Bruno Figueira:
@Michelle Rousset you're absolutly right. my mistake. Just use as the figure and it will work nicelly. As you can see in my last photo last night
NGC2244.jpg
*** Nice! Is this picture from your other cameras - or did you finally get your Duo?? Nice stars all the way to the corners! How was the guiding (if taken with the Duo.)
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Michelle Rousset:
Bruno Figueira:
@Michelle Rousset you're absolutly right. my mistake. Just use as the figure and it will work nicelly. As you can see in my last photo last night
NGC2244.jpg
*** Nice! Is this picture from your other cameras - or did you finally get your Duo?? Nice stars all the way to the corners! How was the guiding (if taken with the Duo.)
@Michelle Rousset ASI533MC Pro with the Altair Astro Dual Band SII OIII 4nm. Only 35min due weather.
AM3 Mount with ASI290MM guiding paired with the ASKAR 30mm guide scope.
Unfortunatly the DUO has not yet arrived (last information in the next month)
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Bruno Figueira:
Michelle Rousset:
Bruno Figueira:
@Michelle Rousset you're absolutly right. my mistake. Just use as the figure and it will work nicelly. As you can see in my last photo last night
NGC2244.jpg
*** Nice! Is this picture from your other cameras - or did you finally get your Duo?? Nice stars all the way to the corners! How was the guiding (if taken with the Duo.)
@Michelle Rousset ASI533MC Pro with the Altair Astro Dual Band SII OIII 4nm. Only 35min due weather.
AM3 Mount with ASI290MM guiding paired with the ASKAR 30mm guide scope.
Unfortunatly the DUO has not yet arrived (last information in the next month)
Bruno, the waiting continues for your delivery! I will get the 135mm from Amazon (next day delivery) but now I just need some clear nights. Clouds forecasted for at least another week! Let's see what @Andy finds out when he gets his adapter! Probably a lot of concern for nothing regarding the guiding. We'll see! Thanks again for your input.
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Michelle Rousset:
Andy:
I’m about to pair my Samyang 135mm with the Duo, just waiting on the EOS T2 adapter to arrive. I’ll update everyone once it’s here.
During the summer, I had a blast using my Samyang 135mm lens. I paired it with the 533MCP without any tilt issues at f/2.
*** Thanks, Andy! I was playing around with the various combinations (I have the EOS T2 adapter and Duo, but waiting to pull the trigger on the 135mm) and noticed that the adapter has 3 components. The actual component with the bayonet has M54 thread. I'm wondering if there is an 15mm extender with M54 thread to reach 44mm back focus. It would be adapter (~11.5mm) + extender (15mm) + Duo (17.5mm) = 44mm. This way, it would have a wide open access of 54mm all the way through to the camera sensor with the correct back focus.
Thoughts?
Hi Michelle,
So the 2600mc Duo comes with two adapters that are m54: 16.5mm and 21mm. You will not need the extenders you mention because if you just purchase the ZWO EOS T2 adapter lens (bayonet) which measures 26.5 and you attach your Duo (17.5), that will satisfy the 44mm backfocus with the Samyang 135mm. If you have a 2” filter, your backfocus will be 44.66 (2”* 1/3 of the filter size). I hope this makes sense.
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Andy:
Michelle Rousset:
Andy:
I’m about to pair my Samyang 135mm with the Duo, just waiting on the EOS T2 adapter to arrive. I’ll update everyone once it’s here.
During the summer, I had a blast using my Samyang 135mm lens. I paired it with the 533MCP without any tilt issues at f/2.
*** Thanks, Andy! I was playing around with the various combinations (I have the EOS T2 adapter and Duo, but waiting to pull the trigger on the 135mm) and noticed that the adapter has 3 components. The actual component with the bayonet has M54 thread. I'm wondering if there is an 15mm extender with M54 thread to reach 44mm back focus. It would be adapter (~11.5mm) + extender (15mm) + Duo (17.5mm) = 44mm. This way, it would have a wide open access of 54mm all the way through to the camera sensor with the correct back focus.
Thoughts?
