23 replies to this topic

[piyushCK]

Hello,

 

This is my first post here. I am a beginner astrophotographer.

Kindly help with what I may be missing in the setup.

I have:

1. ZWO ASI294 MC Pro

2. Canon-EF 17-40 mm f/4L and Canon-EF  50 mm f 1.8 STM lens

3. ZWO-Filter Drawer for EOS Lens

4. IDAS -NBZ Nebula Booster FIlter-48 mm

 

Yesterday, I was using the Canon 50 mm lens on the setup with the APT tool to see the live View. I tried the EXP 3-6 settings. I disabled debayering, otherwise, it was showing a pink screen.

I could see 4-5 very tiny star-like objects in the Live View. Changing the focus ring on the lens could not change their shape.

 

I was able to control the Camera temperature using the APT.

 

I am not sure if I am even able to focus. Shall I need any hardware or software controller to see if the focus changes(Am I missing something here?) I have attached an Image.

https://drive.google...iew?usp=sharing

 

Would I be able to control the two lenses that I have for focusing while I am viewing the Live View? Could you also please recommend other wide lenses that I can use with the EOS adapter I have?

 

Kindly let me know.

 

Thanks!

Edited by piyushCK, 30 June 2022 - 01:45 PM.

[Borodog]

Try focusing on distant objects during the daytime.

[piyushCK]

Thanks so much! Shall I need any separate driver or hardware as well to control the focus? Is my setup complete to test the focus during daytime?

https://drive.google...iew?usp=sharing

[Borodog]

Can you not manually focus those lenses? If they are electronic focus only I don't think there's anything you can do except switch to manual lenses.

[piyushCK]

There is a manual focus option on that lens. I tried that but could not get any farby object sharp. Could it be because of the NBZ filter that's placed in the drawer? Sorry for these questions. I am just starting out.

[FrostByte]

How much back-spacing do you have between the back of the lens and the camera sensor? It looks like you have a couple fairly long extensions in there, but it's kind of hard to tell. A Canon sensor is recessed 44mm into the camera body, behind the bayonet mount. If you have more than that between the lens mount and the sensor, you might just be too far from the lens to achieve focus.

 

The 50mm f/1.8 lens is REALLY HARD to focus on a starfield as the focus ring is so touchy. But start out by making sure you're close to the correct back-spacing requirement and go from there.

[Borodog]

There is a manual focus option on that lens. I tried that but could not get any farby object sharp. Could it be because of the NBZ filter that's placed in the drawer? Sorry for these questions. I am just starting out.

Did it appear that it was moving *toward* focus in either direction and you just ran out of focus travel?

[piyushCK]

Ohh, thanks @

 

How much back-spacing do you have between the back of the lens and the camera sensor? It looks like you have a couple fairly long extensions in there, but it's kind of hard to tell. A Canon sensor is recessed 44mm into the camera body, behind the bayonet mount. If you have more than that between the lens mount and the sensor, you might just be too far from the lens to achieve focus.

 

The 50mm f/1.8 lens is REALLY HARD to focus on a starfield as the focus ring is so touchy. But start out by making sure you're close to the correct back-spacing requirement and go from therThanks.e.

Thanks, I see. The Filter drawer right behind the lens is 26.5 mm thick. There is some more spacer behind that right in front of the camera.( I would say maybe 20 mm). Should I try removing the spacer?

[piyushCK]

Did it appear that it was moving *toward* focus in either direction and you just ran out of focus travel?

No, I could not see the shape of the objects changing with the rotation of the focus dial.
 

[FrostByte]

Ohh, thanks @

 

Thanks, I see. The Filter drawer right behind the lens is 26.5 mm thick. There is some more spacer behind that right in front of the camera.( I would say maybe 20 mm). Should I try removing the spacer?

Just so that I understand, you have the lens mount, the adapter, filter drawer, an extension tube, and then the camera? I just looked up the specs for your camera, and it looks like the sensor is recessed 6.5mm into the camera body. Then you have your 26.5mm thick filter drawer, which puts you at 33mm. You need to make up 11mm additional space between the mounting flange for the lens and the surface of the sensor. By chance is the adapter for the lens 11mm thick? If so, then the adapter plus filter drawer plus camera back focus distance puts you at the specified 44mm for your lens.

