve found a Backfocus choice that gives good star shapes to aps-c corners. Any joy on this?
Nice tutorial! I think the real issue is the stars quality at corners. I tried last night to adjust the back focus of my Apex 0.65 without success. Vignetting can be solved easily. It is possible to show corners closeup so we can see stars quality? Thank you, Mario
Check out my previous videos on the APEX. I'm working also on getting the BF correct to fix the stars in the corner. This video about vignetting I did because I had complaints that the APEX had bad vignetting. But as I demonstrated it can be removed.
@@VisibledarkAstro thank you! Please review my comments and your replies on video 1 and 2. Still waiting to see your stars at corners! Thx, Mario
I've heard a lot of people say this reducer is not meant for APS-C sensors when used with the Esprit 100ED. The argument over on cloudy nights is that since you only have a 26mm image circle, the corner stars will ALWAYS be subpar and require cropping. I don't own this reducer myself, but I'm wondering what your honest opinion is on the corner performance with APS-C?
I had the same problem in my svbony triplet . The vignette was enormous (about 20% of frame), not usefull for me... For his sensor ( I think) minor than 1 inch will be not a problem...
@@olholij which Svbony? The SV503 102mm?
Great video Shawn! 👍👍 I have two questions for you:
1. During a long exposure, seeing blurs/enlarges the star images. Has the incorrect spacing between the reducer & the sensor produced abberations that are significantly larger than the typical blurring/enlargement of stars due to seeing during long exposures?
2. Given that vignetting means less signal reaching the edges & corners of the image, but still similar levels of thermal & read noise, I would think that the S/N ratio & the resulting dynamic range would be less along those edges & in the corners (even after applying flats, Dynamic Backround Extraction, and other processing). Have you noticed any signs of the reduced dynamic range when stretching, applying curves & other processing? I guess it would not be terribly problematic when the target subject is centred & doesn't reach the outer part of the field, but in some cases (large object like IC1396, doing mosaics...) I wonder if the vignetting could still become problematic because the outermost part of the field lacks the dynamic range of the inner portion.
I've done flats with t-shirts (even a black one!), handkerchiefs, or no cover at all, illuminated by the sky or a local lamp, and with a dedicated flat field device (Alnitak flip-flat).
I've never experienced any issues. They just work.
I don't understand how people have problems. Maybe I've just been lucky.
Also, as suggested by the masterful (venerable?) Olly Penrice, I've just used the luminance flat master to calibrate my subs, whatever the imaging filter is. Again, it just works.
Am I charmed? lol ;)
Unless maybe each filter has some dust on it in different places from each other.
Thanks for the comment. I usually shoot falts for all filters. As Tim points out, there can be slight differences, such as dust. But interesting approach to just use the lum flat master. If it works for you that's great!
"I've just used the luminance flat master to calibrate my subs, whatever the imaging filter is. Again, it just works."
I believe that would only work if your filters are spotlessly clean. Generally you should take flats on a per-filter basis.
Did you ever tried the TSRED379 with that scope? I am waiting for clear nights to test out this combination. It is not reducing that strong and should give less vignetting and better stars at the edge. Maybe ;)
Interesting. Let me know how it works. Are you using an Esprit 100? Did you need a special adapter to connect it?
@@VisibledarkAstro Yes, I am using the ESPRIT 100. I got an adapter from TS that is specifically made for connecting this reducer to the Skywatcher focuser. I also own the QHY268C. Can't test full frame but APS-C.
@@angryBOT Super! Well let me know your results. Can email as well. shawn@visibledark.ca
That's less vignetting than I get with my Newtonian and GPU corrector. Still fixable by flats 👍
Yes indeed! Thanks for the comment.
Your sensor is to large. That is all.
Yes but the point I wanted to make is that the vignetting can be dealt with and obtain a good result. Some people complain about the vignetting. I wouldn't use larger than APS-C with the Apex. Rumour is they are developing one for larger sensors.
@@VisibledarkAstro Better to use a sensor that is the right size if your image goes all the way to the edges. Otherwise you are just stretching the edges more and creating more noise there. Why spend extra $$$ on a larger sensor if it just means it knocks you back a stop.
@@TheNarrowbandChannel this wasn't about buying larger sensors. And most aren't using small sensors anymore for deepsky. Was demonstrating how the vignetting could be addressed with it.
@@VisibledarkAstro Yes I see that. Just saying an even easier solution is just to go with a smaller sensor. Then you do not loos the speed that you gain with a focal reducer.
It is like sampling. You do not want to buy a sensor that is over or under sampled.
Also bear in mind that larger sensors have mainly older technology in them. The smaller ones ie Cell phone sensor have like 4-5years newer technology in them.
Good info, but the haphazard camera angle switching is distracting and annoying (even more in previous video).
Always someone that complains! Lol. Cheers.
@@VisibledarkAstro if I can offer a suggestion - wait to switch between paragraphs, not just sentences? It's a lot less jarring if it's in the middle of a longer pause (and less frequent) if I compare to other YT channels.
@@VisibledarkAstro Video was fine Shawn nothing wrong with it.👍
@@OlliesSpace Thank you. I appreciate your positive comment. A lot of time, money and knowledge go into making the videos and keeping the channel going for the benefit and help of the astro community. Thanks again.