Hi Michelle,
So the 2600mc Duo comes with two adapters that are m54: 16.5mm and 21mm. You will not need the extenders you mention because if you just purchase the ZWO EOS T2 adapter lens (bayonet) which measures 26.5 and you attach your Duo (17.5), that will satisfy the 44mm backfocus with the Samyang 135mm. If you have a 2” filter, your backfocus will be 44.66 (2”* 1/3 of the filter size). I hope this makes sense.
*Thanks, Andy! That makes perfect sense! My main concern was whether or not the M42 diameter of the EOS T2 adapter is wide enough for guiding on the Duo. The EOS T2 adapter comes in 3 pieces. The 2nd and 3rd pieces (not the bayonet piece) have an M42 end. I feel it will not be a wide enough diameter to expose the guide sensor. I figured if I used only the bayonet portion of the EOS T2 adapter (11.5mm) with the M54 threads, I would only need an 15mm M54 extender to connect the bayonet piece to the Duo. It would be 11.5mm + 15mm + 17.5mm (plus a little extra for the 1/3 of the filter) to reach 44.6mm - all at M54 (minus the filter diameter inside the T2 adapter, which shouldn't be an issue.) I hope that makes sense.
I am looking forward to hearing how your guiding works when you get the EOS T2 adapter! If you have issues, we may have to go with the 15mm M54 extender option! Thank you so much for your input.
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Michelle Rousset:
Andy:
Michelle Rousset:
Andy:
I’m about to pair my Samyang 135mm with the Duo, just waiting on the EOS T2 adapter to arrive. I’ll update everyone once it’s here.
During the summer, I had a blast using my Samyang 135mm lens. I paired it with the 533MCP without any tilt issues at f/2.
*** Thanks, Andy! I was playing around with the various combinations (I have the EOS T2 adapter and Duo, but waiting to pull the trigger on the 135mm) and noticed that the adapter has 3 components. The actual component with the bayonet has M54 thread. I'm wondering if there is an 15mm extender with M54 thread to reach 44mm back focus. It would be adapter (~11.5mm) + extender (15mm) + Duo (17.5mm) = 44mm. This way, it would have a wide open access of 54mm all the way through to the camera sensor with the correct back focus.
Thoughts?
Hi Michelle,
So the 2600mc Duo comes with two adapters that are m54: 16.5mm and 21mm. You will not need the extenders you mention because if you just purchase the ZWO EOS T2 adapter lens (bayonet) which measures 26.5 and you attach your Duo (17.5), that will satisfy the 44mm backfocus with the Samyang 135mm. If you have a 2” filter, your backfocus will be 44.66 (2”* 1/3 of the filter size). I hope this makes sense.
*Thanks, Andy! That makes perfect sense! My main concern was whether or not the M42 diameter of the EOS T2 adapter is wide enough for guiding on the Duo. The EOS T2 adapter comes in 3 pieces. The 2nd and 3rd pieces (not the bayonet piece) have an M42 end. I feel it will not be a wide enough diameter to expose the guide sensor. I figured if I used only the bayonet portion of the EOS T2 adapter (11.5mm) with the M54 threads, I would only need an 15mm M54 extender to connect the bayonet piece to the Duo. It would be 11.5mm + 15mm + 17.5mm (plus a little extra for the 1/3 of the filter) to reach 44.6mm - all at M54 (minus the filter diameter inside the T2 adapter, which shouldn't be an issue.) I hope that makes sense.
I am looking forward to hearing how your guiding works when you get the EOS T2 adapter! If you have issues, we may have to go with the 15mm M54 extender option! Thank you so much for your input.
Totally understand now. I’ll keep you posted.
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Andy:
If you have a 2” filter, your backfocus will be 44.66 (2”* 1/3 of the filter size)
Hi Andy,
Allow me to add a small correction.
you don't need to account for the filter size but for the filter thickness. So, if your filter is for example 3mm thick (most common case), than you need to add 1mm of backfocus.
Light waves don't care if they pass through 2" or 1.25" or 36mm filters ;)
Also, 2" is 5.08cm. So 1/3 of that is 1.69cm (or 16.9mm). Gotta love the metric system.