 

APT does allow you to control the focus of an EOS lens via software, but I believe you need to be connected to a Canon body in order to be able to do this. But try to get to 44mm back focus distance with all the adapters and spacers and then try to focus during the daytime at a far-off object. Manually adjust the focus ring to the infinity focus mark and you should be really close. Start looping exposures and adjust from there until you can see an image.

[piyushCK]

Just so that I understand, you have the lens mount, the adapter, filter drawer, an extension tube, and then the camera? I just looked up the specs for your camera, and it looks like the sensor is recessed 6.5mm into the camera body. Then you have your 26.5mm thick filter drawer, which puts you at 33mm. You need to make up 11mm additional space between the mounting flange for the lens and the surface of the sensor. By chance is the adapter for the lens 11mm thick? If so, then the adapter plus filter drawer plus camera back focus distance puts you at the specified 44mm for your lens.

 

APT does allow you to control the focus of an EOS lens via software, but I believe you need to be connected to a Canon body in order to be able to do this. But try to get to 44mm back focus distance with all the adapters and spacers and then try to focus during the daytime at a far-off object. Manually adjust the focus ring to the infinity focus mark and you should be really close. Start looping exposures and adjust from there until you can see an image.

Appreciate your response. I'll measure the exact distances and aim for the 44 mm back focus. I think the filter drawer including the lens adapter is 26.5 mm.  The extension tube is 21 mm. This maybe leading to the focus falling short of the sensor. Maybe, I'll try a thinner extension tube or remove it at first.

Edited by piyushCK, 30 June 2022 - 02:41 PM.

[FrostByte]

Let us know if you make any progress! But certainly test it out during the day... a starfield is a really difficult target for troubleshooting focus issues.

[piyushCK]

Let us know if you make any progress! But certainly test it out during the day... a starfield is a really difficult target for troubleshooting focus issues.

For sure! Thank you.

[Dren]

Appreciate your response. I'll measure the exact distances and aim for the 44 mm back focus. I think the filter drawer including the lens adapter is 26.5 mm.  The extension tube is 21 mm. This maybe leading to the focus falling short of the sensor. Maybe, I'll try a thinner extension tube or remove it at first.

So your camera body should have come with a T2 ring (black circular part) attached at the front.  This part, which is 11mm, should be connected to the lens adapter.  

 

6.5 (image sensor distance from the metal body) + 11 (T2 ring) + 26.5 (adapter) = 44.

Edited by Dren, 30 June 2022 - 03:00 PM.

[Dren]

There is a manual focus option on that lens. I tried that but could not get any farby object sharp. Could it be because of the NBZ filter that's placed in the drawer? Sorry for these questions. I am just starting out.

When you put the lens into manual focus and rotate the focus control, do you see the lens moving?  I thought the STM model always used the motor to change lens--meaning even when you're in manual mode, it's the motor that is changing the focus of the lens when you rotate the focus control.  And I don't think the motor works without the lens being attached to a Canon body.

Edited by Dren, 30 June 2022 - 03:06 PM.

[Borodog]

When you put the lens into manual focus and rotate the focus control, do you see the lens moving?  I thought the STM model always used the motor to change lens--meaning even when you're in manual mode, it's the motor that is changing the focus of the lens when you rotate the focus control.  And I don't think the motor works without the lens being attached to a Canon body.

I should have made clear this is what I was asking; my Sony lenses are the same. Only the manual only lenses will actually change focus without being connected to the camera body.

[PRastro]

You need a backfocus distance of 44mm from the lens flange to the sensor. The back focus distance of your camera (camera T2 connector to sensor distance) is 6.5mm without the 11mm t2-t2 adapter or 17.5mm with. With your curent setup your sensor is too far behind. Remove the 21mm extension tube and just use the 11mm t2-t2 adapter that came with your camera. That will give you a total BF distance of exactly 44mm.

 

You would need a bhatinov mask to get perfect manual focus. Get a fairly large bright star in frame and use a bhatinov mask. If you want to autofocus, you need one of these https://www.astromec....org/ascom.html

[KungFood]

If the dots you are seeing do not change at all when you adjust focus, it's likely that they are not stars at all, but hot/cold pixels on the sensor. I would try focusing without the filter at first, just to verify where rough focus is. Once you find that, plop the filter back in and adjust.