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Andy:
If you have a 2” filter, your backfocus will be 44.66 (2”* 1/3 of the filter size)
Hi Andy,
Allow me to add a small correction.
you don't need to account for the filter size but for the filter thickness. So, if your filter is for example 3mm thick (most common case), than you need to add 1mm of backfocus.
Light waves don't care if they pass through 2" or 1.25" or 36mm filters ;)
Also, 2" is 5.08cm. So 1/3 of that is 1.69cm (or 16.9mm). Gotta love the metric system.
Thanks for the clarification!! So in that case, the backfocus for the samyang 135, 2” filters, and the asi2600 should be 60.933 [44mm+2”. *(1/3)].
An eaf will do its magic to find the focus without the need of fine tuning spacers. Although soacers can be considered and incorporated in the imaging train as well.
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Michelle Rousset:
Andy:
Michelle Rousset:
Andy:
I’m about to pair my Samyang 135mm with the Duo, just waiting on the EOS T2 adapter to arrive. I’ll update everyone once it’s here.
During the summer, I had a blast using my Samyang 135mm lens. I paired it with the 533MCP without any tilt issues at f/2.
*** Thanks, Andy! I was playing around with the various combinations (I have the EOS T2 adapter and Duo, but waiting to pull the trigger on the 135mm) and noticed that the adapter has 3 components. The actual component with the bayonet has M54 thread. I'm wondering if there is an 15mm extender with M54 thread to reach 44mm back focus. It would be adapter (~11.5mm) + extender (15mm) + Duo (17.5mm) = 44mm. This way, it would have a wide open access of 54mm all the way through to the camera sensor with the correct back focus.
Thoughts?
Hi Michelle,
So the 2600mc Duo comes with two adapters that are m54: 16.5mm and 21mm. You will not need the extenders you mention because if you just purchase the ZWO EOS T2 adapter lens (bayonet) which measures 26.5 and you attach your Duo (17.5), that will satisfy the 44mm backfocus with the Samyang 135mm. If you have a 2” filter, your backfocus will be 44.66 (2”* 1/3 of the filter size). I hope this makes sense.
*Thanks, Andy! That makes perfect sense! My main concern was whether or not the M42 diameter of the EOS T2 adapter is wide enough for guiding on the Duo. The EOS T2 adapter comes in 3 pieces. The 2nd and 3rd pieces (not the bayonet piece) have an M42 end. I feel it will not be a wide enough diameter to expose the guide sensor. I figured if I used only the bayonet portion of the EOS T2 adapter (11.5mm) with the M54 threads, I would only need an 15mm M54 extender to connect the bayonet piece to the Duo. It would be 11.5mm + 15mm + 17.5mm (plus a little extra for the 1/3 of the filter) to reach 44.6mm - all at M54 (minus the filter diameter inside the T2 adapter, which shouldn't be an issue.) I hope that makes sense.
I am looking forward to hearing how your guiding works when you get the EOS T2 adapter! If you have issues, we may have to go with the 15mm M54 extender option! Thank you so much for your input.
Here’s my imaging train.
samyang 135+ 11.5 ZWO EOS T2 adapter for 2” efw+efw (20mm)+asi2600mm (12.5 tilt plate removed) = 44mm (not accounting for the 2” filters I have in the fw). |
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Hi Andy,
Still no, 2" refers to the diameter not the thickness. The thickness can vary from filter to filter. Some are 3mm, some are 1.8mm (millimeters, not inches).
Also to clarify, the backfocus is 44mm, you cannot add 2"/3 backfocus to it without converting inches to mm. (see my post above)
If 44.67mm backfocus has worked out for you, than that is perfect and keep it like that. But also here, to be pedantic, the backfocus has nothing to do to find the focus, it has to be set correctly, so that every corner of your FOV is in focus. If you noticed wonky stars in the corners that are either inward or outward pointing, than your backfocus is not set correctly and you might need to adjust. this is especially important for f/2 systems.
I hope that helps to clarify, especially if someone new would follow your recommendations which would not necessarily work for them.
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Hi Andy,
Still no, 2" refers to the diameter not the thickness. The thickness can vary from filter to filter. Some are 3mm, some are 1.8mm (millimeters, not inches).
Also to clarify, the backfocus is 44mm, you cannot add 2"/3 backfocus to it without converting inches to mm. (see my post above)
If 44.67mm backfocus has worked out for you, than that is perfect and keep it like that. But also here, to be pedantic, the backfocus has nothing to do to find the focus, it has to be set correctly, so that every corner of your FOV is in focus. If you noticed wonky stars in the corners that are either inward or outward pointing, than your backfocus is not set correctly and you might need to adjust. this is especially important for f/2 systems.
I hope that helps to clarify, especially if someone new would follow your recommendations which would not necessarily work for them.
Correct. I Did not see you replied so quickly. I edited my previous response to you. Correct backfocus should be 60.933 not 44.7.
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Andy:
Correct backfocus should be 60.933 not 44.7
No, that is completely wrong now, sorry. Here is a link for you to read on backfocus:
https://optcorp.com/blogs/deep-sky-imaging/how-to-set-the-correct-back-focus
As an example, I used to have an L-Extreme which is 3mm THICK, the diameter of the filter (either 2" or 1.25") does not matter. So I added 1mm to the 44mm backfocus to reach 45mm. Now I have another filter which is 1.8mm thick, so I should add 0.6mm to a total of 44.6mm.
Also, backfocus adjustments are done by physically adding spacers or similar to you imaging train. You cannot adjust backfocus with an EAF.
Do 1mm or 0.6mm matter for backfocus? Depends, I guess. Some people dont like elongated stars in the corners, some will never notice they even have those.
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Andy:
Correct backfocus should be 60.933 not 44.7
No, that is completely wrong now, sorry. Here is a link for you to read on backfocus:
https://optcorp.com/blogs/deep-sky-imaging/how-to-set-the-correct-back-focus
As an example, I used to have an L-Extreme which is 3mm THICK, the diameter of the filter (either 2" or 1.25") does not matter. So I added 1mm to the 44mm backfocus to reach 45mm. Now I have another filter which is 1.8mm thick, so I should add 0.6mm to a total of 44.6mm.
Also, backfocus adjustments are done by physically adding spacers or similar to you imaging train. You cannot adjust backfocus with an EAF.
Do 1mm or 0.6mm matter for backfocus? Depends, I guess. Some people dont like elongated stars in the corners, some will never notice they even have those.
Okay that makes more sense now. If I recall correctly in the summer I only added .6 fine tuning spacer or I must have done .4 and .3 spacer to reach 44.7. Either way, I was fine.
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Seems to me someone go their filter thickness wrong:
L-Extreme Thickness: 1.85mm (see: https://www.optolong.com/cms/document/detail/id/100.html). Which is what mine is.
Also, concept of optimum backfocus do not apply to lens in general as well as this specifically. The only things that matters is the right distance lens flange to sensor which, for Canon EF lenses is 44 mm. If you add a filter the focus will shift toward the sensor by approximately 1/3 of the filter thickness so you should add this back into the adapter by adding the right spacer.
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andrea tasselli:
L-Extreme Thickness: 1.85mm
Ah, interesting, it is also 1.85mm then.
andrea tasselli:
If you add a filter the focus will shift toward the sensor by approximately 1/3 of the filter thickness so you should add this back into the adapter by adding the right spacer.
This is exactly what I meant. Thickness is relevant, not filter diameter.
But anyways as always, theory is theory, praxis is a totally different story. In most cases, those 0.6mm should not make such a big difference, but it is good to know where to look if you want to troubleshoot such fast systems as the Samyang 135mm.
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This is exactly what I meant. Thickness is relevant, not filter diameter.
Absolutely!
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Back to @Bruno Figueira and @Andy’s original question… I have paired the Duo to my new Samyang 135mm with the ZWO EOS-T2 adapter. I didn’t include a filter so as not to add yet one more variable.
The regular EOS T2 adapter narrows down to M42, and the question is whether the Duo still guides at that width. I have confirmed, it does! Over a short 10 minute period, I was guiding at 0.53. HOWEVER, I was getting terrible vignetting (or light drop-off.)