Edited by KungFood, 30 June 2022 - 04:41 PM.

[piyushCK]

So your camera body should have come with a T2 ring (black circular part) attached at the front.  This part, which is 11mm, should be connected to the lens adapter.  

 

6.5 (image sensor distance from the metal body) + 11 (T2 ring) + 26.5 (adapter) = 44.

Thank you! I'll remove the 21 mm spacer. Glad to see you're from San Diego. I also live here.

[piyushCK]

I should have made clear this is what I was asking; my Sony lenses are the same. Only the manual only lenses will actually change focus without being connected to the camera body.

Sorry, I could not get then. I could not see the lens moving after rotating the focus wheel.

[piyushCK]

You need a backfocus distance of 44mm from the lens flange to the sensor. The back focus distance of your camera (camera T2 connector to sensor distance) is 6.5mm without the 11mm t2-t2 adapter or 17.5mm with. With your curent setup your sensor is too far behind. Remove the 21mm extension tube and just use the 11mm t2-t2 adapter that came with your camera. That will give you a total BF distance of exactly 44mm.

 

You would need a bhatinov mask to get perfect manual focus. Get a fairly large bright star in frame and use a bhatinov mask. If you want to autofocus, you need one of these https://www.astromec....org/ascom.html

Thanks for letting me know.

[piyushCK]

If the dots you are seeing do not change at all when you adjust focus, it's likely that they are not stars at all, but hot/cold pixels on the sensor. I would try focusing without the filter at first, just to verify where rough focus is. Once you find that, plop the filter back in and adjust.

I think that could be true. Thanks, I'll try without the filter.

[Dren]

Sorry, I could not get then. I could not see the lens moving after rotating the focus wheel.

I don't think you can use the STM lens with 294MC because you can't change the focus. I think some people may make special adapters to control STM lens without Canon body, but I think it's super expensive.  

 

How about Canon-EF 17-40 mm f/4L?  Does this one have manual lens control without being connected to Canon body?

 

I just saw the image you posted of your setup.  You're using a tripod with a ballhead?  You will need an equatorial mount if you want to take long exposure images for AP.  Most of us on this forum capture images using long exposure. 

 

Entry mounts, like Star Adventurer, cost around $400.  There is a new version coming out, Star Adventurer GTI, which looks pretty awesome but costs more.  Mount is generally considered the most important piece of equipment for AP.  Advantage of mounts like SA is that it's small and light, so it's easier to take with you and setup at remote locations.  Disadvantage is that they are made for short focal lengths and light camera+lens combo.  If you upgrade to longer/heavier setup, you'll need a better mount.  

 

Without a mount, you can use 500 rule to calculate the length of your exposure to avoid star trails.   

[piyushCK]

I don't think you can use the STM lens with 294MC because you can't change the focus. I think some people may make special adapters to control STM lens without Canon body, but I think it's super expensive.  

 

How about Canon-EF 17-40 mm f/4L?  Does this one have manual lens control without being connected to Canon body?

 

I just saw the image you posted of your setup.  You're using a tripod with a ballhead?  You will need an equatorial mount if you want to take long exposure images for AP.  Most of us on this forum capture images using long exposure. 

 

Entry mounts, like Star Adventurer, cost around $400.  There is a new version coming out, Star Adventurer GTI, which looks pretty awesome but costs more.  Mount is generally considered the most important piece of equipment for AP.  Advantage of mounts like SA is that it's small and light, so it's easier to take with you and setup at remote locations.  Disadvantage is that they are made for short focal lengths and light camera+lens combo.  If you upgrade to longer/heavier setup, you'll need a better mount.  

 

Without a mount, you can use 500 rule to calculate the length of your exposure to avoid star trails.   

Ohh okay. I saw a link from this thread of Astromechanics website where there are adapters to control the focus and aperture externally. I'll try my 17-40 mm f/4L tonight. I was using this setup(in the image) only for focusing. I have been using an iOptron Skyguider mount. I had tough times aligning to the Polaris, probably because I headed to the dark location after the twilight. Yesterday night,(from my room near UCSD-possibly a high bortle zone), I was able to see the Polaris for the first time and was able to almost align it where the app suggested. I am looking forward to getting more robust mounts once I get some experience with basic setups.

Edited by piyushCK, 30 June 2022 - 06:14 PM.