Tonight I will test stopping the aperture down to see if it helps the vignetting, and I will ALSO test the EOS adapter with a separately purchased 15mm M54 extender to replace the M42 one supplied with the original adapter, to see if that helps as well.
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Michelle Rousset:
Back to @Bruno Figueira and @Andy’s original question… I have paired the Duo to my new Samyang 135mm with the ZWO EOS-T2 adapter. I didn’t include a filter so as not to add yet one more variable.
The regular EOS T2 adapter narrows down to M42, and the question is whether the Duo still guides at that width. I have confirmed, it does! Over a short 10 minute period, I was guiding at 0.53. HOWEVER, I was getting terrible vignetting (or light drop-off.)
Tonight I will test stopping the aperture down to see if it helps the vignetting, and I will ALSO test the EOS adapter with a separately purchased 15mm M54 extender to replace the M42 one supplied with the original adapter, to see if that helps as well.
@Michelle Rousset thanks for the update. My 2600MC Duo is on its way to me.. Expected to receive next monday so next week I will try to take some shots
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Bruno Figueira:
Michelle Rousset:
Back to @Bruno Figueira and @Andy’s original question… I have paired the Duo to my new Samyang 135mm with the ZWO EOS-T2 adapter. I didn’t include a filter so as not to add yet one more variable.
The regular EOS T2 adapter narrows down to M42, and the question is whether the Duo still guides at that width. I have confirmed, it does! Over a short 10 minute period, I was guiding at 0.53. HOWEVER, I was getting terrible vignetting (or light drop-off.)
Tonight I will test stopping the aperture down to see if it helps the vignetting, and I will ALSO test the EOS adapter with a separately purchased 15mm M54 extender to replace the M42 one supplied with the original adapter, to see if that helps as well.
@Michelle Rousset thanks for the update. My 2600MC Duo is on its way to me.. Expected to receive next monday so next week I will try to take some shots
*** @Bruno Figueira hopefully, you will have some clear skies! I look forward to your findings!
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andrea tasselli:
Seems to me someone go their filter thickness wrong:
L-Extreme Thickness: 1.85mm (see: https://www.optolong.com/cms/document/detail/id/100.html). Which is what mine is.
Also, concept of optimum backfocus do not apply to lens in general as well as this specifically. The only things that matters is the right distance lens flange to sensor which, for Canon EF lenses is 44 mm. If you add a filter the focus will shift toward the sensor by approximately 1/3 of the filter thickness so you should add this back into the adapter by adding the right spacer.
That makes sense too so I’ve only added a .6 fine adjustment spacer which brings the distance flange to 44.6mm.
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The thickness of this ZWO Canon adapter with filter holder (Adapter) is 26.5 mm. The backfocus of the camera ASI 2600MC Duo is 17.5 mm. 26.5 + 17.5 = 44 mm, just the backfocus distante of the Samyang-EF Canon. I use the Samyang with the ASI 1600 mm (backfocus 6.5mm) + ZWO adapter (without filter holder) 17.5 mm + ZWO filter wheel (20 mm) = 44 mm.
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According to one of the ccd suitability calculators, you'll get significant under sampling using this combination. I'm interested to know if it works as wish to try my 2600 duo with a Canon 135 f2 lens.under sampling.png |
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According to one of the ccd suitability calculators, you'll get significant under sampling using this combination. I'm interested to know if it works as wish to try my 2600 duo with a Canon 135 f2 lens.under sampling.png
No problem with the undersampling. I already use the 533MC and MM with this lens and got very good results
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Bruno Figueira:
According to one of the ccd suitability calculators, you'll get significant under sampling using this combination. I'm interested to know if it works as wish to try my 2600 duo with a Canon 135 f2 lens.under sampling.png
No problem with the undersampling. I already use the 533MC and MM with this lens and got very good results
That's good news. I'll have a go with my Canon lens and the 2600 🙂 |
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So, I have tested the Duo with the Rokinon 135 lens with both the M54 and M42 adapters. Both guide very well. My current issue now is that I’m still getting vignetting/light dropoff. It seems to be my surrounding lights, since I get the same effect with all of my canon lenses.
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0.00
0.90
0.00
3.31
7.90
0.90
0.00
